CN116931296A

CN116931296A - Optical resonant cavity and optical filter

Info

Publication number: CN116931296A
Application number: CN202210371684.0A
Authority: CN
Inventors: 葛柯廷; 昌钟璨; 万助军; 欧阳奎
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-04-11
Filing date: 2022-04-11
Publication date: 2023-10-24

Abstract

The application provides an optical resonant cavity and an optical filter, which relate to the technical field of optical communication and can improve the filtering effect of the optical resonant cavity, wherein the optical resonant cavity comprises an electro-optic crystal; a first reflective film and a second reflective film; the first electrode and the second electrode are used for adjusting the refractive index of the electro-optic crystal by applying an electric field to the electro-optic crystal; a first reflective film for transmitting an input light ray to the electro-optical crystal in a propagation direction; an electro-optical crystal for transmitting light transmitted by the first reflective film to the second reflective film with a predetermined refractive index under the action of an electric field; a second reflection film for outputting light of a predetermined wavelength among light transmitted by the electro-optical crystal and reflecting light of other wavelengths than the predetermined wavelength to the electro-optical crystal; the electro-optical crystal is also used for transmitting the light rays reflected by the second reflecting film to the first reflecting film with a preset refractive index; the first reflecting film is also used for reflecting the light transmitted by the electro-optical crystal to the electro-optical crystal.

Description

Optical resonant cavity and optical filter

Technical Field

The present disclosure relates to the field of optical communications, and in particular, to an optical resonant cavity and an optical filter.

Background

The optical fiber transmission uses light as a carrier wave, and uses an optical fiber as a transmission medium to transmit signals. Among them, a backbone network is a high-speed network for connecting a plurality of areas or regions, and in the backbone network, optical fiber transmission is generally used. With the development of communication technology and the increase of data transmission requirements, reconfigurable optical add-drop multiplexers (ROADMs) in backbone networks need to sink to metropolitan area networks to achieve the purpose of network upgrade. In general, the reconfigurable optical add/drop multiplexer needs to use an optical performance monitor (optical performance monitor, OPM) to detect the signal-to-noise ratio and power of the optical signal transmitted by the optical fiber, so as to ensure that the crosstalk level and the bit error rate of the optical signal transmitted by the optical fiber are controllable.

The core component of the optical performance monitor is an optical filter (tunable optical filter, TOF), wherein the optical filter comprising a Fabry-perot cavity (FP cavity) is most common and widely used, and the FP cavity is composed of two parallel planar reflecting surfaces and an optical medium between the two planar reflecting surfaces, and performs interference filtering by using the interference principle of light. However, in order to achieve the purpose of filtering out light rays with a predetermined wavelength, the conventional optical filter comprising an FP cavity is often controlled by a driving voltage to mechanically move a distance between two plane reflecting surfaces in the FP cavity so as to adjust a cavity length of the FP cavity, thereby adjusting the wavelength of the filtered light rays by the FP cavity. Therefore, the optical filter comprising the FP cavity has high requirements on mechanical control precision for controlling the distance between two plane reflecting surfaces, and has limited filtering effect.

Disclosure of Invention

The embodiment of the application provides an optical resonant cavity and an optical filter, which can improve the filtering effect of the optical resonant cavity.

In order to achieve the above purpose, the embodiment of the application adopts the following technical scheme:

in a first aspect, there is provided an optical resonator comprising: an electro-optic crystal; the first reflection film and the second reflection film are respectively arranged at two sides of the electro-optic crystal along the propagation direction of the electro-optic crystal; the first electrode and the second electrode are arranged on the electro-optic crystal, and an electric field applied to the electro-optic crystal by the first electrode and the second electrode is used for adjusting the refractive index of the electro-optic crystal; the electric field has a component perpendicular to the propagation direction; a first reflective film for transmitting an input light ray to the electro-optical crystal in a propagation direction; an electro-optical crystal for transmitting light transmitted by the first reflective film to the second reflective film with a predetermined refractive index under the action of an electric field; a second reflection film for outputting light of a predetermined wavelength among light transmitted by the electro-optical crystal and reflecting light of other wavelengths than the predetermined wavelength to the electro-optical crystal; the electro-optical crystal is also used for transmitting the light rays reflected by the second reflecting film to the first reflecting film with a preset refractive index; the first reflecting film is also used for reflecting the light transmitted by the electro-optical crystal to the electro-optical crystal. In the optical resonator described above, the first reflection film, the second reflection film, and the electro-optical crystal filter the input light by providing the first reflection film and the second reflection film on both sides of the electro-optical crystal in the propagation direction of the electro-optical crystal. And, there are also the first electrode and the second electrode on the electro-optic crystal, when the driving voltage is applied to the first electrode and the second electrode, an electric field will be formed in the electro-optic crystal, and there is a component perpendicular to the propagation direction of the electro-optic crystal in the electric field, so that the electro-optic crystal can generate an electro-optic effect perpendicular to the propagation direction (i.e. a transverse electro-optic effect), and the refractive index of the electro-optic crystal will become a predetermined refractive index under the action of the electric field. Then, when the electric fields formed in the electro-optic crystal are different, the input light transmitted by the first reflective film in the propagation direction will be transmitted to the second reflective film at a predetermined refractive index corresponding to the electric field in the electro-optic crystal. The second reflecting film outputs light rays of a predetermined wavelength among the light rays transmitted through the electro-optical crystal, that is, transmits the light rays of the predetermined wavelength out of the second reflecting film and reflects the light rays of other wavelengths than the predetermined wavelength back to the electro-optical crystal, and then the electro-optical crystal transmits the light rays reflected by the second reflecting film to the first reflecting film with a predetermined refractive index, and the first reflecting film is also used for reflecting the light rays transmitted by the electro-optical crystal to the electro-optical crystal. This is repeated so that light of a predetermined wavelength is output from the second reflection film. In addition, in the optical resonant cavity, the electric field formed by the driving voltage arranged between the electrodes can be directly used for adjusting the refractive index of the electro-optical crystal, when the refractive index of the electro-optical crystal is changed, the purpose of filtering out light rays with preset wavelength can be achieved, the modulation of the cavity length of the optical resonant cavity by using a mechanical control mode is avoided, and the purpose of improving the filtering effect is achieved.

Optionally, an embodiment of the present application provides an arrangement of a first electrode and a second electrode, where the first electrode and the second electrode are disposed on two sides of the electro-optical crystal, respectively, parallel to the propagation direction. The electrodes are directly arranged on the surface of the electro-optic crystal, when driving voltage is applied to the two electrodes, electric fields are directly formed between the two electrodes in opposite directions (wherein the direction of the electric fields is perpendicular to the propagation direction), namely, the most uniform electric fields are formed on the electro-optic crystal, so that the refractive index of the electro-optic crystal is adjusted.

Optionally, the electro-optic crystal comprises: an incident surface located on the light-incident side and an exit surface located on the light-exit side in the propagation direction; the incident surface comprises a first light-transmitting area positioned at the center and a first light-non-transmitting area surrounding the first light-transmitting area; the emergent surface comprises a second light-transmitting area positioned at the center and a second non-light-transmitting area surrounding the second light-transmitting area; the first reflecting film is arranged in the first light transmission area, and the second reflecting film is arranged in the second light transmission area; the first electrode and the second electrode are arranged in the first non-light-transmitting area; or the first electrode and the second electrode are arranged in the second non-light-transmitting area. In the alternative mode, the embodiment of the application provides another arrangement mode of the first electrode and the second electrode, when driving voltage is applied to the two electrodes, an electric field positioned on one side of a plane where the two electrodes are positioned penetrates through the electro-optic crystal, and the adjustment of the refractive index of the electro-optic crystal is realized; the first electrode and the second electrode are arranged on the incident surface or the emergent surface at the same time, and the two electrodes can be formed through one manufacturing process, so that the manufacturing process difficulty of the first electrode and the second electrode is reduced.

Optionally, the first non-light-transmitting region includes a first region and a second region symmetrically distributed with the first light-transmitting region as a center; the second non-light-transmitting area comprises a third area and a fourth area which are symmetrically distributed by taking the second light-transmitting area as a center; wherein, along the propagation direction, the first region overlaps the third region, and the second region overlaps the fourth region; the first electrode is arranged in the first area, and the second electrode is arranged in the fourth area; alternatively, the first electrode is disposed in the second region and the second electrode is disposed in the third region. In this alternative, the embodiment of the present application provides still another arrangement of the first electrode and the second electrode, in which, when the driving voltages are applied to the two electrodes, the first region overlaps the third region and the second region overlaps the fourth region since the first electrode and the second electrode are located on both sides of the electro-optic crystal, respectively, in the propagation direction; therefore, the electric field formed by the first electrode and the second electrode can pass through the part of the electro-optical crystal between the first light transmission area and the second light transmission area, the adjustment of the refractive index of the electro-optical crystal between the first light transmission area and the second light transmission area is realized, and the direction of the electric field is not perpendicular to the propagation direction, but has a certain angle deviation from the direction perpendicular to the propagation direction, but the current electric field has a larger electric field component perpendicular to the propagation direction.

Optionally, the first electrode comprises a first portion and a second portion; the second electrode comprises a third portion and a fourth portion; a first part of the first electrode is arranged in the first area, and a second part of the first electrode is arranged in the third area; the third part of the second electrode is arranged in the second area, and the fourth part of the second electrode is arranged in the fourth area; the first part and the second part of the first electrode are electrically connected through a wire; the third portion and the fourth portion of the second electrode are electrically connected by a wire. In this alternative, the embodiment of the present application provides a fourth arrangement of the first electrode and the second electrode, the first region overlapping the third region and the second region overlapping the fourth region due to the first region overlapping the third region in the propagation direction when the driving voltage is applied to the two electrodes; thus, the electric fields formed by the two parts of the first electrode and the two parts of the second electrode can pass through the part of the electro-optical crystal between the first light transmission area and the second light transmission area, the adjustment of the refractive index of the electro-optical crystal between the first light transmission area and the second light transmission area is realized, and the direction of the electric field is perpendicular to the propagation direction at the moment, so that the minimum voltage applied to the two electrodes realizes the maximum electric field intensity, and the power consumption is reduced.

Optionally, the distance between the first electrode and the second electrode is 2 mm or less in a direction perpendicular to the propagation direction. In this alternative, the smaller the distance between the first electrode and the second electrode, the greater the strength of the electric field when the same driving voltage is applied to both electrodes, resulting in a greater change in refractive index of the electro-optic crystal under the influence of the lower driving voltage.

Optionally, the optical resonator further comprises: and the temperature control structure is used for applying temperature to the electro-optic crystal so as to adjust the refractive index of the electro-optic crystal. In this alternative, a temperature control structure is also provided on the electro-optic crystal, which temperature control structure is connected to a power supply to form a current loop, under the influence of which resistive heat will be generated, which resistive heat forms the temperature transmitted to the electro-optic crystal. The refractive index of the electro-optic crystal will become a predetermined refractive index under the combined action of temperature and electric field; in addition, the change range of the refractive index of the temperature control electro-optic crystal is larger, so that the wavelength tuning range of the optical resonant cavity is also enlarged; furthermore, the combined action of temperature and electric field provides a smaller voltage applied to the first electrode and/or the second electrode by the optical resonator than adjusting the refractive index of the electro-optic crystal to a predetermined refractive index by the electric field alone, resulting in improved filtering.

Optionally, the temperature control structure is disposed on a side of the first reflective film away from the electro-optic crystal; and/or the temperature control structure is arranged on one side of the second reflecting film far away from the electro-optical crystal. In this alternative mode, the temperature control structure is arranged at the light-passing position, and the temperature applied to the electro-optic crystal by the temperature control structure is uniformly distributed on the plane perpendicular to the propagation direction, so that the temperature is better transmitted to the light-passing position of the electro-optic crystal, and the refractive index of the electro-optic crystal is better adjusted. Among these, the alternatives include the following three cases: in the first case, the temperature control structure generates resistance heat under the action of the current loop, and the resistance heat is transmitted to the electro-optical crystal through the first reflecting film, so that the temperature control structure applies temperature to the electro-optical crystal, and the refractive index of the electro-optical crystal is changed under the action of the temperature. In the second case, the temperature control structure will generate resistance heat under the action of the current loop, and the resistance heat is transmitted to the electro-optical crystal through the second reflection film, so that the temperature control structure applies temperature to the electro-optical crystal, and under the action of the temperature, the refractive index of the electro-optical crystal will change. In a third case, the temperature control structure generates resistance heat under the action of the current loop, the resistance heat is transmitted to the electro-optical crystal through the first reflecting film and is also transmitted to the electro-optical crystal through the second reflecting film, so that the temperature control structure applies uniform temperature to the electro-optical crystal, and the refractive index of the electro-optical crystal is changed under the action of the temperature.

Optionally, the temperature control structure is arranged on one side of the electro-optic crystal in parallel to the propagation direction, and/or the temperature control structure is arranged on the other side of the electro-optic crystal in parallel to the propagation direction. In this alternative, the temperature control structure is arranged in a non-light passing position, so that the requirement of the temperature control structure on the light transmittance is reduced.

Optionally, the temperature control structure comprises a light transmissive resistive film.

Optionally, the material of the resistive film includes: indium tin oxide.

Optionally, in the propagation direction, the distance between the first reflective film and the second reflective film is equal to or greater than 50 micrometers and equal to or less than 300 micrometers of the cavity length of the optical resonant cavity. In this alternative, the size of the cavity length is inversely proportional to the free spectral range of the optical resonator, so to achieve a larger free spectral range, the cavity length can be reduced as much as possible, so the current cavity length needs to be 300 microns or less; then the electro-optic crystal may become brittle when the cavity length is too small, so the cavity length needs to be 50 microns or more.

Optionally, the material of the electro-optic crystal includes any one of: lithium niobate, lanthanum doped lead zirconate titanate, lead magnesium niobate-lead titanate, potassium niobium tantalate.

Optionally, the material of the first electrode includes any of: gold, indium tin oxide; the material of the second electrode includes any one of the following: gold, indium tin oxide.

In a second aspect, there is provided an optical filter comprising: a first optical fiber collimator, a second optical fiber collimator, a plurality of optical resonant cavities arranged on an optical path between the first optical fiber collimator and the second optical fiber collimator, and a first reflecting element; the first optical fiber collimator is used for carrying out collimation treatment on the received first light to generate collimated light, and the collimated light sequentially passes through the plurality of optical resonant cavities along a first direction; the optical resonant cavities are used for carrying out filtering treatment on the collimated light rays to generate first filtered light rays with preset wavelengths, and the cavity lengths of any two optical resonant cavities in the plurality of optical resonant cavities are different; the first reflecting element is used for reflecting the first filtering light rays to the plurality of optical resonant cavities so that the first filtering light rays sequentially pass through the plurality of optical resonant cavities along a second direction, and the second direction is opposite to the first direction; the plurality of optical resonant cavities are also used for carrying out filtering treatment on the first filtering light rays reflected by the first reflecting element to generate output filtering light rays containing preset wavelengths; and a second fiber collimator for coupling the output filtered light to the first fiber output. In the above optical filter, first, the first optical fiber collimator collimates the received light to generate collimated light, and sequentially passes the collimated light through the plurality of optical resonators along the first direction, so that each of the plurality of optical resonators performs filtering processing on the collimated light to generate a first filtered light including a predetermined wavelength. The cavity lengths of any two optical resonant cavities among the plurality of optical resonant cavities are different, so that the wavelengths of light rays filtered out by any two optical resonant cavities among the plurality of optical resonant cavities are not identical, and the wavelengths of the blocked light rays are different. For example, when two optical resonators are included in the plurality of optical resonators, it is assumed that the first optical resonator can filter out light having a wavelength λa and a wavelength λd, and block light having a wavelength other than λa and a wavelength λd; it is assumed that the second optical resonator filters out light having a wavelength λb and a wavelength λd, and blocks light having a wavelength other than λb and λd, so that the first optical resonator and the second optical resonator cooperate to filter out light having a wavelength λd, which is a predetermined wavelength, and the first optical resonator and the second optical resonator block light having a wavelength other than the predetermined wavelength. That is, when the plurality of optical resonators perform filtering processing on the straight light, more light rays with other wavelengths than the predetermined wavelength are blocked, and the generated first filtered light rays with the predetermined wavelength contain less light rays with other wavelengths than the predetermined wavelength. And when the first filtering light is transmitted to the first reflecting element, the first reflecting element reflects the first filtering light to the plurality of optical resonant cavities, so that the first filtering light sequentially passes through the plurality of optical resonant cavities along the second direction, and the plurality of optical resonant cavities perform filtering processing on the first filtering light to generate output filtering light with preset wavelength. Although the first filtered light contains less light with other wavelengths than the preset wavelength, the light with other wavelengths than the preset wavelength needs to be blocked, so that the plurality of optical resonant cavities further block the residual light with other wavelengths needing to be blocked in the first filtered light to generate output filtered light containing the preset wavelength, and the filtering effect is improved. The output filtered light is finally coupled to the first fiber output by a second fiber collimator. And in the optical filter, the existence of the plurality of optical resonant cavities can carry out multiple filtering treatment on the straight light, and the increase of the filtering treatment times also reduces the reflectivity requirement of the optical filter on the material used by the reflecting film of each optical resonant cavity, thereby further improving the filtering effect of the optical filter.

Optionally, the optical path between the first optical fiber collimator and the second optical fiber collimator further comprises a second reflecting element; the plurality of optical resonant cavities are specifically used for carrying out filtering treatment on the first filtering light rays reflected by the first reflecting element to generate second filtering light rays with preset wavelengths; the second reflecting element is used for reflecting the second filtering light rays to the plurality of optical resonant cavities so that the second filtering light rays sequentially pass through the plurality of optical resonant cavities along the first direction; the optical resonant cavities are also used for carrying out filtering treatment on the second filtering light rays reflected by the second reflecting element to generate output filtering light rays containing the preset wavelength. In this alternative, the second reflection element reflects the second filtered light to the plurality of optical resonant cavities, so that the plurality of optical resonant cavities filter the second filtered light, and therefore the plurality of optical resonant cavities further block the remaining light with other wavelengths to be blocked in the second filtered light, and generate output filtered light with predetermined wavelengths, so as to improve the filtering effect.

Optionally, the optical path between the first optical fiber collimator and the second optical fiber collimator further comprises a polarization beam splitting element and a polarization beam combining element; on the light path, the polarization beam splitting element is positioned between the first optical fiber collimator and the plurality of optical resonant cavities, and the polarization beam combining element is positioned between the plurality of optical resonant cavities and the second optical fiber collimator; a polarizing beam splitting element for separating a second light ray having a first polarization direction from a third light ray having a second polarization direction from the collimated light rays, wherein the first polarization direction and the second polarization direction are different; the polarization beam splitting element is further used for setting the polarization direction of the second light to be the second polarization direction; a polarization beam combining element for setting a polarization direction of the second light or the third light for outputting the filtered light to a first polarization direction; the polarization beam combining element is further used for combining the second light ray of the output filter light ray and the third light ray of the output filter light ray into the output filter light ray. In this alternative manner, when the electro-optical crystal in any one of the plurality of optical resonators generates an electro-optical effect perpendicular to the propagation direction (i.e., a transverse electro-optical effect), the transverse electro-optical effect is more sensitive to the light having the polarization direction of the second polarization direction (the polarization direction of the P-polarized light), and then the polarization direction of the second light having the first polarization direction in the collimated light can be set to the second polarization direction by setting the polarization beam splitting element in the optical filter, so that the second light and the third light in the collimated light are respectively transmitted to the plurality of optical resonators, so that the plurality of optical resonators are aligned with the second light and the third light in the straight light to perform filtering, thereby achieving a better filtering effect. And then, restoring the polarization direction of the second light ray or the third light ray in the output filtered light rays into the first polarization direction through the polarization beam combination element, and combining the second light ray in the output filtered light rays and the third light ray in the output filtered light rays into the output filtered light rays.

Optionally, the device further comprises a band separation membrane, a first reflecting mirror and a third optical fiber collimator; on the light path, the wave band separating membrane is positioned between the polarization beam combining element and the second optical fiber collimator; the band separation membrane is used for transmitting light belonging to a first band in the output filtering light to the second optical fiber collimator; the second optical fiber collimator is used for coupling light rays belonging to a first wave band in the output filtering light rays to the first optical fiber output; the wave band separating diaphragm is also used for transmitting the light belonging to the second wave band in the output filtering light to the first reflecting mirror; the first reflector is used for transmitting the light belonging to the second wave band in the output filtering light to the third optical fiber collimator; and the third optical fiber collimator is used for coupling the light belonging to the second wave band in the output filtered light to the second optical fiber output. In this alternative, since the band separating diaphragm, the first reflecting mirror and the third optical fiber collimator are present in the optical filter, then, the first collimating optical fiber receives the light display containing two different bands, and the two different bands of light are separated in the band separating diaphragm, then the optical filter can perform filtering processing on the two bands of light, and the filtering range of the optical filter is improved, where the optical filter can filter the first band of light in the first time period and transmit the output filtered light to the second optical fiber collimator for output; and filtering the light rays of the second wave band in the second time period, and transmitting the output filtered light rays to a third optical fiber collimator for output.

Optionally, the first reflective element comprises a second mirror and a third mirror; the second reflector is used for receiving the first filtered light and reflecting the first filtered light to the third reflector; the third reflector is used for reflecting the first filtered light rays reflected by the second reflector to the plurality of optical resonant cavities, wherein an included angle between the second reflector and the third reflector is more than or equal to 89.5 degrees and less than or equal to 90.5 degrees; alternatively, the first reflective element comprises a first right angle prism; the first right angle prism comprises a first right angle surface and a second right angle surface; the first right-angle surface is used for receiving the first filtered light and reflecting the first filtered light to the second right-angle surface; and the second right-angle surface is used for reflecting the first filtered light reflected by the first right-angle surface to the plurality of optical resonant cavities, wherein the included angle between the first right-angle surface and the second right-angle surface is more than or equal to 89.5 degrees and less than or equal to 90.5 degrees. In this alternative, two configurations of the first reflective element are provided.

Optionally, the second reflecting element includes a fourth reflecting mirror and a fifth reflecting mirror; the fourth reflector is used for receiving the second filtering light and reflecting the second filtering light to the fifth reflector; the fifth reflector is used for reflecting the second filtered light rays reflected by the fourth reflector to the plurality of optical resonant cavities, wherein an included angle between the fourth reflector and the fifth reflector is more than or equal to 89.5 degrees and less than or equal to 90.5 degrees; alternatively, the second reflecting element comprises a second right angle prism, and the second right angle prism comprises a third right angle surface and a fourth right angle surface; the third right-angle surface is used for receiving the second filtered light and reflecting the second filtered light to the fourth right-angle surface; and the fourth right angle surface is used for reflecting the second filtered light reflected by the third right angle surface to the plurality of optical resonant cavities, wherein the included angle between the third right angle surface and the fourth right angle surface is more than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

Optionally, the difference in cavity length between any two of the plurality of optical resonators is greater than or equal to 5 microns. In this alternative, when the difference in the cavity lengths of any two of the plurality of optical resonators is 5 μm or more, the free spectral range of any two of the plurality of optical resonators will change so that the wavelengths of the filtered light of any two of the plurality of optical resonators are not exactly the same.

Optionally, the plurality of optical resonators includes an optical resonator as in any one of the first aspect above.

In a third aspect, a filtering system is provided, the filtering system comprising an inter-band filter, and two optical filters as described in any of the second aspects above; the first output end of the inter-band filter is connected to the first optical filter, and the second output end of the inter-band filter is connected to the second optical filter; the band-to-band filter is used for receiving light rays of a first wave band and light rays of a second wave band, transmitting the light rays of the first wave band to the first optical filter through the first output end, and transmitting the light rays of the second wave band to the second optical filter through the second output end; the first optical filter is used for filtering the light rays of the first wave band and outputting the filtered light rays of the first wave band; and the second optical filter is used for filtering the light rays of the second wave band and outputting the filtered light rays of the second wave band.

In a fourth aspect, a filtering system is provided, the filtering system comprising an inter-band filter, a first switch, a second switch and an optical filter according to any of the second aspects above; the first output end of the inter-band filter is connected to the optical filter through a first switch, and the second output end of the inter-band filter is connected to the optical filter through a second switch; the inter-band filter is used for receiving light rays of the first wave band and light rays of the second wave band; transmitting light rays of a first wave band to the optical filter through the first switch when the first switch is turned on and the second switch is turned off; transmitting light rays of a second wave band to the optical filter through the second switch when the first switch is closed and the second switch is opened; the optical filter is used for filtering the light rays of the first wave band and outputting the filtered light rays of the first wave band; the optical filter is also used for filtering the light rays of the second wave band and outputting the filtered light rays of the second wave band. Wherein reference may be made to the detailed description of the first and second aspects and their various implementations for the detailed description of the third and fourth aspects and their various implementations; and, the advantageous effects of the third aspect and the fourth aspect and various implementations thereof may be referred to for advantageous effect analysis in the first aspect and the second aspect and various implementations thereof.

Drawings

FIG. 1 is a schematic diagram of an FP chamber provided by a first embodiment of the application;

fig. 2 is a schematic structural diagram of an optical network according to a first embodiment of the present application;

FIG. 3 is a schematic diagram of an optical performance monitor according to an embodiment of the present application;

FIG. 4 is a schematic diagram of an optical filter according to an embodiment of the present application;

FIG. 5 is a schematic diagram of another structure of an optical filter according to a first embodiment of the present application;

FIG. 6 is a schematic diagram of a first structure of an optical resonator according to a second embodiment of the present application;

FIG. 7 is a schematic diagram of a second structure of an optical resonator according to a second embodiment of the present application;

FIG. 8 is a schematic diagram of a third structure of an optical resonator according to a second embodiment of the present application;

FIG. 9 is a schematic diagram of a fourth structure of an optical resonator according to a second embodiment of the present application;

FIG. 10 is a schematic diagram of a fifth embodiment of an optical resonator according to the second embodiment of the application;

FIG. 11 is a schematic diagram of a sixth structure of an optical resonator according to a second embodiment of the present application;

FIG. 12 is a schematic diagram of a seventh structure of an optical resonator according to a second embodiment of the present application;

FIG. 13 is a schematic diagram of an eighth structure of an optical resonator according to a second embodiment of the application;

FIG. 14 is a schematic diagram of a ninth structure of an optical resonator according to a second embodiment of the present application;

FIG. 15 is a schematic view of a tenth structure of an optical resonator according to a second embodiment of the present application;

FIG. 16 is a schematic view of an eleventh embodiment of an optical resonator according to the second embodiment of the application;

FIG. 17 is a schematic diagram of a twelfth structure of an optical resonator according to the second embodiment of the application;

FIG. 18 is a thirteenth schematic structural view of an optical resonator according to a second embodiment of the application;

FIG. 19 is a schematic view of a fourteenth optical resonator according to a second embodiment of the present application;

FIG. 20 is a schematic diagram of a fifteenth embodiment of an optical resonator according to the second embodiment of the present application;

FIG. 21 is a diagram illustrating a sixteenth structure of an optical resonator according to a second embodiment of the present application;

FIG. 22 is a seventeenth schematic diagram of an optical resonator according to a second embodiment of the present application;

FIG. 23 is a schematic diagram of an eighteenth structure of an optical resonator according to a second embodiment of the application;

FIG. 24 is a nineteenth schematic diagram of an optical resonator according to a second embodiment of the application;

FIG. 25 is a diagram showing a twentieth configuration of an optical resonator according to a second embodiment of the present application;

Fig. 26 is a schematic diagram of a first structure of an optical filter according to a third embodiment of the present application;

fig. 27 is a schematic diagram of a second structure of an optical filter according to a third embodiment of the present application;

fig. 28 is a schematic structural diagram of an optical filter according to a fourth embodiment of the present application;

fig. 29 is a schematic view of a first structure of an optical filter according to a fifth embodiment of the present application;

FIG. 30 is a simulation diagram of an optical filter according to a fifth embodiment of the present application;

fig. 31 is a schematic diagram of a second structure of an optical filter according to a fifth embodiment of the present application;

fig. 32 is a schematic diagram of a third structure of an optical filter according to a fifth embodiment of the present application;

fig. 33 is a schematic diagram of a fourth configuration of an optical filter according to a fifth embodiment of the present application;

fig. 34 is a schematic diagram of a fifth configuration of an optical filter according to a fifth embodiment of the present application;

fig. 35 is a schematic view of a first structure of an optical filter according to a sixth embodiment of the present application;

fig. 36 is a schematic view of a second structure of an optical filter according to a sixth embodiment of the present application;

FIG. 37 is a first simulation of an optical filter according to a sixth embodiment of the present application;

FIG. 38 is a second simulation of an optical filter according to a sixth embodiment of the present application;

FIG. 39 is a third simulation diagram of an optical filter according to a sixth embodiment of the present application;

FIG. 40 is a fourth simulation diagram of an optical filter according to a sixth embodiment of the present application;

FIG. 41 is a fifth simulation diagram of an optical filter according to a sixth embodiment of the present application;

FIG. 42 is a sixth simulation diagram of an optical filter according to a sixth embodiment of the present application;

fig. 43 is a schematic diagram of a first configuration of a filtering system according to a seventh embodiment of the present application;

fig. 44 is a schematic diagram of a second structure of a filtering system according to a seventh embodiment of the present application.

Detailed Description

The technical solutions of the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In the present application, "plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a alone, a and B together, and B alone, wherein a, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship. In addition, in the embodiments of the present application, the words "first", "second", and the like do not limit the number and order.

In the present application, the words "exemplary" or "such as" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.

Technical terms provided in the embodiments of the present application are described as follows:

electro-optic effect: under the action of the external electric field, the refractive index of the electro-optic crystal is changed. The linear electro-optic effect is that the variation of the refractive index of the electro-optic crystal is in linear relation with the electric field, and the secondary electro-optic effect is that the variation of the refractive index of the electro-optic crystal is in linear relation with the square of the electric field. The linear electro-optic effect of the electro-optic crystal is divided into two kinds of longitudinal electro-optic effect and transverse electro-optic effect. The longitudinal electro-optic effect is an electro-optic effect generated when the direction of an electric field applied to the electro-optic crystal is parallel to the propagation direction of light in the electro-optic crystal; the transverse electro-optic effect is an electro-optic effect that occurs when the direction of an electric field applied to the electro-optic crystal is perpendicular to the direction of propagation of light in the electro-optic crystal.

Fabry-perot cavity: in short, referring to fig. 1, an embodiment of the present application provides a schematic diagram of an FP cavity 10, in the FP cavity 10, two reflecting surfaces, that is, a reflecting surface 101 and a reflecting surface 102 are provided, respectively, the reflecting surface 101 is disposed opposite to the reflecting surface 102, and an optical medium 103 (for example, glass, air, electro-optical crystal, etc.) is filled between the reflecting surface 101 and the reflecting surface 102. When an incident light ray having a wavelength λ1 is incident on the reflection surface 101 at an incident angle α, a part of the incident light ray having a wavelength λ1 is reflected to form a reflected light ray, the reflected light ray cannot enter the optical medium 103, and another part of the incident light ray having a wavelength λ1 is transmitted to the optical medium 103 to form a transmitted light ray. The optical medium 103 transmits the transmitted light to the reflection surface 102 with the refractive index n of the optical medium 103, the reflection surface 102 transmits light having the wavelength of a predetermined wavelength λ out of the transmitted light out of the reflection surface 102, and the reflection surface 102 reflects light having other wavelengths than the light having the wavelength of the predetermined wavelength λ out of the transmitted light to the optical medium 103, and the optical medium 103 transmits light having other wavelengths to the reflection surface 101, so that the FP cavity 10 filters out light having the wavelength of the predetermined wavelength λ out of the incident light having the wavelength of λ1, thereby realizing a filtering effect. Specifically, the interference effect occurs during the back and forth reflection between the reflecting surface 101 and the reflecting surface 102, so that the light transmitted out of the reflecting surface 102 actually belongs to the light generated by the interference of the transmitted light. Where the FP cavity 10 has a cavity length L, assuming a thickness L of the optical medium 103. Then, the predetermined wavelength λ satisfies the following equation 1.

2nlcosα=mλ (m=1, 2,3 …) (formula 1).

In formula 1, m is specifically an interference order, and is an integer.

Referring to equation 1, it can be seen that when the wavelength of the light to be filtered out by the FP cavity 10 is changed, the cavity length L of the FP cavity 10, the refractive index n of the optical medium 103, or the incident angle α of the incident light can be adjusted.

Wherein in the FP cavity 10 the spectrum of light of the predetermined wavelength filtered out by the FP cavity 10 is periodic and the difference between the wavelength of the nth filtered out light and the wavelength of the n+1th filtered out light represents the free spectral range (free spectral range, FSR) of the FP cavity 10. The FSR of FP cavity 10 is expressed as Deltav, then Deltav satisfies equation 3 below.

Δv=c/(2 nL) (formula 2).

In formula 2, c represents the speed of light.

Referring to equation 2, the free spectral range FSR of the FP cavity 10 is related to the cavity length L of the FP cavity 10 and the refractive index n of the optical medium 103 in the FP cavity 10.

In addition, the difference between the peaks and the valleys of the light of the predetermined wavelength filtered out by the FP cavity 10 is related to the reflectivities of the reflective surface 101 and the reflective surface 102.

Referring to fig. 2, an embodiment of the present application provides a schematic structural diagram of an optical network 20, where the optical network 20 includes a network 1 and a network 2, where a plurality of optical amplifiers and a plurality of optical cross connect devices are connected to the network 1 through optical fibers, the optical amplifiers are used to amplify optical signals transmitted in the optical fibers, the optical cross connect devices are used to provide optical communication services for a predetermined area (for example, an area covered by a small building or a large building as shown in fig. 2) and/or a network (for example, the network 2 shown in fig. 2), and in the network 1, a plurality of optical performance monitors OPM are further included, for example, the optical performance monitor OPM1, the optical performance monitor OPM2, and the optical performance monitor OPM3 shown in fig. 2, where each optical performance monitor is used to detect a signal-to-noise ratio and power of the optical signals transmitted by a certain number of optical amplifiers and/or the optical cross connect devices. The network 2 communicates with the optical cross-connect device in the network 1 through the optical cross-connect device in the network 2, so that the network 2 obtains an optical signal transmitted in the network 1, or transmits an optical signal generated by a certain transceiver in the network 2 to the network 1. A plurality of optical amplifiers and a plurality of optical cross-connect devices are also connected to the network 2, and a plurality of optical performance monitors OPM, such as the optical performance monitor OPM4 and the optical performance monitor OPM5 shown in fig. 2, are also included in the network 2, each for detecting the signal-to-noise ratio and the power of the optical signals transmitted by a certain number of optical amplifiers and/or optical cross-connect devices. In addition, in the network 2, the optical add/drop multiplexer ROADM may be further included, where the reconfigurable optical add/drop multiplexer ROADM is connected to the combiner 201 through the optical fiber 202, the combiner 201 receives a plurality of optical signals with wavelengths sent by different transceiver devices, combines the plurality of optical signals with wavelengths into a beam of optical signals with a unified wavelength, and transmits the beam of optical signals to the reconfigurable optical add/drop multiplexer ROADM through the optical fiber 202, where the wavelength of the beam of optical signals is adjusted by the reconfigurable optical add/drop multiplexer ROADM, so that the beam of optical signals can be transmitted in the network 2 and does not cross-talk with other optical signals transmitted in the network 2. The reconfigurable optical add/drop multiplexer ROADM is also connected to the demultiplexer 203 through the optical fiber 204, and the reconfigurable optical add/drop multiplexer ROADM obtains an optical signal to be sent to the demultiplexer 203 from the network 2, and transmits the optical signal to the demultiplexer 203 through the optical fiber 204, so that the demultiplexer 203 demultiplexes the optical signal and sends the optical signal to different transceiver devices. The optical signal generated by the multiplexer 201, the optical signal received by the demultiplexer 203, and the optical signal transmitted by the optical fiber 204 are also detected by the optical performance monitor OPM6 in terms of signal-to-noise ratio and power.

Referring to fig. 3, an embodiment of the present application provides a schematic structural diagram of an optical performance monitor 30, in the optical performance monitor 30, a core component of the optical performance monitor 30 is an optical filter (tunable optical filter, TOF), referring to fig. 3, the optical performance monitor 30 includes an optical filter 301, a detector 302 and a data processing structure 303, where the optical filter 310 performs filtering processing on an input optical signal to obtain an optical signal with a predetermined wavelength; the detector 302 photoelectrically converts the filtered optical signal to generate an electrical signal; the data processing structure 303 processes the electric signal generated by the detector 302, calculates various parameter indexes of the electric signal, and outputs the monitoring result.

The core component of optical performance monitor 30 is the optical filter TOF, and optical filters comprising FP cavities are the most common and most widely used.

The optical signal is generated by modulating a transmission signal on an optical wave. Furthermore, the optical filter TOF may filter not only the optical signal, but also a plurality of light waves of different wavelengths, and for clarity, embodiments of the present application collectively refer to the optical signal and/or the light waves as light rays.

Referring to fig. 4, an embodiment of the present application provides a piezoelectric ceramic-based optical filter 40, the optical filter 40 including a piezoelectric ceramic structure 401, and an input end positioning jig 402 and an output end positioning jig 403 are provided in the piezoelectric ceramic structure 401. A glass ferrule 404 is arranged in the middle of the input end positioning clamp 402, an input optical fiber 405 is arranged in the glass ferrule 404, and a reflecting film 407 is arranged on the end face of the input optical fiber 405, which is close to the output optical fiber 406; a glass ferrule 408 is provided in the middle of the output end positioning jig 403, an output optical fiber 406 is provided in the glass ferrule 408, and a reflection film 409 is provided on the end face of the output optical fiber 406 near the input optical fiber 405. In the optical filter, a glass cover 410 is further disposed between the input end positioning jig 402 and the output end positioning jig 403, and the glass cover 410 is used to provide an air gap between the reflective film 407 and the reflective film 409. The reflective film 407, the reflective film 409, and the air gap between the reflective film 407 and the reflective film 409 constitute an FP cavity in the optical filter 40.

The optical filter 40 operates on the principle that the optical fiber 405 transmits incident light, the incident light is filtered through the FP cavity in the optical filter 40, and the filtered light is output through the optical fiber 406. In order to enable the wavelength of the light filtered out by the optical filter 40 to be changed, in general, a driving voltage may be applied to the input end positioning jig 402 and/or the output end positioning jig 403, and the position of the input end positioning jig 402 and/or the output end positioning jig 403 is mechanically moved, so as to control the distance between the reflective film 407 and the reflective film 409 (that is, to control the cavity length of the FP cavity in the optical filter 40). According to the above formula 1, when the FP cavities in the optical filter 40 have different cavity lengths, the FP cavities in the optical filter 40 can filter out light rays with different wavelengths.

However, in order to control the cavity length of the FP cavity in the optical filter 40, it is often necessary to apply a high driving voltage to the input end positioning jig 402 and the output end positioning jig 403 so that the input end positioning jig 402 and/or the output end positioning jig 403 can mechanically move, and it is also necessary to set the reflectivities of the reflective film 407 and the reflective film 409 to be high so as to ensure the filtering effect of the optical filter 40, so that the reflectivity requirement of the material used for the reflective film is high for the optical filter 40.

As described with reference to fig. 5, an embodiment of the present application provides another optical filter 50, in which the optical filter 50 includes an upper case 501, and a lower case 502, the upper case 501 includes an opening portion 5011 therein, and an electrode 5031, a micro-electro-mechanical-system (MEMS) mirror 504, and an electrode 5032 are sequentially provided in the opening portion 5011 in the first direction; the lower case 502 includes an opening portion 5021 therein, an electrode 5051, a MEMS mirror 506, and an electrode 5052 are sequentially provided in a first direction in opposite faces of the opening portion 5021 of the lower case 502, and both ends of the upper case 501 where the opening portion 5011 is formed are bonded to opposite faces of the opening portion 5021 of the lower case 502 by an adhesive 5071 and an adhesive 5072 such that the electrode 5031 is disposed opposite to the electrode 5051, the MEMS mirror 504 is disposed opposite to the MEMS mirror 506, and the electrode 5032 is disposed opposite to the electrode 5052. Wherein MEMS mirror 504, MEMS mirror 506, and the air gap between MEMS mirror 504 and MEMS mirror 506 form the FP cavity in optical filter 50.

The optical filter 50 operates on the principle that incident light is transmitted from the opposite side of the opening portion in the upper housing 501 to the FP cavity in the optical filter 50 in the second direction, the FP cavity in the optical filter 50 filters the incident light, and the filtered light is output through the opening portion 5021 of the lower housing 502. In order to allow the wavelength of the light filtered out by the optical filter 50 to be changed, typically, a driving voltage may be applied to the electrode 5041, the electrode 5042, the electrode 5043, and the electrode 5044 to control the movement of the MEMS mirror 504 and/or the MEMS mirror 506 (e.g., to control the MEMS mirror to move up and down according to the position shown in fig. 5), and thus to control the distance between the MEMS mirror 504 and the MEMS mirror 506 (i.e., to control the cavity length of the FP cavity in the optical filter 50). From the above equation 1, it can be seen that when the FP cavity in the optical filter 50 has different cavity lengths, the optical filter 50 can filter out light rays with different wavelengths.

However, in the optical filter 50, it is necessary to apply accurate driving voltages to the electrode 5041, the electrode 5042, the electrode 5043, and the electrode 5044, so that the MEMS mirror 504 and/or the MEMS mirror 506 mechanically move, and thus the cavity length of the FP cavity in the optical filter 50 will achieve the purpose of filtering out light rays of a predetermined wavelength. In addition, the reflectances of the MEMS mirrors 504 and 506 need to be set high to ensure the filtering effect of the optical filter 50, so that the optical filter 50 has a high requirement on the reflectances of the materials used for the mirrors or the materials of the film layers coated on the MEMS mirrors.

Accordingly, embodiments of the present application provide an optical resonator, as shown with reference to fig. 6, the optical resonator 60 may be disposed in the optical filter shown in fig. 4 or 5, the optical resonator 60 comprising: an electro-optical crystal 601, a reflective film 602, and a reflective film 603, wherein the reflective film 602 and the reflective film 603 are disposed on both sides of the electro-optical crystal 601, respectively, in a propagation direction of the electro-optical crystal 601. An electrode 604 and an electrode 605, wherein the electrode 604 and the electrode 605 are disposed on the electro-optic crystal 601, and an electric field applied to the electro-optic crystal 601 by the electrode 604 and the electrode 605 is used to adjust the refractive index of the electro-optic crystal 601; wherein the electric field has a component perpendicular to the propagation direction. As an example, referring to fig. 6, an embodiment of the present application provides (a) in fig. 6 and (b) in fig. 6 in a front view and a top view of an optical resonator 60, in which the propagation direction of an electro-optic crystal 601 is in the x-direction, and a reflective film 602 and a reflective film 603 are sequentially disposed on both sides of the electro-optic crystal 601 in the x-direction, and an electrode 604 and an electrode 605 are respectively disposed on both sides of the electro-optic crystal 601 in the direction parallel to the x-direction, specifically, an electrode 604 and an electrode 605 are sequentially disposed on both sides of the electro-optic crystal 601 in the y-direction. Then, a wire 604a is provided in the electrode 604 by a wire bonding (also called bonding, wire bonding) process, a wire 605a is provided in the electrode 605, or a wire 604a is provided in the electrode 604 by glue bonding, and a wire 605a is provided in the electrode 605. Then, when electrode 604 is connected to a positive voltage terminal in a driving voltage via wire 604a and electrode 605 is connected to a negative voltage terminal in the driving voltage via wire 605a, an electric field E is formed between electrode 604 and electrode 605, the direction of the electric field E is directed in the direction y to y, wherein the direction of the electric field E is perpendicular to the propagation direction, and the material of electro-optic crystal 601 has an electro-optic effect, so that the electro-optic crystal 601 generates a transverse electro-optic effect under the action of the electric field E, and the refractive index of the electro-optic crystal 601 is changed under the action of the electric field E. In addition, referring to the arrangement of the electrode 604 and the electrode 605 shown in fig. 6, when a driving voltage is applied to the electrode 604 and the electrode 605, an electric field is directly formed in a region where the electrode 604 and the electrode 605 face each other, that is, a most uniform electric field is formed in the electro-optical crystal, and the refractive index of the electro-optical crystal is adjusted.

Illustratively, the material of the electro-optic crystal 601 includes any one of the following: lithium niobate, lanthanum-doped lead zirconate titanate (PLZT), lead magnesium niobate-lead titanate (Pb (Mg) _1/ ₃ Nb _2/3 )O ₃ –bTiO ₃ PMN-PT), potassium niobate, wherein lithium niobate, PLZT, and PMN-PT are solid materials, and the above materials have electro-optical effects. In order to make the filtering effect of the optical resonator 60 better, the distance L1 between the reflective film 602 and the reflective film 603 in the direction of the propagation direction-x pointing to x (or the direction of x pointing to-x), that is, the cavity length of the optical resonator 60, is required to be 50 micrometers (um) or more and 300 micrometers (um) or less, because the size of the cavity length is inversely proportional to the free spectral range of the optical resonator as seen with reference to the above formula 2, and thus the cavity length can be reduced as much as possible in order to achieve a larger free spectral range, and thus the current cavity length needs to be 300 micrometers or less; then the electro-optic crystal may become brittle when the cavity length is too small, so the cavity length needs to be 50 microns or more. .

Illustratively, the materials of electrode 604 and electrode 605 include gold (Au), indium Tin Oxide (ITO), and the distance between electrode 604 and electrode 605 needs to be controlled within 2 millimeters (mm) in the y-direction perpendicular to the propagation direction (or the y-direction), for example, the distance between electrode 604 and electrode 605 can be controlled to be 0.3mm, because the smaller the distance between electrode 604 and electrode 605, the greater the strength of the electric field when the same driving voltage is applied to both electrodes, resulting in a greater refractive index change of the electro-optic crystal under the effect of a lower driving voltage.

The optical resonator 60 operates on the principle that:

when an input light ray is incident on the reflective film 602 in the propagation direction (i.e., the incident direction) in which-x is directed to x, the reflective film 602 serves to transmit the input light ray in the propagation direction to the electro-optical crystal 601. Wherein a part of the input light is reflected by the reflective film 602 to form a reflected light, and the reflected light is not transmitted to the electro-optical crystal 601; another part of the input light is transmitted to the electro-optical crystal 601 through the reflective film 602, forming a transmitted light, and the transmitted light is transmitted to the electro-optical crystal 601.

An electro-optical crystal 601 for transmitting light transmitted by the reflective film 602 to the reflective film 603 at a predetermined refractive index n1 under the action of an electric field E; wherein the predetermined refractive index n1 will change when the electric field E is different, and wherein the input light rays incident along a fixed angle of incidence will propagate different distances at different angles of refraction in the electro-optic crystal 601 when the predetermined refractive index n1 changes.

A reflection film 603 for outputting light of a predetermined wavelength among light transmitted by the electro-optical crystal 601 and reflecting light of other wavelengths than the predetermined wavelength to the electro-optical crystal 601; wherein, the light rays with the predetermined wavelength that can be transmitted satisfy the above formula 1, in the optical resonator 60, the refractive index n substituted in the formula 1 is the predetermined refractive index n1 formed under the action of the electric field E, the cavity length L substituted in the formula 1 is the distance L1 between the reflective film 602 and the reflective film 603, the incident angle α substituted in the formula 1 is the incident angle α1 of the incident light rays, and in the optical resonator 60, the incident angle α1 of the incident light rays is 0, so that a specific value of the predetermined wavelength can be calculated, and the reflective film 603 outputs the light rays with the predetermined wavelength. And, light rays of wavelengths other than the predetermined wavelength will be transmitted to the electro-optical crystal 601 at the predetermined refractive index n 1.

An electro-optical crystal 601 further for transmitting the light reflected by the reflective film 603 to the reflective film 602 at a predetermined refractive index n 1; the reflective film 602 is also used to reflect the light transmitted by the electro-optic crystal 601 to the electro-optic crystal 601.

Light having a wavelength other than the predetermined wavelength reflected by the reflective film 603 may be transmitted through the reflective film 602, may be transmitted through the electrode 604, may be transmitted through the electrode 605, or may be transmitted through the electro-optic crystal in the-z direction or the z direction.

It should be noted that the optical resonator may be set large enough in the z-axis to satisfy the purpose of transmitting light multiple times in the propagation direction.

In the optical resonator described above, the first reflection film (i.e., the reflection film 602) and the second reflection film (i.e., the reflection film 603) are provided on both sides of the electro-optical crystal in the propagation direction of the electro-optical crystal, so that the first reflection film, the second reflection film, and the electro-optical crystal filter the input light. And, a first electrode (i.e., electrode 604) and a second electrode (i.e., electrode 605) are further disposed on the electro-optic crystal, when a driving voltage is applied to the first electrode and the second electrode, an electric field is formed in the electro-optic crystal, and a component perpendicular to the propagation direction of the electro-optic crystal exists in the electric field, so that the electro-optic crystal can generate an electro-optic effect perpendicular to the propagation direction (i.e., a transverse electro-optic effect), and the refractive index of the electro-optic crystal becomes a predetermined refractive index under the action of the electric field. Then, when the electric fields formed in the electro-optic crystal are different, the input light transmitted by the first reflective film in the propagation direction will be transmitted to the second reflective film at a predetermined refractive index corresponding to the electric field in the electro-optic crystal. The second reflecting film outputs light rays of a predetermined wavelength among the light rays transmitted through the electro-optical crystal, that is, transmits the light rays of the predetermined wavelength out of the second reflecting film and reflects the light rays of other wavelengths than the predetermined wavelength back to the electro-optical crystal, and then the electro-optical crystal transmits the light rays reflected by the second reflecting film to the first reflecting film with a predetermined refractive index, and the first reflecting film is also used for reflecting the light rays transmitted by the electro-optical crystal to the electro-optical crystal. This is repeated so that light of a predetermined wavelength is output from the second reflection film. In addition, in the optical resonant cavity, the electrodes are directly arranged on the surface of the electro-optical crystal, an electric field formed by arranging driving voltage between the electrodes can be directly used for adjusting the refractive index of the electro-optical crystal, and when the refractive index of the electro-optical crystal is changed, the purpose of filtering out light rays with preset wavelength can be achieved, the modulation of the cavity length of the optical resonant cavity by using a mechanical control mode is avoided, and the purpose of improving the filtering effect is achieved.

Illustratively, referring to FIG. 7, embodiments of the present application provide front view (a) of FIG. 7 and top view (b) of FIG. 7 of optical cavity 60. Embodiments of the present application provide optical cavity 60 that may further include a temperature control structure 608, where temperature control structure 608 applies a temperature to electro-optic crystal 601 to adjust the refractive index of electro-optic crystal 601. When both electrode 604 and electrode 605 and temperature control structure 608 are disposed in the optical resonator, the refractive index of the electro-optic crystal 601 will change under the combined action of the electric field provided by electrode 604 and electrode 605 and the temperature provided by temperature control structure 608, resulting in a new predetermined refractive index.

The temperature control structure 608 shown in fig. 7 is disposed on a side of the reflective film 602 away from the electro-optical crystal 601. The wire 608a is disposed at a first end of the temperature control structure 608 by a wire bonding (also referred to as pressure bonding, binding, bonding, wire bonding) process, the wire 608b is disposed at a second end of the temperature control structure 608, or the wire 608a is disposed at the first end of the temperature control structure 608 by glue bonding, and the wire 608b is disposed at the second end of the temperature control structure 608. Then, a first end of the temperature control structure 608 is connected to a positive power supply electrode through a wire 608a, and a second end of the temperature control structure 608 is connected to a negative power supply electrode through a wire 608b, so that a current loop is formed in the temperature control structure 608, and the temperature control structure 608 includes a light-transmitting resistive film, specifically, materials of the resistive film include: indium tin oxide. Then, the resistive film in the temperature control structure 608 will generate resistive heat under the action of the current loop, and the resistive heat is transmitted to the electro-optic crystal 601 through the reflective film 602, so that the temperature control structure 608 applies a temperature to the electro-optic crystal 601, and under the action of the temperature, the refractive index of the electro-optic crystal 601 will change.

Referring to fig. 8, an embodiment of the present application provides that (a) in fig. 8 and (b) in fig. 8 in a front view and a top view of the optical resonator 60, and the temperature control structure 608 may also be disposed on a side of the reflective film 603 away from the electro-optic crystal 601. Then when the temperature control structure 608 is connected to an electrode to form a current loop, the temperature control structure 608 illustratively includes a light transmissive resistive film, the resistive film material including: indium tin oxide. Then, the resistive film in the temperature control structure 608 will generate resistive heat under the action of the current loop, and the resistive heat is transmitted to the electro-optical crystal 601 through the reflective film 603, so that the temperature control structure 608 applies a temperature to the electro-optical crystal 601, and under the action of the temperature, the refractive index of the electro-optical crystal 601 will change.

As an example, referring to fig. 9, where an embodiment of the present application provides (a) in fig. 9 and (b) in fig. 9 in a front view of the optical resonant cavity 60, the temperature control structure 608 includes two parts, and the first part 6081 of the temperature control structure 608 may be disposed on a side of the reflective film 602 away from the electro-optic crystal 601, then when the first part 6081 of the temperature control structure 608 is connected to the power supply 1 to form a current loop, the first part of the temperature control structure 608 will generate resistive heat under the effect of the current loop, and the resistive heat is transmitted to the electro-optic crystal 601 through the reflective film 602, so that the first part 6081 of the temperature control structure 608 applies a temperature to the electro-optic crystal 601, and the refractive index of the electro-optic crystal 601 will change under the effect of the temperature. The second portion 6082 of the temperature control structure 608 may be disposed on a side of the reflective film 603 remote from the electro-optic crystal 601, and when the second portion 6082 of the temperature control structure 608 is connected to the power source 2 to form a current loop, the second portion 6082 of the temperature control structure 608 will generate resistive heat under the influence of the current loop, which is transferred to the electro-optic crystal 601 through the reflective film 603, such that the second portion 6082 of the temperature control structure 608 applies a temperature to the electro-optic crystal 601, and the refractive index of the electro-optic crystal 601 will change under the influence of the temperature.

For example, referring to fig. 9, the first end of the first portion 6081 of the temperature control structure 608 and the first end of the second portion 6082 of the temperature control structure 608 may be connected by a wire, then the second end of the first portion 6081 of the temperature control structure 608 and the second end of the second portion 6082 of the temperature control structure 608 are connected to the power source 1 (or the power source 2, that is, the current first portion 6081 and the second portion 6082 of the temperature control structure 608 are connected in series and then connected to the same power source) through a wire, then the first portion 6081 of the temperature control structure 608 and the second portion 6082 of the temperature control structure 608 are in the same current loop, and the temperature variation amplitude of the two portions is the same, so that the first portion 6081 of the temperature control structure 608 and the second portion 6082 of the temperature control structure 608 apply a more uniform temperature to the electro-optic crystal 601, and the speed of temperature variation is increased.

Referring to fig. 10, an embodiment of the present application provides that (a) in fig. 10 and (b) in fig. 10 in front view and top view of the optical resonator 60, the temperature control structure 608 may also be disposed on a side of the electro-optic crystal parallel to the propagation direction, specifically, according to the placement position of the optical resonator shown in fig. 10, the side may be the y side of the electro-optic crystal 601, and since the electrode 604 is also disposed on the y side of the electro-optic crystal, the temperature control structure 608 may be disposed on a side of the electrode 604 away from the electro-optic crystal 601, and insulation of the electrode 604 from the temperature control structure 608 is required.

Referring to fig. 11, an embodiment of the present application provides that (a) in fig. 11 and (b) in fig. 11 of the front view and the top view of the optical resonator 60, the temperature control structure 608 may also be disposed on the other side of the electro-optic crystal parallel to the propagation direction, specifically, depending on the placement position of the optical resonator shown in fig. 11, the other side may be the-y side of the electro-optic crystal 601, and since the electrode 605 is also disposed on the-y side of the electro-optic crystal 601, the temperature control structure 608 may be disposed on the side of the electrode 605 away from the electro-optic crystal 601, and insulation of the electrode 605 from the temperature control structure 608 may be required.

Alternatively, referring to fig. 12, an embodiment of the present application provides that (a) in fig. 12 and (b) in fig. 12 in front view and (b) in top view of the optical resonator 60, the temperature control structure 608 includes two parts, and the first part 6081 of the temperature control structure 608 may be disposed on one side of the electro-optical crystal 601 parallel to the propagation direction, and the second part 6082 of the temperature control structure 608 may be disposed on the other side of the electro-optical crystal 601 parallel to the propagation direction. Specifically, a first portion 6081 of the temperature control structure 608 is disposed on a side of the electrode 604 remote from the electro-optic crystal 601 and it is desirable to insulate the electrode 604 from the first portion 6081 of the temperature control structure 608, and a second portion 6082 of the temperature control structure 608 is disposed on a side of the electrode 605 remote from the electro-optic crystal 601 and it is desirable to insulate the electrode 605 from the second portion 6082 of the temperature control structure 608.

Referring to fig. 13, an embodiment of the present application provides that (a) in fig. 13 and (b) in fig. 13 in front view and in top view of the optical resonator 60, the temperature control structure 608 may also be disposed on one side of the electro-optic crystal parallel to the propagation direction, and in particular, the one side may be the z-side of the electro-optic crystal 601 according to the placement position of the optical resonator shown in fig. 13. Referring to fig. 14, an embodiment of the present application provides that (a) in fig. 14 and (b) in fig. 14 in front view and top view of the optical resonator 60, the temperature control structure 608 may also be disposed on the other side of the electro-optic crystal parallel to the propagation direction, and in particular, the other side may be the-z side of the electro-optic crystal 601 according to the placement position of the optical resonator shown in fig. 14. Alternatively, referring to fig. 15, an embodiment of the present application provides that (a) in fig. 15 and (b) in fig. 15 in front view and top view of the optical resonator 60, the temperature control structure 608 includes two parts, and the first part 6081 of the temperature control structure 608 may be disposed on one side of the electro-optical crystal 601 parallel to the propagation direction, and the second part 6082 of the temperature control structure 608 may be disposed on the other side of the electro-optical crystal 601 parallel to the propagation direction. Specifically, a first portion 6081 of the temperature control structure 608 is disposed on the z-side of the electro-optic crystal 601 and a second portion 6082 of the temperature control structure 608 is disposed on the-z-side of the electro-optic crystal 601.

It should be noted that, the temperature control structure may be selected and set according to actual requirements, and the embodiment of the present application does not limit the portion included in the temperature control structure and the setting position of the temperature control structure.

Illustratively, when the electrodes 604 and 605 in the optical resonator 60 are fabricated in accordance with the schematic structural diagrams of the optical resonator 60 shown in fig. 6 to 15 in consideration of the fact that the cavity length of the electro-optic crystal is in the order of micrometers (the cavity length of the electro-optic crystal is equal to or greater than 50um and equal to or less than 300um as described above), the fabrication process thereof is difficult, and then, referring to fig. 16, the embodiment of the present application provides (a) in fig. 16 and (b) in fig. 16 in the front view of the optical resonator 60. In the optical resonator 60 shown in fig. 16, the electro-optical crystal 601 includes an incident surface 606 on the light-incident side and an exit surface 607 on the light-exiting side in the propagation direction; the entrance face 606 includes a light-transmitting region 606a at the center, and a light-non-transmitting region 606b surrounding the light-transmitting region; the exit face 607 includes a light transmission region 607a at the center, and a light transmission region 607b surrounding the light transmission region 607a; wherein the reflective film 602 is disposed in the light-transmitting region 606a, and the reflective film 603 is disposed in the light-transmitting region 607a; the electrode 604 and the electrode 605 are disposed in the non-light-transmitting region 606b. Illustratively, referring to fig. 16, at this time, both the electrode 604 and the electrode 605 are disposed on the incident surface 606, and an electric field direction E formed between the electrode 604 and the electrode 605 passes through the electro-optic crystal 601, the electric field E has a component Ey perpendicular to the propagation direction, and the refractive index of the electro-optic crystal 601 is changed by the component Ey perpendicular to the propagation direction of the electric field E. Then, referring to fig. 16, according to the placement position of the optical resonator 60 shown in fig. 16 in the top view (b), that is, the electrode 604 is disposed in the non-light-transmitting region 606b above the light-transmitting region 606a, and the electrode 605 is disposed in the non-light-transmitting region 606b below the light-transmitting region 606a, two electrodes can be formed by one manufacturing process, so that the difficulty of the manufacturing process of the electrode 604 and the electrode 605 will be reduced.

For example, a temperature control structure may be further disposed on the basis of the optical resonant cavity 60 provided in fig. 16, and referring to fig. 17, an embodiment of the present application provides that (a) in fig. 17 and (b) in fig. 17 in the front view of the optical resonant cavity 60, a temperature control structure 608 is disposed on a side of the reflective film 602 away from the electro-optical crystal 601, where, because the reflective film 602 is disposed on a light-transmitting region 606a of the incident surface 606 and the electrode 604 and the electrode 605 are disposed on a non-light-transmitting region 606b of the incident surface 606 surrounding the light-transmitting region, when the temperature control structure 608 is disposed, the temperature control structure 608 may also be in contact with the electrode 604 and the electrode 605, but the electrode 604 needs to be insulated from the temperature control structure 608, so that the electrode 605 is insulated from the temperature control structure 608. Alternatively, the temperature control structure 608 is disposed on a side of the reflective film 603 remote from the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature control structure 608 is disposed on a side of the reflective film 602 that is remote from the electro-optic crystal 601, and the second portion 6082 of the temperature control structure 608 is disposed on a side of the reflective film 6023 that is remote from the electro-optic crystal 601. Alternatively, the temperature control structure 608 may be disposed on one side of the electro-optic crystal 601 in a direction parallel to the propagation direction, for example, the y-side of the electro-optic crystal 601. Alternatively, the temperature control structure 608 is arranged on the other side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the-y side of the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature-controlled structure 608 is disposed on one side of the electro-optic crystal 601 parallel to the propagation direction, which may be the y-side of the electro-optic crystal 601, for example, and the second portion 6082 of the temperature-controlled structure 608 is disposed on the other side of the electro-optic crystal 601 parallel to the propagation direction, which may be the-y-side of the electro-optic crystal 601, for example. Alternatively, the temperature control structure 608 is arranged on one side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the z-side of the electro-optic crystal 601. Alternatively, the temperature control structure 608 is arranged on the other side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the-z side of the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature-controlled structure 608 is disposed on one side of the electro-optic crystal 601 parallel to the propagation direction, which may be, for example, the z-side of the electro-optic crystal 601, and the second portion 6082 of the temperature-controlled structure 608 is disposed on the other side of the electro-optic crystal 601 parallel to the propagation direction, which may be, for example, the-z-side of the electro-optic crystal 601.

Alternatively, referring to fig. 18, an embodiment of the present application provides (a) in fig. 18 and (b) in fig. 18 in front view and top view of the optical resonator 60, wherein the electrode 604 and the electrode 605 are disposed in the non-light-transmitting region 607b in the third structural schematic view of the optical resonator 60 shown in fig. 18, compared to the second structural schematic view of the optical resonator 60 provided in fig. 16. Illustratively, referring to fig. 18, at this time, both the electrode 604 and the electrode 605 are disposed on the exit surface 607, and an electric field direction E formed between the electrode 604 and the electrode 605 passes through the electro-optic crystal 601, the electric field E has a component Ey perpendicular to the propagation direction, and the refractive index of the electro-optic crystal 601 is changed by the component Ey perpendicular to the propagation direction of the electric field E. Then, referring to fig. 18, according to the placement position of the optical resonator 60 shown in fig. 18 in the top view (b), that is, the electrode 604 is disposed in the non-light-transmitting region 607b above the light-transmitting region 607a, and the electrode 605 is disposed in the non-light-transmitting region 607b below the light-transmitting region 607a, two electrodes can be formed by one manufacturing process, so that the difficulty of the manufacturing process of the electrode 604 and the electrode 605 will be reduced.

For example, a temperature control structure may be further disposed on the basis of the optical resonator 60 provided in fig. 18, and referring to fig. 19, an embodiment of the present application provides that (a) in fig. 19 and (b) in fig. 19 in front view of the optical resonator 60, and the temperature control structure 608 is disposed on a side of the reflective film 602 away from the electro-optical crystal 601. Alternatively, the temperature control structure 608 is disposed on a side of the reflective film 603 away from the electro-optical crystal 601, where, since the reflective film 603 is disposed on the light-transmitting region 607a of the exit surface 607 and the electrode 604 and the electrode 605 are disposed on the non-light-transmitting region 607b of the exit surface 607 surrounding the light-transmitting region, when the temperature control structure 608 is disposed, the temperature control structure 608 may also be in contact with the electrode 604 and the electrode 605, but the electrode 604 needs to be insulated from the temperature control structure 608, so that the electrode 605 is insulated from the temperature control structure 608. Alternatively, the first portion 6081 of the temperature control structure 608 is disposed on a side of the reflective film 602 that is remote from the electro-optic crystal 601, and the second portion 6082 of the temperature control structure 608 is disposed on a side of the reflective film 6023 that is remote from the electro-optic crystal 601. Alternatively, the temperature control structure 608 may be disposed on one side of the electro-optic crystal 601 in a direction parallel to the propagation direction, for example, the y-side of the electro-optic crystal 601. Alternatively, the temperature control structure 608 is arranged on the other side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the-y side of the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature-controlled structure 608 is disposed on one side of the electro-optic crystal 601 parallel to the propagation direction, which may be the y-side of the electro-optic crystal 601, for example, and the second portion 6082 of the temperature-controlled structure 608 is disposed on the other side of the electro-optic crystal 601 parallel to the propagation direction, which may be the-y-side of the electro-optic crystal 601, for example. Alternatively, the temperature control structure 608 is arranged on one side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the z-side of the electro-optic crystal 601. Alternatively, the temperature control structure 608 is arranged on the other side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the-z side of the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature-controlled structure 608 is disposed on one side of the electro-optic crystal 601 parallel to the propagation direction, which may be, for example, the z-side of the electro-optic crystal 601, and the second portion 6082 of the temperature-controlled structure 608 is disposed on the other side of the electro-optic crystal 601 parallel to the propagation direction, which may be, for example, the-z-side of the electro-optic crystal 601.

It should be noted that, the temperature control structure may be selected and set according to actual requirements, and the embodiment of the present application does not limit the portion included in the temperature control structure and the setting position of the temperature control structure. Illustratively, referring to fig. 20, an embodiment of the present application provides (a) in fig. 20 and (b) in fig. 20 in front view and plan view of the optical resonator 60, and in the optical resonator 60 shown in fig. 20, the non-light-transmitting region 606b includes a first region 606b1 and a second region 606b2 symmetrically distributed about the light-transmitting region 606a as a center; the non-light-transmitting region 607b includes a third region 607b1 and a fourth region 607b2 symmetrically distributed about the light-transmitting region 607; wherein, along the propagation direction, the first region 606b1 overlaps the third region 607b1, and the second region 606b2 overlaps the fourth region 607b2; then, the electrode arrangement 604 is in the first region 606b1 and the electrode 605 is arranged in the fourth region 607b2. For example, referring to fig. 20, when the electrode 604 is disposed on the incident surface 606 and the electrode 605 is disposed on the exit surface 607, the direction of the electric field E formed between the electrode 604 and the electrode 605 is angularly offset from the direction along the y-direction, but when the electric field E is maximum in the electric field component Ey perpendicular to the propagation direction. More specifically, when the cavity length of the optical resonator 60 is 50 micrometers (um) or more and 32 micrometers (um) or less, the above-described angular deviation is negligible, and it is also considered that the direction of the electric field in the optical resonator 60 shown in fig. 20 is directed in the direction y to-y, the direction of the electric field E is perpendicular to the propagation direction, and the refractive index of the electro-optic crystal 601 is changed by the electric field E.

For example, a temperature control structure may be further disposed on the basis of the optical resonant cavity 60 provided in fig. 20, and referring to fig. 21, an embodiment of the present application provides that (a) in fig. 21 and (b) in fig. 21 in the front view of the optical resonant cavity 60, the temperature control structure 608 is disposed on a side of the reflective film 602 away from the electro-optical crystal 601, where, since the reflective film 602 is disposed on the light-transmitting region 606a of the incident surface 606, the electrode 604 is disposed on the first region 606b1 of the incident surface 606 surrounding the light-transmitting region, and then, when the temperature control structure 608 is disposed, the temperature control structure 608 may also be in contact with the electrode 604, but the electrode 604 needs to be insulated from the temperature control structure 608. Alternatively, the temperature control structure 608 is disposed on a side of the reflective film 603 away from the electro-optical crystal 601, where, since the reflective film 603 is disposed on the light-transmitting region 607a of the exit surface 607 and the electrode 605 is disposed on the fourth region 607b2 of the exit surface 607 surrounding the non-light-transmitting region 607b of the light-transmitting region, the temperature control structure 608 may be in contact with the electrode 605 when the temperature control structure 608 is disposed, but the electrode 605 needs to be insulated from the temperature control structure 608. Alternatively, the first portion 6081 of the temperature control structure 608 is disposed on a side of the reflective film 602 that is remote from the electro-optic crystal 601, and the second portion 6082 of the temperature control structure 608 is disposed on a side of the reflective film 6023 that is remote from the electro-optic crystal 601. Alternatively, the temperature control structure 608 may be disposed on one side of the electro-optic crystal 601 in a direction parallel to the propagation direction, for example, the y-side of the electro-optic crystal 601. Alternatively, the temperature control structure 608 is arranged on the other side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the-y side of the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature-controlled structure 608 is disposed on one side of the electro-optic crystal 601 parallel to the propagation direction, which may be the y-side of the electro-optic crystal 601, for example, and the second portion 6082 of the temperature-controlled structure 608 is disposed on the other side of the electro-optic crystal 601 parallel to the propagation direction, which may be the-y-side of the electro-optic crystal 601, for example. Alternatively, the temperature control structure 608 is arranged on one side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the z-side of the electro-optic crystal 601. Alternatively, the temperature control structure 608 is arranged on the other side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the-z side of the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature-controlled structure 608 is disposed on one side of the electro-optic crystal 601 parallel to the propagation direction, which may be, for example, the z-side of the electro-optic crystal 601, and the second portion 6082 of the temperature-controlled structure 608 is disposed on the other side of the electro-optic crystal 601 parallel to the propagation direction, which may be, for example, the-z-side of the electro-optic crystal 601.

It should be noted that, the temperature control structure may be selected and set according to actual requirements, and the embodiment of the present application does not limit the portion included in the temperature control structure and the setting position of the temperature control structure. Alternatively, referring illustratively to FIG. 22, embodiments of the present application provide for (a) in FIG. 22 and (b) in FIG. 22 in a front view of the optical cavity 60 and (b) in a top view of the optical cavity 60 shown in FIG. 22, with electrode 604 disposed in the third region 607b1 and electrode 605 disposed in the second region 606b2. For example, referring to fig. 22, when the electrode 604 is disposed on the exit surface 607 and the electrode 605 is disposed on the entrance surface 606, the direction of the electric field E formed between the electrode 604 and the electrode 605 is angularly offset from the direction along the y-direction, but when the electric field E is maximum in the electric field component Ey perpendicular to the propagation direction. More specifically, when the cavity length of the optical resonator 60 is 50 micrometers (um) or more and 32 micrometers (um) or less, the above-described angular deviation is negligible, and it is also considered that the direction of the electric field in the optical resonator 60 shown in fig. 22 is directed in the direction y to-y, the direction of the electric field E is perpendicular to the propagation direction, and the refractive index of the electro-optic crystal 601 is changed by the electric field E.

For example, a temperature control structure may be further disposed on the basis of the optical resonant cavity 60 provided in fig. 22, and referring to fig. 23, an embodiment of the present application provides that (a) in fig. 23 and (b) in fig. 23 in front view of the optical resonant cavity 60, the temperature control structure 608 is disposed on a side of the reflective film 602 away from the electro-optic crystal 601, where, because the reflective film 602 is disposed on the light-transmitting region 606a of the incident surface 606 and the electrode 605 is disposed on the second region 606b2 of the incident surface 606 surrounding the light-transmitting region, the temperature control structure 608 may also be in contact with the electrode 605 when the temperature control structure 608 is disposed, but the electrode 605 needs to be insulated from the temperature control structure 608. Alternatively, the temperature control structure 608 is disposed on a side of the reflective film 603 away from the electro-optical crystal 601, where, since the reflective film 603 is disposed on the light-transmitting region 607a of the exit surface 607 and the electrode 604 is disposed on the third region 607b1 of the exit surface 607 surrounding the non-light-transmitting region 607b of the light-transmitting region, the temperature control structure 608 may be in contact with the electrode 604 when the temperature control structure 608 is disposed, but the electrode 604 needs to be insulated from the temperature control structure 608. Alternatively, the first portion 6081 of the temperature control structure 608 is disposed on a side of the reflective film 602 that is remote from the electro-optic crystal 601, and the second portion 6082 of the temperature control structure 608 is disposed on a side of the reflective film 6023 that is remote from the electro-optic crystal 601. Alternatively, the temperature control structure 608 may be disposed on one side of the electro-optic crystal 601 in a direction parallel to the propagation direction, for example, the y-side of the electro-optic crystal 601. Alternatively, the temperature control structure 608 is arranged on the other side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the-y side of the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature-controlled structure 608 is disposed on one side of the electro-optic crystal 601 parallel to the propagation direction, which may be the y-side of the electro-optic crystal 601, for example, and the second portion 6082 of the temperature-controlled structure 608 is disposed on the other side of the electro-optic crystal 601 parallel to the propagation direction, which may be the-y-side of the electro-optic crystal 601, for example. Alternatively, the temperature control structure 608 is arranged on one side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the z-side of the electro-optic crystal 601. Alternatively, the temperature control structure 608 is arranged on the other side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the-z side of the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature-controlled structure 608 is disposed on one side of the electro-optic crystal 601 parallel to the propagation direction, which may be, for example, the z-side of the electro-optic crystal 601, and the second portion 6082 of the temperature-controlled structure 608 is disposed on the other side of the electro-optic crystal 601 parallel to the propagation direction, which may be, for example, the-z-side of the electro-optic crystal 601.

It should be noted that, the temperature control structure may be selected and set according to actual requirements, and the embodiment of the present application does not limit the portion included in the temperature control structure and the setting position of the temperature control structure. Illustratively, referring to FIG. 24, an embodiment of the present application provides a front view of optical cavity 60, FIG. 24 (a), and a top view of FIG. 24 (b), where in optical cavity 60 shown in FIG. 24, electrode 604 includes a first portion 6041 and a second portion 6042; the electrode 605 includes a third portion 6051 and a fourth portion 6052; the first portion 6041 of the electrode 604 is disposed in the first region 606b1 and the second portion 6042 of the electrode 604 is disposed in the third region 607b1; the third portion 6051 of the electrode 605 is disposed in the second region 606b2 and the fourth portion 6052 of the electrode 605 is disposed in the fourth region 607b2; the first portion 6041 and the second portion 6042 of the electrode 604 are electrically connected by a wire; the third portion 6051 and the fourth portion 6052 of the electrode 605 are electrically connected by a wire. In the optical resonator 60 shown in fig. 24, the first portion 4041 and the second portion 4042 of the electrode 604 are electrically connected by a wire and are also connected to the positive voltage terminal of the driving voltage by the wire, the first portion 4051 and the second portion 4052 of the electrode 605 are connected by a wire and are also connected to the negative voltage terminal of the driving voltage by the wire, and then an electric field E is formed between the electrode 604 and the electrode 605, the direction of the electric field E being directed in the y-y direction, so that the voltage applied to the electrode 604 and the electrode 605 realizes the most uniform electric field, wherein the direction of the electric field E is perpendicular to the propagation direction, and the refractive index of the electro-optic crystal 601 is changed by the electric field E.

For example, a temperature control structure may be further disposed on the basis of the optical resonator 60 provided in fig. 24, and referring to fig. 25, an embodiment of the present application provides that (a) in fig. 25 and (b) in fig. 25 in front view of the optical resonator 60, the temperature control structure 608 is disposed on a side of the reflective film 602 away from the electro-optical crystal 601, where, because the reflective film 602 is disposed on the light-transmitting region 606a located in the center of the incident surface 606, the first portion 6041 of the electrode 604 is disposed on the first region 606b1 of the non-light-transmitting region 606b of the incident surface 606 surrounding the light-transmitting region, and the second portion 6042 of the electrode 604 is disposed on the second region 606b2 of the non-light-transmitting region 606b of the incident surface 606 surrounding the light-transmitting region, when the temperature control structure 608 is disposed, the temperature control structure 608 may also be in contact with the electrode 604, but the electrode 604 needs to be insulated from the temperature control structure 608. Alternatively, the temperature control structure 608 is disposed on a side of the reflective film 603 away from the electro-optical crystal 601, where, since the reflective film 603 is disposed on the light-transmitting region 607a of the exit surface 607 at the center, the first portion 6051 of the electrode 605 is disposed on the third region 607b1 of the exit surface 607 surrounding the light-transmitting region 607b, and the second portion 6052 of the electrode 605 is disposed on the fourth region 607b2 of the exit surface 607 surrounding the light-transmitting region 607b, the temperature control structure 608 may be in contact with the electrode 605 when the temperature control structure 608 is disposed, but the electrode 605 needs to be insulated from the temperature control structure 608. Alternatively, the first portion 6081 of the temperature control structure 608 is disposed on a side of the reflective film 602 that is remote from the electro-optic crystal 601, and the second portion 6082 of the temperature control structure 608 is disposed on a side of the reflective film 6023 that is remote from the electro-optic crystal 601. Alternatively, the temperature control structure 608 may be disposed on one side of the electro-optic crystal 601 in a direction parallel to the propagation direction, for example, the y-side of the electro-optic crystal 601. Alternatively, the temperature control structure 608 is arranged on the other side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the-y side of the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature-controlled structure 608 is disposed on one side of the electro-optic crystal 601 parallel to the propagation direction, which may be the y-side of the electro-optic crystal 601, for example, and the second portion 6082 of the temperature-controlled structure 608 is disposed on the other side of the electro-optic crystal 601 parallel to the propagation direction, which may be the-y-side of the electro-optic crystal 601, for example. Alternatively, the temperature control structure 608 is arranged on one side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the z-side of the electro-optic crystal 601. Alternatively, the temperature control structure 608 is arranged on the other side of the electro-optic crystal 601 in parallel to the propagation direction, which may be, for example, the-z side of the electro-optic crystal 601. Alternatively, the first portion 6081 of the temperature-controlled structure 608 is disposed on one side of the electro-optic crystal 601 parallel to the propagation direction, which may be, for example, the z-side of the electro-optic crystal 601, and the second portion 6082 of the temperature-controlled structure 608 is disposed on the other side of the electro-optic crystal 601 parallel to the propagation direction, which may be, for example, the-z-side of the electro-optic crystal 601.

It should be noted that, the temperature control structure may be selected and set according to actual requirements, and the embodiment of the present application does not limit the portion included in the temperature control structure and the setting position of the temperature control structure. In addition, an embodiment of the present application also provides an optical filter, referring to fig. 26, fig. 26 shows (a) in fig. 26 and (b) in fig. 26 in a plan view of the optical filter 11, wherein the optical filter 11 includes an optical fiber collimator 70a on an input side, an optical fiber collimator 70b on an output side, and a plurality of optical resonators 80 and reflecting elements 90a disposed on an optical path between the optical fiber collimator 70a and the optical fiber collimator 70 b. Referring to fig. 26, the plurality of optical resonators 80 includes an optical resonator 80a and an optical resonator 80b, and in the arrangement position of the optical filter 11 shown in fig. 26, the optical collimator 70a, the optical resonator 80b, and the reflecting element 90a are sequentially disposed along a first direction of-x to x, in fig. 26, an optical path is a solid line with an arrow, and in the optical path, the optical collimator 70a and the optical collimator 70b are located on a first side of the plurality of optical resonators 80, and the reflecting element 90a is located on a second side of the optical resonator 80. In order to make the free spectral ranges of any two of the plurality of optical resonators 80 different, the cavity lengths of any two of the plurality of optical resonators 80 need to be set differently.

The optical fiber collimator 70a is provided with an optical fiber 701a, the optical fiber 701a is used for transmitting input light, the optical fiber collimator 70b is provided with an optical fiber 701b, and the optical fiber 701b is used for transmitting output light.

Then, the optical fiber collimator 70a is configured to collimate the received first light (i.e. the input light transmitted by the optical fiber 701 a) to generate collimated light, and sequentially pass the collimated light through the plurality of optical resonators along the first direction. And the plurality of optical resonant cavities are used for carrying out filtering treatment on the collimated light rays and generating first filtered light rays containing a preset wavelength.

The first light ray received by the fiber collimator 70a includes a plurality of light rays with different wavelengths, including a light ray with a wavelength λa, a light ray with a wavelength λb, a light ray with a wavelength λc, and a light ray with a wavelength λd, and the fiber collimator 70a collimates the first light ray with different wavelengths to generate a collimated light ray, and then the collimated light ray still includes the light ray with the wavelength λa, the light ray with the wavelength λb, the light ray with the wavelength λc, and the light ray with the wavelength λd, wherein each of the light rays with different wavelengths of the collimated light rays passes through the optical resonant cavity 80a along the first direction according to the same incident angle α2. The incident angle α2 may be, for example, 0 degrees. Illustratively, embodiments of the present application are not limited to the angle at which the collimated light is incident on the optical resonator 80 b.

Specifically, the optical resonator 80a may be any one of the optical resonators 60 described above, and the optical resonator 80b may be any one of the optical resonators 60 described above, and more specifically, the difference in the cavity length between the optical resonator 80a and the optical resonator 80b is 5um or more.

Assuming that the light with the predetermined wavelength is the light with the wavelength λd, in an ideal state, that means that the plurality of optical resonators 80 need to filter out the light with the wavelength λd in the collimated light, when the driving voltage is set to the electrode of the optical resonator 80a to form the electric field E1, the refractive index of the electro-optic crystal in the optical resonator 80a is changed under the action of the electric field E1, so that the optical resonator 80a performs the first filtering process on the collimated light, that is, the optical resonator 80a receives the light with the wavelength λa, the light with the wavelength λb, the light with the wavelength λc and the light with the wavelength λd under the action of the electric field E1, and filters out the light with the wavelength λa and the light with the wavelength λd. When a driving voltage is applied to the electrode of the optical resonator 80b to form an electric field E2, the refractive index of the electro-optic crystal in the optical resonator 80b is changed under the action of the electric field E2, so that the optical resonator 80b performs a second filtering process on the straight light, that is, the optical resonator 80b receives the light with the wavelength λa and the light with the wavelength λd under the action of the electric field E2, and filters out the light with the wavelength λd. In this ideal state, the light with wavelength λd is the first filtered light.

However, in the operation of the optical filter 11, the above-mentioned ideal state rarely occurs, and in most cases, the collimated light includes light rays with a plurality of wavelengths, and when the collimated light rays sequentially pass through the plurality of optical resonators 80 along the first direction, each of the plurality of optical resonators 80 sequentially filters the collimated light rays, and the generated first filtered light rays include light rays with predetermined wavelengths but also light rays with wavelengths other than the predetermined wavelengths (also referred to as interference light rays).

The magnitude of the driving voltage applied to the electrode of the optical resonator 80a may be the same as or different from the magnitude of the driving voltage applied to the electrode of the optical resonator 80 b.

The reflecting element 90a is configured to reflect the first filtered light to the plurality of optical resonators 80, so that the first filtered light sequentially passes through the plurality of optical resonators 80 along a second direction, and the second direction is opposite to the first direction.

Specifically, the reflecting element 90a includes a reflecting mirror 901a and a reflecting mirror 902a, where when an included angle between the reflecting mirror 901a and the reflecting mirror 902a is exactly 90 degrees, the reflecting mirror 901a is configured to receive a first filtered light, where the first filtered light reflects on the reflecting mirror 901a for the first time, and the reflecting mirror 901a reflects the first filtered light onto the reflecting mirror 902 a; the first filtered light ray then reflects a second time on a mirror 902a, which mirrors 902a to reflect the first filtered light ray to the plurality of optical resonators 80 such that the first filtered light ray passes through the plurality of optical resonators 80 in a second direction exactly pointing in x-x. Wherein, the angle between the mirror 901a and the mirror 902a may tolerate a process error of 0.5 degrees, for example, the angle between the mirror 901a and the mirror 902a may be 89.5 degrees or more and 90.5 degrees or less, and within the range of the process error of 0.5 degrees, the first filtered light reflected by the reflecting element 90a may also be considered to sequentially pass through the plurality of optical resonant cavities 80 in the second direction of x-x.

Alternatively, the reflecting element 90a includes a right angle prism, where the right angle prism includes a first right angle surface and a second right angle surface, and then the first right angle surface of the right angle prism is configured to receive the first filtered light, and the first right angle surface of the right angle prism reflects the first filtered light to the second right angle surface of the right angle prism; the second right angle surface is configured to reflect the first filtered light reflected by the first right angle surface to the plurality of optical resonant cavities 80, so that the first filtered light sequentially passes through the plurality of optical resonant cavities 80 along the second direction of x-direction. The angle between the first right-angle surface of the right-angle prism and the second right-angle surface of the right-angle prism may tolerate a process error of 0.5 degrees, for example, the angle between the first right-angle surface of the right-angle prism and the second right-angle surface of the right-angle prism may be 89.5 degrees or more and 90.5 degrees or less, and within the range of the process error of 0.5 degrees, the first filtered light reflected by the reflecting element 90a may also be considered to pass through the plurality of optical resonant cavities 80 again in the second direction of x-x.

The plurality of optical resonators 80 are further configured to filter the first filtered light reflected by the reflecting element 90a to generate an output filtered light including light with a predetermined wavelength. Specifically, when the reflection element 90a is configured to reflect the first filtered optical fiber to the plurality of optical resonant cavities 80, so that the first filtered light passes through the optical resonant cavities 80b and 80a again, the optical resonant cavities 80b perform the filtering treatment on the first filtered light, the optical resonant cavities 80a perform the second filtering treatment on the first filtered light to obtain the second filtered light, and compared with the first filtered light, a part of interference light in the second filtered light is blocked, so that the filtering effect is improved.

A fiber collimator 70b for coupling the output filtered light to the fiber output. Specifically, the optical fiber collimator may collimate a plurality of light rays having different propagation directions so that the propagation directions of the plurality of light rays are the same, and the optical fiber collimator may couple the light rays to a certain optical fiber for output, and in the optical filter 11 shown in fig. 26, the optical fiber collimator 70b couples the output filtered light rays to the optical fiber 701b for output.

In the above optical filter, first, the first optical fiber collimator (that is, the optical fiber collimator 70 a) collimates the received light to generate collimated light, and sequentially passes the collimated light through the plurality of optical resonators along the first direction, so that each of the plurality of optical resonators performs filtering processing on the collimated light to generate a first filtered light including a predetermined wavelength. The cavity lengths of any two optical resonant cavities among the plurality of optical resonant cavities are different, so that the wavelengths of light rays filtered out by any two optical resonant cavities among the plurality of optical resonant cavities are not identical, and the wavelengths of the blocked light rays are different. That is, when the plurality of optical resonators perform filtering processing on the straight light, more light rays with other wavelengths than the predetermined wavelength are blocked, and the generated first filtered light rays with the predetermined wavelength contain less light rays with other wavelengths than the predetermined wavelength. Next, when the first filtered light is transmitted to the first reflecting element (i.e., the reflecting element 90 a), the first reflecting element reflects the first filtered light to the plurality of optical resonators, so that the first filtered light sequentially passes through the plurality of optical resonators along the second direction, and the plurality of optical resonators performs a filtering process on the first filtered light to generate an output filtered light with a predetermined wavelength. Although the first filtered light contains less light with other wavelengths than the preset wavelength, the light with other wavelengths than the preset wavelength needs to be blocked, so that the plurality of optical resonant cavities further block the residual light with other wavelengths needing to be blocked in the first filtered light to generate output filtered light containing the preset wavelength, and the filtering effect is improved. The output filtered light is finally coupled to the first fiber output by a second fiber collimator (i.e., fiber collimator 70 b). And in the optical filter, the existence of the plurality of optical resonant cavities can carry out multiple filtering treatment on the straight light, and the increase of the filtering treatment times also reduces the reflectivity requirement of the optical filter on the material used by the reflecting film of each optical resonant cavity, thereby further improving the filtering effect of the optical filter.

For example, referring to fig. 26, the fiber collimator 70a and the fiber collimator 70b may be replaced by a dual fiber collimator having two optical fibers, one of the two optical fibers of the dual fiber collimator may be used to transmit the input light, and the other of the two optical fibers of the dual fiber collimator may be used to transmit the output filtered light.

Illustratively, referring to fig. 27, an embodiment of the present application provides that (a) in fig. 27 and (b) in fig. 27 in a top view and a front view of another optical filter 12, the plurality of optical resonators 80 in the optical filter 12 may further include, compared to the optical filter 11: an optical resonator 80c. Then in the optical filter 12, there are 3 optical resonators, and the cavity lengths of the 3 optical resonators are different from each other, and more specifically, the difference in the cavity lengths of any two of the three optical resonators is 5um or more. In the optical filter 12, since there are 3 optical resonators, the 3 optical resonators have different cavity lengths, and therefore, the wavelengths of light filtered out by the 3 optical resonators are not exactly the same, in which case the number of times of filtering increases to 3 times so that the reflectance requirement of the optical filter 12 for the material used for the reflective film of each optical resonator decreases again.

It should be noted that, the number of optical resonant cavities included in the plurality of optical resonant cavities 80 is not limited in the embodiment of the present application.

Illustratively, referring to fig. 28, in addition to the optical filter 11 shown in fig. 26, in fig. 28 (a) in the top view and fig. 28 (b) in the front view of the optical filter 13 shown in fig. 28, a reflecting element 90b is further included in the optical path between the optical fiber collimator 70a and the optical fiber collimator 70b, and then, in the optical path of the optical filter 13 shown in fig. 28, the optical fiber collimator 70a and the reflecting element 90b are located on the first side of the plurality of optical resonant cavities 80; the fiber collimator 70b and the reflective element 90a are located on a second side of the plurality of optical resonant cavities 80. And the plurality of optical resonators 80 are exemplified by the optical resonator 80a and the optical resonator 8080b to explain the operation principle of the optical filter 13.

The optical resonator 80a and the optical resonator 80b may be any of the optical resonators 60 described above.

In the optical filter 13, the optical fiber collimator 70a is configured to collimate the received first light (i.e. the input light transmitted by the optical fiber 701 a) to generate collimated light, and sequentially pass the collimated light through the optical resonant cavity 80a and the optical resonant cavity 80b along a first direction (i.e. -x pointing in the x direction). An optical resonator 80a for performing a first filtering process on the collimated light; the optical resonator 80b is configured to perform a second filtering process on the collimated light, so as to generate a first filtered light with a predetermined wavelength.

The reflecting element 90a is configured to reflect the first filtered light to the plurality of optical resonators 80, so that the first filtered light sequentially passes through the optical resonators 80b and the optical resonators 80a along a second direction (i.e., the x-direction-x direction), and the second direction is opposite to the first direction.

The plurality of optical resonators 80 filter the first filtered light reflected by the reflecting element 90a to generate a second filtered light having a predetermined wavelength. Specifically, the optical resonant cavity 80b is configured to perform a first filtering process on the first filtered light; the optical resonator 80a is configured to perform a second filtering process on the first filtered light, so as to generate a second filtered light with a predetermined wavelength.

The reflecting element 90b is configured to reflect the second filtered light beam to the plurality of optical resonators 80, so that the second filtered light beam sequentially passes through the optical resonators 80a and the optical resonators 80b along the first direction, that is, the reflecting element 90b reverses the propagation direction of the second filtered light beam.

The plurality of optical resonators 80 filter the second filtered light reflected by the reflecting element 90b to generate an output filtered light including a predetermined wavelength. An optical resonator 80a for performing a first filtering process on the second filtered light; the optical resonator 80b is configured to perform a second filtering process on the second filtered light, so as to generate an output filtered light with a predetermined wavelength.

Then, a fiber collimator 70b is used to couple the output filtered light to the output of fiber 701 b.

Then, in the optical filter 13 shown in fig. 28, since the reflecting element 90b is present, the reflecting element 90b reflects the second filtered light to the plurality of optical resonant cavities 80, so that the plurality of optical resonant cavities 80 filter the second filtered light, and therefore the plurality of optical resonant cavities 80 further block the remaining light with other wavelengths to be blocked in the second filtered light, and generate the output filtered light with predetermined wavelengths, so as to enhance the filtering effect.

Specifically, the reflecting element 90b includes a reflecting mirror 901b and a reflecting mirror 902b, where when an included angle between the reflecting mirror 901b and the reflecting mirror 902b is exactly 90 degrees, the reflecting mirror 901b is configured to receive the second filtered light, where the second filtered light reflects on the reflecting mirror 901b for the first time, and the reflecting mirror 901b reflects the second filtered light onto the reflecting mirror 902 b; the second filtered light ray then reflects a second time on a mirror 902b, which mirror 902b is configured to reflect the second filtered light ray toward the plurality of optical resonators 80 such that the second filtered light ray passes through the plurality of optical resonators 80 in sequence in exactly the first direction in which-x is directed toward x. Wherein, the angle between the mirror 901b and the mirror 902b may tolerate a process error of 0.5 degrees, for example, the angle between the mirror 901b and the mirror 902b may be 89.5 degrees or more and 90.5 degrees or less, and within the range of the process error of 0.5 degrees, the second filtered light passing through the reflecting element 90b may also be considered to sequentially pass through the plurality of optical resonant cavities 80 in the first direction of-x pointing x.

Alternatively, the reflecting element 90b includes a right angle prism including a third right angle surface and a fourth right angle surface, and then the third right angle surface of the right angle prism is configured to receive the second filtered light, and the third right angle surface of the right angle prism reflects the second filtered light to the fourth right angle surface of the right angle prism; and a fourth right angle surface for reflecting the second filtered light reflected by the third right angle surface to the plurality of optical resonators 80 such that the second filtered light sequentially passes through the plurality of optical resonators 80 in the first direction in which-x is directed to x. The angle between the third right angle surface of the right angle prism and the fourth right angle surface of the right angle prism may tolerate a process error of 0.5 degrees, for example, the angle between the third right angle surface of the right angle prism and the fourth right angle surface of the right angle prism may be 89.5 degrees or more and 90.5 degrees or less, and within the range of the process error of 0.5 degrees, the second filtered light passing through the reflecting element 90b may also be considered to pass through the plurality of optical resonant cavities 80 again in the first direction of-x pointing to x.

Illustratively, referring to fig. 29, on the basis of the optical filter 13 shown in fig. 28, in fig. 29 (a) and fig. 29 (b) in the plan view of the optical filter 14 shown in fig. 29, the optical path between the optical fiber collimator 70a and the optical fiber collimator 70b further includes a polarization beam splitting element 100a and a polarization beam combining element 110a; then, on the optical path of the optical filter 14 shown in fig. 29, the polarization beam splitting element 100a is located between the optical fiber collimator 70a and the plurality of optical resonators (i.e., the optical resonator 8080a and the optical resonator 8080 b), and the polarization beam combining element 110a is located between the plurality of optical resonators (i.e., the optical resonator 80a and the optical resonator 80 b) and the optical fiber collimator 70 b. In addition, in the optical filter 14 shown in fig. 29, the optical resonator 80a may be any one of the optical resonators 60, the optical resonator 80b may also be any one of the optical resonators 60, and the transverse electro-optic effect of the material used for the electro-optic crystal in the optical resonator 80a and the optical resonator 80b is better than the longitudinal electro-optic effect, so that the filtering effect of the optical filter 14 is better, a polarizing beam splitting element 100a is disposed between the optical collimator 70a and the plurality of optical resonators (that is, the optical resonator 80a and the optical resonator 80 b), so as to split the S-polarized light and the P-polarized light in the collimated light generated by the optical collimator 70a, and the polarizing beam splitting element 100a further includes a 1/2 glass, and the polarizing beam splitting element 110a converts the S-polarized light in the collimated light into the P-polarized light through the 1/2 glass, because the transverse electro-optic effect is more sensitive to the P-polarized light, where the polarization direction of the P-polarized light in the collimated light is parallel to the direction of the electric field of the optical resonator 80a and also parallel to the electric field of the optical resonator 80 b. In the optical filter 14, the optical fiber collimator 70a is configured to collimate the received first light ray (i.e., the input light ray transmitted by the optical fiber 701 a), generate a collimated light ray, and transmit the collimated light ray to the polarization beam splitter 100a.

The polarization beam splitting element 100a is configured to separate a second light ray (for example, S-polarized light, where the first polarization direction is the polarization direction of the S-polarized light) having a first polarization direction from a third light ray (for example, P-polarized light, where the second polarization direction is the polarization direction of the P-polarized light) having a second polarization direction. The specific structures of the optical resonator 80a and the optical resonator 80b are shown in fig. 6, where the transverse electro-optic effect of the materials used for the electro-optic crystals in the optical resonator 80a and the optical resonator 80b is better than the longitudinal electro-optic effect, and the electric field direction in the optical resonator 80a is the same as the electric field direction in the optical resonator 80b, and the electric field direction is perpendicular to the propagation direction of the light (i.e., the electro-optic crystals in the optical resonator 80a and the optical resonator 80b have the transverse electro-optic effect). The transverse electro-optic effect of optical cavity 80a and optical cavity 80b is more sensitive to light having a second polarization (i.e., P-polarized light) among the aligned light. Then, the polarization direction d of the second light ray (S polarized light) of the collimated light ray may be set to the second polarization direction (i.e., the polarization direction of the P polarized light) by disposing a 1/2 slide in the polarization beam splitting element 100a such that the second light ray (S polarized light) of the collimated light ray passes through the 1/2 slide.

At this time, in the optical filter 14 shown in fig. 29, the second light of the collimated light sequentially passes through the optical resonator 80a and the optical resonator 80b in the first direction (i.e., -x is directed in the x direction). An optical resonator 80a for performing a first filtering process on a second light ray of the collimated light ray; an optical resonator 80b for performing a second filtering process on the second light of the collimated light, thereby generating a second light including the first filtered light of the predetermined wavelength; the third ray of collimated light passes sequentially through optical cavity 80a and optical cavity 80b in a first direction (i.e., -x pointing in the x direction). An optical resonator 80a for performing a first filtering process on a third light ray of the collimated light ray; the optical resonator 80b is configured to perform a second filtering process on the third light of the collimated light, so as to generate a third light including the first filtered light with the predetermined wavelength.

A reflecting element 90a for reflecting the second light of the first filtered light to the plurality of optical resonators such that the second light of the first filtered light sequentially passes through the optical resonator 80b and the optical resonator 80a in a second direction (i.e., the direction in which x is directed to-x), the second direction being opposite to the first direction; and also to reflect a third light of the first filtered light such that the third light of the first filtered light passes through the optical cavity 80b and the optical cavity 80a in sequence in a second direction (i.e., the x-direction-x direction).

An optical resonator 80b for performing a first filtering process on the second light of the first filtered light reflected by the reflecting element 90 a; an optical resonator 80a for performing a second filtering process on the second light of the first filtered light reflected by the reflecting element 90a, so as to generate a second light including a second filtered light with a predetermined wavelength; an optical resonator 80b for performing a first filtering process on the third light of the first filtered light reflected by the reflecting element 90 a; the optical resonator 80a is configured to perform a second filtering process on the third light of the first filtered light reflected by the reflecting element 90a, so as to generate a third light including the second filtered light with the predetermined wavelength.

A reflecting element 90b for reflecting the second light of the second filtered light to the plurality of optical resonators such that the second light of the second filtered light sequentially passes through the optical resonator 80a and the optical resonator 80b along the first direction, that is, the reflecting element 90b reverses the second light propagation direction of the second filtered light; the reflecting element 90b is further configured to reflect the third light of the second filtered light, so that the third light of the second filtered light sequentially passes through the optical resonant cavity 80a and the optical resonant cavity 80b along the first direction, that is, the reflecting element 90b reverses the propagation direction of the third light of the second filtered light.

An optical resonator 80a for performing a first filtering process on the second light of the second filtered light reflected by the reflecting element 90 b; the optical resonator 80b is configured to perform a second filtering process on the second light of the second filtered light reflected by the reflecting element 90b, so as to generate a second light including the output filtered light with the predetermined wavelength. An optical resonator 80a for performing a first filtering process on the third light of the second filtered light reflected by the reflecting element 90 b; the optical resonator 80b is configured to perform a second filtering process on the third light of the second filtered light reflected by the reflecting element 90b, so as to generate a third light including the output filtered light with the predetermined wavelength. The second light ray outputting the filtered light ray and the third light ray outputting the filtered light ray are transmitted to the polarization beam combining element 110a.

The polarization beam combining element 110a includes a 1/2 glass slide, and transmits the first light of the output filtered light to the 1/2 glass slide, so that the 1/2 glass slide sets the polarization direction of the second light of the output filtered light to the first polarization direction, that is, restores the polarization direction of the second light of the output filtered light.

The polarization beam combining element 110a is further configured to combine the second light beam of the output filtered light beam with the third light beam of the output filtered light beam into the output filtered light beam.

In other embodiments, the polarization beam combining element 110a includes a 1/2 glass slide, and the third light of the output filtered light may be transmitted to the 1/2 glass slide, so that the 1/2 glass slide sets the polarization direction of the third light of the output filtered light to the first polarization direction. The polarization beam combining element 110a is further configured to combine the second light beam of the output filtered light beam with the third light beam of the output filtered light beam into the output filtered light beam.

For example, when the reflective element 90b is not included in the optical filter 14, the second light of the output filtered light may be generated by filtering the second light of the first filtered light by the plurality of optical resonators 80, and the third light of the output filtered light may be generated by filtering the third light of the first filtered light by the plurality of optical resonators 80. That is, the above-mentioned polarization beam combining element 110a and polarization beam splitting element 100a may be disposed in the optical filter 120, and the polarization beam combining element 110a and polarization beam splitting element 100a may be disposed in a regular arrangement in which the polarization beam splitting element 100a is disposed between the optical fiber collimator 70a and the plurality of optical resonators and the polarization beam combining element 110a is disposed between the plurality of optical resonators and the optical fiber collimator 70 b.

For example, when the beam waist radius of the spot beam of the collimated light is 100um, the effective aperture of the collimated light is about 300um, and then the distance between the two electrodes of the optical resonator 80a and the optical resonator 80b in the optical filter 14 shown in fig. 29 may be set to 300um or 350um, so that the collimated light may just pass through the optical resonator 8080a and the optical resonator 80b.

In the optical filter 14 shown in fig. 29, when the distance between the first electrode and the second electrode in the optical resonator 80a is 0.3mm, the cavity length of the optical resonator 80a is 89um, the distance between the first electrode and the second electrode in the optical resonator 80b is 0.3mm, and the cavity length of the optical resonator 80b is 99um, and when the wavelength of the light received by the optical fiber collimator 70a is 1524nm to 1572nm and the total wavelength range is 48nm of the input light, the filtered light outputted from the optical fiber collimator 70b is as shown in fig. 30, and the abscissa represents the wavelength (wavelength, expressed in terms of WL, in terms of nanometers (nm)) of the output filtered light outputted from the optical fiber collimator 70b, and the ordinate represents the Insertion Loss (expressed in terms of IL, expressed in terms of decibels (dB)) of the output filtered light outputted from the optical fiber collimator 70 b. Wherein the wavelength of the output filtered light outputted from the optical fiber collimator 70b is approximately 1543nm, 1548nm and 1553nm, and the insertion loss (i.e. the energy loss of the light) of the output filtered light with the wavelength of approximately 1543nm is-32 dB, i.e. the energy of the output filtered light with the wavelength of 1543nm is less than 0.1% of the energy of the input light; the insertion loss of the output filtered light with the wavelength of about 1548nm is-2 dB, that is, the energy of the output filtered light with the wavelength of 1548nm is more than 63% of the energy of the input light, and the output filtered light is the output filtered light which can be obtained and is output by the optical filter 130; the insertion loss of the output filtered light with the wavelength of approximately 1553nm is approximately-32 dB, namely the energy of the output filtered light with the wavelength of 1553nm is less than 0.1% of the energy of the input light. Then, it is considered that the optical filter 14 can filter out the single output filtered light having a wavelength of 1548nm from the input light having a wavelength range of 48nm, and the insertion loss of the single output filtered light having a wavelength of approximately 1548nm can be controlled within 5dB or even 3dB, the insertion loss of the disturbing light is less than-28 dB, and the bandwidth of the single output filtered light having a wavelength of approximately 1548nm is less than 0.1nm.

By way of example, referring to fig. 31, an embodiment of the present application provides another optical filter 15, shown in fig. 31 in a top view and fig. 31 in a front view, (a) and fig. 31 in a front view, the optical filter 15 is different from the optical filter 14 described above in that specific structures of an optical resonator 80a and an optical resonator 80b in the optical filter 14 are shown in fig. 6, and specific structures of the optical resonator 80a and the optical resonator 80b in the optical filter 15 are shown in fig. 24. The working principle of which is referred to the working principle of the optical filter 14 and is not described in detail here.

As an example, referring to fig. 32, the embodiment of the present application provides (a) in fig. 32 and (b) in fig. 32 in a top view and a front view of another optical filter 16, where the optical filter 16 is different from the optical filter 14 described above in that specific structures of an optical resonant cavity 80a and an optical resonant cavity 80b in the optical filter 14 are shown in fig. 6, and specific structures of the optical resonant cavity 80a and the optical resonant cavity 80b in the optical filter 16 are shown in fig. 20, and the working principle thereof is not repeated herein with reference to the working principle of the optical filter 14.

As an example, referring to fig. 33, the embodiment of the present application provides (a) in fig. 33 and (b) in fig. 33 in a top view and a front view of another optical filter 17, where the optical filter 17 is different from the optical filter 14 described above in that specific structures of an optical resonant cavity 80a and an optical resonant cavity 80b in the optical filter 14 are shown in fig. 6, and specific structures of the optical resonant cavity 80a and the optical resonant cavity 80b in the optical filter 17 are shown in fig. 22, and the working principle thereof is not repeated herein with reference to the working principle of the optical filter 14.

By way of example, referring to fig. 34, an embodiment of the present application provides (a) in fig. 34 and (b) in fig. 34 in a top view of another optical filter 18, the optical filter 18 differs from the optical filter 14 described above in that the plurality of optical resonators in the optical filter 14 includes an optical resonator 80a and an optical resonator 80b, and a reflective element 90b is present in the optical filter 14; the plurality of optical resonators in the optical filter 18 includes an optical resonator 80a, an optical resonator 80b, and an optical resonator 80c, and the reflecting element 90b is not present in the optical filter 18, and the working principle thereof is referred to the working principle of the optical filter 14 and is not described herein.

Note that, since the electric field directions of the optical resonator 80a and the optical resonator 80b shown in fig. 10 and 22 have a slight deviation from the electric field directions of the optical resonator 80a and the optical resonator 80b shown in fig. 6 or 14, in the optical filter 16 and the optical filter 17, in order to reduce the problem of the change of the filtering effect due to the electric field directions, the incident angle of the second light ray of the collimated light ray and the third light ray of the collimated light ray to the plurality of optical resonators 80 may be adjusted by fine adjustment so that the polarization direction of the second light ray of the collimated light ray incident on the optical resonator 80a and the polarization direction of the third light ray of the collimated light ray are completely parallel to the electric field direction of the optical resonator 80 a.

In order to enable the optical filter to filter light of a larger wavelength range, the embodiment of the present application further provides an optical filter, and referring to fig. 35, the optical filter 21 includes an optical fiber collimator 70a located at an input side, an optical fiber collimator 70b located at an output side, and an optical fiber collimator 2103 located at an output side (instead, "output side"), a polarization beam splitting element 100a disposed on an optical path between the optical fiber collimator 70a and the optical fiber collimator 70b, a plurality of optical resonator cavities 80, a reflecting element 90a, a polarization beam combining element 110a, and a band splitting diaphragm 120; a polarization beam splitting element 100a, a plurality of optical resonators 80, a reflecting element 90a, a polarization beam combining element 110a, a band splitting diaphragm 120, and a reflecting mirror 130, which are disposed on the optical path between the fiber collimator 70a and the fiber collimator 2103. Specifically, the plurality of optical resonators 80 includes an optical resonator 80a, an optical resonator 80b, and an optical resonator 80c. In order to make the free spectral ranges of any two of the plurality of optical resonators 80 different, it is necessary to make the cavity lengths of any two of the plurality of optical resonators 80 different.

Illustratively, optical cavity 80a may be any of optical cavities 60 described above, optical cavity 80b may be any of optical cavities 60 described above, and optical cavity 80c may be any of optical cavities 60 described above.

In the optical filter 21, the optical fiber collimator 70a receives the light including the C-band light and the first light including the L-band light transmitted by the optical fiber 701a, for example, the light including the light having a wavelength range of 48nm and a wavelength range of 1524nm to 1572 nm; the L-band light includes light having a wavelength in the range of 50nm and a wavelength in the range of 1575nm to 1625 nm. The fiber collimator 1601 collimates the received light of the C-band and the light of the L-band, and generates collimated light including the light of the C-band and the light of the L-band.

The polarization beam splitting element 100a is configured to separate a second light ray (for example, S polarized light, where the first polarized direction is the polarization direction of the S polarized light) having a first polarized direction from a third light ray (for example, P polarized light, where the second polarized direction is the polarization direction of the P polarized light) having a second polarized direction in the collimated light rays, set the polarization direction of the second light ray in the collimated light rays to be the second polarized direction, sequentially pass through the plurality of optical resonator cavities 80 along a first direction (-x-direction +x direction), and sequentially pass through the plurality of optical resonator cavities 80 along the first direction (-x-direction +x direction). Wherein the second light of the collimated light includes light of the C-band and light of the L-band, and the third light of the collimated light includes light of the C-band and light of the L-band.

A plurality of optical resonators 80 for performing a filtering process on the second light of the aligned light to generate a second light including the first filtered light of the predetermined wavelength; and filtering the third light ray of the aligned light rays to generate third light rays containing the first filtered light rays with the preset wavelength. Specifically, the optical resonator 80a is configured to perform a first filtering process on the second light of the collimated light; an optical resonator 80b for performing a second filtering process on a second light ray of the collimated light ray; the optical resonator 80c is configured to perform a third filtering process on the second light of the collimated light, so as to generate a second light including the first filtered light with the predetermined wavelength. An optical resonator 80a for performing a first filtering process on a third light ray of the collimated light ray; an optical resonator 80b for performing a second filtering process on a third light ray of the collimated light ray; the optical resonator 80c is configured to perform a third filtering process on the third light of the collimated light, so as to generate a third light including the first filtered light with the predetermined wavelength. Wherein the second light of the first filtered light includes light of certain wavelengths in the C-band light and light of certain wavelengths in the L-band light, and the third light of the first filtered light includes light of certain wavelengths in the C-band light and light of certain wavelengths in the L-band light.

A reflecting element 90a for reflecting the second light of the first filtered light to the plurality of optical resonators 80 such that the second light of the first filtered light sequentially passes through the plurality of optical resonators 80 in a second direction (i.e., the direction in which x is directed to-x), the second direction being opposite to the first direction; and also to reflect a third light of the first filtered light such that the third light of the first filtered light passes sequentially through the plurality of optical resonators 80 in the second direction (i.e., the x-direction).

A plurality of optical resonators 80 for filtering the second light of the first filtered light reflected by the reflecting element 90a to generate a second light including an output filtered light of a predetermined wavelength; the third light of the first filtered light reflected by the reflecting element 90a is subjected to a filtering process to generate a third light including an output filtered light of a predetermined wavelength. Specifically, the optical resonator 80a is configured to perform a first filtering process on a second light of the first filtered light; an optical resonator 80b for performing a second filtering process on a second light of the first filtered light; the optical resonator 80c is configured to perform a third filtering process on the second light of the first filtered light, so as to generate a second light including the output filtered light with the predetermined wavelength. An optical resonator 80a for performing a first filtering process on a third light ray of the first filtered light ray; an optical resonator 80b for performing a second filtering process on a third light of the first filtered light; the optical resonator 80c is configured to perform a third filtering process on the third light of the first filtered light, so as to generate a third light including the output filtered light with the predetermined wavelength. Wherein the second light of the output filtered light includes light of a predetermined wavelength in the light of the C-band and light of a predetermined wavelength in the light of the L-band, and the third light of the output filtered light includes light of a predetermined wavelength in the light of the C-band and light of a predetermined wavelength in the light of the L-band.

The polarization beam combining element 110a is configured to set a polarization direction of the second light beam of the output filtered light beam to be a first polarization direction, and is further configured to combine the second light beam of the output filtered light beam with a third light beam of the output filtered light beam to be the output filtered light beam. Wherein the output filtered light includes light of certain wavelengths in the C-band light and light of predetermined wavelengths in the L-band light.

A band separating diaphragm 120 for transmitting a predetermined wavelength of light among the light belonging to the C-band among the output filtered light to the optical fiber collimator 70b; and also serves to transmit a predetermined wavelength of light among the light belonging to the L-band among the output filtered light to the mirror 130.

The mirror 130 transmits the light belonging to the L-band among the third filtered light to the fiber collimator 70c.

The fiber collimator 70b is configured to couple light belonging to the C-band of the third filtered light to the output of the fiber 701 b.

The fiber collimator 70c is configured to couple light belonging to the L-band of the third filtered light to the output of the optical fiber 701 c.

It should be noted that, the optical filter 21 cannot filter the light of the C-band and the light of the L-band at the same time, so in practical applications, the light of the input C-band and the light of the L-band need to be filtered in different time periods, so that the electric field intensity of each of the plurality of optical resonators 80 is adjusted according to the currently input light of the C-band or the light of the L-band.

In some examples, the fiber collimator 70a, the fiber collimator 70b, and the fiber collimator 70c shown in fig. 35 may be replaced with one fiber collimator array. In the collimator array, at least 3 fiber collimators are included, and a first fiber collimator of the 3 fiber collimators is used for realizing the function of the fiber collimator 70 a; a second one of the 3 fiber collimators, for performing the function of fiber collimator 70 b; the third of the 3 fiber collimators is used to perform the function of fiber collimator 70 c.

For example, the above-mentioned band separating diaphragm 120 and the reflecting mirror 130 may be disposed in the optical filter 11, the optical filter 12, the optical filter 13, the optical filter 14, the optical filter 15, the optical filter 16 and the optical filter 17, so that the optical filter 11, the optical filter 12, the optical filter 13, the optical filter 14, the optical filter 15, the optical filter 16 and the optical filter 17 may also filter light rays of a larger wavelength range.

For example, referring to fig. 36, the band separating diaphragm 120 and the reflecting mirror 130 may be disposed between the optical fiber collimator 70a and the polarization beam splitting element 100a, in which case, the optical filter 21 needs to further include a polarization beam splitting element 100b and a polarization beam combining element 110b, where the polarization beam splitting element 100a and the polarization beam combining element 110a are used to process light rays of one band, and the polarization beam splitting element 100b and the polarization beam combining element 110b are used to process light rays of another band.

Illustratively, after the fiber collimator 70a receives the first light including the C-band light and the L-band light, the fiber collimator 70a collimates the C-band light and the L-band light to generate collimated light, and transmits the collimated light to the band split diaphragm 120. The collimated light rays comprise light rays in the C wave band and light rays in the L wave band.

The band separating film 120 is configured to transmit light of a C-band of the collimated light to the polarizing beam splitting element 100a, and the band separating film 120 is also configured to transmit light of an L-band of the collimated light to the reflecting mirror 130, so that the reflecting mirror 130 transmits light including the L-band of the collimated light to the polarizing beam splitting element 100b.

Then, the polarization beam splitting element 100a is configured to separate a second light ray (for example, S polarized light, where the first polarized direction is the polarization direction of the S polarized light) having a first polarization direction from a third light ray (for example, P polarized light, where the second polarized direction is the polarization direction of the P polarized light) having a second polarization direction in the C band light ray in the collimated light ray, set the polarization direction of the second light ray in the C band light ray in the collimated light ray to be the second polarized direction, sequentially pass through the plurality of optical resonant cavities 80 along a first direction (-x-direction +x direction) in the C band light ray in the collimated light ray, and sequentially pass through the plurality of optical resonant cavities 80 along the first direction (-x-direction +x direction) in the C band light ray in the collimated light ray.

The polarization beam splitting element 100b is configured to separate a second light ray (for example, S-polarized light, where the first polarization direction is the polarization direction of the S-polarized light) having a first polarization direction from a third light ray (for example, P-polarized light, where the second polarization direction is the polarization direction of the P-polarized light) having a second polarization direction in the L-band light of the collimated light, set the polarization direction of the second light ray in the L-band light of the collimated light to be the second polarization direction, sequentially pass through the plurality of optical resonant cavities 80 along a first direction (-x-pointing +x direction) in the L-band light of the collimated light, and sequentially pass through the third light ray in the L-band light of the collimated light through the plurality of optical resonant cavities 80 along the first direction (-x-pointing +x direction).

That is, light rays of different wavebands are transmitted to the plurality of optical resonators 80 and the reflecting element 90a through different polarization beam combining elements; then, the output filtered light belonging to the C-band is transmitted to the fiber collimator 70b through the polarization beam combining element 110a, and the output filtered light belonging to the C-band is coupled to the fiber 701b by the fiber collimator 70b for output; the output filtered light belonging to the L-band is transmitted to the fiber collimator 70c through the polarization beam combining element 110b, and the output filtered light belonging to the L-band is coupled to the fiber 701c for output by the fiber collimator 70 c.

In the optical filter 21, when the transverse electro-optic effect of the material used for the electro-optic crystal in each of the optical resonators 80 is similar to the longitudinal electro-optic effect, the polarizing beam splitting element and the polarizing beam combining element may not be provided, and the number and types of the elements included in the optical filter are not limited in the embodiments of the present application.

Illustratively, the optical filter 21 shown in fig. 35 is used to filter the light in the C-band and the light in the L-band received by the optical collimator 70a, wherein the light in the C-band includes light in a wavelength range of 48nm and a wavelength range of 1524nm to 1572 nm; the L-band light includes light having a wavelength in the range of 50nm and a wavelength in the range of 1575nm to 1625 nm. In the optical filter 21 shown in fig. 35, the distance between the first electrode and the second electrode in the optical resonator 80a is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80a is 15 volts (V), and the cavity length of the optical resonator 80a is 146.3um; the distance between the first electrode and the second electrode in the optical resonator 80b is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80b is 22.3V, and the cavity length of the optical resonator 80b is 155.9um; the distance between the first electrode and the second electrode in the optical resonator 80c was 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80c was 1V, and the cavity length of the optical resonator 80c was 174.8um. In this example, when the plurality of optical resonators filter the light in the C-band, the wavelengths of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70C are shown with reference to fig. 27, and in fig. 37, the abscissa indicates the wavelength (WL in nm) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70C, and the ordinate indicates the insertion loss (IL in dB) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 2103. Wherein the wavelength of the output filtered light outputted by the optical fiber collimator 70b is between 1524nm and 1572nm, and the wavelength of the output filtered light outputted by the optical fiber collimator 70c is between 1575nm and 1625 nm. The insertion loss of the output filtered light with the wavelength of 1524nm is approximately-2 dB, which indicates that the current optical filter 210 can filter out a single output filtered light in the C-band. And in this example, output filtered rays will also appear for rays belonging to the L-band, but these output filtered rays are all less than-12 dB in insertion loss.

Illustratively, the optical filter 21 shown in fig. 35 is used to filter the light in the C-band and the light in the L-band received by the optical collimator 70a, wherein the light in the C-band includes light in a wavelength range of 48nm and a wavelength range of 1524nm to 1572 nm; the L-band light includes light having a wavelength in the range of 50nm and a wavelength in the range of 1575nm to 1625 nm. In the optical filter 21 shown in fig. 35, the distance between the first electrode and the second electrode in the optical resonator 80a is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80a is 18 volts (V), and the cavity length of the optical resonator 80a is 146.3um; the distance between the first electrode and the second electrode in the optical resonator 80b is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80b is 36.5V, and the cavity length of the optical resonator 80b is 155.9um; the distance between the first electrode and the second electrode in the optical resonator 80c is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80c is 48.5V, and the cavity length of the optical resonator 80c is 174.8um. In this example, when the plurality of optical resonators filter the light in the C-band, the wavelengths of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70C are shown with reference to fig. 24, and in fig. 38, the abscissa represents the wavelength (WL in nanometer (nm)) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70C, and the ordinate represents the insertion loss (IL in dB) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70C. Wherein the wavelength of the output filtered light outputted by the optical fiber collimator 70b is between 1524nm and 1572nm, and the wavelength of the output filtered light outputted by the optical fiber collimator 70c is between 1575nm and 1625 nm. The insertion loss of the output filtered light with the wavelength of 1543.4nm belonging to the C-band is approximately-2 dB, and the insertion loss of other output filtered light is less than-36 dB, which means that the current optical filter 21 can filter out a single output filtered light in the C-band. And in this example, output filtered rays will also appear for rays belonging to the L-band, but these output filtered rays are all less than-18 dB in insertion loss.

Illustratively, the optical filter 21 shown in fig. 35 is used to filter the light in the C-band and the light in the L-band received by the optical collimator 70a, wherein the light in the C-band includes light in a wavelength range of 48nm and a wavelength range of 1524nm to 1572 nm; the L-band light includes light having a wavelength in the range of 50nm and a wavelength in the range of 1575nm to 1625 nm. In the optical filter 21 shown in fig. 35, the distance between the first electrode and the second electrode in the optical resonator 80a is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80a is 28 volts (V), and the cavity length of the optical resonator 80a is 146.3um; the distance between the first electrode and the second electrode in the optical resonator 80b is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80b is 9V, and the cavity length of the optical resonator 80b is 155.9um; the distance between the first electrode and the second electrode in the optical resonator 80c is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80c is 51.2V, and the cavity length of the optical resonator 80c is 174.8um. In this example, when the plurality of optical resonators filter the light in the C-band, the wavelengths of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70C are shown with reference to fig. 39, and in fig. 39, the abscissa indicates the wavelength (WL in nm) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70C, and the ordinate indicates the insertion loss (IL in dB) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70C. Wherein the wavelength of the output filtered light outputted by the optical fiber collimator 70b is between 1524nm and 1572nm, and the wavelength of the output filtered light outputted by the optical fiber collimator 70c is between 1575nm and 1625 nm. The insertion loss of the output filtered light rays with the wavelength of 1562nm belonging to the C-band is approximately-2 dB, and the insertion loss of other output filtered light rays is less than-36 dB, which means that the current optical filter 21 can filter out a single output filtered light ray in the C-band. And in this example, output filtered rays will also appear for rays belonging to the L-band, but these output filtered rays are all less than-20 dB in insertion loss.

Illustratively, the optical filter 21 shown in fig. 35 is used to filter the light in the C-band and the light in the L-band received by the optical collimator 70a, wherein the light in the C-band includes light in a wavelength range of 48nm and a wavelength range of 1524nm to 1572 nm; the L-band light includes light having a wavelength in the range of 50nm and a wavelength in the range of 1575nm to 1625 nm. In the optical filter 21 shown in fig. 35, the distance between the first electrode and the second electrode in the optical resonator 80a is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80a is 15V, and the cavity length of the optical resonator 80a is 146.3um; the distance between the first electrode and the second electrode in the optical resonator 80b is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80b is 24.5V, and the cavity length of the optical resonator 80b is 155.9um; the distance between the first electrode and the second electrode in the optical resonator 80c was 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80c was 3V, and the cavity length of the optical resonator 80c was 174.8um. In this example, when the plurality of optical resonators filter light in the L-band, the wavelengths of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70c are shown with reference to fig. 40, and in fig. 40, the abscissa indicates the wavelength (WL in nm) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70c, and the ordinate indicates the insertion loss (IL in dB) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70 c. Wherein the wavelength of the output filtered light outputted by the optical fiber collimator 70b is between 1524nm and 1572nm, and the wavelength of the output filtered light outputted by the optical fiber collimator 70c is between 1575nm and 1625 nm. The insertion loss of the output filtered light rays with the wavelength of 1574nm belonging to the L-band is approximately-2 dB, and the insertion loss of other output filtered light rays is less than-36 dB, which means that the current optical filter 21 can filter out a single output filtered light ray in the L-band. And in this example, output filtered rays will also appear for rays belonging to the C-band, but these output filtered rays are all less than-12 dB in insertion loss.

Illustratively, the optical filter 21 shown in fig. 35 is used to filter the light in the C-band and the light in the L-band received by the optical collimator 70a, wherein the light in the C-band includes light in a wavelength range of 48nm and a wavelength range of 1524nm to 1572 nm; the L-band light includes light having a wavelength in the range of 50nm and a wavelength in the range of 1575nm to 1625 nm. In the optical filter 21 shown in fig. 35, the distance between the first electrode and the second electrode in the optical resonator 80a is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80a is 18V, and the cavity length of the optical resonator 80a is 146.3um; the distance between the first electrode and the second electrode in the optical resonator 80b is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80b is 40.5V, and the cavity length of the optical resonator 8080b is 155.9um; the distance between the first electrode and the second electrode in the optical resonator 8080c was 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80c was 53V, and the cavity length of the optical resonator 80c was 174.8um. In this example, when the plurality of optical resonators filter light in the L-band, the wavelengths of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70c are shown with reference to fig. 41, and in fig. 41, the abscissa indicates the wavelength (WL in nm) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70c, and the ordinate indicates the insertion loss (IL in dB) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70 c. Wherein the wavelength of the output filtered light outputted from the fiber collimator 70b is between 1524nm and 1572nm, and the wavelength of the output filtered light outputted from the fiber collimator 2103 is between 1575nm and 1625 nm. The insertion loss of the output filtered light with the wavelength of 1594nm belonging to the L-band is approximately-2 dB, and the insertion loss of other output filtered light is less than-36 dB, which means that the current optical filter 21 can filter out a single output filtered light in the L-band. And in this example, output filtered rays will also appear for rays belonging to the C-band, but these output filtered rays are all less than-20 dB in insertion loss.

Illustratively, the optical filter 21 shown in fig. 35 is used to filter the light in the C-band and the light in the L-band received by the optical collimator 70a, wherein the light in the C-band includes light in a wavelength range of 48nm and a wavelength range of 1524nm to 1572 nm; the L-band light includes light having a wavelength in the range of 50nm and a wavelength in the range of 1575nm to 1625 nm. In the optical filter 21 shown in fig. 35, the distance between the first electrode and the second electrode in the optical resonator 80a is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80a is 28V, and the cavity length of the optical resonator 80a is 146.3um; the distance between the first electrode and the second electrode in the optical resonator 80b is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80b is 11V, and the cavity length of the optical resonator 80b is 155.9um; the distance between the first electrode and the second electrode in the optical resonator 80c is 0.3mm, the voltage between the first electrode and the second electrode of the optical resonator 80c is 55.5V, and the cavity length of the optical resonator 80c is 174.8um. In this example, when the plurality of optical resonators filter light in the L-band, the wavelengths of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70c are shown with reference to fig. 42, and in fig. 42, the abscissa indicates the wavelength (WL in nm) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70c, and the ordinate indicates the insertion loss (IL in dB) of the output filtered light outputted from the optical fiber collimator 70b and the optical fiber collimator 70 c. Wherein the wavelength of the output filtered light outputted by the optical fiber collimator 70b is between 1524nm and 1572nm, and the wavelength of the output filtered light outputted by the optical fiber collimator 70c is between 1575nm and 1625 nm. The insertion loss of the output filtered light with the wavelength of 1614.8nm belonging to the L-band is approximately-2 dB, and the insertion loss of other output filtered light is less than-36 dB, which means that the current optical filter 21 can filter out a single output filtered light in the L-band. And in this example, output filtered rays will also appear for rays belonging to the C-band, but these output filtered rays are all less than-18 dB in insertion loss.

Illustratively, referring to fig. 43, in order to implement the filtering process for the light of the C-band and the light of the L-band, the embodiment of the present application further provides a filtering system, and referring to fig. 43, the filtering system 31 includes an inter-band filter 311, an optical filter 312, and an optical filter 313. Wherein an input of the inter-band filter 311 is connected to an optical fiber 314, a first output of the inter-band filter 311 is connected to an optical filter 312, and a second output of the inter-band filter 311 is connected to an optical filter 313. The optical fiber 314 transmits input light, wherein the input light comprises light in a C wave band and light in an L wave band; the inter-band filter transmits the light of the C-band in the input light to the optical filter 312 through the first output end, so that the optical filter 312 performs filtering processing on the light of the C-band and outputs the filtered light of the C-band; the inter-band filter transmits the L-band light of the input light to the optical filter 313 through the second output end, so that the optical filter 313 performs filtering processing on the L-band light and outputs the L-band filtered light. The optical filter 312 may be any one of the optical filters 11, 12, 13, 14, 15, 16, 17, and 18 described above; the optical filter 313 may be any one of the optical filters 11, 12, 13, 114, 15, 16, 17, and 18 described above.

The filtering system 31 may include only one optical filter, and as shown in fig. 44, the filtering system 32 may include an inter-band filter 321, an optical switch 322, an optical switch 323, and an optical filter 324. Wherein an input end of the inter-band filter 321 is connected to the optical fiber 325, a first output end of the inter-band filter 321 is connected to the optical filter 324 through the optical switch 322, and a second output end of the inter-band filter 321 is connected to the optical filter 324 through the optical switch 323. The optical fiber 325 transmits an input light, where the input light includes a light of a C-band and a light of an L-band; when the optical switch 322 is turned on and the optical switch 323 is turned off, the inter-band filter 321 transmits the light of the C-band of the input light to the optical filter 324 through the optical switch 322, so that the optical filter 324 performs filtering processing on the light of the C-band; when the optical switch 322 is turned off and the optical switch 323 is turned on, the inter-band filter 321 transmits the L-band light of the input light to the optical filter 324 through the optical switch 323, so that the optical filter 324 performs the filtering process on the C-band light. The optical filter 324 may be any one of the optical filters 11, 12, 13, 14, 15, 16, 17, and 18 described above.

Although the invention has been described in connection with specific features and embodiments thereof, it will be apparent that various modifications and combinations can be made without departing from the spirit and scope of the invention. Accordingly, the specification and drawings are merely exemplary illustrations of the present invention as defined in the appended claims and are considered to cover any and all modifications, variations, combinations, or equivalents that fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. An optical resonator, comprising:

an electro-optic crystal; a first reflective film and a second reflective film, wherein the first reflective film and the second reflective film are respectively disposed on both sides of the electro-optic crystal along a propagation direction of the electro-optic crystal; a first electrode and a second electrode, wherein the first electrode and the second electrode are arranged on the electro-optic crystal, and an electric field applied to the electro-optic crystal by the first electrode and the second electrode is used for adjusting the refractive index of the electro-optic crystal; the electric field has a component perpendicular to the propagation direction;

The first reflective film is used for transmitting input light rays to the electro-optical crystal in the propagation direction;

the electro-optical crystal is used for transmitting the light transmitted by the first reflecting film to the second reflecting film with a preset refractive index under the action of the electric field;

the second reflection film is used for outputting light rays with a preset wavelength in the light rays transmitted by the electro-optical crystal and reflecting the light rays with other wavelengths except the preset wavelength to the electro-optical crystal;

the electro-optical crystal is further used for transmitting the light reflected by the second reflecting film to the first reflecting film at the preset refractive index;

the first reflecting film is also used for reflecting the light transmitted by the electro-optical crystal to the electro-optical crystal.

2. The optical resonator according to claim 1, characterized in that,

the first electrode and the second electrode are respectively arranged at two sides of the electro-optic crystal in parallel to the propagation direction.

3. The optical resonator according to claim 1, characterized in that,

the electro-optic crystal includes: an incident surface located on the light-incident side and an exit surface located on the light-exit side in the propagation direction;

the incident surface comprises a first light-transmitting area positioned at the center and a first light-non-transmitting area surrounding the first light-transmitting area; the emergent surface comprises a second light-transmitting area positioned at the center and a second non-light-transmitting area surrounding the second light-transmitting area; the first reflecting film is arranged in the first light-transmitting area, and the second reflecting film is arranged in the second light-transmitting area; the first electrode and the second electrode are arranged in the first non-light-transmitting area; alternatively, the first electrode and the second electrode are disposed in the second non-light-transmitting region.

4. An optical resonator according to claim 3, characterized in that,

the first non-light-transmitting area comprises a first area and a second area which are symmetrically distributed by taking the first light-transmitting area as a center;

the second non-light-transmitting area comprises a third area and a fourth area which are symmetrically distributed by taking the second light-transmitting area as a center; wherein, along the propagation direction, the first region overlaps the third region, and the second region overlaps the fourth region;

the first electrode is arranged in the first area, and the second electrode is arranged in the fourth area; alternatively, the first electrode is disposed in the second region, and the second electrode is disposed in the third region.

5. The optical resonator according to claim 4, characterized in that,

the first electrode includes a first portion and a second portion; the second electrode includes a third portion and a fourth portion;

a first part of the first electrode is arranged in the first area, and a second part of the first electrode is arranged in the third area; a third part of the second electrode is arranged in the second area, and a fourth part of the second electrode is arranged in the fourth area;

The first part and the second part of the first electrode are electrically connected through a wire; the third portion and the fourth portion of the second electrode are electrically connected by a wire.

6. An optical resonator according to any of claims 1-5, characterized in that,

the distance between the first electrode and the second electrode is 2 mm or less in a direction perpendicular to the propagation direction.

7. The optical resonator according to any of claims 1-6, further comprising: the temperature control structure comprises a temperature control structure and a temperature control structure,

the temperature control structure applies a temperature to the electro-optic crystal to adjust a refractive index of the electro-optic crystal.

8. The optical resonator according to claim 7, characterized in that,

the temperature control structure is arranged on one side of the first reflecting film far away from the electro-optic crystal; and/or the temperature control structure is arranged on one side of the second reflecting film far away from the electro-optical crystal.

9. The optical resonator according to claim 7, characterized in that,

the temperature control structure is arranged on one side of the electro-optic crystal along the direction parallel to the propagation direction, and/or the temperature control structure is arranged on the other side of the electro-optic crystal along the direction parallel to the propagation direction.

10. The optical resonator according to any of claims 7-9, wherein the temperature-controlled structure comprises a light-transmissive resistive film.

11. The optical resonator according to claim 10, wherein the resistive film material comprises: indium tin oxide.

12. An optical resonator according to any of claims 1-11, characterized in that,

in the propagation direction, the distance between the first reflecting film and the second reflecting film is the cavity length of the optical resonant cavity; the cavity length is greater than or equal to 50 microns and less than or equal to 300 microns.

13. An optical resonator according to any of claims 1-12, characterized in that,

the material of the electro-optic crystal comprises any one of the following materials: lithium niobate, lanthanum doped lead zirconate titanate, lead magnesium niobate-lead titanate, potassium niobium tantalate.

14. An optical resonator according to any of claims 1-13, characterized in that,

the material of the first electrode includes any one of the following: gold, indium tin oxide;

the material of the second electrode comprises any one of the following materials: gold, indium tin oxide.

15. An optical filter, comprising: a first optical fiber collimator, a second optical fiber collimator, and a plurality of optical resonant cavities and a first reflecting element disposed on an optical path between the first optical fiber collimator and the second optical fiber collimator;

The first optical fiber collimator is used for carrying out collimation treatment on the received first light to generate collimated light, and the collimated light sequentially passes through the plurality of optical resonant cavities along a first direction;

the plurality of optical resonant cavities are used for carrying out filtering treatment on the collimated light rays and generating first filtering light rays with preset wavelengths; any two optical resonant cavities in the plurality of optical resonant cavities have different cavity lengths;

the first reflecting element is configured to reflect the first filtered light to the plurality of optical resonant cavities, so that the first filtered light sequentially passes through the plurality of optical resonant cavities along a second direction, and the second direction is opposite to the first direction;

the plurality of optical resonant cavities are further used for performing filtering processing on the first filtered light rays reflected by the first reflecting element to generate output filtered light rays containing the preset wavelength;

the second fiber collimator is used for coupling the output filtered light to the first fiber output.

16. The optical filter of claim 15, wherein the optical path between the first fiber collimator and the second fiber collimator further comprises: a second reflective element;

The plurality of optical resonant cavities are specifically configured to perform filtering processing on the first filtered light reflected by the first reflecting element, so as to generate a second filtered light containing the predetermined wavelength;

the second reflecting element is configured to reflect the second filtered light to the plurality of optical resonant cavities, so that the second filtered light sequentially passes through the plurality of optical resonant cavities along the first direction;

the plurality of optical resonant cavities are further configured to perform filtering processing on the second filtered light reflected by the second reflecting element, so as to generate the output filtered light containing the predetermined wavelength.

17. The optical filter of claim 15 or 16, wherein the optical path between the first fiber collimator and the second fiber collimator further comprises: a polarization beam splitting element and a polarization beam combining element; on the optical path, the polarization beam splitting element is positioned between the first optical fiber collimator and the plurality of optical resonant cavities, and the polarization beam combining element is positioned between the plurality of optical resonant cavities and the second optical fiber collimator;

the polarization beam splitting element is used for separating second light rays with a first polarization direction from third light rays with a second polarization direction in the collimated light rays, wherein the first polarization direction and the second polarization direction are different;

The polarization beam splitting element is further configured to set a polarization direction of the second light to the second polarization direction;

the polarization beam combining element is configured to set a polarization direction of the second light ray or the third light ray of the output filtered light ray to the first polarization direction;

the polarization beam combining element is further configured to combine the second light ray of the output filtered light ray and the third light ray of the output filtered light ray into the output filtered light ray.

18. The optical filter of any of claims 15-17, further comprising: a band separation membrane, a first mirror, and a third fiber collimator; on the optical path, the band separation membrane is positioned between the polarization beam combining element and the second optical fiber collimator;

the wave band separation membrane is used for transmitting the light belonging to the first wave band in the output filtering light to the second optical fiber collimator;

the second optical fiber collimator is used for coupling light rays belonging to a first wave band in the output filtering light rays to the first optical fiber output;

the wave band separating diaphragm is further used for transmitting light belonging to a second wave band in the output filtering light to the first reflecting mirror;

The first reflecting mirror is used for transmitting light belonging to a second wave band in the output filtering light to the third optical fiber collimator;

and the third optical fiber collimator is used for coupling the light belonging to the second wave band in the output filtered light to the second optical fiber output.

19. An optical filter as claimed in any one of claims 15 to 18, wherein,

the first reflecting element comprises a second reflecting mirror and a third reflecting mirror;

the second reflector is used for receiving the first filtered light and reflecting the first filtered light to the third reflector;

the third reflector is configured to reflect the first filtered light reflected by the second reflector to the plurality of optical resonant cavities, where an included angle between the second reflector and the third reflector is greater than or equal to 89.5 degrees and less than or equal to 90.5 degrees;

or,

the first reflecting element comprises a first right angle prism; the first right angle prism comprises a first right angle surface and a second right angle surface;

the first right-angle surface is used for receiving the first filtered light and reflecting the first filtered light to the second right-angle surface;

the second right angle surface is configured to reflect the first filtered light reflected by the first right angle surface to the plurality of optical resonant cavities, where an included angle between the first right angle surface and the second right angle surface is greater than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

20. The optical filter of any of claims 16-19, wherein,

the second reflecting element comprises a fourth reflecting mirror and a fifth reflecting mirror;

the fourth reflecting mirror is used for receiving the second filtering light and reflecting the second filtering light to the fifth reflecting mirror;

the fifth reflecting mirror is configured to reflect the second filtered light reflected by the fourth reflecting mirror to the plurality of optical resonant cavities, where an included angle between the fourth reflecting mirror and the fifth reflecting mirror is greater than or equal to 89.5 degrees and less than or equal to 90.5 degrees;

or,

the second reflecting element comprises a second right angle prism, and the second right angle prism comprises a third right angle surface and a fourth right angle surface;

the third right-angle surface is used for receiving the second filtered light and reflecting the second filtered light to the fourth right-angle surface;

the fourth right angle surface is configured to reflect the second filtered light reflected by the third right angle surface to the plurality of optical resonant cavities, where an included angle between the third right angle surface and the fourth right angle surface is greater than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

21. The optical filter of any of claims 15-20, wherein any two of the plurality of optical resonators have a difference in cavity length of 5 microns or greater.

22. The optical filter of any of claims 15-21, wherein the plurality of optical resonators includes an optical resonator of any of claims 1-14.

23. A filtering system comprising an inter-band filter and two optical filters according to any of claims 15-22;

a first output end of the inter-band filter is connected to the first optical filter, and a second output end of the inter-band filter is connected to the second optical filter;

the inter-band filter is configured to receive light of a first band and light of a second band, transmit the light of the first band to the first optical filter through the first output end, and transmit the light of the second band to the second optical filter through the second output end;

the first optical filter is configured to filter the light of the first band and output the filtered light of the first band;

the second optical filter is configured to filter the light in the second band, and output the filtered light in the second band.

24. A filter system comprising an inter-band filter, a first switch, a second switch, and an optical filter according to any of claims 15-22;

A first output end of the inter-band filter is connected to the optical filter through the first switch, and a second output end of the inter-band filter is connected to the optical filter through the second switch;

the inter-band filter is used for receiving light rays of a first wave band and light rays of a second wave band; transmitting the light of the first wave band to the optical filter through the first switch when the first switch is turned on and the second switch is turned off; transmitting the light of the second wave band to the optical filter through the second switch when the first switch is closed and the second switch is opened;

the optical filter is used for filtering the light rays of the first wave band and outputting the filtered light rays of the first wave band;

the optical filter is further configured to filter the light of the second band, and output the filtered light of the second band.