CN213843577U

CN213843577U - Band-pass filter with linearly-changed insertion loss

Info

Publication number: CN213843577U
Application number: CN202022189522.4U
Authority: CN
Inventors: 苏炎; 李昱; 陈居凯
Original assignee: Suzhou Zhongwei Photoelectric Co ltd
Current assignee: Suzhou Zhongwei Photoelectric Co ltd
Priority date: 2020-09-29
Filing date: 2020-09-29
Publication date: 2021-07-30
Anticipated expiration: 2030-09-29

Abstract

The utility model provides a linear change's of insertion loss band pass filter, include the basic unit and pile up the membrane system in the basic unit, the membrane system structure of membrane system includes a plurality of fabry-perot chamber and articulamentum, and every fabry-perot chamber cascades next fabry-perot chamber through the articulamentum, and the articulamentum is the low refracting index layer of the optical thickness of non-quarter wavelength. The utility model discloses a passband insertion loss or transmissivity have the linear variation, realized in the passband that the insertion loss is the linear variation along with the wavelength in specific wavelength range, realized the function of wavelength discernment in specific wavelength range.

Description

Band-pass filter with linearly-changed insertion loss

Technical Field

The utility model relates to the field of optical technology, concretely relates to linear variable bandpass filter of insertion loss.

Background

Bandpass Filters (Bandpass Filters) only pass light of a particular wavelength or narrow band, and do not pass light outside the passband. The optical indexes of the band-pass filter are mainly as follows: center Wavelength (CWL), half bandwidth (FWHM). The method is divided into the following steps according to the bandwidth size: a narrow-band filter with the bandwidth less than 30 nm; the bandwidth is more than 60nm and is a broadband filter.

Bandpass filters are commonly used in interferometers, imaging instruments, inspection instruments, data centers, optical communications, industrial lasers, and wavelength identification.

The devices currently used for wavelength identification include grating devices, bandpass filter combination devices, and the like. The bandpass filter is generally applied to the use directions of light splitting and the like, the passband insertion loss or transmittance of the bandpass filter is generally required to be as flat as possible, the ripple wave is small, the bandpass filter is difficult to realize the linear change of the insertion loss along with the wavelength due to the characteristics of the bandpass filter, and the bandpass filter in the prior art can not realize the linear change of the insertion loss along with the wavelength in the passband.

SUMMERY OF THE UTILITY MODEL

To the weak point of prior art, the utility model aims to provide a band pass filter that insertion loss linear variation changes.

The technical scheme of the utility model outlines as follows:

the utility model provides a pass-band filter of insertion loss linear variation, including basic unit and the membrane system of piling up on the basic unit, the membrane system structure of membrane system includes a plurality of fabry-perot chamber and articulamentum, every fabry-perot chamber cascades next fabry-perot chamber through the articulamentum, the articulamentum is the low refractive index layer of the optical thickness of non-quarter wavelength;

the structure of the Fabry-Perot cavity is as follows: ahhlhl 4HLHLHLH, bhhlhl 4HLHL3HLHLH, chhlhl 4 hlhlhlhlh, dhhl 4HLHLA, wherein dhhl 4HLHLA is the last layer fabry-perot cavity;

h is a high refractive index layer of quarter-center wavelength optical thickness, L is a low refractive index layer of quarter-center wavelength optical thickness; 4H is the four quarter-center wavelength optical thicknesses, a is a high refractive index layer of non-quarter optical thickness; a. b, c, d are coefficients of the optical thickness of the quarter-center wavelength of the first high refractive index layer of each of said fabry-perot cavities.

Further, the coefficient of the quarter-center wavelength optical thickness of the first high index layer of the fabry-perot cavity is optimized by the optical thickness of the last layer of the last of the fabry-perot cavities.

Further, a, b, c and d are 0.974-1.015, the optical thickness of the quarter-wave center of the first high refractive index layer of the fabry-perot cavity is 0.974-1.015 quarter-wave optical thickness, so that the transmittance at the end of the layer reaches an extreme value, and an extreme value method is adopted for monitoring coating, so that the next film layer with the optical thickness of the quarter-wave of each layer can be monitored by the extreme value method.

Further, the optical thickness of the connecting layer is a non-integer number of quarter-wave optical thicknesses in the range of 0.675-2.451.

Further, the insertion loss of the optical filter increases or decreases linearly with the wavelength under the incident angle of 0-13.5 degrees.

Further, the insertion loss of the filter in the 1304.5-1317nm band is increased from-5 dB to-0.2 dB with the slope of 0.3846 dB/nm.

Further, the number of the fabry-perot cavities is 9.

Further, the material of the high-refractive-index layer is at least one of Ta2O5, Nb2O5 and TiO2, and the refractive index of the high-refractive-index layer is 1.85-2.5 in the range of 1304.5-1317 nm.

Further, the material of the low-refractive-index layer is at least one of SiO2, Al2O3 and MgF2, and the refractive index of the low-refractive-index layer ranges from 1.38 to 1.6 in the range from 1304.5 nm to 1317 nm.

Further, the base layer is a silicon dioxide material or a silicon material substrate, and the refractive index of the base layer is 1.45-3.5 in the range of 1304.5-1317 nm.

Compared with the prior art, the beneficial effects of the utility model reside in that:

the utility model provides a pair of insert and decrease linear change's band pass filter, this band pass filter's passband insertion loss or transmissivity have linear change, realized in the passband that the interpolation loss is linear change along with the wavelength in specific wavelength range, realize the function of wavelength discernment in specific wavelength range, for the technical scheme of grating and band pass filter composite member, have obvious advantage in the cost. The scheme can also be applied to the fields of interferometers, imaging instruments, detecting instruments, data centers, optical communication, industrial laser, wavelength identification and the like.

The above description is only an overview of the technical solution of the present invention, and in order to make the technical means of the present invention clearer and can be implemented according to the content of the description, the following detailed description is made with reference to the preferred embodiments of the present invention and accompanying drawings. The detailed description of the present invention is given by the following examples and the accompanying drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without undue limitation to the invention. In the drawings:

fig. 1 is a schematic diagram of a bandpass filter with linearly changing insertion loss according to the present invention;

FIG. 2 is a schematic diagram of a target slope in the present invention;

fig. 3 is a graph of the relationship between the wavelength of 8-degree incidence and the insertion loss and the target slope in the range of 0-30dB according to an embodiment of the bandpass filter with linearly changing insertion loss provided by the present invention;

fig. 4 is a graph of the relationship between the wavelength of 8-degree incidence and the insertion loss and the target slope in the range of 0-6dB according to an embodiment of the bandpass filter with linearly changing insertion loss provided by the present invention;

fig. 5 is a graph showing the relationship between the wavelength of 0 degree incidence and the insertion loss and the target slope in the range of 0-30dB for a bandpass filter with linearly changing insertion loss according to the present invention;

fig. 6 is a graph showing the relationship between the wavelength of 13.5 degree incidence and the insertion loss and the target slope in the range of 0-30dB for the bandpass filter with linearly changing insertion loss according to the present invention.

Reference numerals: 1. a base layer; 2. a high refractive index layer; 3. a low refractive index layer; 4. a connecting layer; 5. fabry-perot cavity.

Detailed Description

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a more detailed description of the present invention, which will enable those skilled in the art to make and use the present invention. In the drawings, the shape and size may be exaggerated for clarity, and the same reference numerals will be used throughout the drawings to designate the same or similar components. In the following description, terms such as center, thickness, height, length, front, back, rear, left, right, top, bottom, upper, lower, and the like are used based on the orientation or positional relationship shown in the drawings. In particular, "height" corresponds to the dimension from top to bottom, "width" corresponds to the dimension from left to right, and "depth" corresponds to the dimension from front to back. These relative terms are for convenience of description and are not generally intended to require a particular orientation. Terms concerning attachments, coupling and the like (e.g., "connected" and "attached") refer to a relationship wherein structures are secured or attached, either directly or indirectly, to one another through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.

The present invention will be further described with reference to the accompanying drawings and the detailed description, and it should be noted that any combination of the following embodiments or technical features can be used to form a new embodiment without conflict. It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.

Filters are optical devices used to select a desired wavelength band of radiation. The optical filter is formed by stacking a substrate and a plurality of film layers on the substrate, and the thickness of the film layers can be divided into two description modes of physical thickness and optical thickness. Physical thickness refers to thickness on a physical scale, such as 100nm or the like; the optical thickness refers to the path traveled by the light, which relates to the refractive index of the material through which the light travels and the wavelength of the light QW ═ n x d)/λ, where n is the refractive index of the material through which the light travels, d is the physical thickness, and λ is the wavelength of the light.

The devices currently used for wavelength identification include grating devices, bandpass filter combination devices, and the like. The bandpass filter is generally applied to the use directions of light splitting and the like, the passband insertion loss or transmittance of the bandpass filter is generally required to be as flat as possible, the ripple wave is small, the bandpass filter is difficult to realize the linear change of the insertion loss along with the wavelength due to the characteristics of the bandpass filter, and the bandpass filter in the prior art can not realize the linear change of the insertion loss along with the wavelength in the passband. Therefore, the present invention is to provide a bandpass filter with linearly changing insertion loss, which realizes that the insertion loss or transmittance linearly changes with the wavelength in a specific wavelength range in the passband, realizes the function of wavelength identification in the specific wavelength range, and can obtain the wavelength of the measuring light by measuring the size of the insertion loss value. Meanwhile, the characteristic of the band-pass filter can cut off the wavelength outside the band-pass with high isolation, and the influence of stray light on the test result is reduced.

As shown in fig. 1, the bandpass filter with linearly changing insertion loss of the present invention includes a base layer 1 and a film system stacked on the base layer, the film system structure of the film system includes a plurality of fabry-perot cavities 5 and a connecting layer 4, each fabry-perot cavity 5 is cascaded to the next fabry-perot cavity 5 through the connecting layer 4, and the connecting layer 4 is a low refractive index layer with optical thickness other than a quarter wavelength;

The insertion loss of the wavelength of the optical filter is increased or decreased linearly along with the wavelength under the incident angle of 0-13.5 degrees.

The insertion loss of the filter in the 1304.5-1317nm wave band range is increased from-5 dB to-0.2 dB with the slope of 0.3846 dB/nm.

The number of fabry-perot cavities is 9.

The factor of the optical thickness of the quarter-center wavelength of the first high-index layer of the fabry-perot cavity is optimized by the optical thickness of the last layer of the last of said fabry-perot cavities. a. b, c and d are integers of 1 or approximate 1. The purpose of this design is to better cascade with the connecting layer 4 (i.e. a refractive index layer that is not one-quarter of the optical thickness). And the optical thickness of approximate quarter wavelength is used for compensating the transmittance of the central wavelength at the end of the layer to reach an extreme value, and an extreme value method is adopted for monitoring in coating monitoring, so that the subsequent film layer with the optical thickness of the quarter wavelength of each layer can be monitored by the extreme value method, the optical thickness can be accurately controlled, and the optical filter with the accurate linear transmittance change can be obtained.

Specifically, a, b, c and d are 0.974-1.015, namely the optical thickness of the quarter-center wavelength of the first high-refractive-index layer of the Fabry-Perot cavity is 0.974-1.015 quarter-wavelength optical thickness, so that the transmittance of the layer reaches an extreme value when the layer is finished, an extreme value method is adopted for monitoring the change trend of light intensity in coating monitoring, and the light intensity signal is switched to the next layer after the light intensity signal reaches an extreme value point; this algorithm has the function of compensating for the errors of the front film layer.

The optical thickness of the connecting layer is a non-integer number of quarter-wave optical thicknesses in the range of 0.675-2.451. The connection layer 4 is used for film coating monitoring by a crystal control/time control method, and the process curves are monitored by various monitoring methods so as to achieve the required filtering effect, errors can not be accumulated, and the accuracy in the thickness of the film layer in the band-pass filter is improved.

The principle of the crystal control/time control method is as follows: in the coating process, a film layer can be deposited on the surface of a crystal oscillator wafer of the crystal controller; the oscillation frequency of the crystal oscillator wafer can change along with the increase of the thickness of the upper surface film layer of the crystal oscillator wafer; the thickness change of the film layer on the crystal oscillator is obtained by obtaining the change of the oscillation frequency of the crystal oscillator plate on the crystal oscillator controller. The control method has the defect that the control precision often cannot meet the requirement of a high-precision optical film, so that the control method is often only used for controlling the deposition rate of a coating process. For a high-precision optical filter, it is often considered to control the film thickness by using a direct light control method. The reason is that the characteristics of the film layer often deviate from the theoretical characteristics due to the inherent characteristics of the film and the differences of the production process and equipment in the film coating process, for example, the refractive index of the film layer is lower compared with that of the bulk material, and the refractive index of the film layer is different due to different processes. And the final application of the filter is light, it is contemplated that the optical thickness can be controlled by monitoring the light signal during the deposition process.

Preferably, the material of the high refractive index layer is at least one of Ta2O5, Nb2O5 and TiO2, and the refractive index of the high refractive index layer is 1.85 to 2.5 in the range of 1304.5-1317 nm.

The material of the low-refractive-index layer is at least one of SiO2, Al2O3 and MgF2, and the refractive index of the low-refractive-index layer ranges from 1.38 to 1.6 in the range of 1304.5-1317 nm.

The base layer is made of silicon dioxide material or silicon material substrate, and the refractive index of the base layer is in the range of 1304.5-1317nm and is 1.45-3.5. The base layer is at least one of D263T, WMS-15, BK7, FS and Si. Preferably, the substrate material is ordinary K9 optical glass.

Specific examples are as follows:

the present embodiment is a bandpass filter with a linearly varying passband insertion loss. FIG. 2 is a graph showing the relationship between the wavelength and the insertion loss of this embodiment at the target slope of the insertion loss in the passband range, wherein the slope is 0.3846dB/nm, and the insertion loss in the 1304.5-1317nm range is increased from-5 dB to-0.2 dB at a slope of 0.3846dB/nm according to the target slope curve of Table 1.

TABLE 1 target slope Curve

Fig. 3 and 4 are graphs showing the comparison between the actual insertion loss value and the target insertion loss value in the range of 1304.5-1317nm in this example under the condition of the incident angle of 8 degrees. The solid line is a product insertion loss curve actually measured by the product, the black points are insertion loss target values of different wavelengths, and fig. 3 is a relation graph of the wavelength, the insertion loss and the target slope in the range of 0-30dB in the embodiment; FIG. 4 is a graph of wavelength versus insertion loss and target slope for the present example in the 0-6dB range.

The film structure comprises 138 layers of film system formed by stacking two materials. The initialization structure with characteristic wavelength of 1319nm is as follows:

HLHL4HLHLHB

HLHLHL4HLHLHLHB

HLHLHLHL4HLHL3HLHLHB

HLHLHL4HLHLHLHB

HLHL4HLHLAB

the structure of the Fabry-Perot cavity with characteristic wavelength of 1319nm is as follows: ahhlhl 4HLHLH, bhhlhl 4HLHL3HLHLH, chhlhl 4 hlhlhlhlh, dhhl 4HLHLA, wherein dhhl 4HLHLA is the last layer fabry-perot cavity.

In the embodiment, 9 Fabry-Perot cavities are formed by cascading low-refractive-index materials B with optical thicknesses different from 1/4; a is a high refractive index material with optical thickness of not 1/4, A is a high refractive index material with optical thickness of not 1/4, and the thickness of A and B and the thickness of the first H of the next Fabry-Perot cavity are optimized to obtain a corresponding film system. The order of the layers of the stack and the control of the film thickness of each layer are shown in table 2 below:

TABLE 2 film system Structure and control method

In the embodiment, the material of the high-refractive-index layer is Ta2O5, and the refractive index near 1310nm is 2.094; the material of the low-refractive index layer is SiO2, and the refractive index near 1310nm is 1.473; the substrate material is ordinary K9 optical glass with the refractive index of 1.52. As can be seen from fig. 3, 4, 5, and 6, the wavelength varies linearly with the insertion loss.

Therefore, the CWDM with linearly changing passband insertion loss in this embodiment can satisfy the linear change of the insertion loss of the P-polarized light with a certain slope at the commonly used 8-degree angle; the hard medium film coating of sputtering or ion beam assisted deposition is adopted, and the requirements of communication products and automobile products on friction resistance, high temperature resistance and high humidity resistance can be met.

It should be noted that: the above sequence of the embodiments of the present invention is only for description, and does not represent the advantages and disadvantages of the embodiments. And specific embodiments thereof have been described above. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the embodiments and still achieve desirable results.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments.

The foregoing description has disclosed fully the embodiments of the present invention. It should be noted that those skilled in the art can make modifications to the embodiments of the present invention without departing from the scope of the claims of the present invention. Accordingly, the scope of the claims of the present invention is not to be limited to the specific embodiments described above.

Claims

1. The bandpass filter with the linearly-changed insertion loss is characterized by comprising a base layer and a film system stacked on the base layer, wherein the film system structure of the film system comprises a plurality of Fabry-Perot cavities and connecting layers, each Fabry-Perot cavity is cascaded with the next Fabry-Perot cavity through the connecting layers, and the connecting layers are low-refractive-index layers with optical thickness not equal to one quarter wavelength;

2. The linearly lossy bandpass filter of claim 1, wherein the index of the quarter-center-wavelength optical thickness of the first high-index layer of the fabry-perot cavity is optimized by the optical thickness of the last layer of the last fabry-perot cavity.

3. The bandpass filter according to claim 1 wherein a, b, c, d are 0.974-1.015, the first high index layer of the fabry-perot cavity has a quarter-wave center optical thickness of 0.974-1.015 to the end of the layer to achieve an extreme transmission, and the monitoring of the coating is carried out by extrema so that subsequent layers of each quarter-wave optical thickness can be monitored by extrema.

4. The bandpass filter according to claim 1, wherein the optical thickness of the connecting layer is a non-integer number of quarter-wavelengths of optical thickness in the range of 0.675-2.451.

5. The bandpass filter according to claim 1, wherein the filter has a linear variation of insertion loss with wavelength that increases or decreases linearly with wavelength at an incident angle of 0 to 13.5 degrees.

6. The bandpass filter according to claim 1, wherein the insertion loss of the filter in the 1304.5-1317nm band increases from-5 dB to-0.2 dB with a slope of 0.3846 dB/nm.

7. The bandpass filter of claim 1 wherein the number of fabry-perot cavities is 9.

8. The bandpass filter according to claim 1, wherein the high refractive index layer has a refractive index in the range of 1304.5-1317nm of 1.85 to 2.5.

9. The bandpass filter according to claim 1, wherein the low refractive index layer has a refractive index in the range of 1304.5-1317nm of 1.38 to 1.6.

10. The bandpass filter according to claim 1, wherein the base layer is a silica material or a silicon material substrate, and the refractive index of the base layer is in the range of 1304.5-1317nm and is 1.45-3.5.