CN111781676B - Bragg waveguide grating modulator - Google Patents
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/27—Optical coupling means with polarisation selective and adjusting means
- G02B6/2726—Optical coupling means with polarisation selective and adjusting means in or on light guides, e.g. polarisation means assembled in a light guide
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- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
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- G02B6/2753—Optical coupling means with polarisation selective and adjusting means characterised by their function or use, i.e. of the complete device
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
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Abstract
The invention discloses a Bragg waveguide grating modulator, comprising: main waveguide, resonant cavity waveguide, antisymmetric directional coupler; one end of the main waveguide comprises a forward input optical port for receiving TE 0 The other end of the mode includes a backward output port for outputting TE 0 The output light of the mode; the antisymmetric directional coupler is connected with the coupling sections of the main waveguide and the resonant cavity waveguide and is used for realizing TE of the main waveguide 0 TE of mode light and the resonant cavity waveguide 1 Mode conversion of mode light; the resonant cavity waveguide is provided with an anti-symmetric grating for realizing TE in the resonant cavity waveguide 1 Mode light and TE 0 Conversion of mode light. The invention solves the problem that the reflected light of the existing Bragg grating modulator has adverse effect on an incident port device.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a Bragg waveguide grating modulator.
Background
The modulator is an important device for loading signals in optical fiber communication, the types of structures of the silicon optical modulator are many, and the commonly used structures comprise a Mach-Zehnder modulator, a micro-ring modulator and a Bragg grating modulator. The arm length of the Mach-Zehnder modulator is generally larger than 2mm in practical application, and the Mach-Zehnder modulator is large in size; the micro-ring modulator is easy to crosstalk among different channels; the intrinsic grating reflected light of the existing Bragg grating modulator can cause adverse effects on other devices of an incident port, particularly the light source of a semiconductor laser is very sensitive to external reflected light, and the existing reflected light can cause adverse effects on other devices of the incident port, so that the Bragg grating modulator loses the advantages of external modulation to a great extent.
Disclosure of Invention
The invention provides a Bragg waveguide grating modulator, which solves the problem that the reflected light of the conventional Bragg grating modulator has adverse effect on an incident port device.
In order to solve the problems, the invention is realized as follows:
embodiments of the invention provide a Bragg waveguide grating modulator, packageComprises the following components: main waveguide, resonant cavity waveguide, antisymmetric directional coupler; one end of the main waveguide comprises a forward input optical port for receiving TE 0 Incident light of the mode, the other end including a backward output port for outputting TE 0 The output light of the mode; the antisymmetric directional coupler is connected with the coupling sections of the main waveguide and the resonant cavity waveguide and is used for realizing TE of the main waveguide 0 TE of mode light and the resonant cavity waveguide 1 Mode conversion of mode light; the resonant cavity waveguide is provided with an anti-symmetric grating for realizing TE in the resonant cavity waveguide 1 Mode light and TE 0 Conversion of mode light.
Furthermore, the antisymmetric grating is engraved on the side wall of the resonant cavity waveguide and comprises a first antisymmetric grating and a second antisymmetric grating; the incident light enters from the forward input port and is converted by the antisymmetric directional coupler to output a first TE 1 Mode light to the resonant cavity waveguide; the first TE 1 The module light respectively outputs a first forward TE through the first and second antisymmetric gratings 1 Mode-optical, first backward TE 0 Performing mold polishing; the first forward TE 1 The mode light outputs second backward TE through the second antisymmetric grating 0 Mode light, the first backward TE 0 The mode light outputs second forward TE through the first anti-symmetric grating 1 Performing mold polishing; the first and second forward direction TE 1 Mode light is converted into the TE through the antisymmetric directional coupler mode 0 The output light of the mode is output from the backward output light port.
Further, the resonant cavity waveguide is a ridge waveguide and comprises a PN junction and doped carriers, metal electrodes are arranged on two sides of the ridge waveguide, and if no electric signal is applied, TE in the main waveguide is detected 0 The effective refractive index of the mode light is equal to the TE of the resonant cavity waveguide 1 An effective refractive index of the mode light; TE in the resonant cavity waveguide if an electrical signal is applied 0 Mode light and TE 1 The effective refractive index of the mode light is changed and is not equal to TE in the main waveguide 0 The effective refractive index of the mode light.
Preferably, the main waveguide is a rectangular waveguide.
Preferably, the grating period of the antisymmetric grating is:
wherein Λ is the grating period, λ is the wavelength of the incident light, n eff0 、n eff1 Respectively TE of the resonant cavity waveguide 0 Mode light, TE 1 The effective refractive index of the mode light.
Preferably, the antisymmetric grating satisfies the bragg condition: beta is a 0 +β 1 -K 01 0, wherein, beta 0 And beta 1 Respectively TE in the resonant cavity waveguide 0 Mode light and TE 1 Propagation constant of mode light, K 01 In the form of a vector of a grating,
and Λ is the grating period of the Bragg waveguide grating modulator.
Preferably, the main waveguide and the resonant cavity waveguide are both manufactured on a silicon dioxide silicon substrate wafer.
Preferably, the antisymmetric grating is fabricated by one-step lithography and etching.
Preferably, the antisymmetric grating contains a pi phase shift structure and is positioned between the first antisymmetric grating and the second antisymmetric grating.
The beneficial effects of the invention include: in the side-coupled antisymmetric Bragg waveguide grating modulator, the main waveguide TE 0 Mode light effective refractive index and resonant cavity waveguide backward TE 0 Unequal effective refractive index of mode light, resulting in backward TE 0 The mode cannot be coupled back to the main waveguide by an anti-symmetric directional coupler (ADC), reducing reflected light; in addition, the invention enables light to be emitted from two sides of the resonant cavity waveguide by increasing the ports, thereby avoiding the situation that the light is reflected from the input port of the main waveguide.
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 specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not limit the invention. In the drawings:
FIG. 1 is a diagram of one embodiment of a Bragg waveguide grating modulator;
figure 2 is an embodiment of a resonant cavity waveguide.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the disclosed embodiments are merely exemplary of the invention, and are not intended to be exhaustive or exhaustive. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
With the advent of the information age, the demand for high-performance data transmission is increasing. In particular, the requirements of people are not limited to the traditional conversation services, but are more focused on the communication at the level of voice, image and the like. Various new services are emerging, such as multimedia services like video conferencing and video call. Optical fiber communication has been widely used and studied because it exhibits advantages in transmission capacity, transmission speed, and the like. As an important device for loading signals in optical fiber communication, a modulator has become one of the main research fields.
Silicon has many advantages over other materials: first, the band gap of silicon is 1.12 eV. Therefore, it is transparent in both O-band and C-band. Second, the refractive index of silicon is 3.45, while the refractive index of silicon dioxide is 1.45. The silicon and the silicon dioxide have large refractive index difference, and the silicon optical device has large limiting effect on light, so that the size of the device can be smaller. Then, the silicon optical device can be perfectly compatible with the CMOS process, and the cost is lower. Finally, the silicon optical device has better mechanical performance and can work in a higher temperature environment. Therefore, silicon optical modulators have shown great potential in the field of optical communications. Nowadays, there are many kinds of structures of silicon optical modulators, and the more commonly used structures include mach-zehnder modulators, micro-ring modulators, bragg grating modulators, and the like.
Currently, the mach-zehnder modulator has the greatest advantage that the operating bandwidth is the full bandwidth, and thus it is widely used. However, the mach-zehnder modulator is large in size. Although the dimensions can be made 0.5mm or less in arm length, the arm length is typically greater than 2mm in practical applications in order to ensure the performance of the modulator. In contrast, micro-ring modulators and bragg grating modulators are resonance-based and therefore may be relatively small in size.
The size of the micro-ring modulator is smaller than that of the mach-zehnder modulator. However, the resonance peaks of the micro-ring modulator are periodic, and when the micro-ring modulators are cascaded, crosstalk between different channels is easy. To avoid channel crosstalk, the diameter of the micro-ring modulator must be small, even less than 10 μm.
The bragg grating modulator is smaller in size than the mach-zehnder modulator. Meanwhile, the Bragg grating modulator is single-mode resonant, so that the Bragg grating modulator only has one resonant peak near the working wavelength, and crosstalk between channels is not easy to occur. However, the grating of a bragg grating modulator inherently reflects light, which can adversely affect the rest of the devices at the input port. In particular, semiconductor lasers are very sensitive to ambient reflected light. This defect is similar to that of the inner modulation. The bragg grating modulator loses the advantage of the outer modulation to a large extent.
Compared with other mainstream silicon optical modulators such as Mach-Zehnder modulators and micro-ring modulators, the Bragg grating modulator has the advantages of small size, single-mode resonance and the like, and crosstalk between different channels is not easy to occur. However, bragg grating modulators also have deficiencies. The reflected light that it presents can have an adverse effect on the rest of the device at the input port. If the isolator or the like is adopted to solve the problem, the cost of the communication system is greatly increased, and the complexity of the structure is increased.
The innovation points of the invention are as follows: first, the present inventionBy adjusting the effective refractive index of the TE0 mode in the primary waveguide to be equal to the effective refractive index of the TE1 mode of the resonator waveguide, the TE0 mode of the primary waveguide can be coupled to the resonator waveguide through the ADC, and the forward TE1 mode of the resonator waveguide can also be coupled back to the primary waveguide, but the backward TE mode of the resonator waveguide 0 The mode can not be coupled back to the main waveguide due to the difference of the effective refractive index, so that the effect of reducing the reflected light is achieved; second, when the present invention applies an electrical signal, the electrical signal changes the resonator cavity waveguide TE 0 And TE 1 The effective refractive index of the mode enables incident light to be directly output from an output light port of the main waveguide, and reflected light is avoided; thirdly, the invention comprises two ports besides the two ports of the main waveguide, and the resonant cavity waveguide also comprises two ports, so that light can be emitted from two sides of the resonant cavity waveguide, and the condition that the light is reflected from the input port of the main waveguide is avoided.
The technical solutions provided by the embodiments of the present invention are described in detail below with reference to the accompanying drawings.
Fig. 1 shows an embodiment of a bragg waveguide grating modulator, which can effectively reduce reflected light at an output optical port, and as an embodiment of the present invention, a bragg waveguide grating modulator includes: the waveguide structure comprises a main waveguide 1, a resonant cavity waveguide 2 and an anti-symmetric directional coupler 3, wherein an anti-symmetric grating 21 is arranged on the resonant cavity waveguide.
One end of the main waveguide comprises a forward input optical port for receiving TE 0 The other end of the mode includes a backward output port for outputting TE 0 The output light of the mode; the antisymmetric directional coupler is connected with the coupling sections of the main waveguide and the resonant cavity waveguide and is used for realizing TE of the main waveguide 0 TE of mode light and the resonant cavity waveguide 1 Mode conversion of mode light; the resonant cavity waveguide is provided with an anti-symmetric grating for realizing TE in the resonant cavity waveguide 1 Mode light and TE 0 Conversion of mode light.
In the embodiment of the present invention, the port 1 of the main waveguide is the forward input optical port, the port 2 is the backward output optical port, the port 3 of the resonant cavity waveguide and the forward input optical port are located on the same side of the bragg waveguide grating modulator, and the port 4 of the resonant cavity waveguide and the backward output optical port are located on the same side of the bragg waveguide grating modulator.
The invention aims to use an edge-coupled antisymmetric Bragg waveguide grating modulator, namely the Bragg waveguide grating modulator in the application of the invention, to reduce the inherent reflected light of the traditional Bragg grating modulator and relieve the adverse effect of the reflected light on other devices of an incident port. The side-coupled antisymmetric Bragg waveguide grating modulator is technically based on: TE in resonant cavity waveguide 0 And TE 1 Mode can resonate in the antisymmetric grating (ASBWG), and TE 1 Effective refractive index of mode less than TE 0 The effective refractive index of the mode. Therefore, TE in the main waveguide can be adjusted 0 Effective refractive index of the mode is made equal to TE of the resonant cavity waveguide 1 The mode effective index. At this time, the main waveguide TE 0 Mode energy coupled to the resonant cavity waveguide through the ADC, forward TE of the resonant cavity waveguide 1 Modes can also couple back to the main waveguide, but backward to the TE of the cavity waveguide 0 The mode cannot be coupled back to the main waveguide due to the difference in effective refractive index, thereby achieving the effect of reducing reflected light.
Note that the antisymmetric grating is an antisymmetric bragg grating.
Further, the antisymmetric grating is engraved on the side wall of the resonant cavity waveguide, and comprises a first antisymmetric grating 22 and a second antisymmetric grating 23.
The incident light enters from the forward input port and outputs a first TE through mode conversion of the antisymmetric directional coupler 1 Mode light to the resonant cavity waveguide; the first TE 1 The module light respectively outputs a first forward TE through the first and second antisymmetric gratings 1 Mode-optical, first backward TE 0 Performing mold polishing; the first forward TE 1 The mode light outputs second backward TE through the second antisymmetric grating 0 Mode light, the first backward TE 0 The mode light outputs second forward TE through the first anti-symmetric grating 1 Performing mold polishing; the first and second forward direction TE 1 Mode light is converted into the TE through the antisymmetric directional coupler mode 0 The output light of the mode is output from the backward output light port.
In the embodiment of the present invention, the grating period of the antisymmetric grating is:
wherein Λ is the grating period, λ is the wavelength of the incident light, neff 0 、neff 1 Respectively TE of the resonant cavity waveguide 0 Mode light, TE 1 The effective refractive index of the mode light.
In the embodiment of the invention, the antisymmetric grating further comprises a pi phase shift structure 24 positioned between the first and second antisymmetric gratings.
The phase shift of the antisymmetric Bragg grating is realized by adopting any one of the following modes: and a pi phase shift structure is inserted in the middle of the antisymmetric Bragg grating or a planar waveguide moire grating is adopted, namely two lines of waveguide gratings with small grating period difference are adopted.
The antisymmetric grating provides a grating vector K 01 And phase matching between different modes is realized, so that mode conversion is realized. The antisymmetric grating satisfies the Bragg condition:
β 0 +β 1 -K 01 ＝0 (2)
wherein, beta 0 And beta 1 Respectively TE in the resonant cavity waveguide 0 Mode light and TE 1 Propagation constant of mode light, K 01 Is a vector of a light grid,
modulating the Bragg waveguide grating by ΛThe grating period of the device.
Further, TE in the antisymmetric grating 0 Mode light and TE 1 The coupling coefficient of the mode light is:
wherein, κ 01 For the coupling coefficient, ω is the angular velocity of the incident and reflected light, ε 0 To dielectric constant, Ψ (x) 0 Transverse electric field distribution function of 0 order mode, psi (x) 1 Δ ε (x) is the transverse permittivity distribution as a function of the transverse electric field distribution for the 1 st order mode.
In the embodiment of the present invention, further, the resonant cavity waveguide is a ridge waveguide, which includes a PN junction, doped carriers and metal electrodes disposed on two sides, and if no electrical signal is applied, TE in the main waveguide 0 The effective refractive index of the mode light is equal to the TE of the resonant cavity waveguide 1 The effective refractive index of the mode light; TE in the resonant cavity waveguide if an electrical signal is applied 0 Mode light and TE 1 The effective refractive index of the mode light is changed and is not equal to TE in the main waveguide 0 The effective refractive index of the mode light.
The main waveguide is a rectangular waveguide without PN junction doping, metal electrodes are not arranged on two sides of the main waveguide, no electric signal is applied, and the effective refractive index of TE0 mode light in the main waveguide is not changed.
In this embodiment, when no electrical signal is applied, the incident light enters the primary waveguide through the port 1 and becomes TE 0 A mode optically coupled to the resonant cavity waveguide and becoming a first forward TE through the antisymmetric directional coupler 1 Mode light, passing through a second antisymmetric grating, first forward TE 1 The mode light is reflected as a first backward TE 0 And (4) performing mode light. Due to TE in the resonant cavity waveguide 0 The effective refractive index of the mode light is not equal to the main waveguide TE 0 Effective refractive index of mode, so first backward TE 0 Mode light cannot be coupled back into the main waveguide, thus reducing reflected light.
At this time, the first backward TE 0 The mode light passes through the first antisymmetric grating and is reflected again as a second forward TE 1 And (4) performing mode light. Due to resonant cavity waveguide TE 1 The effective refractive index of the mode light is equal to the main waveguide TE 0 Effective refractive index of mode light, so first forward TE 1 Modulo light and second forward TE 1 The mode light can be coupled back to the main waveguide and become TE of the main waveguide 0 And a mode generating emergent light.
Further, when an electrical signal is applied, the refractive index of the material of the resonant cavity waveguide changes according to the effect of plasma dispersion, and the TE of the resonant cavity waveguide 0 And TE 1 The effective refractive index of the mode light decreases accordingly. At this time, the main waveguide TE 0 The effective refractive index of the mode light is not equal to the TE of the resonant cavity waveguide 1 Effective refractive index of mode light, so TE of the main waveguide 0 The mode light cannot couple to the resonator waveguide and directly exits from port 2 of the main waveguide.
In the present application, the TE of the main waveguide 0 The mode light is all TE including the incident light and the output light 0 Mode light, TE of said resonant cavity waveguide 0 Mode light including the first forward TE 0 Modulo light and second forward TE 0 All TE of mode light 0 Mode light, TE of said resonant cavity waveguide 1 The mode light comprises the first backward TE 1 Modulo light and second backward TE 1 All TE of mode light 1 Mode light.
In the embodiment of the invention, the main waveguide and the resonant cavity waveguide are both manufactured on a silicon dioxide silicon substrate wafer.
In an embodiment of the invention, the antisymmetric grating is manufactured by one-step lithography and etching.
For example, the manufacturing method of the side wall antisymmetric grating sum of the resonant cavity wave band is as follows:
the antisymmetric grating structure is fabricated by a one-step lithography and etching process that is compatible with conventional Complementary Metal Oxide Semiconductor (CMOS) processes. The purpose of photoetching is to transfer the pattern of a mask plate to photoresist on the surface of a silicon wafer. The step can print the image of the mask plate through deep ultraviolet exposure, firstly, the silicon wafer is pretreated, coated with glue, spin-dried, and then the coated silicon wafer is sent into a photoetching machine for exposure. After completion, the wafer is developed, and then the wafer is cleaned and dried.
The purpose of etching is to transfer the pattern on the photoresist on the surface of the silicon wafer to the silicon wafer. This step may be performed by dry etching with Inductively Coupled Plasma (ICP) or wet etching based on chemical reactions. And after the etching is finished, removing the photoresist on the surface of the silicon wafer by using ionized oxygen of a photoresist remover. Alternatively, the lithography may be performed by an electron beam exposure technique, in which a uniform layer of electron beam resist, typically PMMA (polymethyl methacrylate), is first applied to a silicon wafer, and then an electron beam is scanned over the resist using the electron beam exposure technique to form a desired waveguide pattern on the resist by varying the exposure of the electron beam.
As another example, the injection and contact process of the electrical part in the bragg waveguide grating modulator is as follows:
(1) after the etching is completed, the bragg waveguide grating modulator needs to be doped.
Before doping, a layer of silicon dioxide grows on the surface of the wafer, and then the wafer is subjected to photoetching again. And opening a bottom anti-reflection coating (BARC) in the window after photoetching through an etching process after photoetching. And then, carrying out ion implantation on the wafer, removing the photoresist and a bottom anti-reflection coating (BARC) which are used as an implantation mask by a dry photoresist removing method after the implantation is finished, cleaning the wafer by using a hydrofluoric acid solution, a hydrogen peroxide and concentrated sulfuric acid mixed solution and an ammonia water and hydrogen peroxide mixed solution, and then repeating the photoresist removing and cleaning processes after the implantation to finish the doping of PN junction impurities in the ridge waveguide. Then the ridge waveguide flat plate region is doped by injecting the ridge waveguide flat plate region to form an electrical connection structure of a PN junction. In order to form ohmic contact between silicon and metal, a larger dose of dopant ions is implanted into the silicon. And after ion implantation is finished, rapid thermal annealing treatment is carried out to activate implanted impurity ions and repair lattice damage caused by implantation. Here, in order to make the PN junction closer to the abrupt junction, the annealing time is not too long, and 5s may be selected.
(2) Growing silicon dioxide on the surface of the wafer, and flattening the silicon dioxide on the surface of the wafer by a Chemical Mechanical Polishing (CMP) method. The process flow is changed from the front-stage process to the back-stage process. Etching a contact hole of a device on a silicon dioxide layer by using a silicon dioxide etching process, wherein the step is to perform photoetching on a wafer, opening a bottom anti-reflection coating (BARC) coated during photoetching, performing etching by using the silicon dioxide etching process, then performing dry photoresist removal, and finally cleaning to remove residual polymer and photoresist on the surface of the wafer. In order to obtain a better contact resistance, it is usually necessary to metallize the silicon at the contact holes and to form a metal silicide at the contact portions where it is desired to make. And after the etching of the contact hole is finished, cleaning the contact hole by using hydrofluoric acid to remove residual silicon oxide, performing metal deposition after spin-drying, and then performing annealing treatment. And after the treatment is finished, cleaning the wafer, and then annealing the wafer to form the metal silicide with a lower resistance value. After the metal silicide is formed, Ti and TiN are deposited on the surface of the wafer and used as a barrier layer of a contact process. And then growing metal on the wafer through Chemical Vapor Deposition (CVD), filling the silicon oxide contact hole, and removing redundant metal outside the contact hole through Chemical Mechanical Polishing (CMP). And after the contact hole process is finished, depositing Ti and TiN on the surface of the wafer to be used as a metal barrier layer, then depositing a layer of aluminum alloy, and removing metal on the surface of the wafer through photoetching and etching to only leave the metal connecting wire part of the device. And then depositing silicon dioxide on the surface of the wafer to be used as a cladding, and removing an oxide layer covered on the metal of the part, connected with the outside, of the device through photoetching and etching. And finally, annealing the wafer, repairing the metal connecting wire and reducing the resistance of the metal connecting wire.
The embodiment of the invention provides a Bragg waveguide grating modulator, which is a silicon optical modulator based on an antisymmetric Bragg waveguide grating, reduces reflected light on the basis of keeping the advantages of the conventional Bragg grating modulator, and relieves the adverse effect of the reflected light on other devices of an incident port.
Fig. 2 shows an embodiment of a resonant cavity waveguide, which can be used for the resonant cavity waveguide of the bragg waveguide grating modulator of the present invention, in the embodiment of the present invention, metal electrodes 25 are disposed on two sides of the resonant cavity waveguide 2, and are fabricated on a silicon dioxide-based wafer 4.
In the embodiment of the invention, the resonant cavity waveguide is a ridge waveguide and comprises a PN junction and doped carriers, metal electrodes are arranged on two sides of the ridge waveguide, and if no electric signal is applied, TE in the main waveguide is arranged 0 The effective refractive index of the mode light is equal to the TE of the resonant cavity waveguide 1 The effective refractive index of the mode light; TE in the resonant cavity waveguide if an electrical signal is applied 0 Mode light and TE 1 The effective refractive index of the mode light is changed and is not equal to TE in the main waveguide 0 The effective refractive index of the mode light.
Fig. 2 is a cross section of the resonant cavity waveguide, and in the embodiment of the present invention, the main waveguide of the bragg waveguide grating modulator is a rectangular waveguide, and is not doped with a PN junction, and metal electrodes are not disposed on two sides of the main waveguide, and no electrical signal is applied. The Bragg waveguide grating modulator resonant cavity waveguide is a ridge waveguide, comprises a PN junction, is doped with current carriers, and is provided with metal electrodes at two sides.
When an electric signal is applied to the metal electrode, the distribution of current carriers in the resonant cavity waveguide, the width of a PN junction depletion layer and the like are changed. TE in a resonant cavity waveguide based on the effect of plasma dispersion 1 Mode light and TE 0 The effective refractive index of the mode light changes and, ultimately, the TE of the main waveguide 0 Mode light cannot be coupled to the resonator waveguide through an anti-symmetric directional coupler (ADC), and the output optical power of the main waveguide reaches a maximum.
TE of the main waveguide when no electric signal is applied to the metal electrode 0 The mode light energy is coupled to the resonant cavity waveguide through an Antisymmetric Directional Coupler (ADC) and resonates in an antisymmetric grating. The emergent light power of the output light port reaches the minimum value, at the moment, light can be emitted from two sides of the resonant cavity waveguide, light is prevented from being emitted from the main wave guide-in emission port, and reflected light is reduced.
It is to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The above description is only an example of the present invention, and is not intended to limit the present invention. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (8)
1. A bragg waveguide grating modulator comprising: a main waveguide, a resonant cavity waveguide, and an antisymmetric directional coupler;
one end of the main waveguide comprises a forward input optical port for receiving TE 0 The other end of the mode includes a backward output port for outputting TE 0 The output light of the mode;
the antisymmetric directional coupler is connected with the coupling sections of the main waveguide and the resonant cavity waveguide and is used for realizing TE of the main waveguide 0 TE of mode light and the resonant cavity waveguide 1 Mode conversion of mode light;
the resonant cavity waveguide is provided with an anti-symmetric grating for realizing TE in the resonant cavity waveguide 1 Mode light and TE 0 Conversion of mode light;
the resonant cavity waveguide is a ridge waveguide and comprises a PN junction and doped carriers, metal electrodes are arranged on two sides of the ridge waveguide, and TE in the main waveguide is arranged if no electric signal is applied 0 The effective refractive index of the mode light is equal to the TE of the resonant cavity waveguide 1 An effective refractive index of the mode light; TE in the resonant cavity waveguide if an electrical signal is applied 0 Mode light and TE 1 The effective refractive index of the mode light is changed and is not equal to TE in the main waveguide 0 An effective refractive index of the mode light;
the port 3 of the resonant cavity waveguide and the forward input light port are positioned at the same side of the Bragg waveguide grating modulator, and the port 4 of the resonant cavity waveguide and the backward output light port are positioned at the same side of the Bragg waveguide grating modulator; when the metal electrode is coated with a metal oxide
When no electrical signal is applied, light can exit from both sides of the resonator waveguide.
2. A bragg waveguide grating modulator as claimed in claim 1 wherein said anti-symmetric grating is inscribed on the sidewalls of said resonant cavity waveguide and comprises a first anti-symmetric grating, a second anti-symmetric grating;
the incident light enters from the forward input port and outputs a first TE through mode conversion of the antisymmetric directional coupler 1 Mode light to the resonant cavity waveguide;
the first TE 1 The module light respectively outputs a first forward TE through the first and second antisymmetric gratings 1 Mode-optical, first backward TE 0 Performing mold polishing;
the first forward TE 1 The mode light outputs second backward TE through the second anti-symmetric grating 0 Mode light, the first backward TE 0 The mode light outputs second forward TE through the first anti-symmetric grating 1 Performing mold polishing;
the first and second forward direction TE 1 Mode light is converted into the TE through the antisymmetric directional coupler mode 0 The output light of the mode is output from the backward output light port.
3. A bragg waveguide grating modulator as claimed in claim 1 wherein the main waveguide is a rectangular waveguide.
4. A bragg waveguide grating modulator as claimed in claim 1 wherein the anti-symmetric grating has a grating period of:
wherein Λ is the grating period, λ is the wavelength of the incident light, n eff0 、n eff1 Respectively TE of the resonant cavity waveguide 0 Mode light, TE 1 The effective refractive index of the mode light.
5. A bragg waveguide grating modulator as claimed in claim 1, wherein the antisymmetric grating satisfies the bragg condition: beta is a 0 +β 1 -K 01 0, wherein β 0 And beta 1 Respectively TE in the resonant cavity waveguide 0 Mode light and TE 1 Propagation constant of mode light, K 01 In the form of a vector of a grating,
and Λ is the grating period of the Bragg waveguide grating modulator.
6. A bragg waveguide grating modulator as claimed in claim 1 wherein said main waveguide and said cavity waveguide are fabricated on a silica-on-silicon wafer.
7. A bragg waveguide grating modulator as claimed in claim 1 wherein the anti-symmetric grating is fabricated by a single step of lithography and etching.
8. A bragg waveguide grating modulator as claimed in claim 2 wherein said anti-symmetric grating includes a pi phase shifting structure disposed between said first and second anti-symmetric gratings.
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