CN116560001A - Polarization beam splitting-combining device based on cascade adiabatic coupler - Google Patents
Polarization beam splitting-combining device based on cascade adiabatic coupler Download PDFInfo
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Abstract
The invention discloses a polarization beam splitting-combining device based on cascade adiabatic couplers, which adopts a cascade structure of two adiabatic couplers, and achieves beam splitting and combining effects by taking a high-order mode of an intermediate waveguide as an aid. The polarization beam splitting-combining device can realize low-loss and high extinction ratio beam splitting or low-loss beam combining in a larger bandwidth based on the adiabatic coupling technology between waveguides, and has certain manufacturing tolerance.
Description
Technical Field
The invention relates to a polarization control device of an on-chip integrated optical waveguide, in particular to a polarization beam splitting-combining device which can be used for scenes requiring polarization beam splitting, beam combining and filtering in an on-chip optical communication, an on-chip optical sensing and an optical quantum information system.
Background
Today, the age of high-speed information transmission and data processing has been reached, and as moore's law in the microelectronics field approaches a limit, the development of integrated photonics technology is becoming an increasingly popular research field. The waveguide device with high refractive index difference can better restrict the propagation of light to achieve higher integration, but a strong birefringence phenomenon is generated concomitantly, so that the photonic device with high refractive index difference generally has polarization sensitivity and can only work in a single polarization mode. Thus, it is necessary to separate light of different polarizations using a polarizing beam splitter-combiner and output from different ports before the light enters the device, and to separately process the two polarized light. In the field of optical communication, because different polarization modes are in an orthogonal relationship with each other, transmission in the same waveguide can not interfere with each other, so that different polarization modes can be used as different channels for transmitting information, a polarization beam splitter-combiner is arranged at the head end and the tail end of a waveguide bus, different polarized lights are loaded to the bus and transmitted simultaneously, and multiple increase of transmission capacity can be realized. In the field of optical sensing, the sensitivity to environmental perception is far from due to the different characteristics of different polarized light, and different light is separated by using a polarization beam splitter-combiner to obtain accurate sensing data. In the field of quantum information, photons are taken as an ideal information carrier, and a polarization beam splitting-combining device plays an important role in the process that quantum technology leaves a laboratory and goes to large-scale application.
At present, the implementation mode of the polarization beam splitting-combining device based on the silicon-based optical waveguide is mainly based on the principle of an asymmetric directional coupler, two waveguides with different structures are adopted, so that one of two polarized lights of the two waveguides is caused to be matched in phase and coupled to the other waveguide, and the other Shu Pianzhen light is still mismatched in phase and remains in the original waveguide, so that polarization beam splitting is realized. However, the phase matching condition is particularly sensitive to variations in wavelength and waveguide width, and is easily not perfectly matched due to manufacturing errors and variations in wavelength, so it is difficult to realize a large-bandwidth, high manufacturing tolerance device. The use of cascading multiple couplers can increase bandwidth and extinction ratio to some extent, but loss increases at the same time.
Disclosure of Invention
The invention aims to provide a polarization beam splitting-combining device with a novel structure, which is based on the adiabatic coupling technology among waveguides, can realize beam splitting with low loss and high extinction ratio or beam combining with low loss in a larger bandwidth, and has certain manufacturing tolerance.
The above object of the present invention is achieved by the following technical solutions: the polarization beam splitting-combining device based on the cascade adiabatic coupler comprises an intermediate waveguide b and two other waveguides a and c used for light incidence and emergence, wherein the two cascade adiabatic couplers are formed by the waveguide a, the waveguide b and the waveguide c, a first adiabatic coupler formed by the waveguides a and b converts a TM polarization fundamental mode in incident light into a TM high-order mode of the intermediate waveguide b, a second adiabatic coupler formed by the waveguides b and c restores the TM high-order mode into a TM fundamental mode in the waveguide c, and TE polarized light in the incident light is remained in the waveguide a to achieve a polarization beam splitting effect; the beam combining effect can be realized by reversing the flow, namely, TM polarized light and TE polarized light are respectively input through the output ends of the waveguides c and a, and the combined light can be output through the input end of the waveguide a.
The intermediate waveguide b is composed of a first tapered waveguide 1b with a core layer width changing from narrow to wide, a second tapered waveguide 3b with a core layer width changing from wide to narrow, and an intermediate connecting waveguide 2b horizontally connecting the two wide heads;
the first tapered waveguide 1b is connected to the second tapered waveguide 3b via an intermediate connection waveguide 2b, and the intermediate connection waveguide 2b serves as a buffer to reduce crosstalk.
For simplicity, the core layers of the waveguides 1b, 3b adopt a single-sided linear graded structure, wherein the width of the core layer of the first tapered waveguide 1b is from w 2 Linearly change to w 3 The core width of the intermediate connection waveguide 2b is kept at w 3 The second tapered waveguide 3b has a core width from w 3 Linearly change to w 2 ，w 2 <w 3 。
The lengths of waveguides 1b and 3b are determined by the EME algorithm scanning the optimal solution for lengths of 5-70 μm; the length of the waveguide 2b is determined by the FDTD algorithm by calculating the optimal solution for the lengths of the waveguide 2b of 0, 1, 2, 3, 4 μm, etc.
The waveguide a is composed of an input waveguide 1a, a first bent waveguide 2a, an S-bent waveguide 3a and a first output waveguide 4 a;
the input waveguide 1a is connected with the first output waveguide 4a after passing through the first curved waveguide 2a and the S-curved waveguide 3a in sequence, and the S-curved waveguide 3a is used for separating the waveguide a from the second adiabatic coupler far enough to eliminate coupling between the two and reduce crosstalk.
The S-bend waveguide 3a is composed of two sections of circular arcs, and the curvature design thereof is such that part of the remaining TM modes can be filtered out, and the transmission loss to the TE mode is little affected, and is controlled to be below 1%.
The waveguide c is composed of a second bending waveguide 1c and a second output waveguide 2 c;
the second curved waveguide 1c is connected to the second output waveguide 2 c.
The first curved waveguide 2a is similar to the non-gradual change side of the first tapered waveguide 1b, the first curved waveguide 1b is shaped such that the distance between the first curved waveguide 1b and the core layers of the first tapered waveguide 2a changes from large to small and then increases, the width of the core layers of the first tapered waveguide 1b changes, and the distance between the core layers of the first tapered waveguide 1b and the first curved waveguide 2a is designed such that they are adiabatically coupled to form the first adiabatic coupler, and the adiabatic coupling condition satisfies efficient coupling for TM polarization and low loss transmission for TE polarization.
The second curved waveguide 1c is close to the non-gradual change side of the second tapered waveguide 3b, the shape of the second curved waveguide 1c changes the distance between the second curved waveguide 1c and the core layer of the second tapered waveguide 3b from big to small and then from big, the width of the core layer of the second tapered waveguide 3b changes, the distance between the second tapered waveguide 3b and the core layer of the second curved waveguide 1c is designed to ensure that the second adiabatic coupler is formed by adiabatic coupling, and the adiabatic coupling condition satisfies efficient coupling on TM polarization and has extremely low coupling efficiency on TE polarization.
Typically greater than 90%, coupling very low typically means less than 5% and low loss transmission typically means less than 1% loss, even with high coupling.
Each of the waveguides is preferably a rectangular waveguide.
The invention has the beneficial effects that:
the beneficial effects of the system of the present invention (the combiner when the system is used in reverse) will be described by taking a low loss, high efficiency optical ratio beam splitter as an example. Based on the adiabatic evolution principle, the adiabatic evolution is an efficient coupling mode, the TM fundamental mode in the waveguide a is efficiently evolved into the TM high-order mode in the waveguide b, and then is efficiently evolved into the TM fundamental mode in the waveguide c, and the energy remained in the waveguide a is less than 1%; for the TE fundamental mode, less than 5% of the energy may enter waveguide b, but due to the cascaded structure, the energy that eventually enters waveguide c is very small, so the scheme of the invention can achieve low loss and high extinction ratio. The method has the advantages that the influence on the coupling coefficient omega is larger for the wavelength change and the manufacturing error, but the influence on the phase mismatch delta is smaller, and the scheme still can achieve low-loss and high-efficiency light ratio in a certain wavelength range and a certain manufacturing error, so that the method has certain broadband and manufacturing tolerance. For example, the extinction ratio is greater than 19.0dB and the loss is less than 0.34dB for TM polarization in the 1500-1650nm band, greater than 22.4dB and the loss is less than 0.22dB for TE polarization in the 1500-1650nm band, and can tolerate a manufacturing error of + -20 nm. In addition, the invention has the advantages of simple structure, convenient design, easy manufacture and the like.
Drawings
FIG. 1 is a schematic diagram of a polarization beam splitter-combiner according to the present invention;
FIG. 2 is a schematic size diagram of a polarization beam splitter-combiner of the present invention;
FIGS. 3a and 3b are cross-sectional views of exemplary waveguides that may be used in the present invention;
FIG. 4 is a diagram of light field transmission when inputting TE fundamental mode according to an embodiment of the present invention;
FIG. 5 is a diagram showing the light field transmission when the TM fundamental mode is input in an embodiment of the present invention;
FIG. 6 shows the transmittance of the input TE and TM fundamental modes at two output ports obtained by simulation in the embodiment of the present invention;
FIG. 7 shows the transmittance of the input TE and TM fundamental modes at two output ports obtained by simulation when the waveguide width deviates from the design value by-20 nm in the embodiment of the present invention;
FIG. 8 shows the transmittance of the input TE and TM fundamental modes at two output ports obtained by simulation when the waveguide width deviates from the design value by +20nm in the embodiment of the present invention.
Detailed Description
The effect of the present invention is verified by the following specific examples.
As shown in fig. 1, the polarization beam splitter-combiner based on the cascade adiabatic coupler of the present embodiment includes an intermediate waveguide b and two other waveguides a and c serving as light incident and outgoing. The waveguide a is composed of an input waveguide 1a, a first curved waveguide 2a, an S-curved waveguide 3a, and a first output waveguide 4 a; the intermediate waveguide b is composed of a first tapered waveguide 1b, an intermediate connecting waveguide 2b and a second tapered waveguide 3 b; the waveguide c is composed of a second curved waveguide 1c and a second output waveguide 2 c. The input waveguide 1a is connected with the first output waveguide 4a after passing through the first bending waveguide 2a and the S-bending waveguide 3a in turn; the first tapered waveguide 1b is connected with the second tapered waveguide 3b through the intermediate connection waveguide 2 b; the second curved waveguide 1c is connected to the second output waveguide 2 c.
The first curved waveguide 2a is adiabatically coupled to the first tapered waveguide 1b and constitutes a first adiabatic coupler, and the second curved waveguide 1c is adiabatically coupled to the second tapered waveguide 3b and constitutes a second adiabatic coupler. The width of the first tapered waveguide 1b is varied and the distance between the first tapered waveguide 1b and the first curved waveguide 2a is designed such that adiabatic coupling conditions provide for efficient coupling of TM polarization and low loss transmission of TE polarization; the width of the second tapered waveguide 3b is varied and the spacing of the second tapered waveguide 3b from the second curved waveguide 1c is designed such that adiabatic coupling conditions provide for efficient coupling of TM polarization and low loss transmission of TE polarization.
The TM polarization fundamental mode in the input waveguide 1a couples energy to the TM polarization first higher-order mode (or the second and third mode) of the first tapered waveguide 1b through the first adiabatic coupler, and the TM polarization first higher-order mode couples energy to the second curved waveguide 1c through the intermediate connection waveguide 2b and the second adiabatic coupler and outputs from the second output waveguide 2 c; the TE polarization fundamental mode in the input waveguide 1a keeps energy in the first curved waveguide 2a by the first adiabatic coupler, and is output from the first output waveguide 4a via the S-curved waveguide 3 a.
The S-bend waveguide 3a separates the waveguide a and the second adiabatic coupler far enough to cancel the coupling of the two and reduce crosstalk. The S-bend waveguide 3a is composed of two sections of circular arcs, the curvature of the S-bend waveguide is reasonably designed to filter part of the residual TM mode, but the transmission loss of the TE mode is little influenced (the loss of the S-bend to the TE mode is preferably controlled to be less than 1 percent), and the radius R of the S-bend waveguide is designed in the embodiment 0 ＝2.5μm。
This example is based on a Silicon-on-insulator platform (Silicon-on-Insulator Platform), specifically using Silicon as the waveguide material (waveguide parameters set forth herein and below, all for the waveguide core), with a thickness of 220nm and a refractive index of about 3.478 at 1550nm wavelength; silica was used as both the substrate and cladding material, and had a thickness of 2 μm and a refractive index of about 1.444 at 1550nm wavelength. The silica cladding preferably fills the gaps between the silicon waveguides. In this embodiment, the waveguide has a high refractive index difference with the substrate and the cladding. Other materials are chosen, such as cladding layers with air (refractive index 1.0) and waveguides with silicon nitride (refractive index about 2.0). For the high-refractive index difference isotropic on-chip optical waveguide, the scheme of the invention can be applied to realize the high-performance polarization beam splitting-combining device.
In this embodiment, the sidewall inclination angle of all the waveguide structures is 90 degrees, and the cross section of the waveguide 4 is shown in fig. 3a, but the shape is not limited to rectangular waveguide, and the same applies to rib waveguide in fig. 3 b.
Fig. 2 shows the specific dimensions of the polarization beam splitter-combiner of the present embodiment. The input waveguide 1a, the first curved waveguide 2a, the S-curved waveguide 3a, and the first output waveguide 4a have the same width, and the width is w 1 =0.48 μm; the first tapered waveguide 1b has a width from w 2 Linearly change to w 3 The intermediate connection waveguide 2b width remains w 3 The second tapered waveguide 3b has a width from w 3 Linearly change to w 2 Wherein w is 2 ＝0.96μm，w 3 =1.50 μm; the width of the second bending waveguide 1c and the second output waveguide 2c are w 1 =0.48 μm; intermediate the first curved waveguide 2a and the first tapered waveguide 1bFrom g 1 Change to g 2 Then change to g 3 The spacing between the second curved waveguide 1c and the second tapered waveguide 3b is from g 3 Change to g 2 Then change to g 1 According to a circular function, where g 1 ＝0.40μm，g 2 ＝0.25μm，g 3 =0.40 μm; the vertical distance between the first output waveguide 4a and the first tapered waveguide 1b is G 0 =2.5 μm; length L of first thermal insulation coupler 1 And a second adiabatic coupler length L 2 All 28 μm, length L of intermediate connection waveguide 2b 0 The total length of the present invention is 60 μm (here length refers to the sum of the length of the coupling region + the length of the connecting waveguide, i.e. the length of the first adiabatic coupler, the intermediate connecting waveguide, the second adiabatic coupler. The input waveguide 1a, the second output waveguide 2c do not belong to the coupling region, they may be long or short for connecting other optoelectronic devices, and are therefore not calculated as the length of the polarizing beam splitter-combiner).
The tapering structure of the waveguides 1b, 3b, for simplicity, uses a linear taper, i.e. the first tapered waveguide 1b width is from w 2 Linearly change to w 3 The intermediate connection waveguide 2b width remains w 3 The second tapered waveguide 3b has a width from w 3 Linearly change to w 2 Wherein w is 2 ＝0.96μm，w 3 =1.50 μm. The length of the waveguides 1b and 3b can be determined by the EME algorithm scanning the output optimum result for a length of 5-70 μm, with a final choice of 28 μm. The intermediate connection waveguide 2b is used as a buffer to reduce crosstalk, after other parameters are determined, the output results of the waveguide 2b with lengths of 0, 1, 2, 3, 4 μm and the like can be calculated one by one through the FDTD algorithm, the optimal solution is obtained through calculation, and finally the optimal solution is determined to be 4 μm.
Fig. 4 shows a simulation of TE polarized fundamental mode propagation, and fig. 5 shows a simulation of TM polarized fundamental mode propagation.
The simulated spectral response for TE polarized light and TM polarized light inputs is shown in fig. 6. It can be seen that the extinction ratio is greater than 22.4dB and the loss is less than 0.22dB for TE polarized light in the wave band of 1500-1650 nm; the extinction ratio of TM polarized light in the wave band of 1500-1650nm is more than 19.0dB, the loss is less than 0.34dB, and the low-loss polarization beam splitter-combiner is realized on the premise of high extinction ratio.
Figures 7 and 8 show the spectral response of the TE and TM fundamental mode inputs in terms of transmission at two outputs when the waveguide width (e-beam lithography has an error of about 10-20nm for waveguide width, and manufacturing tolerances in the industry are commonly referred to as device width tolerances) deviates from the design by-20 nm and +20nm, respectively. It can be seen that the center band attachment can maintain a extinction ratio greater than 20dB and a loss of about 0.2dB only with a slight degradation in the edge band. In general, the polarizing beam splitter-combiner is capable of withstanding manufacturing tolerances of + -20nm, which is sufficient to cope with manufacturing errors produced by existing processes.
The effects of polarization splitting are stated above, and for polarized light combining, two polarized lights are respectively input from two ports (2 c, 4 a) on the right, and the effect is combining, which will not be described herein.
The polarization beam splitting-combining device based on the cascade adiabatic coupler can realize low-loss and high-extinction-ratio beam splitting and combining in a wider wave band, and has the following mechanism with certain manufacturing tolerance:
the bottom layer principle adiabatic evolution technology is derived from the quantum optical field, and is introduced into the integrated optical field due to the inherent consistency of the Schrodinger equation and the coupling mode equation, so that efficient and robust coupling between waveguides can be realized. Taking the first adiabatic coupler as an example, the coupling mode scheme is shown as follows:
in which A 1 And A 2 The electric field amplitudes of the guided modes in waveguide a and waveguide b, respectively, j being the imaginary unit, Ω representing the coupling coefficient, Δ representing the phase mismatch of waveguide a and waveguide b, in particular Δ= (β) 1 -β 2 ) 2, wherein beta 1 And beta 2 The propagation constants of the guided modes in waveguide a and waveguide b, respectively. We perform a similar diagonalization of the 2 x 2 matrix in equation (1) to obtain two eigenfunctions (also called supermodes) as follows:
Φ + (z)＝sinθ(z)|1>+cosθ(z)|2> (2)
Φ-(z)＝-cosθ(z)|1>+sinθ(z)|2> (3)
where the mixing angle θ (z) = (1/2) arctan (Ω/Δ), vector |1>＝[1,0] T And |2>＝[0,1] T Representing guided modes in waveguide a and waveguide b, respectively, and thus supermodes Φ + And phi is - Is a coherent superposition of guided modes of waveguide a and waveguide b.
When the phase mismatch delta is a very positive number, the coupling coefficient approaches 0, and the mixing angle theta=0, when light is input from the input waveguide 1a and enters the first curved waveguide 2a, the supermode phi is excited - Without overmoulding Φ + Is a function of the excitation of the (c). We can control the phase mismatch delta from a large positive number to a large negative number and the coupling coefficient omega from small to large to small, where the mixing angle theta gradually changes from 0 to pi/2, physically the guided mode in waveguide a will follow the overmode phi - Gradually evolves into the waveguide b. This process must remain adiabatic, i.e. there is no mutual coupling between the two supermodes, so the evolution of the mixing angle proceeds slowly.
For the above embodiment, in order to realize the polarization beam splitter-combiner, the distance between the first tapered waveguide 2a and the first curved waveguide 1b is changed from large to small and then is changed from large to small in the parameter design of the first adiabatic coupler, so that the coupling coefficient Ω is changed from small to large to small; the width of the first tapered waveguide 1b is from w 2 Change to w 3 What is important is w 2 And w 3 For TM polarization, it is possible to achieve a phase mismatch delta that varies from a large positive number to a large negative number to meet adiabatic coupling conditions to evolve into the first higher order mode of TM polarization in waveguide b, whereas for TE polarization, the variation of phase mismatch delta does not meet adiabatic coupling conditions and thus remains continuously transmitted in waveguide a and output from the first output waveguide 4 a. The second adiabatic coupler is the reverse of the first adiabatic evolution, and restores the TM polarized first higher order mode in waveguide b to the TM polarized fundamental mode in waveguide c and outputs from the second output port 2 c.
Adiabatic evolution is an efficient coupling mode, so that the TM fundamental mode in waveguide a will evolve efficiently into the TM first high-order mode in waveguide b, and then evolve efficiently into the TM fundamental mode in waveguide c, and the energy left in waveguide a will be less than 1%; for the TE fundamental mode, less than 5% of the energy may enter waveguide b, but due to the cascaded structure, the energy that eventually enters waveguide c is very small, so the scheme of the invention can achieve low loss and high extinction ratio. The method has the advantages that the influence on the coupling coefficient omega is larger, but the influence on the phase mismatch delta is smaller for the wavelength change and the manufacturing error, and the scheme still can achieve low-loss and high-efficiency light ratio in a certain wavelength range and a certain manufacturing error, so that the method has certain transmission bandwidth and manufacturing tolerance.
Although the above embodiments only verify that high optical ratio and low loss can be achieved in the wavelength band of 1500-1650nm, for other wavelengths, such as 2 μm, it is envisioned that the optimized design parameters (corresponding parameter design is performed for the wavelength) can achieve the beam splitting and combining effects in a wider wavelength band.
It should be stated again that the above embodiments are only used to explain the present invention, and should not be construed as limiting the specific protection scope of the present invention, in principle, a cascade structure of two adiabatic couplers is adopted, and the higher order modes of the intermediate waveguide are used as assistance to achieve the beam splitting and beam combining effects, which should be regarded as falling within the protection scope of the present invention.
Claims (10)
1. The polarization beam splitting-combining device based on the cascade adiabatic coupler is characterized by comprising an intermediate waveguide b and two other waveguides a and c used for light incidence and emergence, wherein the waveguide a, the waveguide b and the waveguide c form two cascade adiabatic couplers, a first adiabatic coupler formed by the waveguides a and b converts a TM polarization fundamental mode in incident light into a TM high-order mode of the intermediate waveguide b, a second adiabatic coupler formed by the waveguides b and c restores the TM high-order mode into a TM fundamental mode in the waveguide c, and TE polarized light in the incident light is remained in the waveguide a to achieve a polarization beam splitting effect; the beam combining effect can be realized by reversing the flow.
2. The polarization beam splitter-combiner according to claim 1, wherein the intermediate waveguide b is composed of a first tapered waveguide 1b whose core width varies from narrow to wide, a second tapered waveguide 3b whose width varies from narrow, and an intermediate connecting waveguide 2b horizontally connecting both wide ends;
the first tapered waveguide 1b is connected to the second tapered waveguide 3b via an intermediate connection waveguide 2b, and the intermediate connection waveguide 2b serves as a buffer to reduce crosstalk.
3. The polarization beam splitter-combiner of claim 2, wherein the core of the waveguides 1b, 3b adopts a single-sided linear graded structure, wherein the first tapered waveguide 1b core width is from w 2 Linearly change to w 3 The core width of the intermediate connection waveguide 2b is kept at w 3 The second tapered waveguide 3b has a core width from w 3 Linearly change to w 2 ，w 2 <w 3 。
4. A polarization beam splitter-combiner according to claim 3, wherein the lengths of waveguides 1b and 3b are determined by an EME algorithm scanning an optimal solution for a length of 5-70 μm; the length of the waveguide 2b is determined by the FDTD algorithm by calculating the optimal solution for the lengths of the waveguide 2b of 0, 1, 2, 3, 4 μm, etc.
5. The polarization beam splitter-combiner according to claim 2, wherein the waveguide a is constituted by an input waveguide 1a, a first curved waveguide 2a, an S-curved waveguide 3a, a first output waveguide 4 a;
the input waveguide 1a is connected with the first output waveguide 4a after passing through the first curved waveguide 2a and the S-curved waveguide 3a in sequence, and the S-curved waveguide 3a is used for separating the waveguide a from the second adiabatic coupler far enough to eliminate coupling between the two and reduce crosstalk.
6. The polarization beam splitter-combiner according to claim 5, wherein the S-bend waveguide 3a is formed of two circular arcs, and the curvature is designed so that part of the remaining TM mode can be filtered out with little influence on the transmission loss of the TE mode, and the transmission loss of the TE mode is controlled to be 1% or less.
7. The polarizing beam splitter-combiner according to claim 2, wherein,
the waveguide c is composed of a second bending waveguide 1c and a second output waveguide 2 c;
the second curved waveguide 1c is connected to the second output waveguide 2 c.
8. The polarization beam splitter-combiner of claim 5, wherein the first curved waveguide 2a is adjacent to the non-tapered side of the first tapered waveguide 1b, the first curved waveguide 1b is shaped such that the spacing between the core layers of the first tapered waveguide 1b and the first tapered waveguide 2a changes from large to small to large, the width of the core layers of the first tapered waveguide 1b changes, and the spacing between the core layers of the first tapered waveguide 1b and the first curved waveguide 2a is designed such that they are adiabatically coupled to form the first adiabatic coupler and the adiabatic coupling condition is such that efficient coupling is satisfied for TM polarization and low loss transmission is satisfied for TE polarization.
9. The polarization beam splitter-combiner according to claim 7, wherein the second curved waveguide 1c is close to the non-graded side of the second tapered waveguide 3b, the second curved waveguide 1c is shaped such that the distance between the core layers of the second tapered waveguide 3b and the second curved waveguide is changed from large to small, and the width of the core layer of the second tapered waveguide 3b is changed, and the distance between the core layers of the second tapered waveguide 3b and the second curved waveguide 1c is designed such that they are adiabatically coupled to form the second adiabatic coupler, and the adiabatic coupling condition satisfies efficient coupling for TM polarization and is extremely low for TE polarization coupling efficiency.
10. The polarizing beam splitter-combiner of claim 7, wherein each of the waveguides is preferably a rectangular waveguide.
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| CN117289390A (en) * | 2023-09-15 | 2023-12-26 | 深圳技术大学 | On-chip integrated polarization beam splitter based on silicon nitride ridge optical waveguide |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117289390A (en) * | 2023-09-15 | 2023-12-26 | 深圳技术大学 | On-chip integrated polarization beam splitter based on silicon nitride ridge optical waveguide |
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