Polarization beam splitter based on stress birefringence effect

Abstract

The invention provides a polarization beam splitter based on a stress birefringence effect, which comprises a first waveguide and a second waveguide, and the first waveguide and the second waveguide are arranged in parallel along a first direction; wherein the first waveguide sequentially comprises a first input waveguide, a first input coupling waveguide, a stress birefringence waveguide, a first output coupling waveguide and a first output waveguide in the second direction; the second waveguide sequentially comprises a second input waveguide, a second input coupling waveguide, a transmission waveguide, a second output coupling waveguide and a second output waveguide in the second direction; a first stress regulation and control groove and a second stress regulation and control groove are respectively formed in two sides of the stress birefringence waveguide along the first direction; and the stress birefringence waveguide, the first stress regulation and control groove and the second stress regulation and control groove jointly form a double-groove regulation and control waveguide stress structure.

Description

Technical Field

[0001] The present invention relates to the field of photon integration technology, and particularly to a polarization beam splitter based on the stress birefringence effect. Background Art

[0002] With the continuous improvement of the requirements for the transmission capacity and rate of optical communication, coherent optical communication has advantages such as high sensitivity and high spectral efficiency, and is a key technology for significantly improving the communication capacity. Technologies such as polarization multiplexing-phase shift keying and polarization multiplexing-orthogonal amplitude modulation can make full use of multi-dimensional information such as the polarization, phase, and amplitude of light to increase the communication capacity and rate. Among them, the polarization beam splitter is an important device for realizing polarization control.

[0003] The polarization beam splitter based on planar optical waveguide technology usually adopts a Mach-Zehnder interferometer structure or a directional coupling structure, and uses the geometric birefringence effect to achieve polarization beam splitting. However, the geometric birefringence effect is very sensitive to the waveguide width, resulting in poor polarization extinction performance and large wavelength correlation. How to improve the polarization extinction ratio in a wide spectral range is a difficult problem that needs to be solved at present. Summary of the Invention

[0004] In view of the above deficiencies, the present invention provides a polarization beam splitter based on the stress birefringence effect, which includes a first waveguide and a second waveguide, and the first waveguide and the second waveguide are arranged side by side along a first direction; wherein, the first waveguide sequentially includes a first input waveguide, a first input coupling waveguide, a stress birefringence waveguide, a first output coupling waveguide, and a first output waveguide along a second direction; the second waveguide sequentially includes a second input waveguide, a second input coupling waveguide, a transmission waveguide, a second output coupling waveguide, and a second output waveguide along the second direction; first stress regulation trenches and second stress regulation trenches are respectively arranged on both sides of the stress birefringence waveguide along the first direction, and the stress birefringence waveguide, the first stress regulation trench, and the second stress regulation trench together form a double-trench regulation waveguide stress structure.

[0005] In the above solution, the first input coupling waveguide and the second input coupling waveguide are arranged side by side along the first direction to form an input coupling region, and the first output coupling waveguide and the second output coupling waveguide are arranged side by side along the first direction to form an output coupling region; both the input coupling region and the output coupling region have coupling functions.

[0006] In the above solution, the process of realizing polarization beam splitting by the polarization beam splitter includes: after the light is coupled into from the first input waveguide or the second input waveguide, it is equally divided into two beams of light with equal power in the input coupling region and respectively enters the stress birefringence waveguide and the transmission waveguide; when the two beams of light respectively entering the stress birefringence waveguide and the transmission waveguide reach the output coupling region, interference will occur and they will be respectively coupled into the first output waveguide and the second output waveguide to realize polarization beam splitting.

[0007] In the above solution, the stress birefringence waveguide causes a refractive index difference in light, and there is a phase difference between the light transmitted by the stress birefringence waveguide and the light transmitted by the transmission waveguide.

[0008] In the above solution, the transmission waveguide and the stress birefringence waveguide have the same length.

[0009] In the above solution, the first stress control trench and the second stress control trench have the same length.

[0010] In the above solution, both the first waveguide and the second waveguide are strip waveguides.

[0011] In the above solution, the height and width of the first waveguide and the second waveguide along the light transmission direction remain unchanged.

[0012] In the above solution, the first direction and the second direction are perpendicular to each other, and the second direction is parallel to the light transmission direction.

[0013] In the above solution, the materials of the waveguide structure in the polarization beam splitter include silicon dioxide, silicon nitride, silicon, III-V materials, lithium niobate, and polymers. Description of the Drawings

[0014] Figure 1 Schematically shows a top view of the structure of a polarization beam splitter based on the stress birefringence effect according to an embodiment of the present invention;

[0015] Figure 2 Schematically shows a cross-sectional view of a double trench controlled waveguide stress structure according to an embodiment of the present invention;

[0016] Figure 3 Schematically shows a graph of the polarization extinction ratio of a polarization beam splitter according to an embodiment of the present invention varying with the input light wavelength.

[0017] [Description of the Reference Numerals]

[0018] 1 - First waveguide; 2 - Second waveguide; 3 - Input coupling region; 4 - Output coupling region; 5 - Upper cladding; 6 - Lower cladding; 7 - Substrate; 8 - Core layer; 11 - First input waveguide; 12 - First input coupling waveguide; 13 - Stress birefringence waveguide; 14 - First output coupling waveguide; 15 - First output waveguide; 16 - First stress control trench; 17 - Second stress control trench; 18 - Double trench controlled waveguide stress structure; 21 - Second input waveguide; 22 - Second input coupling waveguide; 23 - Transmission waveguide; 24 - Second output coupling waveguide; 25 - Second output waveguide. Detailed Embodiments

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to specific embodiments and the accompanying drawings.

[0020] Figure 1 Schematically shows a top view of the structure of a polarization beam splitter based on the stress birefringence effect according to an embodiment of the present invention. Figure 2 Schematically shows a cross-sectional view of a double-groove regulated waveguide stress structure according to an embodiment of the present invention.

[0021] As Figure 1 shown, the polarization beam splitter based on the stress birefringence effect includes a first waveguide 1 and a second waveguide 2, and the first waveguide 1 and the second waveguide 2 are arranged side by side along a first direction X1; wherein, the first waveguide 1 sequentially includes a first input waveguide 11, a first input coupling waveguide 12, a stress birefringence waveguide 13, a first output coupling waveguide 14, and a first output waveguide 15 along a second direction X2; the second waveguide sequentially includes a second input waveguide 21, a second input coupling waveguide 22, a transmission waveguide 23, a second output coupling waveguide 24, and a second output waveguide 25 along the second direction X2.

[0022] As Figure 1 shown, a first stress regulation groove 16 and a second stress regulation groove 17 are respectively arranged on both sides of the stress birefringence waveguide 13 along the first direction X1, and the stress birefringence waveguide 13, the first stress regulation groove 16, and the second stress regulation groove 17 together form a double-groove regulated waveguide stress structure 18.

[0023] Furthermore, as Figure 2 shown, the double-groove regulated waveguide stress structure 18 includes a substrate 7, an upper cladding 5, and a lower cladding 6, wherein the upper cladding 5 includes the stress birefringence waveguide 13 and the first stress regulation groove 16 and the second stress regulation groove 17 are respectively arranged on both sides along the first direction X1, and the stress birefringence waveguide 13 further includes a core layer 8. For example, the substrate 7 can be a silicon substrate, the thickness of the core layer 8 of the waveguide can be 6.5 μm, and the thicknesses of the upper cladding 5 and the lower cladding 6 can both be 20 μm.

[0024] In an embodiment of the present invention, the first direction X1 and the second direction X2 are perpendicular to each other.

[0025] Exemplarily, both the first waveguide 1 and the second waveguide 2 are strip waveguides.

[0026] In an embodiment of the present invention, the height and width of the first waveguide 1 and the second waveguide 2 along the optical transmission direction remain unchanged.

[0027] Exemplarily, the lengths of the transmission waveguide 23 and the stress birefringence waveguide 13 are the same.

[0028] Exemplarily, the lengths of the first stress regulation groove 16 and the second stress regulation groove 17 are the same.

[0029] In an embodiment of the present invention, the material of the waveguide structure in the polarization beam splitter may be silica, silicon nitride, silicon, III-V materials, lithium niobate, polymer, or the like.

[0030] Further, as Figure 1 shown, the first input coupling waveguide 12 and the second input coupling waveguide 22 are arranged side by side along the first direction X1 to form an input coupling region 3, and the first output coupling waveguide 14 and the second output coupling waveguide 24 are arranged side by side along the first direction X1 to form an output coupling region 4; both the input coupling region 3 and the output coupling region 4 have a coupling function.

[0031] Exemplarily, both the input coupling region 3 and the output coupling region 4 may have a 3 dB (polarization extinction ratio) coupling function.

[0032] Based on the above polarization beam splitter based on the stress birefringence effect, in an embodiment of the present invention, the process of realizing polarization beam splitting of light in the polarization beam splitter includes: after light is coupled into from the first input waveguide 11 or the second input waveguide 21, it is equally divided into two beams of light with equal power in the input coupling region 3 and respectively enters the stress birefringence waveguide 13 and the transmission waveguide 23; when the two beams of light respectively entering the stress birefringence waveguide 13 and the transmission waveguide 23 reach the output coupling region 4, interference will occur and they will be respectively coupled into the first output waveguide 15 and the second output waveguide 25, realizing polarization beam splitting.

[0033] Specifically, polarized light in the TE (transverse electric wave) / TM (transverse magnetic wave) mode is input from one side, that is, the polarized light is coupled into the polarization beam splitter from the first input waveguide 11 or the second input waveguide 21. In the input coupling region 3, it is equally divided into two beams of polarized light with equal power and respectively enters the stress birefringence waveguide 13 and the transmission waveguide 23. The stress birefringence effect will cause a refractive index difference of the TE / TM polarized light in the stress birefringence waveguide 13, such that there is a large and different phase difference between the light transmitted in the stress birefringence waveguide 13 and the light transmitted in the transmission waveguide 23. It should be noted that the light transmission direction is parallel to the second direction X2 here.

[0034] Further, by reasonably designing the lengths of the stress birefringence waveguide 13 and the transmission waveguide 23, the TE / TM polarized light can interfere and be respectively coupled into the first output waveguide 15 and the second output waveguide 25 when reaching the output coupling region 4, so that polarization beam splitting with a high polarization extinction ratio can be achieved within a wide spectral range.

[0035] In an embodiment of the present invention, the calculation formula for the length of the stress birefringence waveguide 13 is:

[0036]

[0037]

[0038] Where L is the length of the stress birefringence waveguide 13, λ is the working wavelength, (Δn) TE is the stress-induced refractive index difference for the TE mode, and (Δn) TM is the stress-induced refractive index difference for the TM mode. N and M are positive integers respectively.

[0039] In an embodiment of the present invention, the formula for the polarization extinction ratio is:

[0040]

[0041]

[0042] Where P TE1 and P TM1 are the output optical powers of the TE and TM polarized lights output from the first output waveguide 15 respectively; P TE2 and P TM2 are the output optical powers of the TE and TM polarized lights output from the second output waveguide 25 respectively.

[0043] Through the embodiment of the present invention, the polarization beam splitter based on the stress birefringence effect adopts a double-groove regulated waveguide stress structure, has strong polarization-related mode field distribution regulation characteristics, and separates the transverse electric mode TE and the transverse magnetic mode TM into different output waveguides through the stress birefringence effect. The polarization beam splitter can achieve effective polarization beam splitting in a wide spectral range, has a high polarization extinction ratio, and has a simple preparation process, which is beneficial to compact large-scale photon integration applications.

[0044] Figure 3 Schematically shows the relationship diagram of the polarization extinction ratio of the polarization beam splitter according to the embodiment of the present invention changing with the input optical wavelength.

[0045] Exemplarily, the input lights are TE and TM lights with wavelengths of 1530 - 1570 nm. From Figure 3 the simulation results of the relationship between the polarization extinction ratio and the input optical wavelength, it can be seen that in the wide spectral range of 1530 - 1570 nm, the polarization extinction ratios of TE and TM lights both exceed 25 dB, realizing effective polarization beam splitting.

[0046] In the embodiments of the present invention, for a polarization beam splitter based on the stress birefringence effect where light is coupled into unidirectionally from a waveguide, at the input coupling region, the light is equally divided into two beams with equal power and respectively enters the stress birefringence waveguide and the transmission waveguide. The stress birefringence effect will cause a refractive index difference between TE and TM polarized lights in the stress birefringence waveguide. Therefore, when the TE and TM polarized lights propagate in the stress birefringence waveguide and the transmission waveguide, a large and different phase difference will be generated. By reasonably designing the lengths of the stress birefringence waveguide and the transmission waveguide, the TE and TM polarized lights will interfere and be respectively coupled into the first output waveguide and the second output waveguide when reaching the output coupling region, realizing polarization beam splitting. This polarization beam splitter based on the stress birefringence effect can achieve polarization beam splitting with a high polarization extinction ratio in a wide spectral range.

[0047] Those skilled in the art can understand that although the present invention has been shown and described with reference to specific exemplary embodiments of the present invention, those skilled in the art should understand that various changes in form and details can be made to the present invention without departing from the spirit and scope of the present invention defined by the appended claims and their equivalents. Therefore, the scope of the present invention should not be limited to the above embodiments, but should be determined not only by the appended claims but also by the equivalents of the appended claims.

[0048] In the above specific embodiments, the purpose, technical solutions, and beneficial effects of the present invention have been further described in detail. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A polarization beam splitter based on stress birefringence effect, characterized in that: It comprises a first waveguide (1) and a second waveguide (2), wherein the first waveguide (1) and the second waveguide (2) are arranged in parallel along a first direction; The first waveguide (1) comprises, in sequence along the second direction, a first input waveguide (11), a first input coupling waveguide (12), a stress birefringence waveguide (13), a first output coupling waveguide (14) and a first output waveguide (15); The second waveguide comprises, in sequence along the second direction, a second input waveguide (21), a second input coupling waveguide (22), a transmission waveguide (23), a second output coupling waveguide (24), and a second output waveguide (25); A first stress regulating groove (16) and a second stress regulating groove (17) are respectively arranged on both sides of the stress birefringence waveguide (13) along a first direction; the stress birefringence waveguide (13), the first stress regulating groove (16) and the second stress regulating groove (17) together constitute a double-groove regulating waveguide stress structure (18).

2. The polarization beam splitter based on stress birefringence effect according to claim 1, characterized in that: The first input coupling waveguide (12) and the second input coupling waveguide (22) are arranged in parallel along a first direction to form an input coupling region (3), and the first output coupling waveguide (14) and the second output coupling waveguide (24) are arranged in parallel along the first direction to form an output coupling region (4); The input coupling region (3) and the output coupling region (4) both have a coupling function.

3. The polarization beam splitter based on stress birefringence effect according to claim 2, characterized in that: The process of achieving polarization beam splitting of light in the polarization beam splitter includes: After light is coupled into the first input waveguide (11) or the second input waveguide (21), it is divided into two beams of light with equal power in the input coupling region (3) and enters the stress birefringence waveguide (13) and the transmission waveguide (23) respectively; When the two beams of light respectively entering the stress birefringence waveguide (13) and the transmission waveguide (23) reach the output coupling region (4), interference occurs and the two beams of light respectively couple into the first output waveguide (15) and the second output waveguide (25), thereby achieving polarization beam splitting.

4. The polarization beam splitter based on stress birefringence effect according to claim 1 or 3, characterized in that: The stress birefringence waveguide (13) causes a refractive index difference in light, and there is a phase difference between the light transmitted by the stress birefringence waveguide (13) and the light transmitted by the transmission waveguide (23).

5. The polarization beam splitter based on stress birefringence effect according to claim 1, characterized in that: The transmission waveguide (23) has the same length as the stress birefringence waveguide (13).

6. The polarization beam splitter based on stress birefringence effect according to claim 1, characterized in that: The first stress regulating groove (16) and the second stress regulating groove (17) have the same length.

7. The polarization beam splitter based on stress birefringence effect according to claim 1, characterized in that: The first waveguide (1) and the second waveguide (2) are both strip waveguides.

8. The polarization beam splitter based on stress birefringence effect according to claim 1, characterized in that: The height and width of the first waveguide (1) and the second waveguide (2) along the light transmission direction are maintained unchanged.

9. The polarization beam splitter based on stress birefringence effect according to claim 1 or 3, characterized in that: The first direction and the second direction are perpendicular to each other, and the second direction and the light transmission direction are parallel to each other.

10. The polarization beam splitter based on stress birefringence effect according to claim 1, characterized in that: The materials of the waveguide structure in the polarization beam splitter include silicon dioxide, silicon nitride, silicon, III-V group materials, lithium niobate and polymer.

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