Optical polarization beam splitter

Abstract

The invention belongs to the field of photon integrated circuit systems, and discloses an optical polarization beam splitter which comprises an isolation layer and a waveguide core layer arranged on the isolation layer. A first light transmission section, a polarization section and a second light transmission section are sequentially formed on the waveguide core layer from one side to the other side, a light input section and a reflected light output section which are arranged at intervals are formed on the first light transmission section, and the second light transmission section at least comprises a refracted light output section; at least one group of strip-shaped grooves are formed in the polarization section; the set of strip-shaped grooves comprises a first groove section and a second groove section which are arranged in an intersecting mode. The optical polarization beam splitter can achieve the effects of total reflection in alignment with a TE0 mode and transmission in alignment with a TM0, thereby realizing polarization beam splitting. Total reflection aligned to a TE0 mode can be realized in a single period, a multi-period array is avoided in principle, and the structural complexity and the size of the beam splitter are greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of photonic integrated circuit systems, and in particular relates to an optical polarization beam splitter. Background Art

[0002] Silicon-based integrated photonics has attracted much attention due to its ultra-high integration density and compatibility with complementary metal oxide semiconductor (CMOS) processes, and has become the focus of research and production in the past decade. However, silicon waveguides have a high cladding-core refractive index contrast, which produces a modal birefringence effect. Therefore, integrated silicon photonic devices are often polarization-dependent and bring about a series of problems such as polarization mode dispersion and polarization-dependent loss. Polarization beam splitters are key devices for splitting and combining two orthogonal polarized lights - transverse electric (TE) polarized light and transverse magnetic (TM) polarized light - and are therefore widely used in various optical systems, including coherent optical transceivers, polarization-transparent chips, integrated quantum optics, etc.

[0003] In recent years, many types of polarization beam splitters have been manufactured. Polarization beam splitters based on directional coupler (DC) design are one of the most common polarization beam splitters, including asymmetric DC, hybrid surface plasma DC, bent DC, three-waveguide DC, subwavelength grating structure (SWG) assisted DC, etc. When dealing with different application scenarios, directional coupler-type polarization beam splitters can flexibly design different structural parameters to meet the requirements of insertion loss (IL), extinction ratio (ER) and bandwidth (BW). SWG-assisted directional coupler-type polarization beam splitters have good performance, but often have a large number of fine structures; other types of directional coupler-type polarization beam splitters have simple structures but it is difficult to take into account high extinction ratio and large bandwidth, and the sensitivity of coupling length also reduces the robustness of the process. Polarization beam splitters based on multimode interference coupler (MMI) design have a high tolerance to process errors, and the device length is in the order of hundreds of microns. Some specially designed MMIs such as tilted MMI, SWG-assisted MMI and photonic crystal MMI can reduce the device size and have better performance. Photonic crystal polarization beam splitters and metamaterial polarization beam splitters can design the dispersion relationship of polarized light by designing structural parameters. Therefore, these two types of polarization beam splitters can achieve a relatively ideal beam splitting effect in a small size. However, the more sophisticated structure increases the difficulty and cost of manufacturing. The reverse-designed polarization beam splitter has a small size, high integration, and flexible design, but the design time cost is relatively high.

[0004] SWG provides a new method to manipulate the response of light and control the flow of light, so it is widely used in various silicon-based devices. Adjusting the period and duty cycle of the SWG structure can flexibly control the equivalent refractive index and dispersion relationship, and a properly designed SWG structure can achieve the desired optical properties. Therefore, the SWG structure is widely used in the design of beam splitters. The SWG-assisted DC designed by Li et al. achieved a high extinction ratio of >25dB and an extremely high bandwidth of >220nm, which is the best among DC-type polarization beam splitters; the SWG-assisted polarization beam splitter designed by Xu et al. maintained an extinction ratio of >20dB and a bandwidth of >200nm while compressing the device size to 12μm, achieving high integration and high bandwidth compatibility. When the SWG duty cycle is changed, both TE and TM polarizations are modulated, which will bring certain obstacles to the design of the device. Compared with the vertical SWG with the same period and duty cycle, the inclined SWG mainly regulates the TE mode and has little effect on the TM mode, so it is also often used in the design of polarization beam splitters. Compared with the normal-SWG MMI, the extinction ratio of the tilted-SWG MMI is nearly doubled and the bandwidth is increased by about 50%.

[0005] At present, the number of periods of the structure in high-performance SWG-assisted polarization beam splitters ranges from about 20 to more than 500, which means that light needs to propagate a long distance in the birefringent medium to effectively achieve polarization beam splitting. This greatly limits the minimum line width, processing error and high requirements of the manufacturing process of this type of polarization beam splitter. The large number of fine structure arrangements increases the manufacturing cost and process requirements of the device. Summary of the invention

[0006] In view of the shortcomings of the prior art mentioned above, the object of the present invention is to provide an optical polarization beam splitter for solving the technical problems existing in the prior art of polarization beam splitters with respect to minimum line width, processing errors and high requirements for process manufacturing, while achieving low insertion loss and high extinction ratio, having the characteristics of large operating bandwidth, large minimum line width and high process tolerance.

[0007] The technical concept of the present invention is to set a strip-shaped groove in the waveguide core layer, and embed a medium with a refractive index lower than the refractive index of the waveguide core layer material in the groove to form a sub-wavelength grating structure with a birefringence characteristic, so that the sub-wavelength grating structure forms a polarization-dependent equivalent refractive index (n ⊥,TE and n ⊥,TM ) and placed at a certain angle to two polarized lights in different directions (quasi-TE 0 Polarized light and quasi-TM 0Polarized light) can achieve different degrees of refractive index mismatch, resulting in total reflection of one polarized light and transmission of another polarized light, thereby achieving the purpose of polarization beam splitting using a single-period subwavelength grating structure, and then realizing the design of a high-performance optical polarization beam splitter using a simple structure.

[0008] To achieve the above object, the present invention utilizes the birefringence effect of the sub-wavelength grating structure to form a polarization-dependent equivalent refractive index (n ⊥,TE and n ⊥,TM ), an optical polarization beam splitter is designed. The present invention is implemented by including the following technical solutions.

[0009] The first aspect of the present invention discloses an optical polarization beam splitter, which includes an isolation layer and a waveguide core layer arranged on the isolation layer; the waveguide core layer is sequentially formed with a first light transmission segment, a polarization segment and a second light transmission segment from one side to the other side, the first light transmission segment is formed with a light input segment and a reflected light output segment arranged at intervals, and the second light transmission segment at least includes a refracted light output segment; the polarization segment is formed with at least one group of strip-shaped grooves; the group of strip-shaped grooves includes a first groove segment and a second groove segment arranged to intersect.

[0010] The intersection described in the present application includes one or more of direct intersection and extended line intersection.

[0011] Preferably, the polarization segment is formed with N groups of strip-shaped grooves, N is an integer of 2 to 10, and the first groove segments are arranged in parallel and spaced correspondence with each other, and the second groove segments are arranged in parallel and spaced correspondence with each other. For example, N can be 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0012] More preferably, any one of the first groove segments or the second groove segments and adjacent intervals thereof form a layer of sub-wavelength grating structure.

[0013] Furthermore, N is an integer of 2 to 5. When N is greater than 5, although low insertion loss and high extinction ratio can still be achieved, it is difficult to process due to the large size. In a specific embodiment, N is 3.

[0014] More preferably, the width of any interval is d 1 ; The width of any first groove segment or second groove segment is d 2 ;d 1 150~240nm; d 2 80~120nm; d 1 -d 2 In the present application, the width refers to the distance that the light passes through the interval or the first groove segment or the second groove segment in the direction of arrangement of the vertical strip-shaped grooves.

[0015] As described1 It can be 150-160nm, 160-170nm, 170-180nm, 180-190nm, 190-200nm, 200-210nm, 210-220nm, 220-230nm, 230-240nm. In some specific embodiments, the d 1 It is 190~210nm.

[0016] As described 2 It can be 80-85nm, 85-90nm, 90-95nm, 95-100nm, 100-105nm, 105-110nm, 110-115nm, 115-120nm. In some specific embodiments, the d 2 It is 90~105nm.

[0017] As described 1 -d 2 It may be 30-35 nm, 35-40 nm, 40-45 nm, 45-50 nm, 50-55 nm, 55-60 nm, 60-65 nm, 65-70 nm, 70-75 nm, 75-80 nm, 80-85 nm, 85-90 nm, 90-95 nm, 95-100 nm, 100-105 nm, 105-110 nm, 110-115 nm, 115-120 nm.

[0018] Furthermore, the duty cycle of the sub-wavelength grating structure is 0.55-0.75; the duty cycle is calculated as follows: ρ=d 1 / Λ, ρ is the duty cycle of the sub-wavelength grating structure, Λ is the period of the sub-wavelength grating structure, Λ=d 1 +d 2 As described above, ρ can be 0.55-0.56, 0.56-0.57, 0.57-0.58, 0.58-0.59, 0.59-0.60, 0.60-0.61, 0.61-0.62, 0.62-0.63, 0.63-0.64, 0.64-0.65, 0.65-0.66, 0.66-0.67, 0.67-0.68, 0.68-0.69, 0.69-0.70, 0.70-0.71, 0.71-0.72, 0.72-0.73, 0.73-0.74, 0.74-0.75.

[0019] Furthermore, quasi-TE 0 The equivalent refractive index of the mode light in the subwavelength grating structure perpendicular to the arrangement direction of the strip-shaped grooves is n ⊥,TE ; Quasi TM 0The equivalent refractive index of the mode light in the subwavelength grating structure perpendicular to the arrangement direction of the strip-shaped grooves is n ⊥,TM ;Quasi TE 0 The effective refractive index of the mode light in the first light transmission section is n TE , quasi TM 0 The effective refractive index of the mode light in the first light transmission section is n TM , n TE >n TM ; When the first groove segment and the second groove segment are perpendicular, n ⊥,TE <n TE ·sin45°; n ⊥,TM >n TM ·sin45°.

[0020] Preferably, the first groove segment and the second groove segment arranged to intersect are both filled with a light-splitting material, and the refractive index of the light-splitting material is lower than the refractive index of the material of the waveguide core layer (10).

[0021] More preferably, the spectroscopic material is selected from SiO 2 , SiC, SU-8 photoresist, polymethyl methacrylate, and hydrogen silsesquioxane.

[0022] Preferably, a group of the strip-shaped grooves are in an "X" shape, a "Y" shape, or a "V" shape. More preferably, the strip-shaped grooves are in an "X" shape. In a specific embodiment, the strip-shaped grooves are in an "X" shape and the angle between the first groove segment and the second groove segment is 90°.

[0023] Preferably, the thickness of the isolation layer is 1.5-4 μm. For example, the thickness of the isolation layer may be 1.5-1.6 μm, 1.6-1.7 μm, 1.7-1.8 μm, 1.8-1.9 μm, 1.9-2.0 μm, 2.0-2.1 μm, 2.1-2.2 μm, 2.2-2.3 μm, 2.3-2.4 μm, 2.4-2.5 μm, 2.5-2.6 μm, 2.6-2.7 μm. , 2.7~2.8μm, 2.8~2.9μm, 2.9~3.0μm, 3.0~3.1μm, 3.1~3.2μm, 3.2~3.3μm, 3.3~ 3.4μm, 3.4~3.5μm, 3.5~3.6μm, 3.6~3.7μm, 3.7~3.8μm, 3.8~3.9μm, 3.9~4.0μm.

[0024] Preferably, the material of the isolation layer is SiO 2 .

[0025] Preferably, the material of the waveguide core layer is Si.

[0026] Preferably, the thickness of the waveguide core layer is 200-500 nm. For example, the thickness of the waveguide core layer may be 200-220 nm, 220-240 nm, 240-260 nm, 260-280 nm, 280-300 nm, 300-320 nm, 320-340 nm, 340-360 nm, 360-380 nm, 380-400 nm, 400-420 nm, 420-440 nm, 440-460 nm, 460-480 nm, 480-500 nm. In some specific embodiments, the thickness of the waveguide core layer is 220 nm.

[0027] Preferably, the optical polarization beam splitter further comprises an upper cladding layer for preventing scattering.

[0028] More preferably, the refractive index of the upper cladding material is smaller than the equivalent refractive index of the sub-wavelength grating structure.

[0029] Furthermore, the material of the upper cladding layer is selected from SiO 2 , SiC, SU-8 photoresist, polymethyl methacrylate, and hydrogen silsesquioxane.

[0030] Preferably, the optical polarization beam splitter further comprises a substrate arranged at the bottom layer.

[0031] More preferably, the material of the substrate is selected from one of Si, gallium arsenide, gallium nitride and silicon carbide.

[0032] Preferably, the effective refractive index of the first light transmitting segment is greater than the refractive index of the material of the isolation layer.

[0033] Preferably, when the first groove segment and the second groove segment are perpendicular, the optical polarization beam splitter is quasi-TE at a wavelength of 1549 to 1551 nm. 0 Mode light and quasi TM 0 Under mode light, the extinction ratio is 20~60dB and the insertion loss ratio is 0.1~2dB.

[0034] Preferably, the distance between the light input section and the reflected light output section is w gap , w gap 1 to 10 μm. gap It can be 1 to 2 μm, 2 to 3 μm, 3 to 4 μm, 4 to 5 μm, 5 to 6 μm, 6 to 7 μm, 7 to 8 μm, 6 to 9 μm, or 9 to 10 μm. The w gap The spacing is 1 to 10 μm to reduce the mode coupling effect in the input and output sections.

[0035] Preferably, the width of the light input section, the reflected light output section and the second light transmission section is w taper , wtaper 3.5 to 10 μm. taper It can be 3.5-4 μm, 4-5 μm, 5-6 μm, 6-7 μm, 7-8 μm, 6-9 μm, 9-10 μm. taper 3.5~10μm to reduce the quasi-TE 0 and TM 0 Divergence angles of the two modes.

[0036] The equivalent refractive index in this application refers to the effective refractive index n of the light source in the direction perpendicular to the arrangement direction of the sub-wavelength grating structure. ⊥,TE and n ⊥,TM . The ⊥,TE and n ⊥,TM The calculation method is as follows:

[0037] First, use the wave optics module in COMSOL or the FDTD module in Ansys Lumerical to input d 1 ,d 2 , the refractive index of each layer of the polarization beam splitter and the thickness and size of each layer are used to calculate the quasi-TE in the sub-wavelength grating structure 0 Mode light and quasi TM 0 The propagation constant k of the Bloch eigenmode of the mode light propagating in the direction perpendicular to the arrangement of the subwavelength grating structure is ⊥,TE and k ⊥,TM , then according to the formula:

[0038]

[0039] The equivalent refractive index n can be obtained by calculation ⊥,TE and n ⊥,TM . Where λ is the quasi-TE 0 Mode light and quasi TM 0 The wavelength of the mode light, π is the circumference of a circle.

[0040] In addition to the software listed above, the above calculations can be implemented in software that includes optical numerical calculation methods such as finite element method, finite difference time domain method, beam propagation method, etc.

[0041] In the present application, the refractive index of the isolation layer, the upper cladding layer and the substrate is the refractive index of the material of each layer itself.

[0042] The effective refractive index n TE 、n TM , which is related to the materials and dimensions of the waveguide core layer, the isolation layer and the upper cladding layer. Specifically, by using the wave optics module in the COMSOL software or the MODE module in the Ansys Lumerical software, input d 1 ,d2 , the refractive index of each layer material and the thickness of each layer of the polarization beam splitter are calculated.

[0043] The design process of the polarization beam splitter of the present invention is: within the target wavelength range, according to the changes of the materials of each layer, the cross-sectional dimensions of the first light transmission section and the second light transmission section are reasonably selected to make the quasi-TE 0 and TM 0 The two modes of light satisfy n TE >n TM The light source enters the polarization section through the light input section, and the period Λ and duty cycle ρ of the sub-wavelength grating structure are adjusted to make the quasi-TE 0 and TM 0 The equivalent refractive index of the two modes of light in the subwavelength grating structure perpendicular to the arrangement direction of the periodic structure is similar to the quasi-TE 0 and TM 0 The effective refractive index of the two modes of light in the first light transmission section satisfies n ⊥,TE <n TE sin45° and n ⊥,TM >n TM ·sin45°, thus making quasi-TE 0 The mode light is totally reflected by the sub-wavelength grating structure, so that its energy is mainly concentrated in the reflected light path and output from the reflected light output section; at the same time, it ensures TM 0 The mode light is transmitted through the sub-wavelength grating structure, so that its energy is mainly concentrated in the transmission light path and output from the refracted light output section.

[0044] A second aspect of the present invention provides an optical chip, comprising the optical polarization beam splitter as described above.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1) The present invention realizes alignment of TE by utilizing the birefringence effect of the tilted sub-wavelength grating structure 0 Mode Total Reflection and AlignmentTM 0 The transmission effect can achieve polarization beam splitting. 1 and d 2 Under the condition of TE, a single cycle can achieve alignment 0 The total reflection of the mode avoids the multi-period array of sub-wavelength grating structures in principle, greatly reducing the structural complexity and size of the beam splitter.

[0047] 2) The strip-shaped groove arrangement of the present invention enables the polarization beam splitter to have a very large bandwidth range, with an extinction ratio ER greater than 20 dB and an insertion loss IL less than 2 dB in the wavelength range of 1429 to 1923 nm.

[0048] 3) The polarization beam splitter described in the present invention can achieve polarization fraction in a single cycle, so that its minimum line width can be the minimum width of the strip groove segment, and can still achieve high extinction ratio and low insertion loss within an error of ±10%, with a larger minimum line width and higher process tolerance.

[0049] 4) The present invention has a relatively simple structure and can be manufactured using standard semiconductor manufacturing processes with mature technology, which can effectively reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Shown is a schematic diagram of the three-dimensional structure of the optical polarization beam splitter of the present invention.

[0051] Figure 2 The schematic diagram shows the optical polarization beam splitter of the present invention performing light polarization beam splitting.

[0052] Figure 3 The figure shows one of the cross-sectional schematic diagrams of the optical polarization beam splitter of the present invention.

[0053] Figure 4 The figure shows the second cross-sectional schematic diagram of the optical polarization beam splitter of the present invention.

[0054] Figure 5 Shown is a top view of the sub-wavelength grating structure in the optical polarization beam splitter of the present invention.

[0055] Figure 6 Shown is a mode length distribution diagram of the optical polarization beam splitter of the present invention.

[0056] Figure 7 Shown is a schematic diagram of insertion loss and extinction ratio spectrum simulation curves of the optical polarization beam splitter of the present invention.

[0057] Figure 8 Shown are simulation results of the optical polarization beam splitters of Examples 1 to 9 of the present invention and Comparative Examples 1 to 2.

[0058] Fig. 9 Shown are simulation results of the optical polarization beam splitters of Examples 2, 10 to 16 of the present invention and Comparative Examples 3 to 5.

[0059] Fig.10 Shown are simulation results of the optical polarization beam splitters of Examples 2 and 17 to 24 of the present invention.

[0060] Fig.11 Shown are simulation results of the optical polarization beam splitters of Examples 2, 25-39 of the present invention and Comparative Examples 6-7.

[0061] Fig.12 It is a schematic diagram showing the structure of the "X", "Y" and "V" shaped strip-shaped grooves of the present invention.

[0062] Reference numerals:

[0063] 10 waveguide core layer, 11 first light transmission section, 11a light input section, 11b reflected light output section, 12 polarization section, 121 interval, 13 strip-shaped groove, 13a first groove section, 13b second groove section, 14 refracted light output section, 20 isolation layer, 30 upper cladding layer, 40 substrate, α the angle of "X" type strip-shaped groove, β the angle of "Y" type strip-shaped groove, γ the angle of "V" type strip-shaped groove. DETAILED DESCRIPTION

[0064] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0065] See also Figures 1 to 5 . It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantive technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical content disclosed by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content. In this embodiment, an optical polarization beam splitter is provided.

[0066] like Figures 1 to 5 As shown in Figure 12, the optical polarization beam splitter includes an isolation layer 20 and a waveguide core layer 10 arranged on the isolation layer 20; the waveguide core layer 10 is sequentially formed with a first light transmission segment 11, a polarization segment 12 and a second light transmission segment from one side to the other side, the first light transmission segment 11 is formed with a light input segment 11a and a reflected light output segment 11b arranged at intervals, and the second light transmission segment at least includes a refracted light output segment 14; the polarization segment 12 is formed with at least one group of strip-shaped grooves 13; the group of strip-shaped grooves 13 includes a first groove segment 13a and a second groove segment 13b arranged to intersect.

[0067] The intersection described in this application includes one or more of direct intersection and extended line intersection. Figures 1 to 5 In the specific embodiment of 12, the intersection is a direct intersection.

[0068] In certain specific embodiments, such as Figures 1 to 5As shown in FIG. 12 , the polarization segment 12 is formed with N groups of strip-shaped grooves 13, where N is an integer of 2 to 10; and the first groove segments 13a are arranged in parallel and spaced correspondence to each other; and the second groove segments 13b are arranged in parallel and spaced correspondence to each other. As described above, N can be 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0069] In certain more specific embodiments, Figures 1 to 5 As shown in FIG. 12 , any first groove segment 13 a or second groove segment 13 b and its adjacent interval 121 form a layer of sub-wavelength grating structure.

[0070] In some further embodiments, Figures 1 to 5 As shown in Figure 12, N is an integer of 2 to 5. When N is greater than 5, although low insertion loss and high extinction ratio can still be achieved, it is difficult to process due to the large size. In a specific embodiment, N is 3.

[0071] In certain more specific embodiments, Figures 1 to 5 As shown in 12, the width of any interval 121 is d 1 ; The width of any first groove segment 13a or second groove segment 13b is d 2 ;d 1 150~240nm; d 2 80~120nm; d 1 -d 2 In the present application, the width refers to the distance that the light passes through the interval 121 or the first groove segment 13a or the second groove segment 13b in the direction perpendicular to the arrangement of the strip-shaped grooves.

[0072] As described 1 It can be 150-160nm, 160-170nm, 170-180nm, 180-190nm, 190-200nm, 200-210nm, 210-220nm, 220-230nm, 230-240nm. In some specific embodiments, the d 1 In some specific embodiments, the d 1 It is 190~210nm.

[0073] As described 2 It can be 80-85nm, 85-90nm, 90-95nm, 95-100nm, 100-105nm, 105-110nm, 110-115nm, 115-120nm. In some specific embodiments, the d 2 In some specific embodiments, the d 2It is 90~105nm.

[0074] As described 1 -d 2 It may be 30-35 nm, 35-40 nm, 40-45 nm, 45-50 nm, 50-55 nm, 55-60 nm, 60-65 nm, 65-70 nm, 70-75 nm, 75-80 nm, 80-85 nm, 85-90 nm, 90-95 nm, 95-100 nm, 100-105 nm, 105-110 nm, 110-115 nm, 115-120 nm.

[0075] In some further embodiments, Figures 1 to 5 As shown in FIG. 12 , the duty cycle of the sub-wavelength grating structure is 0.55 to 0.75; the duty cycle is calculated as follows: ρ = d 1 / Λ, ρ is the duty cycle of the sub-wavelength grating structure, Λ is the period of the sub-wavelength grating structure, Λ=d 1 +d 2 As described above, ρ can be 0.55-0.56, 0.56-0.57, 0.57-0.58, 0.58-0.59, 0.59-0.60, 0.60-0.61, 0.61-0.62, 0.62-0.63, 0.63-0.64, 0.64-0.65, 0.65-0.66, 0.66-0.67, 0.67-0.68, 0.68-0.69, 0.69-0.70, 0.70-0.71, 0.71-0.72, 0.72-0.73, 0.73-0.74, 0.74-0.75. In a Figures 1 to 5 In the specific embodiment shown, ρ=2 / 3, Λ*N=0.8 μm, and based on the process that can be achieved, the smaller Λ is, the more likely it is that the sub-wavelength grating structure formed can achieve quasi-TM 0 The coherent decomposition of the reflected light of the mode light achieves a higher extinction ratio.

[0076] In some further embodiments, Figures 1 to 5 As shown in 12, quasi-TE 0 The equivalent refractive index of the mode light in the sub-wavelength grating structure perpendicular to the arrangement direction of the strip-shaped grooves 13 is n ⊥,TE ; Quasi TM 0 The equivalent refractive index of the mode light in the sub-wavelength grating structure perpendicular to the arrangement direction of the strip-shaped grooves 13 is n ⊥,TM ;Quasi TE 0 The effective refractive index of the mode light in the first light transmission section 11 is n TE , quasi TM 0The effective refractive index of the mode light in the first light transmission section 11 is n TM , n TE >n TM ;n ⊥,TE <n TE ·sin45°; e.g. Figures 1 to 5 As shown in Figure 12, when the first groove section 13a and the second groove section 13b are perpendicular, n ⊥,TM >n TM ·sin45°.

[0077] In certain specific embodiments, such as Figures 1 to 5 As shown in Figures 12 and 12, the first groove section 13a and the second groove section 13b arranged to intersect each other are both filled with a light splitting material; the refractive index of the light splitting material is lower than the refractive index of the material of the waveguide core layer (10).

[0078] In certain more specific embodiments, Figures 1 to 5 As shown in 12, the spectroscopic material is selected from SiO 2 , SiC, SU-8 photoresist, polymethyl methacrylate, and hydrogen silsesquioxane.

[0079] In some specific embodiments, a group of the strip-shaped grooves 13 are in an "X" shape, a "Y" shape, or a "V" shape. More preferably, the strip-shaped grooves 13 are in an "X" shape. Figures 1 to 5 In the specific embodiment shown, the strip-shaped groove 13 is in an "X" shape, and the angle between the first groove segment 13a and the second groove segment 13b is 90°.

[0080] Fig.12 It is a schematic diagram of the structure of the "X", "Y" and "V" type strip-shaped grooves of the present invention. The shaded area is the interval 121. 12(a) is a schematic diagram of the structure of a group of "X" type strip-shaped grooves, 12(b) is a schematic diagram of the structure of multiple groups of "X" type strip-shaped grooves, 12(c) is a schematic diagram of the structure of a group of "Y" type strip-shaped grooves, 12(d) is a schematic diagram of the structure of multiple groups of "Y" type strip-shaped grooves, 12(e) is a schematic diagram of the structure of a group of "V" type strip-shaped grooves, and 12(f) is a schematic diagram of the structure of multiple groups of "V" type strip-shaped grooves. It should be noted that Fig.12 The shaded portion in the figure is only used to distinguish the interval 121 from the strip-shaped groove 13 and does not contain any limitation on the material or other meanings.

[0081] In this application, if Fig.12As shown in (a) and 12(b), the "X" shape refers to the intersection of the first groove segment 13a and the second groove segment 13b, with an angle of α, so as to form four extensions at the intersection, forming a letter "X" shape or a quasi-"X" shape. The lengths of the four extensions of the "X" shape can be equal or unequal, and α can be 80-100°, as long as the refraction and reflection paths of the light source pass through the first groove segment 13a and the second groove segment 13b.

[0082] In this application, if Fig.12 (c) and 12 (d), the "Y" shape means that the endpoint of the first groove segment 13a is set on the second groove segment 13b, with an angle of β, forming a letter "Y" shape or a "Y"-like shape. The lengths of the two sides of the endpoint can be equal or unequal, and β can be 80-100°, as long as the refraction and reflection paths of the light source pass through the first groove segment 13a and the second groove segment 13b.

[0083] In this application, if Fig.12 As shown in (e) and 12(f), the "V" shape means that the first groove segment 13a and the second groove segment 13b extend from a common vertex in two directions, with an angle of γ, forming a letter "V" shape or a "V"-like shape. The lengths of the first groove segment 13a and the second groove segment 13b can be equal or different, and γ can be 80-100°, as long as the transmission path of the light source passes through the first groove segment 13a and the second groove segment 13b.

[0084] The light source described in this application is quasi-TE 0 Mode light and quasi TM 0 Mode light.

[0085] In certain specific embodiments, such as Figures 1 to 5 As shown in Figures 1 and 12, the thickness of the isolation layer 20 is 1.5 to 4 μm. For example, the thickness of the isolation layer 20 can be 1.5 to 1.6 μm, 1.6 to 1.7 μm, 1.7 to 1.8 μm, 1.8 to 1.9 μm, 1.9 to 2.0 μm, 2.0 to 2.1 μm, 2.1 to 2.2 μm, 2.2 to 2.3 μm, 2.3 to 2.4 μm, 2.4 to 2.5 μm, 2.5 to 2.6 μm, 2.6 to 2.7 μm. In some specific embodiments, the thickness of the isolation layer 20 is 2 μm.

[0086] In some specific embodiments, the material of the isolation layer 20 is SiO 2 .

[0087] In some specific embodiments, the material of the waveguide core layer 10 is Si.

[0088] In certain specific embodiments, such as Figures 1 to 5 As shown in Figures 1 and 12, the thickness of the waveguide core layer 10 is 200-500 nm. For example, the thickness of the waveguide core layer can be 200-220 nm, 220-240 nm, 240-260 nm, 260-280 nm, 280-300 nm, 300-320 nm, 320-340 nm, 340-360 nm, 360-380 nm, 380-400 nm, 400-420 nm, 420-440 nm, 440-460 nm, 460-480 nm, 480-500 nm. Figures 1 to 5 In the specific embodiments shown in Figures 1 and 12, the thickness of the waveguide core layer 10 is 220 nm.

[0089] In certain specific embodiments, such as Figures 1 to 5 As shown in FIG. 12 , the optical polarization beam splitter further includes an upper cladding layer 30 for preventing scattering.

[0090] In certain more specific embodiments, Figures 1 to 5 As shown in Figures 12 and 12, the refractive index of the material of the upper cladding layer 30 is less than the equivalent refractive index of the sub-wavelength grating structure.

[0091] In certain further embodiments, Figures 1 to 5 As shown in Figure 12, the material of the upper cladding layer 30 is selected from SiO 2 , SiC, SU-8 photoresist, polymethyl methacrylate, hydrogen silsesquioxane. Figures 1 to 5 In the specific embodiment shown in Figure 12, the material of the upper cladding layer 30 is SiO 2 .

[0092] In certain specific embodiments, such as Figures 1 to 5 As shown in Figures 12 and 12, the optical polarization beam splitter further includes a substrate 40 disposed at the bottom layer.

[0093] In certain more specific embodiments, Figures 1 to 5 As shown in FIG. 12 , the material of the substrate 40 is selected from one of Si, gallium arsenide, gallium nitride and silicon carbide. Figures 1 to 5 In the specific embodiments shown in Figures 1 and 12, the material of the substrate 40 is Si.

[0094] In certain specific embodiments, such as Figures 1 to 5As shown in FIG. 12 , the effective refractive index of the first light transmission segment 11 is greater than the refractive index of the isolation layer 20 material.

[0095] In certain specific embodiments, such as Figures 1 to 5 As shown in Figure 12, when the first groove segment 13a and the second groove segment 13b are perpendicular, the optical polarization beam splitter is quasi-TE at a wavelength of 1549 to 1551 nm. 0 Mode light and quasi TM 0 Under mode light, the extinction ratio is 20~60dB and the insertion loss ratio is 0.1~2dB.

[0096] In certain specific embodiments, such as Figures 1 to 5 As shown in FIG. 12 , the distance between the light input section and the reflected light output section is w gap , w gap 1 to 10 μm. gap It can be 1 to 2 μm, 2 to 3 μm, 3 to 4 μm, 4 to 5 μm, 5 to 6 μm, 6 to 7 μm, 7 to 8 μm, 6 to 9 μm, or 9 to 10 μm. The w gap The spacing is 1 to 10 μm to reduce the mode coupling effect in the input and output sections.

[0097] In certain specific embodiments, such as Figures 1 to 5 As shown in Figure 12, the width of the light input section, the reflected light output section and the second light transmission section is w taper , w taper 3.5 to 10 μm. taper It can be 3.5-4 μm, 4-5 μm, 5-6 μm, 6-7 μm, 7-8 μm, 6-9 μm, 9-10 μm. taper 3.5~10μm to reduce the quasi-TE 0 and TM 0 Divergence angles of the two modes.

[0098] The equivalent refractive index in this application refers to the effective refractive index n of the light source in the direction perpendicular to the arrangement direction of the sub-wavelength grating structure. ⊥,TE and n ⊥,TM . The ⊥,TE and n ⊥,TM The calculation method is as follows:

[0099] First, use the wave optics module in COMSOL or the FDTD module in Ansys Lumerical to input d 1 ,d 2 , the refractive index of each layer of the polarization beam splitter and the thickness and size of each layer are used to calculate the quasi-TE in the sub-wavelength grating structure 0 Mode light and quasi TM0 The propagation constant k of the Bloch eigenmode in which the mode light propagates in the direction perpendicular to the arrangement of the subwavelength grating structure is ⊥,TE and k ⊥,TM , then according to the formula:

[0100]

[0101] The equivalent refractive index n can be obtained by calculation ⊥,TE and n ⊥,TM . Where λ is the wavelength of light and π is the circumference of a circle.

[0102] In addition to the software listed above, the above calculations can be implemented in software that includes optical numerical calculation methods such as finite element method, finite difference time domain method, beam propagation method, etc.

[0103] In the present application, the refractive index of the isolation layer 20, the upper cladding layer 30 and the substrate 40 is the refractive index of the material of each layer itself.

[0104] The effective refractive index n TE 、n TM , which is related to the materials and dimensions of the waveguide core layer, the isolation layer and the upper cladding layer. Specifically, by using the wave optics module in the COMSOL software or the MODE module in the Ansys Lumerical software, input d 1 ,d 2 , the refractive index of each layer material and the thickness of each layer of the polarization beam splitter are calculated.

[0105] The design process of the polarization beam splitter of the present invention is: within the target wavelength range, according to the changes of the materials of each layer, the cross-sectional dimensions of the first light transmission segment 11 and the second light transmission segment are reasonably selected to make the quasi-TE 0 and TM 0 The two modes of light satisfy n TE >n TM The light source enters the polarization section 12 through the light input section 11a, and the period Λ and duty cycle ρ of the sub-wavelength grating structure are adjusted to make the quasi-TE 0 and TM 0 The equivalent refractive index of the two modes of light in the sub-wavelength grating structure is perpendicular to the arrangement direction of the periodic structure. When the first groove segment 13a and the second groove segment 13b are perpendicular, the quasi-TE 0 and TM 0 The effective refractive index of the two mode lights in the first light transmission section 11 satisfies n ⊥,TE <n TE sin45° and n ⊥,TM >n TM ·sin45°, thus making quasi-TE 0The mode light is totally reflected by the sub-wavelength grating structure, so that its energy is mainly concentrated in the reflection light path and output from the reflection light output section 11b; at the same time, it ensures the quasi-TM 0 The mode light is transmitted through the sub-wavelength grating structure, so that its energy is mainly concentrated in the transmission light path and output from the refractive light output section 14 .

[0106] In a Figures 1-2 In the specific embodiment shown, the strip-shaped groove 13 is in an "X" shape, and the first groove section 13a and the second groove section 13b intersect vertically. The polarization section 12 is a rectangular parallelepiped, and the light input section 11a, the reflected light output section 11b and the two refractive light output sections 14 are protruding and symmetrically arranged on the side of the rectangular parallelepiped, and extend in the parallel direction of the substrate. The light source can be incident from any of the light input section 11a, the reflected light output section 11b and the two refractive light output sections 14, and the reflected light and the transmitted light can be collected and output.

[0107] In the present application, a method for manufacturing the optical polarization beam splitter is provided.

[0108] In a specific embodiment, a waveguide core layer 10 with strip-shaped grooves is prepared on an isolation layer 20 with a substrate 40, comprising the following steps:

[0109] S1: preliminary etching, photolithography of the outer contour of the waveguide core layer 10 on the isolation layer 20 with the substrate 40;

[0110] S2: further etching the waveguide core layer 10 to form strip-shaped grooves.

[0111] It should be noted that S1 and S2 can also be performed simultaneously according to actual needs. Figures 1 to 5 In a specific embodiment, S1 and S2 are performed synchronously.

[0112] In a more specific embodiment, the material initially etched in S1 is an SOI wafer, whose structure consists of three layers: the top layer is a thin silicon film used to form a semiconductor device, that is, an unetched waveguide core layer 10; the middle is an insulating layer of silicon dioxide, that is, an isolation layer 20; and the bottom layer is a thicker silicon base, that is, a substrate 40.

[0113] In a further specific embodiment, the SOI wafer needs to be pre-treated, and the pre-treatment includes ultrasonically cleaning the wafer using a solvent such as acetone, methanol, isopropanol, etc. to remove an oxide layer on the surface of the wafer, and then drying it.

[0114] In a more specific embodiment, the preliminary etching step in S1 includes photoresist spin coating, pre-baking and photolithography. In a further specific embodiment, the photoresist spin coating is to use a coating machine to spin coat the photoresist, and the photoresist materials that can be used include positive photoresist and negative photoresist, such as SU-8 photoresist, polymethyl methacrylate, hydrogen silsesquioxane.

[0115] In a further specific embodiment, the pre-bake is to remove the solvent in the photoresist and to cure the photoresist.

[0116] In a further specific embodiment, the photolithography is to expose the photoresist using an electron beam lithography machine according to a designed mask plate, and to carve a mask pattern on the photoresist to achieve the transfer of the pattern from the design blueprint to the chip; it should be noted that different photolithography methods such as deep ultraviolet lithography, extreme ultraviolet lithography, electron beam lithography, etc. correspond to different minimum feature sizes; the minimum feature size involved in this application is about 100nm, so it is necessary to select a lithography machine with a minimum feature size not exceeding 90nm for lithography to ensure processing accuracy.

[0117] In a further embodiment, the mask pattern is the outer contour of the waveguide core layer 10, which includes a first light transmission segment 11, a polarization segment 12 and a second light transmission segment from one side to the other, wherein the first light transmission segment 11 includes a light input segment 11a and a reflected light output segment 11b arranged at intervals, and the second light transmission segment includes at least a refracted light output segment 14.

[0118] In a more specific embodiment, the initial etching in S1 further includes the steps of development and post-baking.

[0119] In a further embodiment, the development is to place the exposed chip into a developer to remove excess photoresist.

[0120] In a more specific embodiment, the step of further etching the waveguide core layer 10 in S2 includes photoresist spin coating, pre-baking, developing, etching, stripping and post-baking. The photoresist spin coating, pre-baking, developing and post-baking steps are consistent with S1.

[0121] In a further embodiment, the etching uses dry etching technology to transfer the mask pattern of the strip-shaped grooves to the SOI layer, and the optional etching methods include plasma etching, ion beam milling etching and reactive ion etching, etc. In a further embodiment, the degumming is to place the chip in a degumming solution to remove residues.

[0122] In a more specific embodiment, S1 and S2 are performed simultaneously, and the specific steps include: pre-processing the SOI wafer, photoresist spin coating, pre-baking, developing, etching, stripping and post-baking; during the etching, the outer contour of the waveguide core layer 10 and the mask pattern of the strip-shaped grooves are simultaneously photoetched.

[0123] In a further embodiment, an upper cladding layer 30 can be formed by coating, and the upper cladding layer 30 can be filled in the strip-shaped groove, or it can be left unfilled to form an air dielectric layer, as follows: For a chip without an upper cladding layer 30 and without filling in the strip-shaped groove, this step is omitted. If the upper cladding layer 30 and the strip-shaped groove are filled with polymer materials such as SU-8 photoresist, polymethyl methacrylate, and hydrogen silsesquioxane, the corresponding polymer can be spin-coated as the filler in the upper cladding layer 30 and the strip-shaped groove. If the upper cladding layer 30 and the strip-shaped groove are filled with inorganic crystalline materials such as silicon dioxide and silicon carbide, it is necessary to use chemical vapor deposition (such as PECVD, LPCVD, ICPCVD, etc.) or atomic layer deposition to grow the upper cladding layer 30 and the filler in the strip-shaped groove.

[0124] The optical polarization beam splitter described in the present application has a relatively simple structure, a minimum line width of 100 nm, and an acceptable processing error of ±10 nm. The manufacturing process can adopt standard semiconductor manufacturing technology with mature technology, which can effectively reduce the difficulty and cost of processing.

[0125] The minimum line width in this application is d 1 ,d 2 The minimum size of the optical polarization beam splitter is 10%, and the acceptable processing error is ±10% of the minimum line width. Under the processing error of ±10%, the optical polarization beam splitter can still achieve the requirements of insertion loss lower than 2dB and extinction ratio higher than 20dB.

[0126] The following embodiments 1 to 39 and comparative examples 1 to 7 provide a specific optical polarization beam splitter, wherein the strip-shaped groove 13 is in an "X" shape, the light input segment 11a, the reflected light output segment 11b and the two refracted light output segments 14 are protruding and symmetrically arranged on the side of the rectangular parallelepiped, and extend in a parallel direction of the substrate, the polarization segment 12 is a rectangular parallelepiped, the polarization segment 12 is 15 μm wide, the material of the waveguide core layer 10 is Si, and the thickness is 220 nm; the light splitting material is SiO 2 ; The material of the isolation layer 20 is SiO 2 ; The material of the upper cladding layer 30 is SiO 2 ; The material of the substrate 40 is Si; Quasi-TE 0 and TM 0 The effective refractive index of the mode light is n TM =2.84 and n TM =2.03, which meets the design requirements of nTE >n TM The remaining parameters are shown in Table 1.

[0127] Table 1

[0128]

[0129]

[0130] like Figures 1 to 6 As shown, containing quasi-TE 0 Mode light and quasi TM 0 Mode light Two light sources with different polarization modes are input from the light input section 11a, and after entering the polarization section 12, they are polarization screened by the sub-wavelength grating structure. 0 The mode is totally reflected at 90° to another extension of the "X" shape for total reflection filtering and is output from the reflected light output section 11b; the quasi-TM 0 The mode is transmitted through the sub-wavelength grating structure and passes through another “X”-shaped extension again for transmission filtering and displacement correction, and is output from the refractive light output section 14 .

[0131] In this application, the insertion loss IL and extinction ratio ER are calculated by using the wave optics module in COMSOL or the FDTD module in Ansys Lumerical. 1 ,d 2 , the refractive index of each layer material of the polarization beam splitter and the thickness and size of each layer are obtained, specifically, as Figure 2 As shown, the light input section 11a is defined as the incident port (Input), the refracted light output section 14 is defined as the transmission port (Thru), and the reflected light output section 11b is defined as the reflection port (Back). 0 After the polarized light is injected from the Input port, the TE at the Thru port and the Back port are measured respectively. 0 The intensity of polarized light, calculate TE 0 Polarized light transmittance T TE and reflectivity R TE ; T TE Indicates that the light collected by the Thru port is injected into the TE 0 Percentage of polarized light, R TE Indicates that the light collected by the Back port is injected into the TE 0 Similarly, we inject TM polarized light from the Input port again and measure again to get T TM and R TM The insertion loss IL and extinction ratio ER are defined as:

[0132] IL TE=-10log 10 (R TE ),

[0133] IL TM =-10log 10 (T TM ),

[0134]

[0135] The insertion loss IL indicates how much light is finally collected by the target port, characterizing the loss of polarized light; and the extinction ratio ER indicates the ratio of light leaking to the non-target port to the light collected by the target port, characterizing the ability to separate polarized light.

[0136] At an operating wavelength of 1550 nm, the insertion loss IL and extinction ratio ER of the optical polarization beam splitter of the above embodiments 1 to 42 and comparative example 1 are simulated by the FDTD module in the software Ansys Lumerical as shown in the following results: Figures 8 to 11 shown.

[0137] like Figures 8 to 11 The simulation results show that the optical polarization beam splitter described in Examples 1 to 39 has a quasi-TE 0 Mode light and quasi TM 0 When the mode light is used, the insertion loss is less than 2dB, and the extinction ratio is higher than 20dB. taper Too large or too small, at the input wavelength of 1550nm quasi-TE 0 Mode light and quasi TM 0 When the mode light is on, the requirements of insertion loss lower than 2dB and extinction ratio higher than 20dB are not met.

[0138] The mode field analysis and spectrum response analysis of the optical deflection beam splitter formed in Example 2 were performed, and the results were as follows: Figure 6 and Figure 7 shown. Figure 6 Middle: The left picture is a quasi-TE 0 Mode field distribution diagram of the mode light signal input into the waveguide core layer 10. The right figure is quasi-TM 0 Mode field distribution diagram of the mode light signal input into the waveguide core layer 10.

[0139] from Figure 6 It can be seen that quasi-TE 0 The mode light signal undergoes total reflection near the surface of the "X-shaped" sub-wavelength grating structure, and is finally collected by the reflected light output section 11b after two total reflections; the quasi-TM 0The mode light signal is transmitted through the "X-shaped" sub-wavelength grating structure, and after two polarization screenings, is output from the refraction light output section 14. This indicates that the polarization beam splitter of the present invention has a good polarization beam splitting effect.

[0140] from Figure 7 It can be seen that the input quasi-TE 0 Mode light and quasi TM 0 The insertion loss of the mode light is lower than 1.2dB in the wavelength range of 1429-1923nm, and the extinction ratio is higher than 30dB in the wavelength range of 1429-1923nm. That is, the strip-shaped groove arrangement of the present invention enables the polarization beam splitter to have an extinction ratio ER greater than 20dB and an insertion loss IL less than 2dB in a wide bandwidth range.

[0141] The present invention realizes alignment of TE by utilizing the birefringence effect of the tilted sub-wavelength grating structure. 0 Total reflection and quasi-TM mode 0 The transmission of the mode can achieve the purpose of polarization beam splitting. The present invention avoids the multi-period array of sub-wavelength grating structure in principle, has a larger minimum line width and a simpler structure, and greatly reduces the difficulty and complexity of process manufacturing. Even for a sub-wavelength grating structure with only 2 periods, a higher extinction ratio and extremely wide available bandwidth can be achieved, achieving a very good polarization beam splitting effect, and is expected to be widely used in integrated optical systems with high requirements for extinction ratio.

[0142] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An optical polarization beam splitter, characterized in that: The invention comprises an isolation layer (20) and a waveguide core layer (10) arranged on the isolation layer (20); the waveguide core layer (10) is sequentially formed with a first light transmission section (11), a polarization section (12) and a second light transmission section from one side to the other side, the first light transmission section (11) is formed with a light input section (11a) and a reflected light output section (11b) arranged at intervals, and the second light transmission section at least includes a refracted light output section (14); The polarization segment is formed with at least one group of strip-shaped grooves (13); the group of strip-shaped grooves (13) comprises a first groove segment (13a) and a second groove segment (13b) which are arranged to intersect.

2. The optical polarization beam splitter according to claim 1, wherein: The polarization segment (12) is formed with N groups of strip-shaped grooves (13), where N is an integer of 2 to 10; and the first groove segments (13a) are arranged in parallel and at intervals; and the second groove segments (13b) are arranged in parallel and at intervals; And / or, the first groove section (13a) and the second groove section (13b) arranged to intersect are both filled with a light splitting material, and the refractive index of the light splitting material is lower than the refractive index of the material of the waveguide core layer (10); And / or, a group of the strip-shaped grooves (13) are in an "X" shape, a "Y" shape, or a "V" shape; And / or, the thickness of the isolation layer (20) is 1.5 to 4 μm; And / or, the material of the isolation layer (20) is SiO2; And / or, the material of the waveguide core layer (10) is Si; And / or, the thickness of the waveguide core layer (10) is 200-500 nm.

3. The optical polarization beam splitter according to claim 2, characterized in that Any first groove segment (13a) or second groove segment (13b) and adjacent intervals (121) thereof form a layer of sub-wavelength grating structure; The width of any interval (121) is d1, the width of any first groove section (13a) or second groove section (13b) is d2, d1 is 150 to 240 nm, d2 is 80 to 120 nm, and d1-d2 is 30 to 125 nm; And / or, the spectroscopic material is selected from one of SiO2, SiC, SU-8 photoresist, polymethyl methacrylate, and hydrogen silsesquioxane.

4. The optical polarization beam splitter according to claim 3, characterized in that The duty cycle of the sub-wavelength grating structure is 0.55-0.75; the duty cycle is calculated as follows: ρ=d1 / Λ, ρ is the duty cycle of the sub-wavelength grating structure, Λ is the period of the sub-wavelength grating structure, Λ=d1+d2; And / or, the equivalent refractive index of the quasi-TE0 mode light in the sub-wavelength grating structure perpendicular to the arrangement direction of the strip-shaped grooves (13) is n ⊥,TE The equivalent refractive index of the quasi-TM0 mode light in the sub-wavelength grating structure perpendicular to the arrangement direction of the strip-shaped grooves (13) is n ⊥,TM The effective refractive index of the quasi-TE0 mode light in the first optical transmission section (11) is n TE The effective refractive index of the quasi-TM0 mode light in the first optical transmission section (11) is n TM , n TE >n TM ; When the first groove section (13a) and the second groove section (13b) are perpendicular, n ⊥,TE <n TE ·sin45°; n ⊥,TM >n TM ·sin45°.

5. The optical polarization beam splitter according to claim 4, characterized in that The optical polarization beam splitter further comprises an upper cladding layer (30) for preventing scattering, and the refractive index of the material of the upper cladding layer (30) is smaller than the equivalent refractive index of the sub-wavelength grating structure.

6. The optical polarization beam splitter according to claim 5, characterized in that The material of the upper cladding layer (30) is selected from one or more of SiO2, SiC, SU-8 photoresist, polymethyl methacrylate, and hydrogen silsesquioxane.

7. The optical polarization beam splitter according to claim 1, wherein: The optical polarization beam splitter further comprises a substrate (40) arranged at the bottom layer; And / or, the effective refractive index of the first light transmission section (11) is greater than the refractive index of the material of the isolation layer (20).

8. The optical polarization beam splitter according to claim 7, characterized in that The material of the substrate (40) is selected from one of Si, gallium arsenide, gallium nitride and silicon carbide.

9. The optical polarization beam splitter according to claim 1, wherein: When the first groove segment and the second groove segment are perpendicular, the optical polarization beam splitter has an extinction ratio of 20 to 60 dB and an insertion loss ratio of 0.1 to 2 dB under quasi-TE0 mode light and quasi-TM0 mode light of 1549 to 1551 nm wavelength; And / or, the distance between the light input section (11a) and the reflected light output section (11b) is w gap , w gap 1 to 10 μm; and / or the width of the light input section (11a), the reflected light output section (11b) and the refracted light output section (14) is w taper , w taper 3.5~10μm.

10. An optical chip, characterized in that: Comprising an optical polarization beam splitter as described in any one of claims 1-9.

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