Polarization beam splitter for 2 [mu] m wave band

Abstract

The embodiment of the invention discloses a polarization beam splitter for a 2-micron wave band, and relates to the technical field of optics. According to the polarization beam splitter provided by the embodiment of the invention, a first three-waveguide directional coupler comprises a first waveguide, a second waveguide and a third waveguide which extend along a first direction and are arranged along a second direction, and a second three-waveguide directional coupler comprises a fourth waveguide, a fifth waveguide and a sixth waveguide which extend along the first direction and are arranged along the second direction; an input light beam is input into the polarization beam splitter from the first end of the first waveguide, a TM-mode polarized light beam and a TE-mode polarized light beam are separated through the first three-waveguide directional coupler, the TM-mode polarized light beam is output after being transmitted through the third waveguide, the TE-mode polarized light beam is transmitted to the second three-waveguide directional coupler through the first waveguide, and the TE-mode polarized light beam is output after being transmitted to the second three-waveguide directional coupler through the second waveguide. And after the TM-mode polarized light beam is filtered out by the second three-waveguide directional coupler, the light is output by a sixth waveguide. The polarization beam splitter provided by the embodiment of the invention has a relatively high polarization extinction ratio.

Description

Technical Field

[0001] The invention relates to the field of optical technology, and in particular to a polarization beam splitter for a 2μm waveband. Background Art

[0002] With the emergence of low-loss hollow photonic bandgap fibers, high-gain thulium-doped fiber amplifiers, grating couplers, and photodetectors operating in the 2μm band, the 2μm band has gradually become a new communication band. At the same time, hollow photonic bandgap fibers have a good birefringence effect, which enables on-chip polarization multiplexing communications to be widely used in the 2μm band. Polarization multiplexing technology uses two mutually orthogonal polarization states of light to simultaneously transmit two independent data information to increase system capacity. As one of the basic components in the polarization multiplexing system, the polarization beam splitter can separate two mutually orthogonal polarization states and is the basis for realizing polarization multiplexing communications. Therefore, it is of great practical value to increase the operating wavelength of the polarization beam splitter to the 2μm band.

[0003] Currently, common on-chip polarization beam splitters include directional couplers and three-waveguide directional couplers. The structure of the directional coupler includes a curved waveguide, which has a high processing complexity and is difficult to process. The three-waveguide directional coupler is composed of three straight waveguides, has good enough performance and is easy to manufacture, but the manufacturing tolerance of the three-waveguide directional coupler is currently very small. Summary of the invention

[0004] The embodiment of the present invention provides a polarization beam splitter for the 2 μm band, which has a higher polarization extinction ratio and a higher size tolerance.

[0005] According to one aspect of the present invention, an embodiment of the present invention provides a polarization beam splitter for the 2 μm band, comprising a first three-waveguide directional coupler and a second three-waveguide directional coupler arranged in cascade;

[0006] The first three-waveguide directional coupler includes a first waveguide, a second waveguide and a third waveguide extending along the first direction and arranged along the second direction, and the second three-waveguide directional coupler includes a fourth waveguide, a fifth waveguide and a sixth waveguide extending along the first direction and arranged along the second direction, the first waveguide and the sixth waveguide are connected, and the first direction and the second direction intersect;

[0007] The input light beam is input into the polarization beam splitter from the first end of the first waveguide, and is separated into a TM mode polarized light beam and a TE mode polarized light beam through the first three-waveguide directional coupler. The TM mode polarized light beam is output after being transmitted through the third waveguide, and the TE mode polarized light beam is transmitted to the second three-waveguide directional coupler through the first waveguide, and is output from the sixth waveguide after the TM mode polarized light beam is filtered out through the second three-waveguide directional coupler.

[0008] Optionally, the polarization beam splitter comprises:

[0009] substrate;

[0010] A first cladding layer and a second cladding layer are stacked and arranged on one side of the substrate;

[0011] The waveguide layer is located between the first cladding layer and the second cladding layer, and the waveguide layer includes a first waveguide, a second waveguide, a third waveguide, a fourth waveguide, a fifth waveguide and a sixth waveguide.

[0012] Optionally, the substrate comprises a silicon substrate, the first cladding layer and the second cladding layer comprise silicon dioxide cladding layers, and the waveguide layer comprises a silicon waveguide.

[0013] Optionally, a dimension of the first waveguide in the second direction is greater than a dimension of the sixth waveguide in the second direction, and a spacing between the first waveguide and the second waveguide is equal to a spacing between the fifth waveguide and the sixth waveguide.

[0014] Optionally, the dimension W1 of the first waveguide in the second direction is 1.2 μm, the dimension W3 of the sixth waveguide in the second direction is 0.6 μm, and the interval W between the first waveguide and the second waveguide is gap =0.3μm.

[0015] Optionally, a size of the second waveguide in the first direction is larger than a size of the fifth waveguide in the first direction, and a size of the second waveguide in the second direction is larger than a size of the fifth waveguide in the second direction.

[0016] Optionally, a dimension L1 of the second waveguide in the first direction satisfies 30μm≤L1≤36μm; a dimension L2 of the fifth waveguide in the first direction satisfies 9μm≤L2≤15.5μm, a dimension W2 of the second waveguide in the second direction satisfies 1.2μm≤W2≤1.38μm, and a dimension W4 of the fifth waveguide in the second direction satisfies 0.7μm≤W4≤0.9μm.

[0017] Optionally, the dimensional tolerance of the first waveguide, the second waveguide, the third waveguide, the fourth waveguide, the fifth waveguide and the sixth waveguide in the second direction is within ±60nm, and the dimensional tolerance in the third direction is within ±10nm, wherein the plane where the first direction and the second direction are located is perpendicular to the third direction.

[0018] Optionally, the input light beam is a laser light beam in the 1.9 μm to 2.1 μm band.

[0019] Optionally, a size of the first waveguide, the second waveguide, the third waveguide, the fourth waveguide, the fifth waveguide and the sixth waveguide in the third direction is 220 nm, and a plane where the first direction and the second direction are located is perpendicular to the third direction.

[0020] The polarization beam splitter for the 2 μm band provided by an embodiment of the present invention separates the TM mode polarized beam and the TE mode polarized beam through a first three-waveguide directional coupler, wherein the TE mode polarized beam and part of the residual TM mode polarized beam are coupled to the first waveguide, and the TM mode polarized beam is coupled to the third waveguide. Then, by cascading a second three-waveguide directional coupler after the first three-waveguide directional coupler, the residual TM mode polarized beam is coupled out of the polarization beam splitter through the second three-waveguide directional coupler, so that the TM mode polarized beam in the TE mode polarized beam output by the sixth waveguide is less, thereby improving the polarization extinction ratio of the polarization beam splitter.

[0021] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 is a three-dimensional structural diagram of a polarization beam splitter provided by an embodiment of the present invention;

[0024] Figure 2 is a top view of a polarization beam splitter provided by an embodiment of the present invention;

[0025] Figure 3 is a cross-sectional view of a first three-waveguide directional coupler or a second three-waveguide directional coupler provided in an embodiment of the present invention;

[0026] Figure 4 is a graph showing the relationship between the transmission loss of a TE mode polarized light beam and a TM mode polarized light beam and the size of the sixth waveguide in the second direction when the wavelength is 2 μm;

[0027] Figure 5 is the relationship between the polarization extinction ratio of the polarization beam splitter and W1, L1, W4 and L2;

[0028] Figure 6 is a graph of the loss of the polarization beam splitter versus W1, L1, W4, and L2;

[0029] Figure 7 is a graph showing the relationship between the polarization extinction ratio of the polarization beam splitter provided by an embodiment of the present invention and the wavelength of the input light beam;

[0030] Figure 8is a graph showing the relationship between the loss of the polarization beam splitter provided by an embodiment of the present invention and the wavelength of the input light beam;

[0031] Fig. 9 are the relationship diagrams between the polarization extinction ratio of the TM mode polarized beam and the dimensional tolerances of the waveguide in the second direction and the third direction respectively;

[0032] Fig.10 is a graph showing the relationship between the loss of the TM mode polarized beam and the dimensional tolerance of the waveguide in the second direction and the third direction;

[0033] Fig.11 It is a structural schematic diagram of a testing system for a polarization beam splitter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0035] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0036] Polarization beam splitters that have been reported in the prior art include directional couplers and three-waveguide directional couplers. For example, in 2021, Xinyu Liu, Dajian Liu, Daoxin Dai and others used a cascaded slot waveguide-assisted directional coupler to realize a polarization beam splitter. In the wavelength range of 1.82-2.02μm, the polarization extinction ratio of the polarization beam splitter was greater than 15dB, and the manufacturing tolerance of the core waveguide was ±20nm. Although the polarization beam splitter based on the directional coupler has good performance and a large manufacturing tolerance, the polarization beam splitter based on the directional coupler is realized by bending the waveguide. The processing complexity of the bent waveguide is high and the manufacturing difficulty is greater. Therefore, the polarization beam splitter based on the directional coupler is more difficult to manufacture. The three-waveguide directional coupler consists of three straight waveguides, which is simple to manufacture and has good performance. Yoohan Kim, Moon Hyeok Lee, Yudeuk Kim and others designed a polarization beam splitter based on a three-waveguide directional coupler. The polarization extinction ratios of the TE mode and TM mode are 40.74dB and 39.01dB, respectively. However, the manufacturing tolerance of the polarization beam splitter is very small, and high manufacturing precision is required.

[0037] In order to solve the problem of low polarization extinction ratio and low manufacturing tolerance of the polarization beam splitter at a wavelength of 2 μm, an embodiment of the present invention provides a polarization beam splitter for the 2 μm band. Figure 1 is a three-dimensional structural diagram of a polarization beam splitter provided by an embodiment of the present invention, Figure 2 is a top view of a polarization beam splitter provided by an embodiment of the present invention, combined with Figure 1 and Figure 2 As shown, the polarization beam splitter includes a first three-waveguide directional coupler and a second three-waveguide directional coupler that are cascaded; the first three-waveguide directional coupler includes a first waveguide 101, a second waveguide 102, and a third waveguide 103 extending along a first direction x and arranged along a second direction y, the second three-waveguide directional coupler includes a fourth waveguide 104, a fifth waveguide 105, and a sixth waveguide 106 extending along the first direction x and arranged along the second direction y, the first waveguide 101 and the sixth waveguide 106 are connected, and the first direction x and the second direction y intersect; the input light beam is input into the polarization beam splitter from the first end of the first waveguide 101, and a TM mode polarized light beam and a TE mode polarized light beam are separated through the first three-waveguide directional coupler, the TM mode polarized light beam is transmitted through the third waveguide 103 and then output, the TE mode polarized light beam and a part of the residual TM mode polarized light beam are transmitted to the second three-waveguide directional coupler through the first waveguide 101, and the TM mode polarized light beam is filtered out through the second three-waveguide directional coupler and then output by the sixth waveguide 106.

[0038] Combination Figure 1 and Figure 2As shown, the input light beam is input from the first waveguide 101 along the first direction x, the TE mode polarized light beam in the input light beam propagates along the first waveguide 101 to the sixth waveguide 106, the TM mode polarized light beam in the input light beam is coupled from the first waveguide 101 to the third waveguide 103 via the second waveguide 102, and finally outputs the polarization beam splitter from the third waveguide 103. After passing through the first three-waveguide directional coupler, the input light beam is divided into a TE mode polarized light beam and a TM mode polarized light beam. Since the coupling efficiency of the TM mode polarized light beam from the first waveguide 101 to the third waveguide 103 is less than 100%, there is a small amount of TM mode polarized light beam in the TE mode polarized light beam propagating in the sixth waveguide 106. The TM mode polarized light beam in the sixth waveguide 106 will be coupled to the fourth waveguide 104 via the fifth waveguide 105, and finally coupled out of the polarization beam splitter. After the TE mode polarized light beam passes through the second three-waveguide directional coupler, the intensity of the TM mode polarized light beam is further reduced, and finally output from the sixth waveguide 106.

[0039] The polarization beam splitter for the 2 μm band provided by an embodiment of the present invention separates a TM mode polarized beam and a TE mode polarized beam through a first three-waveguide directional coupler, wherein the TE mode polarized beam and part of the residual TM mode polarized beam are coupled to the first waveguide, and the TM mode polarized beam is coupled to the third waveguide. Then, through a second three-waveguide directional coupler cascaded after the first three-waveguide directional coupler, the residual TM mode polarized beam is coupled out of the polarization beam splitter through the second three-waveguide directional coupler, so that there are fewer TM mode polarized beams in the TE mode polarized beam output by the sixth waveguide, thereby improving the polarization extinction ratio of the polarization beam splitter.

[0040] Figure 3 is a cross-sectional view of a first three-waveguide directional coupler or a second three-waveguide directional coupler provided in an embodiment of the present invention, combined with Figure 1 and Figure 3 As shown, optionally, the polarization beam splitter includes: a substrate 200; a first cladding 201 and a second cladding 202 stacked on one side of the substrate 200; a waveguide layer 100 located between the first cladding 201 and the second cladding 202, and the waveguide layer 100 includes a first waveguide 101, a second waveguide 102, a third waveguide 103, a fourth waveguide 104, a fifth waveguide 105 and a sixth waveguide 106.

[0041] Combination Figure 1 and Figure 3As shown, the substrate 200, the first cladding 201 and the second cladding 202 are stacked along the third direction z, and the waveguide layer 100 is located between the first cladding 201 and the second cladding 202, and is wrapped by the first cladding 201 and the second cladding 202. In the first three-waveguide directional coupler, the first waveguide 101, the second waveguide 102 and the third waveguide 103 are arranged along the second direction y, and in the second three-waveguide directional coupler, the fourth waveguide 104, the fifth waveguide 105 and the sixth waveguide 106 are arranged along the second direction y.

[0042] refer to Figure 3 Optionally, the substrate 200 includes a silicon substrate, the first cladding layer 201 and the second cladding layer 202 include silicon dioxide cladding layers, and the waveguide layer 100 includes a silicon waveguide.

[0043] Combination Figure 1 and Figure 2 As shown, optionally, the dimension W1 of the first waveguide 101 in the second direction y is greater than the dimension W3 of the sixth waveguide 106 in the second direction y, and the interval W between the first waveguide 101 and the second waveguide 102 is gap The interval W between the fifth waveguide 105 and the sixth waveguide 106 gap equal. Since the waveguide with a smaller size in the second direction y has a higher loss for the 2μm TM mode polarized beam, the size W3 of the sixth waveguide 106 in the second direction y is smaller than the size W1 of the first waveguide 101 in the second direction y, which can further cause the loss of the TM mode polarized beam in the sixth waveguide 106, thereby reducing the TM mode polarized beam output from the sixth waveguide 106 and improving the polarization extinction ratio of the polarization beam splitter. Simulation results show that in the wavelength range of 1.9μm to 2.1μm, the polarization extinction ratio of the TE mode polarized beam and the TM mode polarized beam of the polarization beam splitter is greater than 28dB. Experimental results show that the polarization extinction ratio of the device at a wavelength of 2μm is 36dB.

[0044] Combination Figure 1 and Figure 2 As shown, optionally, the dimension W1 of the first waveguide 101 in the second direction y is 1.2 μm, the dimension W3 of the sixth waveguide 106 in the second direction y is 0.6 μm, and the interval W between the first waveguide 101 and the second waveguide 102 is gap =0.3μm. Figure 4 is a graph showing the relationship between the transmission loss of the TE mode polarized beam and the TM mode polarized beam and the size of the sixth waveguide in the second direction when the wavelength is 2 μm, referring to Figure 4 When the dimension W3 of the sixth waveguide 106 in the second direction y is 0.6 μm, the loss of the TE mode polarized light beam is low, while the loss of the TM mode polarized light beam is high.

[0045] Combination Figure 1 and Figure 2 As shown, optionally, the dimension W2 of the second waveguide 102 in the first direction x is greater than the dimension W4 of the fifth waveguide 105 in the first direction x, and the dimension W2 of the second waveguide 102 in the second direction y is greater than the dimension W4 of the fifth waveguide 105 in the second direction y. Since the waveguide with a smaller dimension in the second direction y has a higher loss for the 2μm TM mode polarized light beam, the dimension W4 of the fifth waveguide 105 in the second direction y is smaller than the dimension W2 of the second waveguide 102 in the second direction y, which can further cause the loss of the TM mode polarized light beam coupled into the fifth waveguide 105, thereby reducing the TM mode polarized light beam output from the sixth waveguide 106 and improving the polarization extinction ratio of the polarization beam splitter.

[0046] Combination Figure 1 and Figure 2 As shown, optionally, the dimension L1 of the second waveguide 102 in the first direction x satisfies 30μm≤L1≤36μm; the dimension L2 of the fifth waveguide 105 in the first direction x satisfies 9μm≤L2≤15.5μm, the dimension W2 of the second waveguide 102 in the second direction y satisfies 1.2μm≤W2≤1.38μm, and the dimension W4 of the fifth waveguide 105 in the second direction y satisfies 0.7μm≤W4≤0.9μm. The above data are obtained based on the phase matching conditions of the three-waveguide directional coupler. Figure 5 is the relationship between the polarization extinction ratio of the polarization beam splitter and W1, L1, W4 and L2, Figure 6 is the relationship between the loss of the polarization beam splitter and W1, L1, W4 and L2, combined with Figure 5 and Figure 6 As shown, when W1, W2, L1, W4 and L2 are within the above ranges, the polarization extinction ratio of the polarization beam splitter is greater than 25dB and the loss is less than 2dB.

[0047] Figure 7 is a graph showing the relationship between the polarization extinction ratio of the polarization beam splitter provided by an embodiment of the present invention and the wavelength of the input light beam, Figure 8 is a graph showing the relationship between the loss of the polarization beam splitter provided by an embodiment of the present invention and the wavelength of the input light beam, Figure 7 and Figure 8 is the result of software simulation. Figure 7 and Figure 8 As shown, when the input light beam is in the wavelength range of 1.9μm to 2.1μm, the polarization extinction ratio of the TM mode polarized light beam is greater than 28dB, and the loss is less than 1.3dB. The polarization extinction ratio of the TE mode polarized light beam is greater than 36dB, and the loss is less than 0.4dB.

[0048] Combination Figure 1 and Figure 2As shown, optionally, the dimensional tolerance of the first waveguide 101, the second waveguide 102, the third waveguide 103, the fourth waveguide 104, the fifth waveguide 105 and the sixth waveguide 106 in the second direction y is within the range of ±60nm, and the dimensional tolerance in the third direction z is within the range of ±10nm, wherein the plane where the first direction x and the second direction y are located is perpendicular to the third direction z. Fig. 9 is the relationship between the polarization extinction ratio of the TM mode polarized beam and the dimensional tolerance of the waveguide in the second and third directions, Fig.10 is the relationship between the loss of TM mode polarized beam and the dimensional tolerance of the waveguide in the second and third directions, respectively. Fig. 9 and Fig.10 As shown, since the TE mode polarized light beam is not sensitive to the change of waveguide size, only the influence of the waveguide size change on the TM mode polarized light beam is discussed here. When the size tolerance of the first waveguide 101, the second waveguide 102, the third waveguide 103, the fourth waveguide 104, the fifth waveguide 105 and the sixth waveguide 106 in the second direction y is within the range of ±60nm, and the size tolerance in the third direction z is within the range of ±10nm, the polarization extinction ratio of the TM mode polarized light beam is still greater than 20dB, and the loss is less than 2dB.

[0049] Optionally, the input light beam is a laser light beam in the 1.9 μm to 2.1 μm band. Fig.11 is a schematic diagram of a structure of a test system for a polarization beam splitter provided by an embodiment of the present invention, with reference to Fig.11 The semiconductor single-mode laser controller 301 controls the single-mode laser 302 to emit a single-mode laser with a wavelength of 2μm. The single-mode laser is transmitted to the optical amplifier 303 through the single-mode optical fiber, and then transmitted to the polarization controller 304. The polarization controller 304 can modulate the polarization state of the single-mode laser. The single-mode laser output from the polarization controller 304 is transmitted to the polarization beam splitter 305 provided in the embodiment of the present invention. The polarization beam splitter 305 divides the single-mode laser into a TE mode polarized beam and a TM mode polarized beam. The TE mode polarized beam and the TM mode polarized beam are transmitted to the optical power meter 306 through the single-mode optical fiber. The optical power meter 306 can detect the light intensity of the TE mode polarized beam and the TM mode polarized beam, respectively. By comparing the light intensity detected by the optical power meter 306 and the polarization state of the single-mode laser output from the polarization controller 304, it can be measured through experiments that the polarization extinction ratios of the TE mode polarized beam and the TM mode polarized beam at a wavelength of 2μm are 36.4dB and 36.2dB, respectively. Optionally, the dimensions of the first waveguide 101 , the second waveguide 102 , the third waveguide 103 , the fourth waveguide 104 , the fifth waveguide 105 and the sixth waveguide 106 in the third direction z are 220 nm, and the planes where the first direction x and the second direction y are located are perpendicular to the third direction z.

[0050] Based on the same inventive concept, an embodiment of the present invention provides a polarization beam splitting device, including a light source and a polarization beam splitter provided by any embodiment of the present invention, wherein the output end of the light source is coupled to the input end of the polarization beam splitter.

[0051] The polarization beam splitting device provided in the embodiment of the present invention includes any one of the polarization beam splitters provided in the above embodiments, and has the same or corresponding technical effects as the polarization beam splitter, which will not be described in detail here.

[0052] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A polarization beam splitter for the 2 μm band, characterized in that: comprising a first three-waveguide directional coupler and a second three-waveguide directional coupler arranged in cascade; The first three-waveguide directional coupler includes a first waveguide, a second waveguide and a third waveguide extending along a first direction and arranged along a second direction, the second three-waveguide directional coupler includes a fourth waveguide, a fifth waveguide and a sixth waveguide extending along the first direction and arranged along the second direction, the first waveguide and the sixth waveguide are connected, and the first direction and the second direction intersect; An input light beam is input into the polarization beam splitter from the first end of the first waveguide, and is separated into a TM mode polarized light beam and a TE mode polarized light beam through the first three-waveguide directional coupler. The TM mode polarized light beam is output after being transmitted through the third waveguide, and the TE mode polarized light beam is transmitted to the second three-waveguide directional coupler through the first waveguide, and is output from the sixth waveguide after the TM mode polarized light beam is filtered out through the second three-waveguide directional coupler.

2. The polarization beam splitter for the 2 μm band according to claim 1, characterized in that: include: substrate; A first cladding layer and a second cladding layer stacked and arranged on one side of the substrate; A waveguide layer is located between the first cladding layer and the second cladding layer, and the waveguide layer includes the first waveguide, the second waveguide, the third waveguide, the fourth waveguide, the fifth waveguide and the sixth waveguide.

3. The polarization beam splitter for the 2 μm band according to claim 2, characterized in that: The substrate comprises a silicon substrate, the first cladding layer and the second cladding layer comprise silicon dioxide cladding layers, and the waveguide layer comprises a silicon waveguide.

4. The polarization beam splitter for the 2 μm band according to claim 1, characterized in that: A size of the first waveguide in the second direction is greater than a size of the sixth waveguide in the second direction, and a spacing between the first waveguide and the second waveguide is equal to a spacing between the fifth waveguide and the sixth waveguide.

5. The polarization beam splitter for the 2 μm band according to claim 4, characterized in that: The dimension W1 of the first waveguide in the second direction is 1.2 μm, the dimension W3 of the sixth waveguide in the second direction is 0.6 μm, and the interval W between the first waveguide and the second waveguide is gap =0.3μm.

6. The polarization beam splitter for the 2 μm band according to claim 1, characterized in that: A size of the second waveguide in the first direction is larger than a size of the fifth waveguide in the first direction, and a size of the second waveguide in the second direction is larger than a size of the fifth waveguide in the second direction.

7. The polarization beam splitter for the 2 μm band according to claim 6, characterized in that: A size L1 of the second waveguide in the first direction satisfies 30μm≤L1≤36μm; a size L2 of the fifth waveguide in the first direction satisfies 9μm≤L2≤15.5μm, a size W2 of the second waveguide in the second direction satisfies 1.2μm≤W2≤1.38μm, and a size W4 of the fifth waveguide in the second direction satisfies 0.7μm≤W4≤0.9μm.

8. The polarization beam splitter for the 2 μm band according to claim 1, characterized in that: The dimensional tolerance of the first waveguide, the second waveguide, the third waveguide, the fourth waveguide, the fifth waveguide and the sixth waveguide in the second direction is within the range of ±60nm, and the dimensional tolerance in the third direction is within the range of ±10nm, wherein the plane where the first direction and the second direction are located is perpendicular to the third direction.

9. The polarization beam splitter for the 2 μm band according to claim 1, characterized in that: The input light beam is a laser light beam in the 1.9 μm to 2.1 μm band.

10. The polarization beam splitter for the 2 μm band according to claim 1, characterized in that: The dimensions of the first waveguide, the second waveguide, the third waveguide, the fourth waveguide, the fifth waveguide and the sixth waveguide in the third direction are 220 nm, and the planes where the first direction and the second direction are located are perpendicular to the third direction.

Images