Polarization Beam Splitter Rotator

Abstract

The present invention discloses a polarization beam splitter rotator, which includes: an upper cladding and a lower cladding, and a silicon waveguide layer wrapped in a cavity formed by the upper cladding and the lower cladding, the silicon waveguide layer includes a partially etched adiabatic conical waveguide structure, an asymmetric directional coupling structure and a double asymmetric directional coupling structure, the partially etched adiabatic conical waveguide structure is connected to the asymmetric directional coupling structure, and the asymmetric directional coupling structure is also connected to the double asymmetric directional coupling structure. The present invention adopts a partially etched adiabatic conical waveguide structure to achieve mode hybridization and meet process compatibility; adopts an asymmetric directional coupling structure to achieve mode evolution with a larger bandwidth and increase the manufacturing tolerance at the same time; adopts a double asymmetric directional coupling structure to perform residual mode filtering to achieve a high polarization extinction ratio. The present invention can balance the process compatibility, manufacturing tolerance, polarization extinction ratio and other indicators of the polarization beam splitter rotator, and improve the practicality of the polarization beam splitter rotator.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a polarization beam splitter rotator. Background Art

[0002] Silicon-on-insulator photonic devices are very attractive due to their complementary metal oxide semiconductor (CMOS) compatible manufacturing technology and compact size. However, due to the characteristics of the CMOS process and the material itself, the devices on insulator have strong birefringence, which causes different polarization modes to produce different responses in the loop. The resulting polarization mode dispersion and loss will greatly degrade the system performance. In order to solve the polarization sensitivity problem and achieve polarization independence, polarization diversity technology based on polarization beam splitter rotator is usually used.

[0003] The difficulty of polarization processing is mainly polarization mode conversion. Currently, there are three main ways to achieve polarization mode conversion: First, by using different materials on the vertical structure to achieve asymmetric refractive index in the vertical direction, a hybrid supermode can be generated in a certain width area, and polarization mode conversion can be achieved when the polarization ratio is close to 50%; second, through an asymmetric coupling structure, the refractive index symmetry in both the horizontal and vertical directions is broken at the same time, thereby forming a hybrid supermode between the waveguides, and polarization mode conversion is achieved in the process of polarization separation through the polarization mode coupling effect; third, using a Y-branch structure and utilizing the polarization mode classification principle to achieve conversion between multiple polarization modes.

[0004] However, the above method will make it difficult for the current polarization beam splitter rotator to achieve a balance in process compatibility, manufacturing tolerance, polarization extinction ratio and other indicators, resulting in low practicality of the polarization beam splitter rotator. Summary of the invention

[0005] The main purpose of the present invention is to propose a polarization beam splitter rotator, aiming to solve how to balance the process compatibility, manufacturing tolerance, polarization extinction ratio and other indicators of the polarization beam splitter rotator, so as to improve the practicability of the polarization beam splitter rotator.

[0006] To achieve the above object, the present invention provides a polarization beam splitter rotator, the polarization beam splitter rotator comprising:

[0007] An upper cladding and a lower cladding, and a silicon waveguide layer wrapped in a cavity formed by the upper cladding and the lower cladding, the silicon waveguide layer comprising a partially etched adiabatic tapered waveguide structure, an asymmetric directional coupling structure and a double asymmetric directional coupling structure, the partially etched adiabatic tapered waveguide structure is connected to the asymmetric directional coupling structure, and the asymmetric directional coupling structure is also connected to the double asymmetric directional coupling structure.

[0008] Optionally, the partially etched adiabatic tapered waveguide structure comprises:

[0009] An input waveguide, wherein the width of the input waveguide is a first width;

[0010] A partially etched adiabatic tapered waveguide, wherein the length of the partially etched adiabatic tapered waveguide is a first length, the partially etched adiabatic tapered waveguide comprises a first etched portion and a first unetched portion, the width of the first etched portion is a second width, the etching depth is a preset depth, and the width of the first unetched portion gradually changes from the first width to a third width;

[0011] The input waveguide is connected to a side surface of the first unetched portion of the partially etched adiabatic tapered waveguide having a width equal to the first width.

[0012] Optionally, the asymmetric directional coupling structure includes:

[0013] A partially etched waveguide, the partially etched waveguide comprising a second etched portion and a second unetched portion, the second unetched portion having a third width and a second length, the second etched portion having a second width, an etched depth of a preset depth, and a third length;

[0014] a gradually tapered waveguide, wherein the width of the gradually tapered waveguide gradually changes from a fourth width to a fifth width, and the length of the gradually tapered waveguide is a fourth length;

[0015] The partially etched waveguide is arranged opposite to the gradually tapered waveguide, and the distance between the partially etched waveguide and the gradually tapered waveguide is a preset distance.

[0016] Optionally, the dual asymmetric directional coupling structure includes:

[0017] an upper end, the upper end comprising an S-shaped curved waveguide and a first adiabatic gradually tapered waveguide, the S-shaped curved waveguide having a width of the fifth width, the first adiabatic gradually tapered waveguide having a width gradually changing from the fifth width to the first width, and a length of the fifth length, the S-shaped curved waveguide being connected to a side surface of the first adiabatic gradually tapered waveguide having a width of the fifth width;

[0018] The lower end comprises a second adiabatic gradually changing tapered waveguide, a first gradually changing waveguide, an S waveguide, a second gradually changing waveguide and a 90° waveguide, the width of the second adiabatic gradually changing tapered waveguide gradually changes from the third width to the first width, and the length is the sixth length, the width of the first gradually changing waveguide gradually changes from the sixth width to the seventh width, and the length is the seventh length, and the width of the second gradually changing waveguide gradually changes from the eighth width to the ninth width, and the length is the eighth length.

[0019] The upper end is arranged opposite to the lower end.

[0020] Optionally, the first gradual waveguide and the S waveguide in the lower end are located on one side of the second adiabatic gradually changing tapered waveguide, the second gradual waveguide and the 90° waveguide are located on the other side of the second adiabatic gradually changing tapered waveguide, the S waveguide is connected to the side of the first gradual waveguide whose width is the seventh width, and the 90° waveguide is connected to the side of the second gradual waveguide whose width is the ninth width.

[0021] Optionally, the side surface with a width of the third width in the first unetched portion of the partially etched adiabatic tapered waveguide in the partially etched adiabatic tapered waveguide structure is connected to the partially etched waveguide in the asymmetric directional coupling structure, the partially etched waveguide in the asymmetric directional coupling structure is connected to the side surface with a width of the third width in the second adiabatic gradually tapered waveguide at the lower end of the double asymmetric directional coupling structure, and the side surface with a width of the fifth width in the gradually tapered waveguide in the asymmetric directional coupling structure is connected to the side surface of the curved waveguide at the upper end of the double asymmetric directional coupling structure.

[0022] Optionally, the input waveguide is used to receive an input optical signal, and the partially etched adiabatic tapered waveguide is used to perform mode hybridization on a mode of the optical signal that meets a preset condition.

[0023] Optionally, the partially etched waveguide and the gradually tapered waveguide are used to perform mode evolution on the mode of the optical signal after mode hybridization.

[0024] Optionally, the second adiabatic gradually tapered waveguide, the first gradually tapered waveguide, the S waveguide, the second gradually tapered waveguide and the 90° waveguide can be used to filter out other residual modes that are not target modes in the optical signal after mode hybridization and mode evolution.

[0025] Optionally, the S-shaped curved waveguide and the first adiabatic gradually tapered waveguide are used to output an optical signal of a target mode obtained after mode filtering.

[0026] The polarization beam splitter rotator proposed in the present invention includes: an upper cladding and a lower cladding, and a silicon waveguide layer wrapped in a cavity formed by the upper cladding and the lower cladding, the silicon waveguide layer includes a partially etched adiabatic conical waveguide structure, an asymmetric directional coupling structure and a double asymmetric directional coupling structure, the partially etched adiabatic conical waveguide structure is connected to the asymmetric directional coupling structure, and the asymmetric directional coupling structure is also connected to the double asymmetric directional coupling structure. The present invention adopts a partially etched adiabatic conical waveguide structure to achieve mode hybridization and meet process compatibility; adopts an asymmetric directional coupling structure to achieve mode evolution with a larger bandwidth while increasing the manufacturing tolerance; adopts a double asymmetric directional coupling structure to perform residual mode filtering to achieve a high polarization extinction ratio. The present invention can balance the process compatibility, manufacturing tolerance, polarization extinction ratio and other indicators of the polarization beam splitter rotator, and improve the practicality of the polarization beam splitter rotator. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the three-dimensional structure of the polarization beam splitter rotator according to the first embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of the three-dimensional structure of the lower cladding layer and the silicon waveguide layer of the polarization beam splitter rotator according to the first embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of the planar structure of the polarization beam splitter rotator according to the first embodiment of the present invention;

[0030] Figure 4 For the present invention Figure 2 Schematic diagram of the cross section at A-A';

[0031] Figure 5 For the present invention Figure 2 Schematic diagram of the cross section at B-B';

[0032] Figure 6 A schematic diagram of the effective refractive index corresponding to the strip waveguide and the partially etched waveguide of the present invention at different widths;

[0033] Figure 7 It is a schematic diagram of the simulation distribution of the light field transmission of the optical signal of the TM0 mode through the polarization beam splitter rotator of the present invention;

[0034] Figure 8 This is a schematic diagram of the light field transmission simulation distribution of the TE0 mode optical signal passing through the polarization beam splitter rotator of the present invention;

[0035] Fig. 9 It is a schematic diagram of the transmission efficiency of the Cross port (upper port) of the polarization beam splitter rotator of the present invention under different polarization mode inputs;

[0036] Fig.10It is a schematic diagram of the transmission efficiency of the Through port (lower port) of the polarization beam splitter rotator of the present invention under different polarization mode inputs;

[0037] Fig.11 FIG. 4 is a schematic plan view of the structure of the polarization beam splitter rotator according to the second embodiment.

[0038] Description of Figure Numbers:

[0039]

[0040]

[0041] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0042] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0043] refer to Figure 1 , a first embodiment of the present invention is proposed, and the polarization beam splitter rotator proposed in the first embodiment of the present invention includes:

[0044] An upper cladding layer 111, a lower cladding layer 113, and a silicon waveguide layer 112 enclosed in a cavity formed by the upper cladding layer and the lower cladding layer;

[0045] The silicon waveguide layer 112 includes a partially etched adiabatic tapered waveguide structure, an asymmetric directional coupling structure and a double asymmetric directional coupling structure. The partially etched adiabatic tapered waveguide structure is connected to the asymmetric directional coupling structure, and the asymmetric directional coupling structure is connected to the double asymmetric directional coupling structure.

[0046] The upper cladding layer 111 and the lower cladding layer 113 are both insulating layers, and both are made of silicon dioxide material; the upper cladding layer 111 wraps the upper surface and side surfaces of the silicon waveguide layer 112, and the lower cladding layer 113 wraps the lower surface of the silicon waveguide layer 112; it can be understood that, if Figure 1 and Figure 2 As shown, Figure 1 is a schematic diagram of the three-dimensional structure of the polarization beam splitter rotator according to the first embodiment of the present invention, Figure 2 Schematic diagram of the three-dimensional structure of the lower cladding and silicon waveguide layer of the polarization beam splitter rotator according to the first embodiment of the present invention. The silicon waveguide layer 112 is embedded in the upper cladding 111. The lower surface of the silicon waveguide layer 112 and the lower surface of the upper cladding 111 are located in the same plane. The lower surface of the silicon waveguide layer 112 and the lower surface of the upper cladding 111 are both connected to the upper surface of the lower cladding 113, so that the upper cladding 111 and the lower cladding 113 completely wrap the silicon waveguide layer 112.

[0047] Optionally, the polarization beam splitter rotator is made of silicon on insulator (SOI): the lower cladding layer 113 is made of silicon dioxide; the silicon waveguide layer 112 is made of silicon with a thickness of 220 nm.

[0048] Furthermore, if Figure 3 As shown, Figure 3 FIG. 4 is a schematic plan view of the structure of a polarization beam splitter rotator according to the first embodiment of the present invention.

[0049] The partially etched adiabatic tapered waveguide structure in the polarization beam splitter rotator includes an input waveguide 11 and a partially etched adiabatic tapered waveguide 12 .

[0050] The width of the input waveguide 11 is the first width; optionally, the shape of the input waveguide 11 is a cube or a cuboid; when the shape of the input waveguide 11 is a cube, the length of each side is the first width; when the shape of the input waveguide 11 is a cuboid, the corresponding width is the first width, and the corresponding height and length are not limited here.

[0051] The length of the partially etched adiabatic tapered waveguide 12 is a first length; Figure 4 , Figure 4 for Figure 3 A schematic cross-sectional view at A-A' in the figure, wherein the upper cladding 101 and the lower cladding 102 completely wrap the partially etched adiabatic tapered waveguide structure, the partially etched adiabatic tapered waveguide 12 comprises a first etched portion 103 and a first unetched portion 100, the upper surface of the first etched portion 103 is etched to a corresponding etching depth, the etching depth is a preset depth, and the lower surface of the first etched portion 103 and the lower surface of the first unetched portion 100 are located in the same plane; further, Figure 4 The portion indicated by 100 is the core region of the optical waveguide, and the refractive index of the upper cladding 101 and the lower cladding 102 is equal or different; Figure 3 and Figure 4 The width of the first etched portion 103 is the second width, and the width of the first unetched portion 100 gradually changes from the first width to the third width, wherein the first width is smaller than the third width; the input waveguide 11 is connected to the side of the first unetched portion 100 in the partially etched adiabatic tapered waveguide 12 whose width is the first width.

[0052] The asymmetric directional coupling structure in the polarization beam splitter rotator includes: a partially etched waveguide 21 and a gradually tapered waveguide 22 .

[0053] The partially etched waveguide 21 includes a second etched portion and a second unetched portion, one end of the second etched portion and one end of the second unetched portion are located in the same plane, the other end of the second etched portion and the other end of the second unetched portion are not located in the same plane, the width of the second unetched portion is the third width, and the length is the second length, the width of the second etched portion is the second width, and the length is the third length, wherein the second length is greater than the third length.

[0054] The width of the gradually tapered waveguide 22 gradually changes from the fourth width to the fifth width, and the length is the fourth length.

[0055] The gradually tapered waveguide 22 is located on one side of the second unetched portion of the partially etched waveguide 21 . The partially etched waveguide 21 and the gradually tapered waveguide 22 are arranged opposite to each other. The distance between the partially etched waveguide 21 and the gradually tapered waveguide 22 is a preset distance.

[0056] refer to Figure 5 , Figure 5 for Figure 3 The schematic cross-sectional view at BB' in the figure shows a gradually tapered waveguide 22 on the left and a partially etched waveguide 21 on the right. The partially etched waveguide 21 includes a second etched portion 203 and a second unetched portion 200. The width of the second unetched portion 200 is the third width and the length is the second length. The width of the second etched portion 203 is the second width, the etching depth is the preset depth, and the length is the third length. Furthermore, the portion indicated by 200 is the core area of ​​the optical waveguide, and the refractive indexes of the upper cladding 201 and the lower cladding 202 are equal or different.

[0057] Among them, the dual asymmetric directional coupling structure in the polarization beam splitter rotator includes: an upper end and a lower end, and the upper end is arranged opposite to the lower end, wherein the upper end includes an S-shaped curved waveguide 34 and a first adiabatic gradually changing tapered waveguide 35, and the lower end includes a second adiabatic gradually changing tapered waveguide 31, a first gradually changing waveguide 32a, an S waveguide 32b, a second gradually changing waveguide 33a and a 90° waveguide 33b.

[0058] The width of the S-shaped waveguide 34 is the fifth width, the width of the first adiabatic gradually tapered waveguide 35 gradually changes from the fifth width to the first width, and the length is the fifth length. The S-shaped waveguide 34 is connected to the side of the first adiabatic gradually tapered waveguide 35 whose width is the fifth width.

[0059] The width of the second adiabatic gradually changing tapered waveguide 31 gradually changes from the third width to the first width, and the length is the sixth length. The width of the first gradually changing waveguide 32a gradually changes from the sixth width to the seventh width, and the length is the seventh length. The width of the second gradually changing waveguide 33a gradually changes from the eighth width to the ninth width, and the length is the eighth length.

[0060] Further, the first gradual waveguide 32a and the S waveguide 32b in the lower end are located on one side of the second adiabatic gradually changing tapered waveguide 31, the second gradual waveguide 33a and the 90° waveguide 33b are located on the other side of the second adiabatic gradually changing tapered waveguide 31, the S waveguide 32b is connected to the side of the first gradual waveguide 32a having a width of the seventh width, and the 90° waveguide 33b is connected to the side of the second gradual waveguide 33a having a width of the ninth width.

[0061] Further, in the silicon waveguide layer, a side surface with a width of the third width in a first unetched portion of a partially etched adiabatic tapered waveguide 12 in the partially etched adiabatic tapered waveguide structure is connected to the partially etched waveguide 21 in the asymmetric directional coupling structure, the partially etched waveguide 21 in the asymmetric directional coupling structure is connected to a side surface with a width of the third width in a second adiabatic gradually tapered waveguide 31 at the lower end of the double asymmetric directional coupling structure, and a side surface with a width of the fifth width in a gradually tapered waveguide 22 in the asymmetric directional coupling structure is connected to a side surface of an S-shaped curved waveguide 34 at the upper end of the double asymmetric directional coupling structure.

[0062] Furthermore, the input waveguide 11 is used to receive an input optical signal, and the partially etched adiabatic tapered waveguide 12 is used to perform mode hybridization on a mode of an optical signal that meets preset conditions; specifically, the width of a first unetched portion in the partially etched adiabatic tapered waveguide 12 gradually changes from a first width to a third width, and passes through a polarization mode conversion critical width during the gradual change process. By designing a suitable first length of the partially etched adiabatic tapered waveguide 12, it is possible to complete the conversion of energy of the TM0 polarization mode into the TE1 polarization mode in the partially etched adiabatic tapered waveguide 12, and it is noted that both a shorter coupling length and a high conversion efficiency need to be taken into account.

[0063] Further, the partially etched waveguide 21 and the gradually tapered waveguide 22 are used to perform mode evolution on the mode of the optical signal after mode hybridization; specifically, the TE1 polarization mode in the partially etched waveguide 21 and the TE0 polarization mode in the gradually tapered waveguide 22 meet the phase matching condition:

[0064] n eff1 (TE1) = n eff2 (TE0)

[0065] Among them, n eff1 (TE1) represents the effective refractive index of the TE1 polarization mode in the partially etched waveguide 21, n eff2 (TE0) represents the effective refractive index of the TE0 polarization mode in the tapered waveguide 22. It is worth noting that during the mode evolution process, the coupling efficiency will change periodically with the coupling length.

[0066] Further, the second adiabatic gradually tapered waveguide 31, the first gradually tapered waveguide 32a, the S waveguide 32b, the second gradually tapered waveguide 33a and the 90° waveguide 33b can be used to filter out other residual modes that are not the target mode in the optical signal after mode hybridization and mode evolution; the S-shaped curved waveguide 34 and the first adiabatic gradually tapered waveguide 35 are used to output the converted target mode optical signal; specifically, the S waveguide 32b, the 90° waveguide 33b and the tapered structure at the tail thereof are used to filter the filter coupling. The combined energy is dissipated in the free space; the residual TE1 and TM0 polarization modes in the second adiabatic gradually tapered waveguide 31 respectively meet the phase matching conditions with the TE0 mode in the first gradually tapered waveguide 32a and the TE1 mode in the second gradually tapered waveguide 33a, and the energy of the residual TE1 and TM0 modes in the second adiabatic gradually tapered waveguide 31 can be filtered out; the energy of the TE0 mode in the gradually tapered waveguide 22 is finally output from the first adiabatic gradually tapered waveguide 35 via the S-shaped curved waveguide 34. The specific working process of the polarization beam splitter rotator of this embodiment is as follows:

[0067] An optical signal within the operating wavelength range of the polarization beam rotator is input from the left side of the input waveguide 11 .

[0068] One working situation is that the input optical signal is in TE0 mode:

[0069] When the optical signal input from the input waveguide 11 is in TE0 mode, it passes through the partially etched adiabatic tapered waveguide 12. Since the effective refractive index of the optical signal in TE0 mode does not satisfy the mode hybridization condition in the partially etched adiabatic tapered waveguide 12, mode hybridization will not occur. The optical signal in TE0 mode enters the partially etched waveguide 21. Since the mode evolution condition is not satisfied, it propagates forward along the partially etched waveguide 21 and is output from the second adiabatic gradually tapered output waveguide 31 at the lower end. The TE0 mode does not satisfy the mode evolution condition when transmitted in the second adiabatic gradually tapered output waveguide 31, and the mode energy will not be coupled into the dual asymmetric directional coupling structure.

[0070] Another working situation is that the input optical signal is in TM0 mode:

[0071] When the optical signal input from the input waveguide 11 is in TM0 mode, it passes through the partially etched adiabatic tapered waveguide 12. Since the effective refractive index of the TM0 mode satisfies the mode hybridization condition in the partially etched adiabatic tapered waveguide 12, the input optical signal gradually changes from TM0 mode to TE1 mode. Then the optical signal in TE1 mode enters the partially etched waveguide 21. Since its mode effective refractive index satisfies the supermode evolution condition, the energy of the TE1 mode mainly confined in the partially etched waveguide 21 evolves into the energy of the TE0 mode confined in the tapered waveguide 22, and finally outputs from the first adiabatic tapered waveguide 35 via the S-shaped curved waveguide 34.

[0072] Due to the error in the manufacturing process, the actual waveguide width, etching depth, etc. cannot be completely consistent with the designed size, resulting in the TM0 mode not being able to completely slowly change to the TE1 mode, and the TE1 mode not being able to completely evolve to the TE0 mode. Therefore, the energy of the optical signals of the TM0 mode and the TE1 mode often remains in the second adiabatic slowly tapered waveguide 31 at the lower end; the ADC structure is formed by the second adiabatic slowly tapered waveguide 31 and the first tapered waveguide 32a. By satisfying the phase matching condition, the second adiabatic slowly tapered waveguide 31 can be The energy of the residual TE1 mode optical signal in 31 is converted and dissipated in the free space through the tapered structure at the tail of the S waveguide 32b to filter out the energy of the residual TE1 mode optical signal; the ADC structure is composed of the second adiabatic slowly-varying tapered waveguide 31 and the second gradually-varying waveguide 33a. By satisfying the phase matching condition, the energy of the residual TM0 mode optical signal in the adiabatic slowly-varying tapered waveguide 31 can be converted and dissipated in the free space through the tapered structure at the tail of the 90° waveguide 33b to filter out the energy of the residual TM0 mode optical signal.

[0073] It should be noted that the width, length, etching width and depth of the partially etched adiabatic tapered waveguide 12 are designed to ensure that the optical signal in the TM0 mode can undergo mode hybridization and can completely evolve into the optical signal in the TE1 mode; the length and gradient width of the gradually tapered waveguide 22, as well as the length of the partially etched waveguide 21, are designed to ensure that the optical signal in the TE1 mode in the partially etched waveguide 21 is gradually converted into the optical signal in the TE0 mode in the gradually tapered waveguide 22; the length of the second adiabatic gradually tapered waveguide 31 and the first gradually tapered waveguide 32a are designed to ensure that the energy of the optical signal in the TE1 mode remaining in the second adiabatic gradually tapered waveguide 31 is converted and filtered out; the length of the second adiabatic gradually tapered waveguide 31 and the second gradually tapered waveguide 33a are designed to ensure that the energy of the optical signal in the TM0 mode remaining in the second adiabatic gradually tapered waveguide 31 is converted and filtered out.

[0074] In a feasible embodiment, the upper cladding and the lower cladding are made of silicon dioxide, and the silicon waveguide layer is made of silicon material with a thickness of 220 nm, forming the main body of the polarization beam splitter rotator;

[0075] The first width of the input waveguide 11 is 0.5um; the width of the first unetched portion of the partially etched adiabatic tapered waveguide 12 gradually changes from the first width of 0.5um to the third width of 0.8um; the second width of the first etched portion of the partially etched adiabatic tapered waveguide 12 is 0.2um, and the etching depth is 0.15um. Figure 6As shown in FIG. 1 , by scanning the effective refractive indexes of various modes corresponding to different widths of the first etched portion of the partially etched adiabatic tapered waveguide 12, it can be known that the critical width W≈0.6um for the TM0 mode to be converted into the TE1 mode, and when the etching depth and the narrow waveguide width of the partially etched adiabatic tapered waveguide 12 are within the target value ±10nm error, the corresponding effective refractive index can also be obtained from Figure 6 Therefore, the first length of the partially etched adiabatic tapered waveguide 12 is set to 47.7um. Through simulation, it can be seen that the conversion rate of the partially etched adiabatic tapered waveguide 12 to convert the optical signal of the TM0 polarization mode into the optical signal of the TE1 polarization mode is greater than 98%.

[0076] The width of the second unetched portion in the partially etched waveguide 21 is the third width of 0.8um, and the length is the second length of 25.2um; the width of the second etched portion in the partially etched waveguide 21 is the second width of 0.2um, the etching depth is 0.15um, and the length is the third length of 23.2um; the width of the gradually tapered waveguide 22 gradually changes from the fourth width of 0.382um to the fifth width of 0.422um, and the length is the fourth length of 21.2um; the distance between the partially etched waveguide 21 and the gradually tapered waveguide 22 is the preset distance of 0.2um.

[0077] The second adiabatic tapered waveguide 31 changes from the third width 0.8um to the first width 0.5um, and the length is the sixth length 17um; the first tapered waveguide 32a changes from the sixth width 0.385um to the seventh width 0.3um, and the length is the seventh length 11.6um; the second tapered waveguide 33a changes from the eighth width 0.7um to the ninth width 0.6um, and the length is the eighth length 17um. The S waveguide 32b, the 90° waveguide 33b, and the tapered structure at the tail are used to dissipate the energy of the filter coupling in the free space; the width of the S-shaped curved waveguide 34 is the fifth width 0.422um, and the first adiabatic tapered waveguide 35 changes from the fifth width 0.422um to the first width 0.5um, and the length is the fifth length 10um.

[0078] Under the conditions of this implementation case, after 3D-FDTD scanning calculation and analysis, the light field transmission simulation distribution diagram of the 1550nm TM0 mode and TE0 light source passing through the polarization beam splitter rotator can be obtained, as shown in Figure 7 and Figure 8 The transmission performance of the overall structure of the present invention is shown in Fig. 9 and Fig.10The figure shows the transmission efficiency of the Cross port (upper port) and the Through port (lower port) under different polarization input modes. Under the TM0 polarization input mode, the loss is less than 1dB in the bandwidth of 1480nm-1620nm, and the extinction ratio is greater than 20dB in the bandwidth of 1450nm-1650nm; in the C band (1535-1565nm), the polarization extinction ratio is greater than 25dB and the loss is less than 0.25dB. Under the TE0 polarization input mode, the extinction ratio is greater than 22dB and the loss is less than 0.2dB in the bandwidth of 1450nm-1650nm.

[0079] The polarization beam splitter rotator of this embodiment uses conventional SOI materials and a partially etched adiabatic gradually tapered waveguide structure, while breaking the symmetry in the horizontal and vertical directions, so that the upper and lower claddings are also asymmetric when they are the same, thereby realizing mode hybridization and satisfying large-scale silicon-based optoelectronic integration through CMOS technology; using a gradient waveguide to form an asymmetric directional coupling structure, the device can achieve mode evolution with a larger bandwidth and increase the manufacturing tolerance; a dual asymmetric directional coupling structure is formed by a gradient waveguide, and the residual TM0 and TE1 are coupled and filtered at the same time, so that the device can also achieve a high polarization extinction ratio under large manufacturing errors. The polarization beam splitter rotator of the present invention has excellent performances such as CMOS process compatibility, high polarization extinction ratio, large manufacturing tolerance, and large bandwidth, balances the process compatibility, manufacturing tolerance, polarization extinction ratio and other indicators of the polarization beam splitter rotator, and improves the practicality of the polarization beam splitter rotator.

[0080] Further, refer to Fig.11 , a second embodiment of the present invention is proposed, and the polarization beam splitter rotator proposed in the second embodiment of the present invention includes:

[0081] The first section includes an input waveguide and a partially etched adiabatic tapered waveguide, which is the same as the first embodiment and will not be described in detail.

[0082] The second section, in which the partially etched waveguide in the first embodiment is replaced with a partially etched adiabatic tapered waveguide, and the tapered waveguide remains unchanged;

[0083] The third section, in the third section, the S-shaped curved waveguide and the first adiabatic gradually tapered waveguide at the upper end (Cross end) in the first embodiment are replaced with a rectangular waveguide, and the first adiabatic gradually tapered waveguide at the lower end (Through end) is replaced with an S-shaped curved waveguide and an adiabatic gradually tapered waveguide.

[0084] In a specific implementation, an optical signal within the operating wavelength range of the polarization beam splitter rotator is input from the left side of the input waveguide.

[0085] One working situation is that the input optical signal is in TE0 mode:

[0086] When the optical signal input from the input waveguide is in TE0 mode, it passes through the partially etched adiabatic conical waveguide in the first section. Since the effective refractive index of the optical signal in TE0 mode does not satisfy the mode hybridization condition in the partially etched adiabatic conical waveguide, mode hybridization will not occur. The optical signal in TE0 mode enters the partially etched adiabatic conical waveguide in the second section. Since the mode evolution condition is not satisfied, it propagates forward along the partially etched adiabatic conical waveguide to the third section, and is output from the S-shaped curved waveguide at the lower end (Through end) and finally output from the adiabatic gradually varying conical waveguide. The TE0 mode does not satisfy the mode evolution condition when transmitted in the adiabatic gradually varying conical waveguide in the third section, and the mode energy will not be coupled into the dual asymmetric directional coupling structure.

[0087] Another working situation is that the input optical signal is in TM0 mode:

[0088] When the optical signal input from the input waveguide is in TM0 mode, it passes through the partially etched adiabatic tapered waveguide in the first section. Since the effective refractive index of the TM0 mode satisfies the mode hybridization condition in the partially etched adiabatic tapered waveguide, the input optical signal gradually changes from TM0 mode to TE1 mode. Then the optical signal in TE1 mode enters the partially etched adiabatic tapered waveguide in the second section. Since its mode effective refractive index satisfies the supermode evolution condition, it mainly limits the energy of TE1 mode in the partially etched adiabatic tapered waveguide in the second section to evolve into the energy of TE0 mode limited in the tapered waveguide, and is output through the rectangular waveguide at the upper end (Cross end) in the third section.

[0089] Due to the error in the manufacturing process, the actual waveguide width, etching depth, etc. cannot be completely consistent with the designed size, resulting in the TM0 mode not being able to completely slowly change to the TE1 mode, and the TE1 mode not being able to completely evolve to the TE0 mode. Therefore, the energy of the optical signals of the TM0 mode and the TE1 mode often remains in the adiabatic slowly varying tapered waveguide at the lower end of the third section. The ADC structure is composed of the S-shaped curved waveguide at the lower end (through end) of the third section and the adiabatic slowly varying tapered waveguide and the first gradually varying waveguide. By satisfying the phase matching condition, The device can transform the energy of the residual TE1 mode optical signal in the adiabatic slowly-varying tapered waveguide, and dissipate it in the free space through the tapered structure at the tail of the S waveguide, so as to filter out the energy of the residual TE1 mode optical signal; the ADC structure is composed of the S-shaped curved waveguide, the adiabatic slowly-varying tapered waveguide and the second tapered waveguide, and by satisfying the phase matching condition, the energy of the residual TM0 mode optical signal in the adiabatic slowly-varying tapered waveguide can be transformed, and dissipated in the free space through the tapered structure at the tail of the 90° waveguide, so as to filter out the energy of the residual TM0 mode optical signal.

[0090] It should be noted that the width, length, etching width and depth of the partially etched adiabatic conical waveguide in the first section are designed to satisfy the requirement that the optical signal in the TM0 mode can undergo mode hybridization and can completely evolve into the optical signal in the TE1 mode; the length, gradient width and length of the gradually changing tapered waveguide in the second section, as well as the length of the partially etched adiabatic conical waveguide, are designed to satisfy the requirement that the optical signal in the TE1 mode in the partially etched adiabatic conical waveguide is gradually converted into the optical signal in the TE0 mode in the gradually changing tapered waveguide; the length of the adiabatic gradually changing tapered waveguide and the first gradually changing waveguide in the third section are designed to satisfy the requirement that the energy conversion and filtering of the optical signal in the TE1 mode remaining in the adiabatic gradually changing tapered waveguide is eliminated; the length of the adiabatic gradually changing tapered waveguide and the second gradually changing waveguide are designed to satisfy the requirement that the energy conversion and filtering of the optical signal in the TM0 mode remaining in the adiabatic gradually changing tapered waveguide is eliminated.

[0091] The polarization beam splitter rotator of this embodiment has excellent performances such as CMOS process compatibility, high polarization extinction ratio, large manufacturing tolerance, and large bandwidth. It balances the process compatibility, manufacturing tolerance, polarization extinction ratio and other indicators of the polarization beam splitter rotator and improves the practicality of the polarization beam splitter rotator.

[0092] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0093] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0094] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method.

[0095] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A polarization beam splitter rotator, characterized in that: The polarization beam splitter rotator comprises: An upper cladding layer and a lower cladding layer, and a silicon waveguide layer wrapped in a cavity formed by the upper cladding layer and the lower cladding layer, wherein the silicon waveguide layer comprises a partially etched adiabatic tapered waveguide structure, an asymmetric directional coupling structure and a double asymmetric directional coupling structure, wherein the partially etched adiabatic tapered waveguide structure is connected to the asymmetric directional coupling structure, and the asymmetric directional coupling structure is also connected to the double asymmetric directional coupling structure; Wherein, the partially etched adiabatic tapered waveguide structure comprises: An input waveguide, wherein the width of the input waveguide is a first width; A partially etched adiabatic tapered waveguide, wherein the length of the partially etched adiabatic tapered waveguide is a first length, the partially etched adiabatic tapered waveguide comprises a first etched portion and a first unetched portion, the width of the first etched portion is a second width, the etching depth is a preset depth, and the width of the first unetched portion gradually changes from the first width to a third width; The input waveguide is connected to a side surface of the first unetched portion of the partially etched adiabatic tapered waveguide having a width of the first width; Wherein, the asymmetric directional coupling structure comprises: A partially etched waveguide, the partially etched waveguide comprising a second etched portion and a second unetched portion, the second unetched portion having a third width and a second length, the second etched portion having a second width, an etched depth of a preset depth, and a third length; a gradually tapered waveguide, wherein the width of the gradually tapered waveguide gradually changes from a fourth width to a fifth width, and the length of the gradually tapered waveguide is a fourth length; The partially etched waveguide is arranged opposite to the gradually tapered waveguide, and the distance between the partially etched waveguide and the gradually tapered waveguide is a preset distance; Wherein, the dual asymmetric directional coupling structure comprises: an upper end, the upper end comprising an S-shaped curved waveguide and a first adiabatic gradually tapered waveguide, the S-shaped curved waveguide having a width of the fifth width, the first adiabatic gradually tapered waveguide having a width gradually changing from the fifth width to the first width, and a length of the fifth length, the S-shaped curved waveguide being connected to a side surface of the first adiabatic gradually tapered waveguide having a width of the fifth width; a lower end, the lower end comprising a second adiabatic gradually changing tapered waveguide, a first gradually changing waveguide, an S waveguide, a second gradually changing waveguide and a 90° waveguide, the width of the second adiabatic gradually changing tapered waveguide gradually changes from a third width to the first width, and the length is a sixth length, the width of the first gradually changing waveguide gradually changes from a sixth width to a seventh width, and the length is a seventh length, and the width of the second gradually changing waveguide gradually changes from an eighth width to a ninth width, and the length is an eighth length; The upper end is arranged opposite to the lower end.

2. The polarization beam splitter rotator according to claim 1, wherein: The first gradual waveguide and the S waveguide in the lower end are located on one side of the second adiabatic gradually changing tapered waveguide, the second gradual waveguide and the 90° waveguide are located on the other side of the second adiabatic gradually changing tapered waveguide, the S waveguide is connected to the side of the first gradual waveguide whose width is the seventh width, and the 90° waveguide is connected to the side of the second gradual waveguide whose width is the ninth width.

3. The polarization beam splitter rotator according to any one of claims 1 to 2, characterized in that: The side surface with a width of the third width in the first unetched portion of the partially etched adiabatic tapered waveguide in the partially etched adiabatic tapered waveguide structure is connected to the partially etched waveguide in the asymmetric directional coupling structure, the partially etched waveguide in the asymmetric directional coupling structure is connected to the side surface with a width of the third width in the second adiabatic gradually tapered waveguide at the lower end of the double asymmetric directional coupling structure, and the side surface with a width of the fifth width in the gradually tapered waveguide in the asymmetric directional coupling structure is connected to the side surface of the curved waveguide at the upper end of the double asymmetric directional coupling structure.

4. The polarization beam splitter rotator according to claim 1, wherein: The input waveguide is used to receive an input optical signal, and the partially etched adiabatic tapered waveguide is used to perform mode hybridization on a mode of the optical signal that meets a preset condition.

5. The polarization beam splitter rotator according to claim 1, wherein: The partially etched waveguide and the gradually tapered waveguide are used to perform mode evolution on the mode of the optical signal after mode hybridization.

6. The polarization beam splitter rotator according to claim 1, wherein: The second adiabatic gradually changing tapered waveguide, the first gradually changing waveguide, the S waveguide, the second gradually changing waveguide and the 90° waveguide are used to filter out other residual modes that are not target modes in the optical signal after mode hybridization and mode evolution.

7. The polarization beam splitter rotator according to claim 1, wherein: The S-shaped curved waveguide and the first adiabatic gradually tapered waveguide are used to output an optical signal of a target mode obtained after mode filtering.

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