CN112596254B

CN112596254B - Compact polarization beam splitter based on photonic crystal

Info

Publication number: CN112596254B
Application number: CN202011413836.6A
Authority: CN
Inventors: 陈伟伟; 刘雨潇; 汪鹏君; 张波豪; 姚润葵; 李燕; 戴庭舸; 杨建义
Original assignee: Ningbo University
Current assignee: Ningbo University
Priority date: 2020-12-07
Filing date: 2020-12-07
Publication date: 2022-05-20
Anticipated expiration: 2040-12-07
Also published as: CN112596254A

Abstract

The invention discloses a compact polarization beam splitter based on photonic crystals, which comprises a cladding and a polarization beam splitter main body structure, wherein the polarization beam splitter main body structure comprises a first straight waveguide, a coupling region waveguide, a second straight waveguide, an S-shaped connecting waveguide and a third straight waveguide, the left end surface of the S-shaped connecting waveguide is connected with the right end surface of the first straight waveguide and is superposed with the right end surface of the first straight waveguide, the left end surface of the third straight waveguide is connected with the right end surface of the S-shaped connecting waveguide and is superposed with the right end surface of the S-shaped connecting waveguide, the coupling region waveguide is positioned at the front side of the first straight waveguide, the left end surface of the second straight waveguide is superposed with the right end surface of the coupling region waveguide, the rear end face of the second straight waveguide and the rear end face of the coupling region waveguide are located on the same plane, twenty-five cylindrical photonic crystals with the same structure and size are arranged in the coupling region waveguide in an embedded mode, and the twenty-five cylindrical photonic crystals are arranged in a specific mode; its advantages are high performance and small size.

Description

Compact polarization beam splitter based on photonic crystal

Technical Field

The invention relates to a polarization beam splitter, in particular to a compact polarization beam splitter based on photonic crystals.

Background

"integrated optics" is a technology for integrating various optical devices having different functions on a substrate of a certain material by using a technology similar to that of a semiconductor integrated circuit to realize a certain function. Since 1969, "integrated optics" was proposed by miller, bell laboratory, and experienced rapid development, it has become mature and industrialized. With the rapid development of data communication services and internet technologies, multimedia and social networks are increasingly popularized, and people have an increasingly large demand for information. In order to meet the demand of people for timely receiving information, telecommunication equipment is required to have larger and larger data transmission bandwidth. Compared with the conventional electrical interconnection, the optical interconnection using light as a carrier for information transmission has the advantages of wide frequency band, large transmission capacity, good anti-electromagnetic interference performance, small signal crosstalk, small loss, long relay distance and the like. The bandwidth transmission distance of the optical interconnect is an incomparable great advantage compared with the electrical interconnect. These advantages make the optical interconnection technology as a new approach to solve the electrical interconnection bottleneck problem, and become a hot research point for the new generation of interconnection technology.

Currently, mode multiplexing techniques are being tried in integrated optoelectronic devices, and the focus of research is mainly on mode multiplexing systems (MDM) and polarization multiplexing systems (PDM). The mode multiplexing system mainly increases the number of the same optical signal modes which can be incident so as to achieve the purpose of signal expansion, and the polarization multiplexing system mainly relies on a polarization beam splitter to distinguish two different optical propagation modes which vibrate orthogonally so as to realize the mode multiplexing function. In recent years, Directional Coupler (DC) type Polarization Beam Splitters (PBSs) and Photonic Crystal (PC) based polarization beam splitters have been developed. But in general, although the directional coupler type polarization beam splitter is excellent in performance, it is large in size, typically up to several tens of nanometers. The existing polarization beam splitter based on the Photonic Crystal (PC) relies on the cubic photonic crystal to realize the polarization beam splitting function, and although the polarization beam splitter has a compact structure, the structure correspondingly loses part of the performance, so that the performance is not outstanding.

Disclosure of Invention

The invention aims to provide a compact polarization beam splitter based on a photonic crystal, which has high performance and small size.

The technical scheme adopted by the invention for solving the technical problems is as follows: the compact polarization beam splitter based on the photonic crystal comprises a cladding and a polarization beam splitter main body structure, wherein the polarization beam splitter main body structure is positioned in the cladding and is completely wrapped by the cladding, the cladding is made of silicon dioxide, the polarization beam splitter main body structure comprises a first straight waveguide, a coupling region waveguide, a second straight waveguide, an S-shaped connecting waveguide and a third straight waveguide, the coupling region waveguide is in a straight waveguide shape, the first waveguide, the coupling region waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are made of silicon, the first straight waveguide, the coupling region waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are all in the vertical direction, and the first straight waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are all in the vertical direction, The width directions of the coupling area waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are all front and back directions, the length directions of the first straight waveguide, the coupling area waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are all left and right directions, the S-shaped connecting waveguide is formed by bending the straight waveguides, the heights of the first straight waveguide, the coupling area waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are all 220nm, the lower end surfaces of the first straight waveguide, the coupling area waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are positioned on the same plane, the widths of the first straight waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are all 0.6um, the width of coupling region waveguide be 0.75um, the left end face of first straight waveguide conduct as compact polarization beam splitter' S input, the left end face of S type connection waveguide with the right end face of first straight waveguide connect and both coincide, the left end face of third straight waveguide with the right end face of S type connection waveguide connect and both coincide, the right end face of third straight waveguide be the first output of compact polarization beam splitter, the coupling region waveguide be located the front side of first straight waveguide, the distance between the front end face of first straight waveguide and the rear end face of coupling region waveguide be 0.1um, the right end face of coupling region waveguide with the right end face of first straight waveguide be located the coplanar, the left end face of second straight waveguide with the right end face of coupling region waveguide laminating connect, and the rear end surface of the second straight waveguide and the rear end surface of the coupling region waveguide are positioned on the same plane, the right end surface of the second straight waveguide is a second output end of the compact polarization beam splitter, the right end surface of the third straight waveguide and the right end surface of the second straight waveguide are positioned on the same plane, and the distance between the front end surface of the third straight waveguide and the rear end surface of the second straight waveguide is greater than the distance between the front end surface of the first straight waveguide and the rear end surface of the coupling region waveguide. The coupling region waveguide is provided with twenty-five cylindrical photonic crystals with the same structure and size in an embedded mode, the cylindrical photonic crystals are made of silicon dioxide, the diameter of each cylindrical photonic crystal is 100nm, the height of each cylindrical photonic crystal is 100nm, the axial directions of the twenty-five cylindrical photonic crystals are all along the vertical direction, the upper surfaces of the twenty-five cylindrical photonic crystals and the upper surface of the coupling region waveguide are positioned on the same plane, the central axis of the first cylindrical photonic crystal is positioned on the right side of the left end surface of the coupling region waveguide and the front side of the rear end surface of the coupling region waveguide, the distance between the central axis of the first cylindrical photonic crystal and the left end surface of the coupling region waveguide is 0.3um, the distance between the central axis of the first cylindrical photonic crystal and the rear end surface of the coupling region waveguide is 0.225um, the second cylindrical photonic crystal is positioned on the right side of the first cylindrical photonic crystal, the distance between the central axis of the second cylindrical photonic crystal and the central axis of the first cylindrical photonic crystal is 0.3um, the third cylindrical photonic crystal is positioned on the right side of the second cylindrical photonic crystal, the distance between the central axis of the third cylindrical photonic crystal and the central axis of the second cylindrical photonic crystal is 0.3um, the fourth cylindrical photonic crystal is positioned on the right side of the third cylindrical photonic crystal, the distance between the central axis of the fourth cylindrical photonic crystal and the central axis of the third cylindrical photonic crystal is 0.3um, the fifth cylindrical photonic crystal is positioned on the right side of the fourth cylindrical photonic crystal, the distance between the central axis of the fifth cylindrical photonic crystal and the central axis of the fourth cylindrical photonic crystal is 0.3um, and the sixth cylindrical photonic crystal is positioned on the right side of the fifth cylindrical photonic crystal, the distance between the central axis of the sixth cylindrical photonic crystal and the central axis of the fifth cylindrical photonic crystal is 0.3um, the seventh cylindrical photonic crystal is positioned on the right side of the sixth cylindrical photonic crystal, the distance between the central axis of the seventh cylindrical photonic crystal and the central axis of the sixth cylindrical photonic crystal is 0.9um, the eighth cylindrical photonic crystal is positioned on the right side of the seventh cylindrical photonic crystal, the distance between the central axis of the eighth cylindrical photonic crystal and the central axis of the seventh cylindrical photonic crystal is 0.6um, the ninth cylindrical photonic crystal is positioned on the front side of the first cylindrical photonic crystal and the right side of the left end face of the coupling region waveguide, the distance between the central axis of the ninth cylindrical photonic crystal and the central axis of the first cylindrical photonic crystal is 0.3um, and the distance between the ninth cylindrical photonic crystal and the left end face of the coupling region waveguide is 0.3um, a tenth cylindrical photonic crystal is positioned at the right side of the ninth cylindrical photonic crystal, the distance between the central axis of the tenth cylindrical photonic crystal and the central axis of the ninth cylindrical photonic crystal is 0.3um, an eleventh cylindrical photonic crystal is positioned at the right side of the tenth cylindrical photonic crystal, the distance between the central axis of the eleventh cylindrical photonic crystal and the central axis of the tenth cylindrical photonic crystal is 0.3um, a twelfth cylindrical photonic crystal is positioned at the right side of the eleventh cylindrical photonic crystal, the distance between the central axis of the twelfth cylindrical photonic crystal and the central axis of the eleventh cylindrical photonic crystal is 0.3um, a thirteenth cylindrical photonic crystal is positioned at the right side of the twelfth cylindrical photonic crystal, the distance between the central axis of the thirteenth cylindrical photonic crystal and the central axis of the twelfth cylindrical photonic crystal is 0.3um, the fourteenth cylindrical photonic crystal is located at the right side of the thirteenth cylindrical photonic crystal, the distance between the central axis of the fourteenth cylindrical photonic crystal and the central axis of the thirteenth cylindrical photonic crystal is 0.3um, the fifteenth cylindrical photonic crystal is located at the right side of the fourteenth cylindrical photonic crystal, the distance between the central axis of the fifteenth cylindrical photonic crystal and the central axis of the fourteenth cylindrical photonic crystal is 0.3um, the sixteenth cylindrical photonic crystal is located at the right side of the fifteenth cylindrical photonic crystal, the distance between the central axis of the sixteenth cylindrical photonic crystal and the central axis of the fifteenth cylindrical photonic crystal is 0.3um, the seventeenth cylindrical photonic crystal is located at the right side of the sixteenth cylindrical photonic crystal, the distance between the central axis of the seventeenth cylindrical photonic crystal and the central axis of the sixteenth cylindrical photonic crystal is 0.3um, the eighteenth cylindrical photonic crystal is positioned on the right side of the seventeenth cylindrical photonic crystal, the distance between the central axis of the eighteenth cylindrical photonic crystal and the central axis of the seventeenth cylindrical photonic crystal is 0.3um, the nineteenth cylindrical photonic crystal is positioned on the right side of the eighteenth cylindrical photonic crystal, the distance between the central axis of the nineteenth cylindrical photonic crystal and the central axis of the eighteenth cylindrical photonic crystal is 0.3um, the twentieth cylindrical photonic crystal is positioned on the right side of the nineteenth cylindrical photonic crystal, the distance between the central axis of the twentieth cylindrical photonic crystal and the central axis of the nineteenth cylindrical photonic crystal is 1.2um, the twenty-first cylindrical photonic crystal is positioned on the right side of the twentieth cylindrical photonic crystal, the distance between the central axis of the twenty-first cylindrical photonic crystal and the central axis of the twentieth cylindrical photonic crystal is 0.3um, the twenty-second cylindrical photonic crystal is positioned at the right side of the twenty-first cylindrical photonic crystal, the distance between the central axis of the twenty-second cylindrical photonic crystal and the central axis of the twenty-second cylindrical photonic crystal is 0.3um, the twenty-third cylindrical photonic crystal is positioned at the right side of the twenty-second cylindrical photonic crystal, the distance between the central axis of the twenty-third cylindrical photonic crystal and the central axis of the twenty-second cylindrical photonic crystal is 0.3um, the twenty-fourth cylindrical photonic crystal is positioned at the right side of the twenty-third cylindrical photonic crystal, the distance between the central axis of the twenty-fourth cylindrical photonic crystal and the central axis of the twenty-third cylindrical photonic crystal is 0.3um, the twenty-fifth cylindrical photonic crystal is positioned at the right side of the twenty-fourth cylindrical photonic crystal, the distance between the central axis of the twenty-fifth cylindrical photonic crystal and the central axis of the twenty-fourth cylindrical photonic crystal is 0.3um, the central axes of the first cylindrical photonic crystal, the second cylindrical photonic crystal, the third cylindrical photonic crystal, the fourth cylindrical photonic crystal, the fifth cylindrical photonic crystal, the sixth cylindrical photonic crystal, the seventh cylindrical photonic crystal and the eighth cylindrical photonic crystal are positioned on the same plane, and the plane is parallel to the front end surface of the coupling region waveguide, the ninth cylindrical photonic crystal, the tenth cylindrical photonic crystal, the eleventh cylindrical photonic crystal, the twelfth cylindrical photonic crystal, the thirteenth cylindrical photonic crystal, the fourteenth cylindrical photonic crystal, the fifteenth cylindrical photonic crystal, the sixteenth cylindrical photonic crystal, the seventeenth cylindrical photonic crystal, the eighteenth cylindrical photonic crystal, the nineteenth cylindrical photonic crystal, the twentieth cylindrical photonic crystal, the twenty-fourth cylindrical photonic crystal, the nineteenth cylindrical photonic crystal, the sixteenth cylindrical photonic crystal, the seventeenth cylindrical photonic crystal, the eighteenth cylindrical photonic crystal, the sixteenth cylindrical photonic crystal, the, The central axes of the twenty-first cylindrical photonic crystal, the twenty-second cylindrical photonic crystal, the twenty-third cylindrical photonic crystal, the twenty-fourth cylindrical photonic crystal and the twenty-fifth cylindrical photonic crystal are positioned on the same plane, and the plane is parallel to the front end surface of the coupling region waveguide.

Compared with the prior art, the invention has the advantages that the coupling region waveguide corresponds to TM by arranging twenty-five cylindrical photonic crystals in a specific mode₀Mode and TE₀Change in effective refractive index of mode, TE₀The effective refractive index of a mode propagating in the first straight waveguide does not match the effective refractive index range of the TE mode corresponding to the coupling region waveguide embedded in the twenty-five cylindrical photonic crystals, and TM is₀Effective refractive index of mode transmitted in the first straight waveguide and TM corresponding to coupling region waveguide embedded in twenty-five cylindrical photonic crystals₀The effective refractive index ranges of the modes are matched when mixed mode TE₀/TM₀When the light source is input from the input end, the light source firstly enters the first straight waveguide due to the mixed mode TE₀/TM₀TM in light source₀The mode satisfies the mode coupling condition, when TM₀The mode will be coupled to the coupling region waveguide, so that the TM₀The mode will propagate through the first straight waveguide and the coupling region waveguide, then to the second straight waveguide,finally, the TE is outputted at a second output end out2 of the present invention after passing through a second straight waveguide, and accordingly, the TE is a mixed mode TE₀/TM₀TE in light sources₀The mode does not meet the mode coupling condition, and the mode is not coupled to the coupling area waveguide from the first straight waveguide, but is directly transmitted through the first straight waveguide to enter the S-shaped connecting waveguide, then enters the third straight waveguide after passing through the S-shaped connecting waveguide, and finally is output at the first output end out1 of the invention after passing through the third straight waveguide, so that mode separation is realized₀The effective refractive index range of the mode encompasses TM₀The value of the mode in the first straight waveguide, but not including TE₀The value of the mode in the first straight waveguide, and thus the TM₀The mode can be coupled into the coupling region waveguide in a short distance when transmitted in the first straight waveguide, and TE is in a mixed mode₀/TM₀After the light source enters the first straight waveguide, the capability of the waveguide of the coupling region is changed by means of a specific combination mode of twenty-five cylindrical photonic crystals, so that the TM₀The mode can complete coupling separation in short distance, so that the invention can play a role of mixed mode separation when the waveguide length is short, although the front end surface of the coupling region waveguide and the front end surface of the second straight waveguide are not positioned on the same plane, the TM coupled to the coupling region waveguide can be coupled by virtue of the position distribution of twenty-five cylindrical photonic crystals₀The mode plays a role of regulating the optical path, so that TM₀The mode is transmitted from the coupling region waveguide to the second straight waveguide with little reflection loss and small insertion loss can be obtained at the second output end without connecting an additional silicon waveguide structure between the coupling region waveguide and the second straight waveguide, so that the excellent performance can be kept under the condition of relatively compact structure, and the lower end surfaces of twenty-five cylindrical photonic crystals are at a distance relative to the lower end surface of the coupling region waveguide, which is beneficial to TM₀The mode is transmitted between the waveguide in the coupling area and the second straight waveguide, which further reduces the insertion loss and improves the polarization extinction ratio, and the cylindrical photonic crystal shape not only makes the manufacture simple and increases the manufacture tolerance and the existing structureThe cubic photonic crystal can maintain the considerable performance of the device, and the simulation result shows that the TM can be obtained within the whole range of 1500-1600nm wave band₀The mode light source has an insertion loss of less than 0.2dB and a polarization extinction ratio, TE, of less than-12 dB₀The mode light source has insertion loss less than 0.21dB and polarization extinction ratio less than-14 dB, so that the invention has smaller size on the basis of higher performance.

Drawings

FIG. 1 is a top view of a polarizing beam splitter body structure of a compact photonic crystal-based polarizing beam splitter of the present invention;

FIG. 2 is a cross-sectional view taken at A' -A in FIG. 1;

FIG. 3 shows TE of a compact polarization beam splitter based on photonic crystal in the wavelength band of 1500nm-1600nm₀/TM₀Simulation curve diagram of polarization extinction ratio of mode;

FIG. 4 shows TE of the compact polarization beam splitter based on photonic crystal in the wavelength band of 1500nm-1600nm₀/TM₀Simulation curve diagram of insertion loss of mode;

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

Example (b): as shown in fig. 1 and 2, a compact polarization beam splitter based on photonic crystals comprises a cladding and a polarization beam splitter main body structure, the polarization beam splitter main body structure is located inside the cladding and is completely wrapped by the cladding, the cladding is made of silica, the polarization beam splitter main body structure comprises a first straight waveguide 1, a coupling region waveguide 2, a second straight waveguide 3, an S-shaped connecting waveguide 4 and a third straight waveguide 5, the coupling region waveguide 2 is in a straight waveguide shape, the first straight waveguide 1, the coupling region waveguide 2, the second straight waveguide 3, the S-shaped connecting waveguide 4 and the third straight waveguide 5 are made of silicon, the height directions of the first straight waveguide 1, the coupling region waveguide 2, the second straight waveguide 3, the S-shaped connecting waveguide 4 and the third straight waveguide 5 are all vertical directions, the width directions of the first straight waveguide 1, the coupling region waveguide 2, the second straight waveguide 3, the S-shaped connecting waveguide 4 and the third straight waveguide 5 are all front and back directions, the length directions of the first straight waveguide 1, the coupling area waveguide 2, the second straight waveguide 3, the S-shaped connecting waveguide 4 and the third straight waveguide 5 are all left and right directions, the S-shaped connecting waveguide 4 is formed by bending the straight waveguides, the heights of the first straight waveguide 1, the coupling area waveguide 2, the second straight waveguide 3, the S-shaped connecting waveguide 4 and the third straight waveguide 5 are all 220nm, the lower end surfaces of the first straight waveguide 1, the coupling area waveguide 2, the second straight waveguide 3, the S-shaped connecting waveguide 4 and the third straight waveguide 5 are positioned on the same plane, the widths of the first straight waveguide 1, the second straight waveguide 3, the S-shaped connecting waveguide 4 and the third straight waveguide 5 are all 0.6um, the width of the coupling area waveguide 2 is 0.75um, the left end surface of the first straight waveguide 1 is used as the input end of the compact polarization beam splitter, the left end surface of the S-shaped connecting waveguide 4 is connected with the right end surface of the first straight waveguide 1 and is overlapped with the left end surface of the third straight waveguide 5 and the right end surface of the S-shaped connecting waveguide 4, the right end face of the third straight waveguide 5 is a first output end of the compact polarization beam splitter, the coupling region waveguide 2 is positioned at the front side of the first straight waveguide 1, the distance between the front end face of the first straight waveguide 1 and the rear end face of the coupling region waveguide 2 is 0.15um, the right end face of the coupling region waveguide 2 and the right end face of the first straight waveguide 1 are positioned on the same plane, the left end face of the second straight waveguide 3 is in fit connection with the right end face of the coupling region waveguide 2, the rear end face of the second straight waveguide 3 and the rear end face of the coupling region waveguide 2 are located on the same plane, the right end face of the second straight waveguide 3 is a second output end of the compact polarization beam splitter, the right end face of the third straight waveguide 5 and the right end face of the second straight waveguide 3 are located on the same plane, and the distance between the front end face of the third straight waveguide 5 and the rear end face of the second straight waveguide 3 is larger than the distance between the front end face of the first straight waveguide 1 and the rear end face of the coupling region waveguide 2; twenty-five cylindrical photonic crystals with the same structure and size are arranged in the coupling region waveguide 2 in an embedded mode, each cylindrical photonic crystal is made of silicon dioxide, the diameter and the height of each cylindrical photonic crystal are 100nm and 100nm, the axial directions of the twenty-five cylindrical photonic crystals are all along the vertical direction, the upper surfaces of the twenty-five cylindrical photonic crystals and the upper surface of the coupling region waveguide 2 are positioned on the same plane, the central axis of the first cylindrical photonic crystal 6 is positioned on the right side of the left end surface of the coupling region waveguide 2 and the front side of the rear end surface of the coupling region waveguide 2, the distance between the central axis of the first cylindrical photonic crystal 6 and the left end surface of the coupling region waveguide 2 is 0.3um, the distance between the central axis of the first cylindrical photonic crystal 6 and the rear end surface of the coupling region waveguide 2 is 0.225um, the second cylindrical photonic crystal 7 is positioned on the right side of the first cylindrical photonic crystal 6, the distance between the central axis of the second cylindrical photonic crystal 7 and the central axis of the first cylindrical photonic crystal 6 is 0.3um, the third cylindrical photonic crystal 8 is positioned at the right side of the second cylindrical photonic crystal 7, the distance between the central axis of the third cylindrical photonic crystal 8 and the central axis of the second cylindrical photonic crystal 7 is 0.3um, the fourth cylindrical photonic crystal 9 is positioned at the right side of the third cylindrical photonic crystal 8, the distance between the central axis of the fourth cylindrical photonic crystal 9 and the central axis of the third cylindrical photonic crystal 8 is 0.3um, the fifth cylindrical photonic crystal 10 is positioned at the right side of the fourth cylindrical photonic crystal 9, the distance between the central axis of the fifth cylindrical photonic crystal 10 and the central axis of the fourth cylindrical photonic crystal 9 is 0.3um, the sixth cylindrical photonic crystal 11 is positioned at the right side of the fifth cylindrical photonic crystal 10, the distance between the central axis of the sixth cylindrical photonic crystal 11 and the central axis of the fifth cylindrical photonic crystal 10 is 0.3um, the seventh cylindrical photonic crystal 12 is located at the right side of the sixth cylindrical photonic crystal 11, the distance between the central axis of the seventh cylindrical photonic crystal 12 and the central axis of the sixth cylindrical photonic crystal 11 is 0.9um, the eighth cylindrical photonic crystal 13 is located at the right side of the seventh cylindrical photonic crystal 12, the distance between the central axis of the eighth cylindrical photonic crystal 13 and the central axis of the seventh cylindrical photonic crystal 12 is 0.6um, the ninth cylindrical photonic crystal 14 is located at the front side of the first cylindrical photonic crystal 6 and at the right side of the left end face of the coupling region waveguide 2, the distance between the central axis of the ninth cylindrical photonic crystal 14 and the central axis of the first cylindrical photonic crystal 6 is 0.3um, the distance between the ninth cylindrical photonic crystal 14 and the left end face of the coupling region waveguide 2 is 0.3um, a tenth cylindrical photonic crystal 15 is positioned at the right side of the ninth cylindrical photonic crystal 14, the distance between the central axis of the tenth cylindrical photonic crystal 15 and the central axis of the ninth cylindrical photonic crystal 14 is 0.3um, an eleventh cylindrical photonic crystal 16 is positioned at the right side of the tenth cylindrical photonic crystal 15, the distance between the central axis of the eleventh cylindrical photonic crystal 16 and the central axis of the tenth cylindrical photonic crystal 15 is 0.3um, a twelfth cylindrical photonic crystal 17 is positioned at the right side of the eleventh cylindrical photonic crystal 16, the distance between the central axis of the twelfth cylindrical photonic crystal 17 and the central axis of the eleventh cylindrical photonic crystal 16 is 0.3um, a thirteenth cylindrical photonic crystal 18 is positioned at the right side of the twelfth cylindrical photonic crystal 17, the distance between the central axis of the thirteenth cylindrical photonic crystal 18 and the central axis of the twelfth cylindrical photonic crystal 17 is 0.3um, the fourteenth cylindrical photonic crystal 19 is located at the right side of the thirteenth cylindrical photonic crystal 18, the distance between the central axis of the fourteenth cylindrical photonic crystal 19 and the central axis of the thirteenth cylindrical photonic crystal 18 is 0.3um, the fifteenth cylindrical photonic crystal 20 is located at the right side of the fourteenth cylindrical photonic crystal 19, the distance between the central axis of the fifteenth cylindrical photonic crystal 20 and the central axis of the fourteenth cylindrical photonic crystal 19 is 0.3um, the sixteenth cylindrical photonic crystal 21 is located at the right side of the fifteenth cylindrical photonic crystal 20, the distance between the central axis of the sixteenth cylindrical photonic crystal 21 and the central axis of the fifteenth cylindrical photonic crystal 20 is 0.3um, the seventeenth cylindrical photonic crystal 22 is located at the right side of the sixteenth cylindrical photonic crystal 21, the distance between the central axis of the seventeenth cylindrical photonic crystal 22 and the central axis of the sixteenth cylindrical photonic crystal 21 is 0.3um, the eighteenth cylindrical photonic crystal 23 is located at the right side of the seventeenth cylindrical photonic crystal 22, the distance between the central axis of the eighteenth cylindrical photonic crystal 23 and the central axis of the seventeenth cylindrical photonic crystal 22 is 0.3um, the nineteenth cylindrical photonic crystal 24 is located at the right side of the eighteenth cylindrical photonic crystal 23, the distance between the central axis of the nineteenth cylindrical photonic crystal 24 and the central axis of the eighteenth cylindrical photonic crystal 23 is 0.3um, the twenty cylindrical photonic crystal 25 is located at the right side of the nineteenth cylindrical photonic crystal 24, the distance between the central axis of the twentieth cylindrical photonic crystal 25 and the central axis of the nineteenth cylindrical photonic crystal 24 is 1.2um, the twenty cylindrical photonic crystal 26 is located at the right side of the twentieth cylindrical photonic crystal 25, the distance between the central axis of the twenty cylindrical photonic crystal 26 and the central axis of the twentieth cylindrical photonic crystal 25 is 0.3um, a twenty-second cylindrical photonic crystal 27 is located at the right side of the twenty-first cylindrical photonic crystal 26, the distance between the central axis of the twenty-second cylindrical photonic crystal 27 and the central axis of the twenty-first cylindrical photonic crystal 26 is 0.3um, a twenty-third cylindrical photonic crystal 28 is located at the right side of the twenty-second cylindrical photonic crystal 27, the distance between the central axis of the twenty-third cylindrical photonic crystal 28 and the central axis of the twenty-second cylindrical photonic crystal 27 is 0.3um, a twenty-fourth cylindrical photonic crystal 29 is located at the right side of the twenty-third cylindrical photonic crystal 28, the distance between the central axis of the twenty-fourth cylindrical photonic crystal 29 and the central axis of the twenty-third cylindrical photonic crystal 28 is 0.3um, a twenty-fifth cylindrical photonic crystal 30 is located at the right side of the twenty-fourth cylindrical photonic crystal 29, the central axis of the twenty-fifth cylindrical photonic crystal 30 and the central axis of the twenty-fourth cylindrical photonic crystal 29 are Is 0.3um, the central axes of the first cylindrical photonic crystal 6, the second cylindrical photonic crystal 7, the third cylindrical photonic crystal 8, the fourth cylindrical photonic crystal 9, the fifth cylindrical photonic crystal 10, the sixth cylindrical photonic crystal 11, the seventh cylindrical photonic crystal 12 and the eighth cylindrical photonic crystal 13 are positioned on the same plane, and the plane is parallel to the front end face of the coupling region waveguide 2, the ninth cylindrical photonic crystal 14, the tenth cylindrical photonic crystal 15, the eleventh cylindrical photonic crystal 16, the twelfth cylindrical photonic crystal 17, the thirteenth cylindrical photonic crystal 18, the fourteenth cylindrical photonic crystal 19, the fifteenth cylindrical photonic crystal 20, the sixteenth cylindrical photonic crystal 21, the seventeenth cylindrical photonic crystal 22, the eighteenth cylindrical photonic crystal 23, the thirteenth cylindrical photonic crystal 18, The central axes of the nineteenth cylindrical photonic crystal 24, the twentieth cylindrical photonic crystal 25, the twenty-first cylindrical photonic crystal 26, the twenty-second cylindrical photonic crystal 27, the twenty-third cylindrical photonic crystal 28, the twenty-fourth cylindrical photonic crystal 29, and the twenty-fifth cylindrical photonic crystal 30 are located on the same plane, and the plane is parallel to the front end face of the coupling region waveguide 2.

The working process of the invention is as follows: in the invention, twenty-five cylindrical photonic crystals are arranged in a specific way to make the coupling region waveguide correspond to TM₀Mode and TE₀Change in effective refractive index of mode, TE₀Effective refractive index of mode propagating in the first straight waveguide corresponds to TE of the coupling region waveguide with twenty-five cylindrical photonic crystals embedded therein₀The effective refractive index ranges of the modes are not matched, and the effective refractive index of the TM mode when the TM mode is transmitted in the first straight waveguide is matched with the effective refractive index range of the TM mode corresponding to the coupling region waveguide embedded with twenty-five cylindrical photonic crystals, when the TE is a mixed mode₀/TM₀When light source is input from the input end of the invention, the light source firstly enters the first straight waveguide due to the mixed mode TE₀/TM₀TM in light source₀The mode satisfies the mode coupling condition, when TM₀The mode will be coupled to the coupling region waveguide, so that the TM₀The mode passes through the first straight waveguide and the coupling region waveguide, then is transmitted to the second straight waveguide, finally passes through the second straight waveguide and then is output at the second output end out2 of the present invention, and accordingly, mixed mode TE₀/TM₀TE in light sources₀Because the mode does not meet the mode coupling condition, the mode is not coupled to the coupling area waveguide from the first straight waveguide, but is directly transmitted through the first straight waveguide to enter the S-shaped connecting waveguide, then enters the third straight waveguide after passing through the S-shaped connecting waveguide, and finally is output at the first output end out1 of the invention after passing through the third straight waveguide. In the present invention, TE is mixed mode₀/TM₀After the light source enters the first straight waveguide, the capability of the waveguide of the coupling region is changed by means of a specific combination mode of twenty-five cylindrical photonic crystals, so that the TM₀The mode can complete coupling separation in short distance, so that the invention can play a role of mixed mode separation when the waveguide length is short. Although the front end face of the coupling region waveguide and the front end face of the second straight waveguide are not located on the same plane, the invention can benefit from the position distribution of twenty-five cylindrical photonic crystalsThe TM mode coupled to the coupling region waveguide is regulated to form a regular light path₀The mode is transmitted from the coupling region waveguide to the second straight waveguide with small reflection loss, and the insertion loss at the second output end can be small without connecting an additional silicon waveguide structure between the coupling region waveguide and the second straight waveguide, thereby maintaining excellent performance under the condition of relatively compact structure.

The compact photonic crystal-based polarization beam splitter of the present invention was simulated at the wavelength band 1500nm-1600nm, where TE₀\TM₀The simulation curve of the polarization extinction ratio of the mode is shown in fig. 3, the simulation curve of the insertion loss is shown in fig. 4, PER in fig. 3 represents the polarization extinction ratio, and wavelength represents the wavelength; in fig. 4, IL represents insertion loss and wavelength represents wavelength. As can be seen from the analysis of FIGS. 3 and 4, the TM is within the entire 1500-1600nm band₀The mode light source has an insertion loss less than 0.42dB and a polarization extinction ratio greater than 13.4 dB; TE₀The mode light source has an insertion loss less than 0.3dB and a polarization extinction ratio greater than 11.8dB, and thus it can be understood that the present invention has excellent performance.

In addition to the software simulation data, the compact polarization beam splitter based on the photonic crystal is subjected to layout drawing according to a simulation structure, and a material object is manufactured by performing tape casting according to the drawn layout. After the material object is successfully manufactured, a spectrometer (OSA) is used for testing the material object of the compact polarizing beam splitter based on the photonic crystal in the 1527nm-1580nm waveband range, and the manufactured compact polarizing beam splitter based on the photonic crystal is tested in a TM mode when the wavelength of an incident light mode is changed from 1520nm to 1580nm₀When the mode light source is incident, the obtained insertion loss is less than 1.23dB, the polarization extinction ratio is better than 11.3dB, and the TE₀When the mode light source is incident, the obtained insertion loss is less than 1.32dB, and the polarization extinction ratio is better than 10.8 dB. Therefore, the simulation results of the compact polarization beam splitter object based on the photonic crystal and the compact polarization beam splitter object based on the photonic crystal are well matched.

Claims

1. A compact polarization beam splitter based on photonic crystals comprises a cladding and a polarization beam splitter main body structure, wherein the polarization beam splitter main body structure is positioned in the cladding and is completely wrapped by the cladding, and the cladding is made of silicon dioxide, and the compact polarization beam splitter is characterized in that the polarization beam splitter main body structure comprises a first straight waveguide, a coupling region waveguide, a second straight waveguide, an S-shaped connecting waveguide and a third straight waveguide, the coupling region waveguide is in a straight waveguide shape, the first straight waveguide, the coupling region waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are made of silicon, the first straight waveguide, the coupling region waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are all in the vertical direction, the width directions of the first straight waveguide, the coupling region waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are all front and back directions, the length directions of the first straight waveguide, the coupling region waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are all left and right directions, the S-shaped connecting waveguide is formed by bending the straight waveguides, the heights of the first straight waveguide, the coupling region waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are all 220nm, the lower end faces of the first straight waveguide, the coupling region waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are positioned on the same plane, and the first straight waveguide, the second straight waveguide, the coupling region waveguide, the second straight waveguide, the S-shaped connecting waveguide and the third straight waveguide are positioned on the same plane, The S-shaped connecting waveguide and the third straight waveguide are 0.6um in width, the coupling area waveguide is 0.75um in width, the left end face of the first straight waveguide is used as the input end of the compact polarization beam splitter, the left end face of the S-shaped connecting waveguide is connected with the right end face of the first straight waveguide and coincides with the left end face of the first straight waveguide, the left end face of the third straight waveguide is connected with the right end face of the S-shaped connecting waveguide and coincides with the right end face of the S-shaped connecting waveguide, the right end face of the third straight waveguide is the first output end of the compact polarization beam splitter, the coupling area waveguide is positioned at the front side of the first straight waveguide, the distance between the front end face of the first straight waveguide and the rear end face of the coupling area waveguide is 0.1um, the right end face of the coupling area waveguide and the right end face of the first straight waveguide are positioned on the same plane, the left end surface of the second straight waveguide is in fit connection with the right end surface of the coupling region waveguide, the rear end surface of the second straight waveguide and the rear end surface of the coupling region waveguide are positioned on the same plane, the right end surface of the second straight waveguide is a second output end of the compact polarization beam splitter, the right end surface of the third straight waveguide and the right end surface of the second straight waveguide are positioned on the same plane, and the distance between the front end surface of the third straight waveguide and the rear end surface of the second straight waveguide is greater than the distance between the front end surface of the first straight waveguide and the rear end surface of the coupling region waveguide; twenty-five cylindrical photonic crystals with the same structure and size are arranged in the coupling area waveguide in an embedded mode, each cylindrical photonic crystal is made of silicon dioxide, the diameter of each cylindrical photonic crystal is 100nm, the height of each cylindrical photonic crystal is 100nm, the axial directions of the twenty-five cylindrical photonic crystals are all along the vertical direction, the upper surfaces of the twenty-five cylindrical photonic crystals and the upper surface of the coupling area waveguide are positioned on the same plane, the central axis of the first cylindrical photonic crystal is positioned on the right side of the left end surface of the coupling area waveguide and the front side of the rear end surface of the coupling area waveguide, the distance between the central axis of the first cylindrical photonic crystal and the left end surface of the coupling area waveguide is 0.3um, the distance between the central axis of the first cylindrical photonic crystal and the rear end surface of the coupling area waveguide is 0.225um, the second cylindrical photonic crystal is positioned on the right side of the first cylindrical photonic crystal, the distance between the central axis of the second cylindrical photonic crystal and the central axis of the first cylindrical photonic crystal is 0.3um, the third cylindrical photonic crystal is positioned on the right side of the second cylindrical photonic crystal, the distance between the central axis of the third cylindrical photonic crystal and the central axis of the second cylindrical photonic crystal is 0.3um, the fourth cylindrical photonic crystal is positioned on the right side of the third cylindrical photonic crystal, the distance between the central axis of the fourth cylindrical photonic crystal and the central axis of the third cylindrical photonic crystal is 0.3um, the fifth cylindrical photonic crystal is positioned on the right side of the fourth cylindrical photonic crystal, the distance between the central axis of the fifth cylindrical photonic crystal and the central axis of the fourth cylindrical photonic crystal is 0.3um, and the sixth cylindrical photonic crystal is positioned on the right side of the fifth cylindrical photonic crystal, the distance between the central axis of the sixth cylindrical photonic crystal and the central axis of the fifth cylindrical photonic crystal is 0.3um, the seventh cylindrical photonic crystal is positioned on the right side of the sixth cylindrical photonic crystal, the distance between the central axis of the seventh cylindrical photonic crystal and the central axis of the sixth cylindrical photonic crystal is 0.9um, the eighth cylindrical photonic crystal is positioned on the right side of the seventh cylindrical photonic crystal, the distance between the central axis of the eighth cylindrical photonic crystal and the central axis of the seventh cylindrical photonic crystal is 0.6um, the ninth cylindrical photonic crystal is positioned on the front side of the first cylindrical photonic crystal and the right side of the left end face of the coupling region waveguide, the distance between the central axis of the ninth cylindrical photonic crystal and the central axis of the first cylindrical photonic crystal is 0.3um, and the distance between the ninth cylindrical photonic crystal and the left end face of the coupling region waveguide is 0.3um, a tenth cylindrical photonic crystal is positioned at the right side of the ninth cylindrical photonic crystal, the distance between the central axis of the tenth cylindrical photonic crystal and the central axis of the ninth cylindrical photonic crystal is 0.3um, an eleventh cylindrical photonic crystal is positioned at the right side of the tenth cylindrical photonic crystal, the distance between the central axis of the eleventh cylindrical photonic crystal and the central axis of the tenth cylindrical photonic crystal is 0.3um, a twelfth cylindrical photonic crystal is positioned at the right side of the eleventh cylindrical photonic crystal, the distance between the central axis of the twelfth cylindrical photonic crystal and the central axis of the eleventh cylindrical photonic crystal is 0.3um, a thirteenth cylindrical photonic crystal is positioned at the right side of the twelfth cylindrical photonic crystal, the distance between the central axis of the thirteenth cylindrical photonic crystal and the central axis of the twelfth cylindrical photonic crystal is 0.3um, the fourteenth cylindrical photonic crystal is located at the right side of the thirteenth cylindrical photonic crystal, the distance between the central axis of the fourteenth cylindrical photonic crystal and the central axis of the thirteenth cylindrical photonic crystal is 0.3um, the fifteenth cylindrical photonic crystal is located at the right side of the fourteenth cylindrical photonic crystal, the distance between the central axis of the fifteenth cylindrical photonic crystal and the central axis of the fourteenth cylindrical photonic crystal is 0.3um, the sixteenth cylindrical photonic crystal is located at the right side of the fifteenth cylindrical photonic crystal, the distance between the central axis of the sixteenth cylindrical photonic crystal and the central axis of the fifteenth cylindrical photonic crystal is 0.3um, the seventeenth cylindrical photonic crystal is located at the right side of the sixteenth cylindrical photonic crystal, the distance between the central axis of the seventeenth cylindrical photonic crystal and the central axis of the sixteenth cylindrical photonic crystal is 0.3um, the eighteenth cylindrical photonic crystal is positioned on the right side of the seventeenth cylindrical photonic crystal, the distance between the central axis of the eighteenth cylindrical photonic crystal and the central axis of the seventeenth cylindrical photonic crystal is 0.3um, the nineteenth cylindrical photonic crystal is positioned on the right side of the eighteenth cylindrical photonic crystal, the distance between the central axis of the nineteenth cylindrical photonic crystal and the central axis of the eighteenth cylindrical photonic crystal is 0.3um, the twentieth cylindrical photonic crystal is positioned on the right side of the nineteenth cylindrical photonic crystal, the distance between the central axis of the twentieth cylindrical photonic crystal and the central axis of the nineteenth cylindrical photonic crystal is 1.2um, the twenty-first cylindrical photonic crystal is positioned on the right side of the twentieth cylindrical photonic crystal, the distance between the central axis of the twenty-first cylindrical photonic crystal and the central axis of the twentieth cylindrical photonic crystal is 0.3um, the twenty-second cylindrical photonic crystal is positioned at the right side of the twenty-first cylindrical photonic crystal, the distance between the central axis of the twenty-second cylindrical photonic crystal and the central axis of the twenty-second cylindrical photonic crystal is 0.3um, the twenty-third cylindrical photonic crystal is positioned at the right side of the twenty-second cylindrical photonic crystal, the distance between the central axis of the twenty-third cylindrical photonic crystal and the central axis of the twenty-second cylindrical photonic crystal is 0.3um, the twenty-fourth cylindrical photonic crystal is positioned at the right side of the twenty-third cylindrical photonic crystal, the distance between the central axis of the twenty-fourth cylindrical photonic crystal and the central axis of the twenty-third cylindrical photonic crystal is 0.3um, the twenty-fifth cylindrical photonic crystal is positioned at the right side of the twenty-fourth cylindrical photonic crystal, the distance between the central axis of the twenty-fifth cylindrical photonic crystal and the central axis of the twenty-fourth cylindrical photonic crystal is 0.3um, the central axes of the first cylindrical photonic crystal, the second cylindrical photonic crystal, the third cylindrical photonic crystal, the fourth cylindrical photonic crystal, the fifth cylindrical photonic crystal, the sixth cylindrical photonic crystal, the seventh cylindrical photonic crystal and the eighth cylindrical photonic crystal are positioned on the same plane, and the plane is parallel to the front end surface of the coupling region waveguide, the ninth cylindrical photonic crystal, the tenth cylindrical photonic crystal, the eleventh cylindrical photonic crystal, the twelfth cylindrical photonic crystal, the thirteenth cylindrical photonic crystal, the fourteenth cylindrical photonic crystal, the fifteenth cylindrical photonic crystal, the sixteenth cylindrical photonic crystal, the seventeenth cylindrical photonic crystal, the eighteenth cylindrical photonic crystal, the nineteenth cylindrical photonic crystal, the twentieth cylindrical photonic crystal, the twenty-th cylindrical photonic crystal, the twenty-fourth cylindrical photonic crystal, the sixteenth cylindrical photonic crystal, the eighteenth cylindrical photonic crystal, the nineteenth cylindrical photonic crystal, the second cylindrical photonic crystal, the twenty-fourth cylindrical photonic crystal, the seventh cylindrical photonic crystal, the eighth cylindrical photonic crystal, the twelfth cylindrical photonic crystal, the eleventh cylindrical photonic crystal, the twelfth cylindrical photonic crystal, the sixteenth cylindrical photonic crystal, the eleventh cylindrical photonic crystal, the sixteenth cylindrical photonic crystal, the fourth cylindrical photonic crystal, and the fourth cylindrical photonic crystal, and a fourth cylindrical photonic crystal, the fourth cylindrical photonic crystal, and a fourth cylindrical photonic crystal, the fourth cylindrical photonic crystal, a fourth cylindrical photonic crystal, and a fourth cylindrical photonic crystal, a fourth cylindrical photonic, The central axes of the twenty-first cylindrical photonic crystal, the twenty-second cylindrical photonic crystal, the twenty-third cylindrical photonic crystal, the twenty-fourth cylindrical photonic crystal and the twenty-fifth cylindrical photonic crystal are positioned on the same plane, and the plane is parallel to the front end surface of the coupling region waveguide.