WO2023025065A1

WO2023025065A1 - Polarization rotation beam splitter and photonic integrated chip

Info

Publication number: WO2023025065A1
Application number: PCT/CN2022/113708
Authority: WO
Inventors: 王希琪
Original assignee: 中兴光电子技术有限公司
Priority date: 2021-08-25
Filing date: 2022-08-19
Publication date: 2023-03-02
Also published as: CN115933055A

Abstract

A polarization rotation beam splitter and a photonic integrated chip. The polarization rotation beam splitter comprises a polarization rotation region (100) and a polarization beam splitting region (200), wherein a first ridge waveguide (120) of the polarization rotation region (100) is located above a first slab waveguide (110); a second ridge waveguide (230) and a third ridge waveguide (240) of the polarization beam splitting region (200) are respectively located above a third slab waveguide (220); the third slab waveguide (220) is located above a second slab waveguide (210); and the first slab waveguide (110) and the second slab waveguide (210) are connected and have the same height. The ridge height of the first ridge waveguide (120) of the polarization rotation region (100) is greater than the ridge heights of the second ridge waveguide (230) and the third ridge waveguide (240) of the polarization rotation region (100), and ridge waveguides that have different etching depths are used as waveguides of the polarization rotation region (100) and the polarization beam splitting region (200), wherein a deep etching ridge waveguide is used for the polarization rotation region (100), and a shallow etching ridge waveguide is used for the polarization beam splitting region (200).

Description

Polarization rotating beam splitter and photonic integrated chip

Cross References to Related Applications

This application is based on a Chinese patent application with application number 202110979865.7 and a filing date of August 25, 2021, and claims the priority of this Chinese patent application. The entire content of this Chinese patent application is hereby incorporated by reference into this application.

technical field

The present application relates to the technical field of optical communication, in particular to a polarization rotating beam splitter and a photonic integrated chip.

Background technique

In recent years, the ever-increasing demand for information exchange has put forward higher requirements for communication transmission capacity, so there is also a higher requirement for the bandwidth of polarization rotating beam splitters, but most of the existing polarization rotating beam splitters are only suitable for transmitting C Optical signals in the O-band (conventional band), and polarization rotating beam splitters suitable for the O-band are relatively scarce. Therefore, it is of great significance for the development of silicon-based PIC and the development of optical communication to design a polarization rotating beam splitter with small size, high extinction ratio, low insertion loss, and applicable to O-band.

Contents of the invention

The following is an overview of the topics described in detail in this article. This summary is not intended to limit the scope of the claims.

In the first aspect, the embodiment of the present application provides a polarization rotation beam splitter, including a polarization rotation area and a polarization beam splitting area; wherein, the polarization rotation area includes a first slab waveguide and a first ridge waveguide, and the first The ridge waveguide is arranged on the first slab waveguide, and the width of the first slab waveguide gradually becomes wider toward the direction of the polarization beam splitting area; the polarization beam splitting area includes a second slab waveguide, a third slab waveguide, A second ridge waveguide and a third ridge waveguide, the third slab waveguide is disposed on the second slab waveguide, the second ridge waveguide and the third ridge waveguide are disposed on the third slab waveguide , the second ridge waveguide and the third ridge waveguide are arranged side by side with an interval therebetween, the first slab waveguide and the second slab waveguide are connected and have the same height, the third slab waveguide, the The second ridge waveguide is respectively connected to the first ridge waveguide; the height of the first ridge waveguide is the first height, the heights of the second ridge waveguide and the third ridge waveguide are respectively the second height, and the The first height is greater than the second height.

In the second aspect, the embodiment of the present application further provides a photonic integrated chip, the photonic integrated chip includes the polarization rotation beam splitter as described in the first aspect above.

The polarization rotating beam splitter provided by the embodiment of the present application includes a polarization rotating area and a polarization beam splitting area, wherein the first ridge waveguide of the polarization rotating area is above the first slab waveguide, and the second ridge waveguide and the second ridge waveguide of the polarization beam splitting area The three ridge waveguides are respectively located on the third slab waveguide, the third slab waveguide is located on the second slab waveguide, and the first slab waveguide and the second slab waveguide are connected and have the same height. In the embodiment of the present application, the ridge height of the first ridge waveguide in the polarization rotation region is greater than the ridge heights of the second ridge waveguide and the third ridge waveguide in the polarization rotation region, that is, the embodiment of the present application uses ridge waveguides with different etching depths as The waveguide of the polarization rotation area and the waveguide of the polarization beam splitting area, wherein the polarization rotation area adopts a deep etched ridge waveguide, and the polarization beam splitting area adopts a shallow etched ridge waveguide.

Description of drawings

The accompanying drawings are used to provide a further understanding of the technical solution of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical solution of the present application, and do not constitute a limitation to the technical solution of the present application.

FIG. 1 is a schematic structural diagram of a polarization rotating beam splitter provided in an embodiment of the present application;

Fig. 2 is a schematic cross-sectional view at the A-A' place in Fig. 1;

Fig. 3 is a schematic cross-sectional view at B-B' place in Fig. 1;

Figure 4a and Figure 4b respectively show the variation curves of the refractive index and the TE ratio of the eigenmodes of the DR waveguide in the L1 segment of the polarization rotation region as the slab width changes;

Figure 5a and Figure 5b show the refractive index variation curve and TE ratio variation curve of the DR waveguide eigenmode in the L2 section of the polarization rotation region as the slab width changes;

Fig. 6 is a schematic diagram of the output field intensity of the through end and the cross end after the TE/TM mode optical signal is input into the polarization rotating beam splitter of the embodiment of the present application.

Detailed ways

In order to make the purpose, technical solution and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application, not to limit the present application.

It should be understood that in the description of the embodiments of the present application, if there are descriptions of "first", "second", etc., it is only for the purpose of distinguishing technical features, and should not be understood as indicating or implying relative importance or implicitly indicating The number of indicated technical features or implicitly indicates the order of the indicated technical features. "At least one" means one or more, and "plurality" means two or more. "And/or" describes the association relationship of associated objects, indicating that there may be three kinds of relationships, for example, A and/or B may indicate that A exists alone, A and B exist simultaneously, or B exists alone. Among them, A and B can be singular or plural. The character "/" generally indicates that the contextual objects are an "or" relationship. "At least one of the following" and similar expressions refer to any group of these items, including any group of single or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or, a and b and c, where a, b, c can be a single , or more than one.

Those skilled in the art should appreciate that the connections described in the embodiments of the present application include direct connections and indirect connections through intermediate components.

In addition, the technical features involved in the various embodiments of the present application described below may be combined with each other as long as they do not constitute a conflict with each other.

In recent years, while the size of electronic chips has been continuously reduced, the interaction between electrons has also significantly increased the time delay, heat generation, and energy consumption of the device, thus greatly limiting the development of integrated circuits. Photonic Integrated Chip (PIC) based on Silicon-On-Insulator (Silicon-On-Insulator, SOI) platform has a high refractive index difference and is comparable to the traditional Complementary Metal Oxide Semiconductor (COMS) process. Compatibility and other features have attracted widespread attention, and optical interconnection networks using photonic integration are also expected to break the bottleneck of integrated circuits and achieve high-speed, large-capacity, and low-loss signal transmission and processing. However, the high refractive index difference between the core and cladding of the silicon-based waveguide makes the effective refraction between the optical signal in the Transverse Electric (TE) mode and the optical signal in the Transverse Magnetic (TM) mode The rate difference is very large, so SOI photonic devices are generally sensitive to the polarization state of light, so when the optical signal is transmitted in the device, great transmission loss will be introduced due to polarization mismatch. Therefore, the polarization rotating beam splitter, which can eliminate the influence of polarization state, plays an important role in PIC.

In recent years, the ever-increasing demand for information exchange has put forward higher requirements for communication transmission capacity, so there is also a higher requirement for the bandwidth of polarization rotating beam splitters, but most of the existing polarization rotating beam splitters are only suitable for transmitting C Optical signals in the O-band (conventional band, wavelength 1530-1565nm), while polarization rotating beam splitters suitable for the O-band (wavelength 1260-1360nm) are relatively scarce. Therefore, designing a polarization rotating beam splitter with small size, high extinction ratio, low insertion loss, and applicable to O-band is of great significance for the development of silicon-based PIC and the development of optical communication.

In view of this, embodiments of the present application provide a polarization rotating beam splitter that can reduce device size, increase extinction ratio, and reduce insertion loss, and is suitable for O-band optical signals.

Please refer to FIG. 1 . FIG. 1 is a schematic structural diagram of a polarization rotating beam splitter provided in an embodiment of the present application. As shown in FIG. 1 , the polarization rotating beam splitter of the embodiment of the present application includes a polarization rotating area 100 and a polarization beam splitting area 200 .

Wherein, the polarization rotation region 100 includes a first slab waveguide 110 and a first ridge waveguide 120, the first ridge waveguide 120 is arranged on the first slab waveguide 110, and the width of the first slab waveguide 110 is toward the polarization The direction of the beam splitting area 200 becomes wider gradually.

The polarization beam splitting area 200 includes a second slab waveguide 210, a third slab waveguide 220, a second ridge waveguide 230 and a third ridge waveguide 240, the third slab waveguide 220 is arranged on the second slab waveguide 210, the second The ridge waveguide 230 and the third ridge waveguide 240 are disposed on the third slab waveguide 220, the second ridge waveguide 230 and the third ridge waveguide 240 are arranged side by side with an interval therebetween, the first slab waveguide 110 and the The second slab waveguide 210 is connected and has the same height, and the third slab waveguide 220 and the second ridge waveguide 230 are respectively connected to the first ridge waveguide 120 .

2 and 3, the height of the first ridge waveguide 120 is a first height h1, the heights of the second ridge waveguide 230 and the third ridge waveguide 240 are respectively a second height h2, and the first height h1 is greater than the Second height h2.

It can be understood that, the polarization rotating beam splitter in the embodiment of the present application includes an optical input end (Input), a through end (Through) end and a cross (Cross) end. Wherein, the optical input end is located at the first end of the first ridge waveguide 120, where the first end of the first ridge waveguide 120 refers to the end of the first ridge waveguide 120 away from the polarization beam splitting area 200; the Through end is located at the end of the second ridge waveguide 230 The second end, here the second end of the second ridge waveguide 230 refers to the end of the second ridge waveguide 230 away from the polarization rotation region 100; the Cross end is located at the second end of the third ridge waveguide 240, here the second end of the third ridge waveguide 240 The end refers to the end of the third ridge waveguide 240 away from the polarization rotation region 100 .

It can be understood that the first ridge waveguide 120 in the embodiment of the present application is configured to output the TE polarization fundamental mode (TE0) optical signal input from the optical input end to the second ridge waveguide 230; the first ridge waveguide 120 can also be It is configured to convert the TM polarization fundamental mode (TM0) optical signal input from the optical input end into a TE polarization high order mode (TE1) optical signal, and output the TE1 mode optical signal to the second ridge waveguide 230 .

It can be understood that the second ridge waveguide 230 in the embodiment of the present application is configured to output the input TE0 mode optical signal from the Through end; the second ridge waveguide 230 is also configured to couple the input TE1 mode optical signal to the third Ridge waveguide 240, so that the third ridge waveguide 240 converts the coupled TE1 mode optical signal into a TE0 mode optical signal, and outputs the TE0 mode optical signal from the Cross port.

The working principle of the polarization rotating beam splitter provided in the embodiment of the present application is as follows:

When the polarization mode of the optical signal input from the optical input end is TM0, after the TM0 mode optical signal enters the first ridge waveguide 120, it will gradually become a TE polarization high-order mode (TE) as the width of the first slab waveguide 110 gradually widens The optical signal in the TE1) mode, that is, the optical signal in the TM0 mode is rotated into the optical signal in the TE1 polarization mode. The second end of the first ridge waveguide 120 is an optical rotation output end, and the TE1 mode optical signal is output to the second ridge waveguide 230 from the optical rotation output end. Here, the second end of the first ridge waveguide 120 refers to an end of the first ridge waveguide 120 close to the polarization beam splitting region 200 .

In the polarization beam splitting area 200, the second ridge waveguide 230 and the third ridge waveguide 240 form a coupling area, and the width parameters of the second ridge waveguide 230 and the third ridge waveguide 240 meet the phase matching condition, so that the second ridge waveguide 230 and The third ridge waveguide 240 forms a corresponding phase matching point. After the TE1 mode optical signal enters the second ridge waveguide 230 from the optical rotation output end of the first ridge waveguide 120, the TE1 mode optical signal will be coupled from the second ridge waveguide 230 to the third ridge waveguide 240 through the phase matching point, and in The third ridge waveguide 240 converts the TE0 mode optical signal, and the TE0 mode optical signal converted from the TE1 mode optical signal will be output from the Cross end of the third ridge waveguide 240 .

When the polarization mode of the optical signal input from the optical input end is TE0, the TE0 mode optical signal can directly pass through the first ridge waveguide 120 almost without loss, and output to the second ridge waveguide 230 from the optical rotation output end. After the optical signal in the TE0 mode enters the second ridge waveguide 230 , it will be output from the Through end along the second ridge waveguide 230 .

The polarization rotating beam splitter provided in the embodiment of the present application includes a polarization rotating area 100 and a polarization beam splitting area 200, wherein the first ridge waveguide 120 of the polarization rotating area 100 is above the first slab waveguide 110, and the polarization rotating area 200 The second ridge waveguide 230 and the third ridge waveguide 240 are respectively on the third slab waveguide 220, the third slab waveguide 220 is on the second slab waveguide 210, and the first slab waveguide 110 and the second slab waveguide 210 are connected and equal in height. The ridge height of the first ridge waveguide 120 of the polarization rotation region 100 in the embodiment of the present application is greater than the ridge heights of the second ridge waveguide 230 and the third ridge waveguide 240 of the polarization rotation region 100, that is, the embodiment of the present application uses different etching methods. The deep ridge waveguide is used as the waveguide of the polarization rotation area 100 and the waveguide of the polarization beam splitting area 200, wherein the polarization rotation area 100 adopts a deeply etched ridge waveguide, which can make the polarization rotation area 100 have higher polarization rotation efficiency; the polarization beam splitting area 200 adopts a shallow etched ridge waveguide, which can make the polarization beam splitting region 200 have higher coupling efficiency. Based on the improvement of polarization rotation efficiency and coupling efficiency, it is beneficial to reduce the size of the polarization rotation beam splitter in the embodiment of the present application, and it is also beneficial to improve the extinction ratio and reduce the insertion loss, so that the polarization rotation beam splitter of the embodiment of the application is suitable for O Transmission scenarios of band optical signals.

As an example, the first ridge waveguide 120 includes an input ridge waveguide 121 and at least one first transition ridge waveguide 122, the input ridge waveguide 121 is connected to the third slab waveguide 220, the second The ridge waveguides 230 are connected respectively. Here, the first transition ridge waveguide 122 may include one or more stages of the first transition ridge waveguide 122, and the one or more stages of the first transition ridge waveguide 122 are set to gradually widen the width of the first ridge waveguide 120, so that the The second end of one ridge waveguide 120 has the same width as the first end of the second ridge waveguide 230 . Wherein, the second end of the first ridge waveguide 120 refers to the end of the first ridge waveguide 120 close to the polarization splitting region 200 , and the first end of the second ridge waveguide 230 refers to the end of the second ridge waveguide 230 close to the polarization rotation region 100 .

As an example, the input ridge waveguide 121 may be a straight waveguide or a trapezoidal waveguide.

As an example, the first transition ridge waveguide 122 may comprise a trapezoidal waveguide, for example, the first transition ridge waveguide 122 may comprise a multi-stage trapezoidal waveguide, and the width of the first transition ridge waveguide 122 of each level faces the direction of the polarization beam splitting region 200 gradually widens, and the first end of the first transition ridge waveguide 122 of the latter stage has the same width as the second end of the first transition ridge waveguide 122 of the previous stage, wherein the first end of the first transition ridge waveguide 122 The end refers to the end of the first transition ridge waveguide 122 away from the polarization beam splitting region 200 , and the second end of the first transition ridge waveguide 122 refers to the end of the first transition ridge waveguide 122 close to the polarization beam splitting region 200 . The first transition ridge waveguide 122 can also include a multi-stage rectangular waveguide, and the width of the first transition ridge waveguide 122 of the latter stage is greater than the width of the first transition ridge waveguide 122 of the previous stage, so as to realize that the first transition ridge waveguide 122 is polarized The direction of the beam splitting area 200 becomes wider gradually. The first transition ridge waveguide 122 may also include other shapes or be composed of waveguides of different shapes, as long as the first transition ridge waveguide 122 can gradually become wider toward the polarization beam splitting region 200, it belongs to the protection scope of the embodiment of the present application. The embodiment of the present application does not place too many restrictions on the form of the first transition ridge waveguide 122 .

As an example, the first slab waveguide 110 includes an input slab waveguide 111 and at least one first transition slab waveguide 112 , and the input slab waveguide 111 is connected to the second slab waveguide 210 through the first transition slab waveguide 112 . Here, the first transition slab waveguide 112 may include one or more stages of first transition slab waveguides 112, and the one or more stages of first transition slab waveguides 112 are set to gradually widen the width of the first slab waveguide 110, so that The first slab waveguide 110 gradually widens to the same width as the second slab waveguide 210 , that is, the second end of the first slab waveguide 110 has the same width as the first end of the second slab waveguide 210 . Wherein, the second end of the first slab waveguide 110 refers to the end of the first slab waveguide 110 close to the polarization splitting region 200 , and the first end of the second slab waveguide 210 refers to the end of the second slab waveguide 210 close to the polarization rotation region 100 .

As an example, the input slab waveguide 111 may be a trapezoidal waveguide or a rectangular waveguide.

As an example, the first transition slab waveguide 112 may be a trapezoidal waveguide or a rectangular waveguide respectively. For example, the first transitional slab waveguide 112 may include a multi-stage trapezoidal waveguide, the width of the first transitional slab waveguide 112 of each level gradually becomes wider toward the direction of the polarization beam splitting region 200, and the width of the first transitional slab waveguide 112 of the next level The first end has the same width as the second end of the first transition slab waveguide 112 of the previous stage, wherein the first end of the first transition slab waveguide 112 refers to the end of the first transition slab waveguide 112 away from the polarization beam splitting region 200 , the second end of the first transitional slab waveguide 112 refers to the end of the first transitional slab waveguide 112 close to the polarization beam splitting region 200 . The first transition slab waveguide 112 can also include a multi-stage rectangular waveguide, and the width of the first transition slab waveguide 112 of the latter stage is greater than the width of the first transition slab waveguide 112 of the previous stage, so as to realize that the first transition slab waveguide 112 is polarized The direction of the beam splitting area 200 becomes wider gradually. The first transitional slab waveguide 112 may also include other shapes or be composed of waveguides of different shapes, as long as the first transitional slab waveguide 112 can gradually widen toward the polarization beam splitting region 200, it belongs to the protection scope of the embodiment of the present application. The embodiment of the present application does not place too many restrictions on the form of the first transition slab waveguide 112 .

Exemplarily, the input slab waveguide 111 and the input ridge waveguide 121 have the same length, and the first transition ridge waveguide 122 and the first transition slab waveguide 112 have the same length.

Exemplarily, the first end of the input ridge waveguide 121 and the first end of the input slab waveguide 111 have the same width, and the width of the second end of the input ridge waveguide 121 is smaller than the width of the second end of the input slab waveguide 111 . Here, the first end of the input ridge waveguide 121 refers to the end of the input ridge waveguide 121 away from the polarization beam splitting area 200, the first end of the input ridge waveguide 121 refers to the end of the input ridge waveguide 121 close to the polarization beam splitting area 200, and the input slab waveguide 111 The first end of the input slab waveguide 111 refers to the end of the input slab waveguide 111 away from the polarization beam splitting area 200 , and the first end of the input slab waveguide 111 refers to the end of the input slab waveguide 111 close to the polarization beam splitting area 200 .

As an example, the second ridge waveguide 230 of the embodiment of the present application includes a first connection waveguide 231, a first coupling waveguide 232 and a first output ridge waveguide 233, and the first end of the first connection waveguide 231 is connected to the first ridge waveguide 120, the second end of the first connecting waveguide 231 is connected to the first output ridge waveguide 233 through the coupling waveguide.

Exemplarily, the first connecting waveguide 231 , the first coupling waveguide 232 and the first output ridge waveguide 233 are respectively trapezoidal waveguides.

As an example, the third ridge waveguide 240 includes a second connection waveguide 241, a second coupling waveguide 242 and a second output ridge waveguide 243, the second connection waveguide 241 is connected to the second output ridge waveguide 243 via the second coupling waveguide 242 .

Exemplarily, the second connecting waveguide 241 and the second output ridge waveguide 243 are respectively curved waveguides, and the second coupling waveguide 242 is a trapezoidal waveguide.

In a possible implementation manner, the second connecting waveguide 241 is gradually bent from an end close to the second coupling waveguide 242 to a direction away from the first connecting waveguide 231 . The second output ridge waveguide 243 is an S-shaped curved waveguide.

In a possible implementation manner, the first coupling waveguide 232 is a wide trapezoidal waveguide, and the second coupling waveguide 242 is a narrow trapezoidal waveguide. Wherein, the width of the wide trapezoidal waveguide gradually narrows along the direction of light transmission, and the width of the narrow trapezoidal waveguide gradually becomes wider along the direction of light transmission.

It can be understood that the first connecting waveguide 231 receives the optical signal output from the first ridge waveguide 120 and transmits the optical signal to the first coupling waveguide 232 . The first coupling waveguide 232 and the second coupling waveguide 242 satisfy the phase matching condition for realizing TE1 signal coupling. If the polarization mode of the optical signal is TE1, the TE1 mode optical signal will be coupled from the first coupling waveguide 232 to the The second coupling waveguide 242 converts the optical signal from the TE1 mode to the TE0 mode when passing through the S-shaped curved second output ridge waveguide 243, and the TE0 mode optical signal converted from the TE1 mode optical signal will be output from the second The output of the Cross end of the ridge waveguide 243 .

When the polarization mode of the optical signal output from the first ridge waveguide 120 is TE0, the TE0 mode optical signal will sequentially go through the first connecting waveguide 231, the first coupling waveguide 232 and the first output ridge waveguide 233 from the Through end output.

As an example, the height of the third slab waveguide 220 is the third height h3, and the sum of the second height h2 and the third height h3 is equal to the first height h1. That is to say, the upper surfaces of the first ridge waveguide 120 , the second ridge waveguide 230 and the third ridge waveguide 240 are at the same level.

As an example, the heights of the first slab waveguide 110 and the second slab waveguide 210 are respectively the fourth height h4, and when the sum of the second height h2 and the third height h3 is equal to the first height h1, the fourth The height h4 is greater than the third height h3. Certainly, in some possible implementation manners, the fourth height h4 may also be equal to or smaller than the third height h3, which is not limited in this embodiment of the present application.

The third slab waveguide 220 in the embodiment of the present application is used as a transition layer from the deeply etched ridge waveguide region to the shallow etched ridge waveguide region to ensure that optical signals can be stably transmitted from the first ridge waveguide 120 in the deeply etched ridge waveguide region to the shallow etched ridge waveguide region. The second ridge waveguide 230 in the ridge waveguide region ensures the working reliability of the polarization rotating beam splitter in the embodiment of the present application.

As an example, the second slab waveguide 210 is a rectangular waveguide, the first end of the second slab waveguide 210 has the same width as the second end of the first slab waveguide 110, wherein the first end of the second slab waveguide 210 refers to The end of the second slab waveguide 210 close to the polarization rotation region 100 , the second end of the first slab waveguide 110 refers to the end of the first slab waveguide 110 close to the polarization splitting region 200 .

As an example, the third slab waveguide 220 includes at least one stage of the second transition slab waveguide 221 and a coupled output slab waveguide. In one embodiment, the second transitional slab waveguide 221 is a trapezoidal waveguide, the coupling output slab waveguide is a rectangular waveguide, and the rectangular coupling output slab waveguide has the same width as the rectangular second slab waveguide 210 . Wherein, the first end of the first-stage second transition slab waveguide 221 and the second end of the first ridge waveguide 120 have equal widths, and the second end of the last-stage second transition slab waveguide 221 and the coupled output slab waveguide The first ends of the have equal width. In this way, the third slab waveguide 220 is gradually widened to the same width as the second slab waveguide 210 through one or more stages of trapezoidal waveguides, so as to realize the gradual transition of the polarization beam splitting region 200 from the deeply etched ridge waveguide region to the shallow etched ridge waveguide region. Transition, improve the stability of optical signal transmission.

It can be understood that the first ridge waveguide 120 is connected to the coupled output slab waveguide via the at least one second transition slab waveguide 221 . The first connecting waveguide 231 and the second connecting waveguide 241 are respectively located on the second transition slab waveguide 221, the first coupling waveguide 232, the second coupling waveguide 242, the first output ridge waveguide 233 and the second output Ridge waveguides 243 are respectively located on the coupling-out slab waveguides. During specific implementation, a part of the second connection waveguide 241 may be located on the second slab waveguide 210 .

In order to facilitate a better understanding of the solutions of the embodiments of the present application, a specific embodiment in which the polarization rotating beam splitter is applied to an O-band transmission scenario is given below.

Referring to the polarization rotation beam splitter shown in Figure 1, the first slab waveguide 110 of the polarization rotation region 100 of the polarization rotation beam splitter includes an input slab waveguide 111 and a three-stage first transition slab waveguide 112, where the three-stage first transition The slab waveguides 112 are respectively the first-level first transition slab waveguide 1121, the second-level first transition slab waveguide 1122, and the third-level first transition slab waveguide 1123; the first ridge waveguide 120 of the polarization rotation region 100 includes an input ridge waveguide 121 and three-level first transition ridge waveguides 122, where the three-level first transition ridge waveguides 122 are respectively first-level first transition ridge waveguides 1221, second-level first transition ridge waveguides 1222 and third-level first transition ridge waveguides 1223 . As shown in Fig. 1, the polarization rotation region 100 adopts the mode evolution mode of the trapezoidal slow-changing structure, and the polarization rotation region 100 is divided into four waveguide segments as a whole (represented by L1, L2, L3 and L4 here), and the L1 segment includes Input slab waveguide 111 and input ridge waveguide 121, L2 section includes first-level first transition slab waveguide 1121 and first-level first transition ridge waveguide 1221, L3 section includes second-level first transition slab waveguide 1122 and second-level first transition slab waveguide 1122 and second-level first transition slab waveguide 1121 A transition ridge waveguide 1222 , the L4 section includes a third-level first transition slab waveguide 1123 and a third-level first transition ridge waveguide 1223 .

The overall height of the polarization rotation region 100 is 220nm, wherein the height of the first slab waveguide 110 is h4=70nm, and the height of the first ridge waveguide 120 is h1=150nm. This type of waveguide structure of the polarization rotation region 100 can be called deep etching Ridge waveguide (Deep etch ridge, DR) structure.

The structural size of the polarization rotation region 100 is determined by establishing an EME model and simulating. Referring to Figure 4a and Figure 4b, Figure 4a and Figure 4b respectively show the change curve of the refractive index (neff) and the TE fraction (TE fraction) of the eigenmode of the DR waveguide in the L1 section as the slab width (Wslab) changes . Assuming that the width of the slab waveguide is widened from the initial width w ₀ = 0.42 μm at the Input end, and the end width w _s1 of the L1 segment is 1.5 μm, when the TE1 fraction value is greater than 0.5, it can be considered that the optical signal is converted from the TM0 mode to the TE1 mode, so It can be seen from Fig. 4b that the TM0 mode optical signal can realize the TE1 mode conversion in the L1 segment mode, and the refractive index of the TE1 optical signal also increases with the increase of the slab width.

In order to make the fraction value of TE1 tend to 1, the L2 section continues to widen the width of the slab waveguide. Figure 5a and Figure 5b respectively show the change curve of the refractive index (neff) and the TE fraction (TE fraction) of the eigenmode of the DR waveguide in the L2 segment as the slab width (Wslab) changes. The width of the L2 slab waveguide will be widened to 1.7μm. It can be seen from Figure 5b that when the slab width increases to 1.7 μm, the value of TE1 fraction has reached around 0.95, and the TE1 fraction curve tends to be flat. In the subsequent L3 and L4 sections, the width of the slab waveguide will continue to increase to make the fraction value of TE1 closer to 1.

When the input signal of the polarization rotation region 100 is a TE0 mode signal, it can be seen from FIG. 4 a and FIG. 4 b , and FIG. 5 a and FIG. 5 b that the TE0 mode signal can pass through the polarization rotation region 100 almost without loss.

Through the EME simulation of the four-segment structure of the polarization rotation region 100, the result shows that the total length of the polarization rotation region 100 is between 100-150 μm.

Referring to Fig. 1, for the polarization beam splitting region 200 of the polarization rotating beam splitter, an asymmetric structure mode coupling mode is adopted, and its working principle is that when TM0 is input, the first half rotates to TE1, and the mode coupling part only excites the dual waveguide in the coupling region The even mode with a large refractive index among the TE1 to TE0 supermodes of the structure. The phase matching point is that the effective refractive index of TE1 at the straight-through end is equal to the effective refractive index of TE0 at the crossing end, and the coupling between TE1 and TE0 is realized by changing the waveguide width so that the parameters cross the phase matching point.

When TE0 is input, the effective refractive index of the through-end TE0 of the mode coupling part is much higher than that of the cross-end TE0, so that TE0 remains at the through-end.

As shown in FIG. 1 , the second ridge waveguide 230 of the polarization beam splitting region 200 includes a first connecting waveguide 231, a first coupling waveguide 232 and a first output ridge waveguide 233, and the third ridge waveguide 240 includes a second connecting waveguide 241, a first coupling waveguide 233, and a first coupling waveguide 233. Two coupling waveguides 242 and a second output ridge waveguide 243 , the third slab waveguide 220 includes a first-level second transition slab waveguide 2211 , a second-level second transition slab waveguide 2212 and a coupling output slab waveguide 222 . The overall structure of the polarization beam splitting region 200 is divided into three sections, namely Lstart, Lcoupler and Lend. Wherein, the Lstart segment includes a first connecting waveguide 231, a second connecting waveguide 241, a first-level second transition slab waveguide 2211 and a second-level second transition slab waveguide 2212; Lcoupler includes a first coupling waveguide 232 and a second coupling waveguide 242 ; Lend includes a first output ridge waveguide 233 and a second output ridge waveguide 243 . The second slab waveguide 210 spans the Lstart, Lcoupler and Lend segments.

The overall height of the polarization beam splitting region 200 is 220nm, wherein the height of the second slab waveguide 210 is h4=70nm, the height of the third slab waveguide 220 is h3=60nm, the second ridge waveguide 230, the third ridge waveguide 240 With a height of h2=90nm, this type of waveguide structure of the polarization beam splitting region 200 can be called a shallow etch ridge waveguide (Shallow etch ridge, SR) structure.

By calculating the effective refractive index of the TE0 and TE1 modes of the O-band wavelength, it can be obtained that the phase matching point of the SR waveguide under ideal conditions is the middle position of the coupling region where the first coupling waveguide 232 narrows to 550nm and the second coupling waveguide 242 widens to 420nm. . By performing EME simulation on the coupling region of the SR waveguide, it can be concluded that the total length parameter of the polarization beam splitting region 200 is between 220-260 μm.

From the above simulation results, it can be seen that when the first half of the polarization rotating beam splitter uses DR waveguides and the second half uses SR waveguides, the total length is the shortest. However, the key to this structure lies in the transition region from the DR waveguide to the SR waveguide. The multilayer waveguide structure makes the transition. In the embodiment of the present application, by adding a layer of third slab waveguide 220, the third slab waveguide 220 slowly widens the slab width of the SR waveguide from the width of the input end of the second ridge waveguide 230 to the slab width of the output end of the polarization rotation region 100, thereby realizing DR The waveguide transitions to the SR waveguide, so that the TE1 mode is stably transmitted to the polarization beam splitting region 200 . At the same time, the transition region can serve as the first section Lstart of the polarization beam splitting region 200 .

Based on the above structure, the total length of the O-band polarization rotating beam splitter of the present application is the polarization rotating region 100 plus the polarization beam splitting region 200, and the total length is about 320-410 μm.

Finally, the performance of the O-band polarization rotating beam splitter of the present application is verified experimentally. The method adopted is to record the output field strength of the through (straight-through) end and cross (cross) end after the TE/TM mode optical signal is input, and the result is shown in Figure 6 As shown, it can be seen that when the TE/TM mode is input, the through loss is low, and the crosstalk at the cross end is above 25dB. Therefore, the designed O-band polarization rotating beam splitter has the characteristics of low insertion loss and high extinction ratio.

Based on the above analysis, the O-band polarization rotation beam splitter designed in this application adopts waveguides with different etching depths in the polarization rotation area 100 and polarization beam splitting area 200, the overall structure size is significantly reduced, and it has low transmission loss, extinction advantage over higher grades.

An embodiment of the present application further provides a photonic integrated chip, and the photonic integrated chip includes the polarization rotating beam splitter described in any of the above embodiments.

The photonic integrated chip provided by the embodiment of the present application includes a polarization rotation beam splitter, and the polarization rotation beam splitter includes a polarization rotation area and a polarization beam splitting area, wherein the first ridge waveguide of the polarization rotation area is above the first slab waveguide, The second ridge waveguide and the third ridge waveguide in the polarization beam splitting area are respectively on the third slab waveguide, the third slab waveguide is on the second slab waveguide, and the first slab waveguide and the second slab waveguide are connected and have the same height . In the embodiment of the present application, the ridge height of the first ridge waveguide in the polarization rotation region is greater than the ridge heights of the second ridge waveguide and the third ridge waveguide in the polarization rotation region, that is, the embodiment of the present application uses ridge waveguides with different etching depths as The waveguide in the polarization rotation area and the waveguide in the polarization beam splitting area, wherein the polarization rotation area adopts a deep etched ridge waveguide, which can make the polarization rotation area have higher polarization rotation efficiency; the polarization beam splitting area adopts a shallow etched ridge waveguide, which can make The polarization beam splitter has higher coupling efficiency. Based on the improvement of polarization rotation efficiency and coupling efficiency, the embodiment of the present application can reduce the size of the polarization rotation beam splitter, which is also conducive to improving the extinction ratio and reducing the insertion loss, making the polarization rotation beam splitter of the embodiment of the application suitable for O-band Transmission scenarios of optical signals.

Therefore, embodiments of the present application provide a polarization rotating beam splitter that can reduce device size, increase extinction ratio, and reduce insertion loss, and is suitable for O-band optical signals.

It should be understood that the description of each embodiment in this application has its own focus, and for the parts that are not detailed or recorded in a certain embodiment, refer to the relevant descriptions of other embodiments.

The above is a specific description of the preferred embodiments of the present application, but the present application is not limited to the above embodiments, and those skilled in the art will not deviate from the spirit of the present application. Various equivalent deformations or substitutions can also be made under shared conditions, and these equivalent deformations or substitutions are all included within the scope defined by the claims of the present application.

Claims

A polarization rotating beam splitter, comprising a polarization rotating area and a polarization beam splitting area; wherein,

The polarization rotation region includes a first slab waveguide and a first ridge waveguide, the first ridge waveguide is arranged on the first slab waveguide, and the width of the first slab waveguide gradually moves toward the direction of the polarization beam splitting region. widen;

The polarization beam splitting area includes a second slab waveguide, a third slab waveguide, a second ridge waveguide and a third ridge waveguide, the third slab waveguide is arranged on the second slab waveguide, and the second ridge waveguide and the third ridge waveguide are arranged on the third slab waveguide, the second ridge waveguide and the third ridge waveguide are arranged side by side with an interval therebetween, the first slab waveguide and the second ridge waveguide The slab waveguides are connected and have the same height, and the third slab waveguide and the second ridge waveguide are respectively connected to the first ridge waveguide;

The height of the first ridge waveguide is a first height, the heights of the second ridge waveguide and the third ridge waveguide are respectively a second height, and the first height is greater than the second height.
The polarization rotating beam splitter according to claim 1, wherein the first ridge waveguide comprises an input ridge waveguide and at least one first transition ridge waveguide, and the input ridge waveguide passes through the at least one first transition ridge The waveguide is connected to the third slab waveguide and the second ridge waveguide respectively;

The first slab waveguide includes an input slab waveguide and at least one first transition slab waveguide, and the input slab waveguide is connected to the second slab waveguide through the at least one first transition slab waveguide.
The polarization rotating beam splitter according to claim 2, wherein the input ridge waveguide, the first transition ridge waveguide, the input slab waveguide and the first transition slab waveguide are respectively trapezoidal waveguides.
The polarization rotating beam splitter according to claim 2, wherein the first end of the input ridge waveguide and the first end of the input slab waveguide have the same width, and the width of the second end of the input ridge waveguide is less than The width of the second end of the input slab waveguide.
The polarization rotating beam splitter according to claim 1, wherein the second ridge waveguide comprises a first connection waveguide, a first coupling waveguide and a first output ridge waveguide, the first end of the first connection waveguide is connected to The first ridge waveguide, the second end of the first connecting waveguide is connected to the first output ridge waveguide via the first coupling waveguide;

The first connecting waveguide, the first coupling waveguide and the first output ridge waveguide are respectively trapezoidal waveguides.
The polarization rotating beam splitter according to claim 5, wherein said third ridge waveguide comprises a second connecting waveguide, a second coupling waveguide and a second output ridge waveguide, said second connecting waveguide is coupled via said second coupling waveguide a waveguide connected to the second output ridge waveguide;

The second connecting waveguide and the second output ridge waveguide are curved waveguides respectively, and the second coupling waveguide is a trapezoidal waveguide.
The polarization rotating beam splitter according to claim 6, wherein the second connecting waveguide is gradually curved from an end close to the second coupling waveguide to a direction away from the first connecting waveguide, and the second output ridge The waveguide is an S-shaped curved waveguide.
The polarization rotating beam splitter according to claim 6, wherein the third slab waveguide includes at least one second transition slab waveguide and a coupling-out slab waveguide, and the first ridge waveguide passes through the at least one second transition slab waveguide. The transition slab waveguide is connected to the coupled output slab waveguide;

The second transition slab waveguide of each stage is a trapezoidal waveguide, and the coupled output slab waveguide is a rectangular waveguide, and the first end of the second transition slab waveguide of the first stage and the second end of the first ridge waveguide have equal Width, the second end of the second transition slab waveguide in the last stage and the first end of the coupling-out slab waveguide have the same width.
The polarization rotating beam splitter according to claim 8, wherein the first connecting waveguide and the second connecting waveguide are respectively located on the second transition slab waveguide, the first coupling waveguide, the second coupling waveguide The waveguide, the first output ridge waveguide and the second output ridge waveguide are respectively located on the coupling-out slab waveguide.
The polarization rotating beam splitter according to claim 8, wherein the second slab waveguide is a rectangular waveguide, and the outcoupling slab waveguide and the second slab waveguide have the same width.
The polarization rotating beam splitter according to claim 1, wherein the height of the third slab waveguide is a third height, and the sum of the second height and the third height is equal to the first height.
A photonic integrated chip, comprising the polarization rotating beam splitter according to any one of claims 1 to 11.