阅读说明：本技术 非对称三波导结构的偏振分束器及其制备方法 (Polarization beam splitter with asymmetric three-waveguide structure and preparation method thereof ) 是由 牛超群 刘智 成步文 于 2019-12-02 设计创作，主要内容包括：一种偏振分束器,包括SOI衬底层和波导层,其中,SOI衬底层,包括底部Si材料层和制作在底部Si材料层上的二氧化硅填埋层；波导层,制作在所述二氧化硅填埋层上方,包括输入波导、TM模式耦合波导和TE模式耦合波导；其中,输入波导包括底层波导和介质盖层；所述波导层通过将TE波和TM波分别限制在TE模式耦合波导和TM模式耦合波导,从而实现对所述输入波导中的不同偏振模式的光进行分离。本发明采用三波导结构的波导层,包括输入波导、TM耦合波导以及TE耦合波导,通过将TE和TM模式分别限制在两侧波导中,从而实现对输入波导中不同偏振态的分别耦合,消除输入波导残留模式对器件性能的影响。(A polarization beam splitter comprises an SOI substrate layer and a waveguide layer, wherein the SOI substrate layer comprises a bottom Si material layer and a silicon dioxide filling layer manufactured on the bottom Si material layer; the waveguide layer is manufactured above the silicon dioxide buried layer and comprises an input waveguide, a TM mode coupling waveguide and a TE mode coupling waveguide; the input waveguide comprises a bottom waveguide and a dielectric cover layer; the waveguide layer realizes the separation of light of different polarization modes in the input waveguide by respectively limiting the TE wave and the TM wave to the TE mode coupling waveguide and the TM mode coupling waveguide. The invention adopts the waveguide layer with a three-waveguide structure, which comprises an input waveguide, a TM coupling waveguide and a TE coupling waveguide, and respectively limits TE and TM modes in the waveguides at two sides, thereby respectively coupling different polarization states in the input waveguide and eliminating the influence of the residual mode of the input waveguide on the device performance.)

1. A polarization beam splitter comprising an SOI substrate layer and a waveguide layer, wherein,

the SOI substrate layer comprises a bottom Si material layer and a silicon dioxide filling layer manufactured on the bottom Si material layer;

the waveguide layer is manufactured above the silicon dioxide buried layer and comprises an input waveguide, a TM mode coupling waveguide and a TE mode coupling waveguide; the input waveguide comprises a bottom waveguide and a dielectric cover layer; the waveguide layer realizes the separation of light of different polarization modes in the input waveguide by respectively limiting the TE wave and the TM wave to the TE mode coupling waveguide and the TM mode coupling waveguide.

2. The polarizing beam splitter of claim 1, wherein the input, TM and TE mode coupling waveguides are asymmetrically distributed and are arranged in parallel with a spacing between the waveguides.

3. The polarization beam splitter of claim 1, wherein a cladding layer is formed over the waveguide layer, the cladding layer being made of air or silicon oxide; the waveguide layer is made of silicon or silicon nitride.

4. The polarizing beam splitter of claim 1, wherein the TE mode coupling waveguide has a different thickness than the TM mode coupling waveguide and the underlying waveguide.

5. A method of manufacturing a polarizing beam splitter according to any one of claims 1 to 4, comprising the steps of:

manufacturing and forming the TM mode coupling waveguide, the TE mode coupling waveguide and the bottom layer waveguide above the silicon dioxide buried layer by an etching or corrosion method;

reducing the thickness of the TE mode coupling waveguide by adopting a dry etching or reactive ion etching method;

depositing a medium on the bottom layer waveguide to form a medium cover layer by adopting a plasma enhanced chemical reaction deposition method;

and depositing a medium on the waveguide layer by adopting a chemical vapor deposition method to form a covering layer.

6. The method of claim 5, wherein the waveguide layer separates light of different polarization modes in the input waveguide by confining TE and TM waves to TE and TM mode coupling waveguides, respectively.

7. The method of claim 5, wherein the input waveguide, the TM-mode coupling waveguide and the TE-mode coupling waveguide are asymmetrically distributed and arranged in parallel with a space between the waveguides.

8. The method of manufacturing of claim 5, wherein the TE mode coupling waveguide has a different thickness than the TM mode coupling waveguide and the underlying waveguide.

9. A preparation method according to claim 5, wherein the material of the waveguide layer is silicon or silicon nitride.

10. An optical communication device employing a polarizing beam splitter according to any one of claims 1 to 4.

Technical Field

The invention relates to the field of optical communication, in particular to a polarization beam splitter with an asymmetric three-waveguide structure and a preparation method thereof.

Background

With the rise and development of emerging technologies such as artificial intelligence, cloud computing and cloud storage, the requirements on the speed and capacity of data communication reach unprecedented heights. However, as moore's law breaks through the limits, simple microelectronics technologies have no longer met the demand, and to solve this series of problems, photonic circuits and optical interconnects have gradually moved into the human vision. The photonic integrated optical interconnection network can break the bottleneck of the traditional integrated circuit and realize the signal transmission and processing with ultrahigh speed, ultralow power consumption and ultrahigh capacity.

SiO based on SOI platform ₂The large refractive index difference between the substrate and the Si can realize a small-size and high-performance optical integrated device, but as such, the silicon-based integrated device has strong polarization dependence, which is more obvious in the small-size device. Due to the birefringence, when an optical fiber is coupled with a waveguide device, unstable and random polarization states are introduced into the optical device, which causes mutual interference between different polarization states inside the device, and thus, the proposal of a high-performance polarization diversity (polarization diversity) scheme is increasingly urgent. Polarization beam splitters (polarization beam splitters) confine TE and TM modes in different layers or different waveguides, thereby achieving separation of polarization states. At present, the main polarization beam splitter structures are a Directional Coupling (DC) type, a multimode interferometer (MMI) type, a planar grating (plane grating) type, a slot waveguide type, a metal surface plasma (SPP) type, and the like.

The planar grating type polarization beam splitter adjusts the coupling condition of the waveguide by designing a proper period and duty ratio, realizes the coupling of only one polarization state, and mainly utilizes the Bragg diffraction principle of the grating. But the structure is large in size, narrow in bandwidth and sensitive to structural parameters.

The multimode interferometer type polarization beam splitter utilizes the interference of different modes in multimode areas, so that single images and multiple images of input images can appear at certain positions of a waveguide, a mirror image of a certain polarization state can be obtained at an output end by selecting proper multimode area sizes, pi phase shift is realized, and different polarization states are distinguished. This structure is simple in design, but large in size and sensitive to bandwidth limitations.

The metal surface plasma type polarization beam splitter utilizes the deposition of a metal medium to increase the dispersion phenomenon of different polarization states, and the structure is usually combined with a slot structure, so that different modes are limited in different areas of a waveguide, and the polarization state separation is realized. This improvement in structural performance comes at the expense of losses.

Disclosure of Invention

In view of the above, the present invention provides a polarization beam splitter with an asymmetric three-waveguide structure and a method for manufacturing the same, so as to at least partially solve at least one of the above technical problems.

To achieve the above object, as an aspect of the present invention, there is provided a polarization beam splitter including an SOI substrate layer and a waveguide layer, wherein,

the SOI substrate layer comprises a bottom Si material layer and a silicon dioxide filling layer manufactured on the bottom Si material layer;

the waveguide layer is manufactured above the silicon dioxide buried layer and comprises an input waveguide, a TM mode coupling waveguide and a TE mode coupling waveguide; the input waveguide comprises a bottom waveguide and a dielectric cover layer; the waveguide layer realizes the separation of light of different polarization modes in the input waveguide by respectively limiting the TE wave and the TM wave to the TE mode coupling waveguide and the TM mode coupling waveguide.

The input waveguide, the TM mode coupling waveguide and the TE mode coupling waveguide are asymmetrically distributed and are arranged in parallel, and a space is reserved among the waveguides.

A covering layer is formed above the waveguide layer, and the material is air or silicon oxide; the waveguide layer is made of silicon or silicon nitride.

The thickness of the TE mode coupling waveguide is different from the TM mode coupling waveguide and the underlying waveguide.

An optical communication device employing a polarizing beam splitter as described above.

As another aspect of the present invention, there is provided a method of manufacturing a polarizing beam splitter, including the steps of:

manufacturing and forming the TM mode coupling waveguide, the TE mode coupling waveguide and the bottom layer waveguide above the silicon dioxide buried layer by an etching or corrosion method;

reducing the thickness of the TE mode coupling waveguide by adopting a dry etching or reactive ion etching method;

depositing a medium on the bottom layer waveguide to form a medium cover layer by adopting a plasma enhanced chemical reaction deposition method;

and depositing a medium on the waveguide layer by adopting a chemical vapor deposition method to form a covering layer.

The waveguide layer realizes the separation of light of different polarization modes in the input waveguide by respectively limiting the TE wave and the TM wave to the TE mode coupling waveguide and the TM mode coupling waveguide.

The input waveguide, the TM mode coupling waveguide and the TE mode coupling waveguide are asymmetrically distributed and are arranged in parallel, and a space is reserved among the waveguides.

The thickness of the TE mode coupling waveguide is different from the TM mode coupling waveguide and the underlying waveguide.

The waveguide layer is made of silicon or silicon nitride.

Based on the technical scheme, compared with the prior art, the polarization beam splitter and the preparation method thereof have at least one of the following beneficial effects:

(1) the invention adopts the waveguide layer with a three-waveguide structure, which comprises an input waveguide, a TM coupling waveguide and a TE coupling waveguide, and respectively limits TE and TM modes in the waveguides at two sides, thereby respectively coupling different polarization states in the input waveguide and eliminating the influence of the residual mode of the input waveguide on the device performance.

(2) The polarization beam splitter is designed into a three-waveguide respectively-coupled polarization beam splitter, so that the extinction ratio of a device can be greatly improved, the working bandwidth of the device is increased, the length of a coupling area is reduced, and the polarization beam splitter has the advantages of simple process flow, low manufacturing difficulty, small size, high performance, large working bandwidth and the like.

Drawings

FIG. 1 is a schematic cross-sectional view of a polarizing beam splitter of the present invention;

FIG. 2 is a schematic top view of a polarizing beam splitter according to the present invention;

FIG. 3 is a flow chart of the fabrication of the polarizing beam splitter of the present invention;

FIG. 4 is a diagram of the energy distribution under the condition of TM polarization with the wavelength of the incident light of 1.55um in the present invention;

FIG. 5 is a graph showing the energy distribution of the present invention under TE polarization with an incident light wavelength of 1.55 um.

In the above drawings, the reference numerals have the following meanings:

100. an SOI substrate layer; 110. A cover layer; 120. A silicon dioxide buried layer;

130. a bottom Si material layer;

200. a waveguide layer; 210. An input waveguide; 220. A TM mode coupling waveguide;

230. a TE mode coupling waveguide;

211. a bottom layer waveguide; 212. And a dielectric cover layer.

Detailed Description

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

Referring to fig. 1 and 2, the present invention provides a polarization beam splitter with an asymmetric three-waveguide structure, including: SO1 substrate layer 100 and waveguide layer 200, wherein,

an SOI substrate layer 100 comprising a bottom Si material layer 130, a silicon dioxide buried layer 120 fabricated above the bottom Si material layer, and a cladding layer 110 overlying the waveguide layer;

a waveguide layer 200 formed above the silicon dioxide buried layer 120, including an input waveguide 210, a TM mode coupling waveguide 220 and a TE mode coupling waveguide 230, wherein the input waveguide 210 includes a bottom waveguide 211 and a dielectric cap layer 212; the waveguide layer 200 separates light of different polarization modes in the input waveguide 210 by confining TE and TM waves to the TE mode coupling waveguide 230 and the TM mode coupling waveguide 220, respectively.

The input waveguide 210, the TM mode coupling waveguide 220, and the TE mode coupling waveguide 230 are asymmetrically distributed and arranged in parallel, and a space is left between the waveguides. The material of the covering layer 110 is air or silicon oxide, and the material of the waveguide layer 200 is silicon or silicon nitride. The thickness of the TE mode coupling waveguide 230 is different from the TM mode coupling waveguide 220 and the underlying waveguide.

In the present embodiment, a silicon nitride cap layer with a certain thickness is epitaxially formed on the silicon dioxide buried layer 120 by pecvd, so as to form the dielectric waveguide 212. The three waveguides of the waveguide layer 200 have different sizes and are arranged in parallel, and the same distance of 200nm is reserved between the different waveguides. The waveguides in the waveguide layer 200 are all single-mode waveguides.

Referring to fig. 3 in combination with fig. 1 and fig. 2, the present invention provides a method for manufacturing a polarization beam splitter with an asymmetric three-waveguide structure, including the following steps:

step 1: by etching or etching, the top silicon layer of the SOI substrate 100 is fabricated into a rectangular strip, and the TM mode coupling waveguide 220, the TE mode coupling waveguide 230, and the bottom waveguide 211 are formed. In the embodiment of the present invention, the thickness of the silicon dioxide buried layer 120 is 3 um. And etching the top silicon layer by adopting photoetching and dry etching methods, wherein the etching depth is 350nm, the waveguide widths are different, the widths of the input waveguide 210, the TM coupling waveguide 220 and the TE mode coupling waveguide are respectively 300nm, 367nm and 390nm, and the waveguide intervals are kept consistent 200nm to form the strip waveguide layer 200.

Step 2: the TE mode coupling waveguide 230 in the waveguide layer 200 is reduced in thickness by reactive ion etching. In the embodiment of the present invention, the photoresist is used as a mask to expose the window of the TE mode coupling waveguide 230, and the TE mode coupling waveguide 230 is reduced to 200nm by reactive ion etching.

And step 3: and depositing a medium on the bottom waveguide 211 by using a plasma enhanced chemical reaction deposition (PECVD) method to form a medium cover layer 212. In the embodiment of the present invention, a silicon nitride dielectric layer 212 with a thickness of 80nm is epitaxially formed on the bottom waveguide 211 by a plasma enhanced chemical reaction deposition (PECVD) method, and the silicon nitride dielectric layer 212 and the bottom waveguide 211 are consistent in length and width.

In the present embodiment, the cover layer 110 uses an air medium.

Fig. 4 is an energy distribution diagram of the incident light with a wavelength of 1.55um and TM polarization, and the TM mode is completely confined in the TM coupling waveguide 220, so that the TM mode is hardly coupled into the TE coupling waveguide, and the residual energy distribution in the input waveguide is also very small. The TM coupling region length is 8.3 um.

Fig. 5 is an energy distribution diagram of the incident light with a wavelength of 1.55um and TE polarization, the TE mode is completely confined in the TE coupling waveguide 220, and thus the TE mode is almost entirely coupled into the TE mode coupling waveguide, and the TM coupling waveguide and the input waveguide have almost no energy distribution. The TM coupling region length is 9.9 um.

In summary, in the polarization beam splitter with an asymmetric three-waveguide structure provided in the embodiment of the present invention, by controlling the sizes of the waveguide layer 200 including the input waveguide 210, the TM coupling waveguide 220, and the TE coupling waveguide 230, and by respectively limiting the TM mode and the TE mode in the TM coupling waveguide 220 and the TE coupling waveguide 230, respective coupling of different polarization states in the input waveguide 210 is achieved, and the influence of the residual mode in the input waveguide 210 on the device performance is eliminated. By designing the polarization beam splitter of the three-waveguide respective coupling type, the extinction ratio of the device can be greatly improved, the working bandwidth of the device is increased, and the length of a coupling area is reduced. The method has the advantages of simple process flow, low manufacturing difficulty, small size, high performance, large working bandwidth and the like.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.