Auxiliary thin layer end coupler

Abstract

The invention provides an auxiliary thin-layer end face coupler, comprising a silicon substrate, a buried oxide layer and a silicon dioxide cladding, wherein the silicon dioxide cladding is provided with: an input section waveguide, comprising a strip central waveguide and a plurality of auxiliary thin-layer waveguides, wherein the cross-sectional shape of each of the auxiliary thin-layer waveguides in a direction perpendicular to the extension direction thereof is a long rectangular strip, and the long side size of each cross-sectional shape of each auxiliary thin-layer waveguide in the extension direction gradually decreases, the long sides of the first end faces of the plurality of auxiliary thin-layer waveguides form a closed square, the second end face of the strip central waveguide and the second end faces of each auxiliary thin-layer waveguide are both located on the inner side of the second end face of the end face coupler, and each auxiliary thin-layer waveguide is spaced from the strip central waveguide by a preset distance; and an output section waveguide, wherein the first end of the output section waveguide is connected to the second end of the strip central waveguide, and the cross-sectional area of ​​the output section waveguide in a direction perpendicular to the extension direction thereof gradually increases along the extension direction.

Description

Technical Field

[0001] The invention relates to the technical field of optoelectronic devices, and in particular to an auxiliary thin-layer end-face coupler. Background Art

[0002] With the rapid development of silicon photonics technology, the use of photonic chips to achieve short-distance optical communication between chips or within chips is becoming increasingly realistic. Silicon-based photonic devices have significant advantages such as compatibility with CMOS (Complementary Metal Oxide Semiconductor) processes, large bandwidth, low latency, low energy consumption, and low crosstalk, and can achieve high-performance, low-cost, small-size, and highly integrated on-chip optical interconnection. There is a large refractive index difference between silicon and silicon dioxide or air, which makes the waveguide made of silicon have a strong ability to restrict the mode distribution of light, and can achieve high integration. The rapid development of optical fiber communication has greatly promoted the development of optoelectronic devices. In optical networks, light transmission is completed through low-loss optical fibers, while optical signal processing is completed by optical devices. Various optical devices must be inserted into optical networks to achieve corresponding functions. Therefore, optical couplers play a key role as a bridge in the entire optoelectronic integrated circuit, which is responsible for transmitting light from optical fibers to the waveguide of the integrated chip.

[0003] However, due to the large difference in mode field diameter between single-mode optical fiber and waveguide, direct coupling usually results in large coupling losses. In addition, traditional beam couplers are highly dependent on wavelength and have low coupling efficiency. Therefore, how to reduce the coupling loss of the coupler and how to reduce the dependence of the beam coupler on wavelength and improve the coupling efficiency are technical issues that need to be solved urgently. Summary of the invention

[0004] In view of this, the present invention provides an auxiliary thin-layer end face coupler to reduce the coupling loss of the coupler, reduce the dependence of the beam coupler on the wavelength, and improve the coupling efficiency.

[0005] According to one aspect of the present invention, the present invention discloses an auxiliary thin-layer end-face coupler, the auxiliary thin-layer end-face coupler comprising a silicon substrate, a buried oxide layer arranged on the silicon substrate, and a silicon dioxide cladding layer located on a side of the buried oxide layer away from the silicon substrate, wherein the silicon dioxide cladding layer is provided with:

[0006] An input section waveguide, wherein the input section waveguide comprises a strip central waveguide and a plurality of auxiliary thin-layer waveguides located outside the strip central waveguide, the strip central waveguide and each of the auxiliary thin-layer waveguides extend from the first end of the end face coupler toward the second end of the end face coupler, the cross-sectional shape of each of the auxiliary thin-layer waveguides in a direction perpendicular to the extension direction thereof is a long rectangular strip, and the long side size of each cross-sectional area of ​​each of the auxiliary thin-layer waveguides in the extension direction gradually decreases, the long sides of the first end faces of the plurality of auxiliary thin-layer waveguides form a closed square, the first end face of the strip central waveguide and the first end faces of each of the auxiliary thin-layer waveguides are both located inside the first end face of the end face coupler, the second end face of the strip central waveguide and the second end face of each of the auxiliary thin-layer waveguides are both located inside the second end face of the end face coupler, and each of the auxiliary thin-layer waveguides is spaced a preset distance from the strip central waveguide;

[0007] An output section waveguide extends from the second end of the strip central waveguide toward the second end of the end face coupler, wherein the first end of the output section waveguide is connected to the second end of the strip central waveguide so that optical coupling can be performed between the output section waveguide and the strip central waveguide, and the cross-sectional area of ​​the output section waveguide perpendicular to its extension direction gradually increases along the extension direction.

[0008] In some embodiments of the present invention, the number of the auxiliary thin-layer waveguides is four, and the long sides of the first end faces of the four auxiliary thin-layer waveguides form a square.

[0009] In some embodiments of the present invention, the distance between each of the auxiliary thin-layer waveguides and the strip-shaped central waveguide gradually decreases along the extending direction of the auxiliary thin-layer waveguides.

[0010] In some embodiments of the present invention, the cross-sectional shape of each auxiliary thin-layer waveguide parallel to its extension direction is an isosceles trapezoid.

[0011] In some embodiments of the present invention, the output section waveguide is an inverted tapered waveguide, and the shape of the first end face of the output section waveguide is a square, and the shape of the second end face of the output section waveguide is a rectangle.

[0012] In some embodiments of the present invention, the length of the strip-shaped central waveguide in the extension direction is equal to the length of each of the auxiliary thin-layer waveguides in the extension direction.

[0013] In some embodiments of the present invention, the ratio of the length of the output section waveguide in the extension direction to the length of the strip-shaped central waveguide in the extension direction is in the range of 1:1 to 1:50.

[0014] In some embodiments of the present invention, the thickness of the silicon substrate is not less than 7 μm, the thickness of the buried oxide layer is in the range of 2 μm to 5 μm, the thickness of the silicon dioxide cladding is in the range of 10 μm to 15 μm, and the widths of the silicon substrate, buried oxide layer and silicon dioxide cladding are all in the range of 25 μm to 35 μm.

[0015] In some embodiments of the present invention, the long side dimension of the first end face of each auxiliary thin layer waveguide ranges from 4μm to 6μm, the long side dimension of the second end face of each auxiliary thin layer waveguide ranges from 0.6μm to 1μm, the thickness of each auxiliary thin layer waveguide is 15nm to 25nm, the cross-sectional shape of the strip central waveguide perpendicular to the extension direction is square, and the cross-sectional side length of the strip central waveguide ranges from 110nm to 130nm, the second end face of the output segment waveguide is rectangular, and the long side dimension of the second end face of the output segment waveguide ranges from 400nm to 500nm, and the short side dimension of the second end face of the output segment waveguide ranges from 110nm to 130nm.

[0016] In some embodiments of the present invention, the first end face of the output section waveguide is completely butted against the second end face of the strip-shaped central waveguide and has the same size.

[0017] The auxiliary thin-layer end face coupler in the embodiment of the present invention has an input section waveguide including a strip central waveguide and a plurality of auxiliary thin-layer waveguides arranged outside the strip central waveguide, and the cross-sectional shape of each auxiliary thin-layer waveguide is a long rectangular strip, and the long sides of the first end faces of the plurality of auxiliary thin-layer waveguides form a closed square. This arrangement can capture a large amount of light energy and form a superimposed mode field on the input end face, thereby improving the mode field overlap efficiency between the single-mode optical fiber and the input face of the end face coupler. In addition, the long side size of each cross section of each auxiliary thin-layer waveguide in the extension direction gradually decreases, so that the light captured by the input end face is smoothly transferred to the strip central waveguide, thereby reducing the coupling loss of the coupler and reducing the dependence of the beam coupler on the wavelength, and improving the coupling efficiency.

[0018] In addition, each auxiliary thin-layer waveguide gradually tilts toward the strip central waveguide in the extension direction, so that each auxiliary thin-layer waveguide located around the strip central waveguide has a certain angle, which is more conducive to light transfer and further improves the light coupling efficiency.

[0019] Additional advantages, purposes, and features of the present invention will be described in part in the following description, and will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present invention. The purposes and other advantages of the present invention may be achieved and obtained by the structures specifically pointed out in the written description, claims, and drawings.

[0020] Those skilled in the art will appreciate that the objectives and advantages that can be achieved with the present invention are not limited to the above specific description, and the above and other objectives that can be achieved by the present invention will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute a limitation of the present invention. The components in the drawings are not drawn to scale, but are only for illustrating the principles of the present invention. In order to facilitate the illustration and description of some parts of the present invention, the corresponding parts in the drawings may be enlarged, that is, they may become larger relative to other components in the exemplary device actually manufactured according to the present invention. In the drawings:

[0022] Figure 1 FIG. 4 is a schematic structural diagram of an auxiliary thin-layer end face coupler according to an embodiment of the present invention.

[0023] Figure 2 for Figure 1 A front view of the auxiliary thin-layer end face coupler is shown.

[0024] Figure 3 for Figure 1 A side view of the auxiliary thin-layer end face coupler is shown.

[0025] Figure 4 for Figure 1 A top view of the auxiliary thin-layer end face coupler is shown.

[0026] Figure 5 This is a simulation diagram of the light field distribution on the first end face of the input section waveguide of the auxiliary thin-layer end face coupler according to an embodiment of the present invention.

[0027] Figure 6 This is a simulation diagram of the light field distribution of the first cross section of the input section waveguide of the auxiliary thin-layer end face coupler according to an embodiment of the present invention.

[0028] Figure 7 This is a simulation diagram of the light field distribution on the second end face of the input section waveguide of the auxiliary thin-layer end face coupler according to an embodiment of the present invention.

[0029] Figure 8 This is a simulation diagram of the light field distribution of the first cross section of the output section waveguide of the auxiliary thin-layer end face coupler according to an embodiment of the present invention.

[0030] Fig. 9 This is a simulation diagram of the light field distribution on the second end face of the output section waveguide of the auxiliary thin-layer end face coupler according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0032] It should be noted here that in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0033] It should be emphasized that the terms “include / comprises / has” when used herein refer to the presence of features, elements, steps or components, but do not exclude the presence or addition of one or more other features, elements, steps or components.

[0034] It should also be noted that the directional nouns in this specification are relative to the position directions shown in the drawings; if there is no special explanation, the term "connection" in this article can refer to not only direct connection, but also indirect connection with an intermediate. Direct connection means that two parts are connected without the help of an intermediate part, and indirect connection means that two parts are connected with the help of other parts.

[0035] Since the commonly used end face couplers have the problems of large coupling loss and high dependence of the beam coupler on wavelength, in order to solve the above problems and improve the coupling efficiency of the end face coupler, the inventor has studied an auxiliary thin-layer end face coupler, which is based on the SOI platform and divides the waveguide into an input section waveguide and an output section waveguide along the light propagation direction. The input section waveguide can be composed of a strip center waveguide and a plurality of auxiliary thin-layer waveguides, and the first end of the output section waveguide is connected to the second end of the strip center waveguide. By performing special structural design on the strip center waveguide, the plurality of auxiliary thin-layer waveguides and the output section waveguide, the auxiliary thin-layer end face coupler reduces the coupling loss, reduces the dependence of the beam coupler on wavelength and improves the coupling efficiency.

[0036] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals represent the same or similar components.

[0037] Figure 1 FIG. 1 is a schematic structural diagram of an auxiliary thin-layer end-face coupler according to an embodiment of the present invention. Figure 1As shown, the auxiliary thin-layer end-face coupler includes a silicon substrate 100, a buried oxide layer 200, and a silicon dioxide cladding layer 300, wherein the buried oxide layer 200 is disposed on the silicon substrate 100, and the silicon dioxide cladding layer 300 is disposed on the buried oxide layer 200, and the silicon dioxide cladding layer 300 is specifically located on the side of the buried oxide layer 200 away from the silicon substrate 100. In other words, the silicon substrate 100, the buried oxide layer 200, and the silicon dioxide cladding layer 300 are sequentially disposed from bottom to top, and the overall shapes of the silicon substrate 100, the buried oxide layer 200, and the silicon dioxide cladding layer 300 are all rectangular. The silicon substrate 100, as the substrate 100 of the SOI platform, is made of silicon, the buried oxide layer 200 is made of silicon dioxide, and the silicon dioxide cladding layer 300 is also made of silicon dioxide. It should be understood that the overall shape of the silicon substrate 100 , the buried oxide layer 200 and the silicon dioxide cladding layer 300 is set to be a rectangular parallelepiped, which is only a preferred example. In other application scenarios, they can also be set to other shapes according to actual needs.

[0038] An input section waveguide and an output section waveguide 321 are arranged in the silica cladding 300. The input section waveguide is specifically located at the input section of the end face coupler, and the output section waveguide 321 is located at the output section of the end face coupler. The input section waveguide includes a strip center waveguide 311 and a plurality of auxiliary thin layer waveguides 312. The plurality of auxiliary thin layer waveguides 312 are all arranged at the periphery of the strip center waveguide 311, that is, the plurality of auxiliary thin layer waveguides 312 are circumferentially arranged at the circumferential outer side of the strip center waveguide 311. Specifically, the strip center waveguide 311 extends from the first end of the end face coupler toward the second end of the end face coupler, wherein the first end of the end face coupler can be understood as Figure 2 and Figure 4 The left end of the end coupler shown in FIG. 1 is the left end of the end coupler, and the second end of the end coupler can be understood as Figure 2 and Figure 4 The right end of the end coupler in the embodiment, that is, the strip center waveguide 311 extends from the left end to the right end of the end coupler, wherein the strip center waveguide 311 can extend horizontally to the right or can extend obliquely to the right during the extension. Similarly, the auxiliary thin layer waveguide 312 located at the periphery of the strip center waveguide also extends from the first end of the end coupler to the second end of the end coupler, and similar to the strip center waveguide 311, during the extension process, the auxiliary thin layer waveguide 312 can also extend horizontally to the right or can extend obliquely to the right.

[0039] The cross-sectional shape of each auxiliary thin-layer waveguide 312 in the direction perpendicular to its extension is a long rectangular strip, wherein the cross-sectional shape in the direction perpendicular to its extension can be understood as Figure 3The projection shape on the side view of the auxiliary thin-layer end face coupler shown in FIG. In addition, the long side size of each cross section of each auxiliary thin-layer waveguide 312 in the extension direction gradually decreases, that is, each auxiliary thin-layer waveguide 312 can be regarded as a prism-shaped structure as a whole, that is, the top surface of the prism serves as the second end face of the auxiliary thin-layer waveguide 312, and the bottom surface of the prism serves as the first end face of the auxiliary thin-layer waveguide 312; since each cross section of each auxiliary thin-layer waveguide 312 in the extension direction is a long rectangular strip, the short side size of each cross section of each auxiliary thin-layer waveguide 312 in the extension direction can be equal, wherein the equal short side size of each cross section can also be understood as the equal thickness of the auxiliary thin-layer waveguide 312 from left to right. The long sides of the first end faces of the multiple auxiliary thin layer waveguides 312 are further enclosed into a closed square, that is, two adjacent auxiliary thin layer waveguides 312 are connected on the first end faces. At this time, the multiple auxiliary thin layer waveguides 312 are connected end to end on the first end faces. In order to make the long sides of the first end faces of the multiple auxiliary thin layer waveguides 312 connected end to end, the cross-sectional shape of the auxiliary thin layer waveguides 312 located on the front and rear sides of the strip-shaped central waveguide is a vertical long rectangular strip, and the cross-sectional shape of the auxiliary thin layer waveguides 312 located on the upper and lower sides of the strip-shaped central waveguide is a horizontal long rectangular strip.

[0040] Furthermore, the first end face of the strip central waveguide 311 and the first end face of each auxiliary thin-layer waveguide 312 are both located on the inner side of the first end face of the end face coupler, that is, at this time, there is a certain distance between the first end face of the strip central waveguide 311 and the first end face of each auxiliary thin-layer waveguide 312 and the first end face of the end face coupler. This arrangement not only protects the waveguide in the end face coupler from impact damage, but also reduces the power attenuation of light in a confined space. The second end face of the strip central waveguide 311 and the second end faces of each auxiliary thin-layer waveguide 312 are both located on the inner side of the second end face of the end coupler, which can also be understood as the length of the strip central waveguide 311 and the length of the auxiliary thin-layer waveguide 312 are both smaller than the total length of the end coupler. At this time, there is also a certain distance between the second end face of the strip central waveguide 311 and the second end face of the auxiliary thin-layer waveguide 312 and the second end face of the end coupler. This setting is to ensure the effective coordination between the output section waveguide 321 and the strip central waveguide 311, thereby realizing effective coupling of light. In addition, each auxiliary thin-layer waveguide 312 is spaced from the strip central waveguide 311 by a preset distance, and the specific distance value can be limited according to actual needs, and the distances between the multiple auxiliary thin-layer waveguides 312 and the strip central waveguide 311 can be equal or unequal. When the distances between the multiple auxiliary thin-layer waveguides 312 and the strip central waveguide 311 are equal, the center line of the strip central waveguide is the symmetry center line or rotation axis of the multiple auxiliary thin-layer waveguides 312.

[0041] The output section waveguide 321 extends from the second end of the strip center waveguide 311 toward the second end of the end face coupler, and the first end of the output section waveguide 321 is connected to the second end of the strip center waveguide 311, so that the output section waveguide 321 and the strip center waveguide 311 can be optically coupled, and the cross-sectional area of ​​the output section waveguide 321 perpendicular to its extension direction gradually increases along the extension direction. Among them, the cross-sectional area of ​​the output section waveguide 321 perpendicular to its extension direction is similar to that of the input section waveguide, and is also Figure 3 The cross-sectional area gradually increases along the extension direction, that is, the output section waveguide 321 gradually expands from left to right; this setting is to achieve adiabatic transmission more efficiently.

[0042] In this embodiment, a plurality of auxiliary thin-layer waveguides 312 are arranged on the periphery of the strip central waveguide. The existence of the auxiliary thin-layer waveguides 312 can greatly increase the capture area of ​​light energy. In addition, the long sides of the first end faces of the plurality of auxiliary thin-layer waveguides 312 at the input end of the end face coupler form a closed square. The closed square can increase the mode field overlap efficiency with the single-mode optical fiber. Thus, along the light propagation direction, the arrangement of the auxiliary thin-layer waveguides 312 can gradually transfer the mode field of light to the strip central waveguide 311 without causing excessive loss, thereby improving the mode transmission efficiency.

[0043] In one embodiment of the present invention, the number of the auxiliary thin layer waveguides 312 is four, and the long sides of the first end faces of the four auxiliary thin layer waveguides 312 form a square. In this case, the four auxiliary thin layer waveguides 312 have the same shape and size, and the distances of each auxiliary thin layer waveguide 312 from the center line of the strip central waveguide can also be equal. The four auxiliary thin layer waveguides 312 are respectively located on the upper and lower front and back sides of the strip central waveguide, and the side length of the square formed by the four auxiliary thin layer waveguides 312 on the first end faces is the length of the long side of the first end face of each auxiliary thin layer waveguide 312. Specifically, the two auxiliary thin layer waveguides 312 located on the front and back sides of the strip central waveguide 311 are vertically arranged, and the two auxiliary thin layer waveguides 312 located on the upper and lower sides of the strip central waveguide 311 are horizontally arranged. It should be understood that the strip central waveguide is arranged in the middle of the area surrounded by the four auxiliary thin-layer waveguides 312 so that the light captured by the four auxiliary thin-layer waveguides 312 is uniformly transmitted to the strip central waveguide 311. Therefore, in some other examples, the strip central waveguide 311 may not be limited to the center position of the area surrounded by the four auxiliary thin-layer waveguides 312, that is, at this time, the distances between the four auxiliary thin-layer waveguides 312 and the strip central waveguide are not completely equal.

[0044] Furthermore, the distance between each auxiliary thin layer waveguide 312 and the strip center waveguide gradually decreases along the extension direction of the auxiliary thin layer waveguide 312. If it is assumed that the strip center waveguide extends horizontally to the right, then the auxiliary thin layer waveguide 312 extends horizontally from left to right and gradually approaches the strip center waveguide. Exemplarily, if the overall shape of the strip center waveguide 311 is a rectangular parallelepiped, then each auxiliary thin layer waveguide 312 is inclined with the side surface of the corresponding strip center waveguide 311; it is not difficult to understand that when the strip center waveguide and each auxiliary thin layer waveguide 312 extend horizontally to the right, each auxiliary thin layer waveguide 312 is parallel to the side surface of the corresponding strip center waveguide 311, and the distance between the auxiliary thin layer waveguide 312 and the strip center waveguide at different positions is equal. In this embodiment, along the extension direction of the auxiliary thin layer waveguide 312, the auxiliary thin layer waveguide 312 gradually tilts toward the strip central waveguide 311 while extending to the right, so that the auxiliary thin layer waveguides 312 around the strip central waveguide 311 each have a certain tilt angle, which is more conducive to the transfer of light.

[0045] Since the long side size of each cross section of the auxiliary thin layer waveguide 312 in the extension direction gradually decreases, and since the cross section of the auxiliary thin layer waveguide 312 perpendicular to its extension direction is a long rectangular strip, the overall shape of each auxiliary thin layer waveguide 312 can be regarded as a quadrangular pyramid structure, and the bottom surface of the pyramid serves as the first end surface of the auxiliary thin layer waveguide 312, and the top surface of the pyramid serves as the second end surface of the auxiliary thin layer waveguide 312. Preferably, the cross section of each auxiliary thin layer waveguide 312 parallel to its extension direction is an isosceles trapezoid, and the cross section parallel to its extension direction refers to the auxiliary thin layer waveguides located on the upper and lower sides of the strip-shaped central waveguide in the top view direction (see Appendix 1 of the specification). Figure 4 ) and the projection of the auxiliary thin-layer waveguides on the front and rear sides of the strip-shaped central waveguide in the normal viewing direction (see the manual). Figure 2 ), so the prism-shaped auxiliary thin-layer waveguide 312 is an isosceles trapezoidal prism. It should be understood that considering the auxiliary thin-layer waveguide 312 as an isosceles trapezoidal prism is a preferred example, and it can also be set to other shapes according to specific application occasions, for example, the cross-sectional shape of the auxiliary thin-layer waveguide 312 parallel to its extension direction can also be an irregular trapezoidal shape.

[0046] In one embodiment of the present invention, the output section waveguide 321 is an inverted tapered waveguide, and the first end face shape of the output section waveguide 321 is a square, and the second end face shape is a rectangle. Since the cross-sectional area of ​​the output section waveguide 321 perpendicular to its extension direction gradually increases along the extension direction, the second end face area of ​​the output section waveguide 321 is greater than the first end face area. Exemplarily, the thickness of the output section waveguide 321 at each position can be consistent, but its width gradually increases from left to right; wherein, the thickness of the output section waveguide 321 refers to its Figure 3 The height dimension in the output section waveguide 321 refers to its width in Figure 3 In addition to the above, the width and thickness of the output section waveguide 321 may also gradually increase as it extends from left to right. In this case, the output section waveguide 321 may be in the shape of a right prism as a whole, and the first end face of the output section waveguide 321 is the top face of the right prism, while the second end face of the output section waveguide 321 is the bottom face of the right prism. The output section waveguide 321 is defined as having a cross-sectional area that gradually increases along the extension direction in order to further adiabatically and efficiently couple the light from the input section waveguide to the chip waveguide at the output end.

[0047] Further, the length of the strip-shaped central waveguide 311 in the extension direction is equal to the length of each auxiliary thin-layer waveguide 312 in the extension direction. The length of the strip-shaped central waveguide 311 and the auxiliary thin-layer waveguide 312 in the extension direction is Figure 2 and Figure 4 The purpose of this limitation is to further ensure that the light captured by the input end of the end coupler is smoothly transferred to the strip center waveguide 311, thereby further improving the coupling efficiency between the strip center waveguide 311 and the output section waveguide 321. It should be understood that setting the lengths of the strip center waveguide 311 and the auxiliary thin layer waveguide 312 to be equal is only a preferred example. In other cases, other structures can also be defined according to actual requirements, such as the length of the strip center waveguide 311 is slightly shorter or longer than the length of the auxiliary thin layer waveguide 312.

[0048] Further, the ratio of the length of the output section waveguide 321 in the extension direction to the length of the strip center waveguide 311 in the extension direction can be set in the range of 1:1 to 1:50. Specifically, the length of the output section waveguide 321 is equal to or greater than the length of the strip center waveguide 311. When the strip center waveguide and the auxiliary thin layer waveguide 312 are equal in length, the length of the output section waveguide 321 must also be at least equal to the length of the auxiliary thin layer waveguide 312. Exemplarily, the length of the strip center waveguide can be 20 μm, and the corresponding length of the output section waveguide 321 can be 20 μm, 100 μm, 1000 μm, etc.

[0049] In the auxiliary thin-layer end face coupler in the above embodiment, it is specifically composed of an SOI platform and a coupling structure, the SOI platform includes an SOI substrate 100, a buried oxide layer 200 and a silicon dioxide cladding layer 300, and the coupling structure includes an input section waveguide and an output section waveguide 321 located in the silicon dioxide cladding layer 300. Among them, the thickness of the silicon substrate 100 is not less than 7 μm, the thickness of the buried oxide layer 200 is in the range of 2 μm to 5 μm, the thickness of the silicon dioxide cladding layer 300 is in the range of 10 μm to 15 μm, and the width of the silicon substrate 100, the buried oxide layer 200 and the silicon dioxide cladding layer 300 are all in the range of 25 μm to 35 μm. Exemplarily, the overall shape of the silicon substrate 100, the buried oxide layer 200 and the silicon dioxide cladding 300 can all be a rectangular parallelepiped, and the thickness of the silicon substrate 100 is 7 μm, the thickness of the buried oxide layer 200 is 3 μm, the thickness of the silicon dioxide cladding 300 is 12 μm, and the width of the silicon substrate 100, the buried oxide layer 200 and the silicon dioxide cladding 300 are all 30 μm.

[0050] Furthermore, the long side dimension range of the first end face of each auxiliary thin layer waveguide 312 can be 4μm to 6μm, the long side dimension range of the second end face of each auxiliary thin layer waveguide 312 can be 0.6μm to 1μm, the thickness of each auxiliary thin layer waveguide 312 can be 15nm to 25nm, the cross-sectional shape of the strip central waveguide 311 perpendicular to the extension direction can be square, and the cross-sectional side length range of the strip central waveguide 311 can be 110nm to 130nm, the second end face shape of the output section waveguide 321 is rectangular, and the long side dimension range of the second end face of the output section waveguide 321 can be 400nm to 500nm, and the short side dimension range of the second end face of the output section waveguide 321 can be 110nm to 130nm.

[0051] In a specific implementation, the length of the input section waveguide of the end face coupler is 20 μm, and the length of the output section is 980 μm; the auxiliary thin layer located around the strip central waveguide 311 is composed of four completely identical conical auxiliary thin layer waveguides 312, and the first end face width (the long side dimension of the first end face) of each auxiliary thin layer waveguide 312 is 5 μm, the thickness is 20 nm, the second end face width (the long side dimension of the second end face) is 0.8 μm, and the thickness is also 20 nm; the strip central waveguide 311 is a rectangular parallelepiped structure as a whole, and the width and thickness of its end face are both 120 nm; the four auxiliary thin layer waveguides 312 form a closed square on the first end face, and the geometric center line of each auxiliary thin layer waveguide 312 is 2.5 μm away from the center line of the strip central waveguide. The first end face of the output section waveguide 321 is completely butted against the second end face of the strip center waveguide 311 and has the same size, that is, the output section waveguide 321 and the strip center waveguide 311 are seamlessly butted against each other at the joint, that is, the size of the first end face of the output section waveguide 321 is the same as the size of the second end face of the strip center waveguide 311, and the width of the second end face of the output section waveguide 321 (the long side size of the second end face) is 450nm, and the thickness (the short side size of the second end face) is 120nm. In addition, in order to further protect the coupling structure from damage and further reduce the power attenuation of light in a confined space, a gap distance of 1μm to 3μm is spaced between the first end face of the input section waveguide and the first end face of the end face coupler.

[0052] Furthermore, the substrate 100 of the SOI platform is silicon with a refractive index of 3.48, the material of the buried oxide layer 200 and the silicon dioxide cladding 300 is silicon dioxide with a refractive index of 1.44; the material of the auxiliary thin layer waveguide 312 is silicon nitride, whose refractive index is 2.016 at a wavelength of 1550nm, and the material of the strip center waveguide 311 and the output segment waveguide 321 is also silicon with a refractive index of 3.48.

[0053] By using the auxiliary thin-layer end face coupler in the above embodiment for simulation, it is obtained Figures 5 to 9 The simulation results shown are Figure 5 This is a simulation diagram of the light field distribution on the first end face of the input section waveguide of the end face coupler. Figure 6 This is a simulation diagram of the light field distribution of the first cross section of the input waveguide of the end coupler. Figure 7 This is a simulation diagram of the light field distribution on the second end face of the input section waveguide of the end face coupler. Figure 8 is a light field distribution simulation diagram of the first cross section of the output section waveguide 321 of the end face coupler, Fig. 9The figure is a simulation diagram of the light field distribution of the second end face of the output section waveguide 321 of the end face coupler. The first cross section of the input section waveguide is the cross section between the first end face and the second end face of the input section waveguide, and the first cross section of the output section waveguide 321 is the cross section between the first end face and the second end face of the output section waveguide 321. In addition, it is known in the simulation process that the light from the single-mode optical fiber is first captured by the input end of the end face coupler and is gradually transferred to the strip center waveguide 311, and finally the inverted tapered silicon waveguide of the output section completes the adiabatic transmission; after calculation, it is obtained that the mode overlap efficiency of the end face coupler is 93.9%, the mode transmission efficiency is 98.6%, and the overall coupling efficiency is the product of the two parameters, that is, about 92.6%; in addition, according to the simulation results, it is also obtained that the end face coupler of this structure has the characteristic of being insensitive to wavelength.

[0054] Through the above embodiments, it can be found that the auxiliary thin-layer end face coupler of the present invention combines multiple auxiliary thin-layer waveguides with a strip central waveguide to enable the end face coupler to capture a large amount of light energy and form a superimposed mode field on the input end face, thereby improving the mode field overlap efficiency between the single-mode optical fiber and the input end face of the end face coupler, and smoothly transferring the light captured by the input end face to the strip central waveguide, thereby reducing the coupling loss of the coupler, reducing the dependence of the beam coupler on the wavelength and improving the coupling efficiency of the end face coupler.

[0055] In the present invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with features of other embodiments or replace features of other embodiments.

[0056] The above-listed embodiments show and describe the basic principles and main features of the present invention, but the present invention is not limited to the above-mentioned embodiments. Any modifications, equivalent changes and modifications made to the present invention by those skilled in the art without making any creative work should fall within the scope of protection of the technical solution of the present invention.

Claims

1. An auxiliary thin-layer end face coupler, characterized in that: The auxiliary thin-layer end face coupler comprises a silicon substrate, a buried oxide layer disposed on the silicon substrate, and a silicon dioxide cladding layer located on a side of the buried oxide layer away from the silicon substrate, wherein the silicon dioxide cladding layer is provided with: An input section waveguide, wherein the input section waveguide comprises a strip central waveguide and a plurality of auxiliary thin-layer waveguides arranged on the periphery of the strip central waveguide, the strip central waveguide and each of the auxiliary thin-layer waveguides extend from the first end of the end face coupler toward the second end of the end face coupler, the cross-sectional shape of each of the auxiliary thin-layer waveguides in a direction perpendicular to the extension direction thereof is a long rectangular strip, and the long side size of each cross-sectional shape of each of the auxiliary thin-layer waveguides in the extension direction gradually decreases, the long sides of the first end faces of the plurality of auxiliary thin-layer waveguides form a closed square, the first end face of the strip central waveguide and the first end faces of each of the auxiliary thin-layer waveguides are both located inside the first end face of the end face coupler, the second end face of the strip central waveguide and the second end faces of each of the auxiliary thin-layer waveguides are both located inside the second end face of the end face coupler, and each of the auxiliary thin-layer waveguides is spaced a preset distance from the strip central waveguide; an output section waveguide extending from the second end of the strip central waveguide toward the second end of the end face coupler, wherein the first end of the output section waveguide is connected to the second end of the strip central waveguide so that optical coupling can be performed between the output section waveguide and the strip central waveguide, and the cross-sectional area of ​​the output section waveguide perpendicular to the extension direction thereof gradually increases along the extension direction; The number of the auxiliary thin-layer waveguides is four, and the long sides of the first end faces of the four auxiliary thin-layer waveguides form a square; The distance between each of the auxiliary thin-layer waveguides and the strip-shaped central waveguide gradually decreases along the extension direction of the auxiliary thin-layer waveguide; The cross-sectional shape of each auxiliary thin-layer waveguide parallel to its extension direction is an isosceles trapezoid; The output section waveguide is an inverted tapered waveguide, and the shape of the first end face of the output section waveguide is a square, and the shape of the second end face of the output section waveguide is a rectangle.

2. The auxiliary thin-layer end face coupler according to claim 1, characterized in that: The length of the strip-shaped central waveguide in the extending direction is equal to the length of each of the auxiliary thin-layer waveguides in the extending direction.

3. The auxiliary thin-layer end face coupler according to claim 2, characterized in that: The ratio of the length of the output section waveguide in the extension direction to the length of the strip-shaped central waveguide in the extension direction is in the range of 1:1 to 1:

50.

4. The auxiliary thin-layer end face coupler according to any one of claims 1 to 3, characterized in that: The thickness of the silicon substrate is not less than 7 μm, the thickness of the buried oxide layer is in the range of 2 μm to 5 μm, the thickness of the silicon dioxide cladding is in the range of 10 μm to 15 μm, and the widths of the silicon substrate, buried oxide layer and silicon dioxide cladding are all in the range of 25 μm to 35 μm.

5. The auxiliary thin-layer end face coupler according to claim 4, characterized in that: The long side dimension range of the first end face of each auxiliary thin layer waveguide is 4μm~6μm, the long side dimension range of the second end face of each auxiliary thin layer waveguide is 0.6μm~1μm, the thickness of each auxiliary thin layer waveguide is 15nm~25nm, the cross-sectional shape of the strip central waveguide perpendicular to the extension direction is square, and the cross-sectional side length range of the strip central waveguide is 110nm~130nm, the second end face shape of the output segment waveguide is rectangular, and the long side dimension range of the second end face of the output segment waveguide is 400nm~500nm, and the short side dimension range of the second end face of the output segment waveguide is 110nm~130nm.

6. The auxiliary thin-layer end face coupler according to claim 1, characterized in that: The first end face of the output section waveguide is completely butted against the second end face of the strip-shaped central waveguide and has the same size.

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