A double-layer adiabatic converter for conversion between TE4 mode and TE6 mode

Abstract

The present invention belongs to the field of integrated optoelectronic technology, and specifically relates to a double-layer adiabatic converter for converting between TE4 mode and TE6 mode. The double-layer adiabatic mode converter proposed in the present invention realizes the design of an ultra-compact device, which can be used for cascading between different functional units in a photonic integrated chip, thereby achieving the design goal of higher integration in the photonic integrated chip. The present invention aims to realize the conversion and transmission between the fourth-order mode and the sixth-order mode under the same TE polarization mode, and obtain a double-layer adiabatic mode converter with small size and low loss. The present invention is a miniaturized design of a double-layer adiabatic mode converter, which realizes high-efficiency (low-loss) conversion between the TE4 mode and the TE6 mode with the shortest possible length.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated optoelectronics, and in particular relates to a double-layer adiabatic converter for converting between a TE4 mode and a TE6 mode. Background Art

[0002] Photonic integrated chips are core components of modern optical communication devices. They can integrate multiple photonic chips onto a single chip, enabling the integration and coordination of multiple functions. Silicon photonic optical power couplers, based on a high-refractive-index-contrast silicon-on-insulator (SOI) platform, are ideal candidates for large-scale photonic integration in future large-scale photonic integrated chips. This is demonstrated in the paper K. Solehmainen, M. Kapulainen, M. Harjanne, and T. Aalto, “Adiabatic and Multimode Interference Couplers on Silicon-on-Insulator,” IEEE Photon. Technol. Lett., vol. 18, no. 21, pp. 2287-2289, Nov. 2006.

[0003] Adiabatic mode converters in optical waveguides are essential components of photonic integrated circuits, often used for mode conversion between different modes to improve coupling efficiency between two different cross-sections (e.g., planar optical waveguides and single-mode or optical fibers). To achieve mode conversion between different cross-sections, the most common approach is a conventional lateral adiabatic mode converter, where the waveguide width varies while the etching depth remains constant. This type of adiabatic mode converter has been extensively studied. However, the so-called "double-layer" adiabatic mode converter, which includes two layers of lateral variations and requires a double-layer etching process, has been less widely reported. Double-layer adiabatic mode converters are used to connect two sections with different etching depths, for example, from a shallow-etched ridge waveguide to a deep-etched ridge waveguide. This is demonstrated in the paper D. Dai, Y. Tang, and J. E. Bowers, "Mode conversion in tapered submicron silicon ridge optical waveguides," Opt. Express, vol. 20, no. 12, pp. 13425-13439, May 2012. However, the "double-layer" adiabatic mode converter described in this study only achieves conversion between the TM0 and TE1 modes, not between other modes. Furthermore, no other documentation has been found of a "double-layer" adiabatic mode converter that can achieve conversion between the TE4 and TE6 modes. Furthermore, generally speaking, conversion between different orders of the same TE / TM polarization is much more difficult and challenging to achieve than conversion between TE and TM polarizations. Summary of the Invention

[0004] The purpose of the present invention is to provide a double-layer adiabatic converter for converting between TE4 mode and TE6 mode, aiming to realize the conversion transmission between the fourth-order mode and the sixth-order mode under the same TE polarization mode, and obtain a double-layer adiabatic mode converter with small size and low loss.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0006] A double-layer adiabatic converter for converting between TE4 mode and TE6 mode, comprising a first silicon core, a second silicon core and a cladding; the first silicon core is arranged below the second silicon core; cladding is arranged around the first silicon core and the second silicon core; the refractive index of the first silicon core and the second silicon core is n Si =3.455; the thickness of the second silicon core is h2 = 200nm, and the width is W = 1μm; the thickness of the first silicon core is h1 = 200nm, and the width is w = 2W side +W, where W sideis the side rib width; the wavelength of the incident light beam is set to 1.55 μm; along the propagation direction of the light beam, the first silicon core includes an input end, a first double-layer adiabatic mode converter, a second double-layer adiabatic mode converter and an output end connected in sequence; the first double-layer adiabatic mode converter converts the TE6 mode into the TM1 mode, and the input end side rib width W of the first double-layer adiabatic mode converter is side >2.80μm; output-side rib width W of the first double-layer adiabatic mode converter side <2.80μm; the second double-layer adiabatic mode converter converts the TM1 mode into the TE4 mode; the input-side rib width W of the second double-layer adiabatic mode converter side >1.75μm; width W of the output-side rib of the second double-layer adiabatic mode converter side <1.75μm.

[0007] As a further preferred technical solution of the present invention, the material of the cladding is SiO2, with a refractive index n SiO2 =1.445, width is W0, thickness is h0.

[0008] As a further preferred technical solution of the present invention, the input end and the output end are both parallel plate waveguides; the widths of both ends of the input end are w I =w1=8.2μm; the widths of the two ends of the output end are w O =w3=3.8μm.

[0009] As a further preferred technical solution of the present invention, the width of the side ribs at the input end of the first double-layer adiabatic mode converter is set to W side =3.6μm, the side rib width at the output end is set to W side = 2.4 μm; the width of the first double-layer adiabatic mode converter input is w1 = 2W side +W=8.2μm, the width of the output end is w2=2W side +W=5.8μm; the side rib width at the input end of the second double-layer adiabatic mode converter is set to W side =2.4μm, side rib width W at the output end side =1.4μm; the width of the second double-layer adiabatic mode converter input is w2 = 2W side +W=5.8μm, the width of the output end is w3=2W side +W=3.8 μm.

[0010] As a further preferred technical solution of the present invention, along the propagation direction of the light beam, the first double-layer adiabatic mode converter includes a first segment to a twelfth segment connected in sequence, the first segment is connected in a linear manner, and the initial end waveguide width and the terminal end width are w respectively. a =8.20μm and wb =8.00μm, length L1 = 34.244μm; the second segment is connected in a linear manner, and the initial end waveguide width and the end end width are w b =8.00μm and w c =7.80μm, length L2 = 34.455μm; the third segment is connected in a linear manner, and the initial end waveguide width and the end end width are w c =7.80μm and w d =7.60μm, length L3 = 34.72μm; the fourth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w d =7.60μm and w e =7.40μm, length L4 = 34.967μm; the fifth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w e =7.40μm and w f =7.20μm, length L5 = 35.083μm; the sixth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w f =7.20μm and w g =7.00μm, length L6 = 34.934μm; the seventh segment is connected in a linear manner, and the initial end waveguide width and the end end width are w g =7.00μm and w h =6.80μm, length L7 = 34.391μm; the eighth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w h =6.80μm and w i =6.60μm, length L8 = 33.386μm; the ninth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w i =6.60μm and w j =6.40μm, length L9 = 31.945μm; the tenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w j =6.40μm and w k =6.20μm, length L 10 =30.20 μm; the eleventh segment is connected in a linear manner with a width of w k =6.20μm and w l =6.00μm, length L 11 =28.356μm; the twelfth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w l =6.00μm and w m =5.80μm, length L 12=26.638μm;

[0011] Along the beam propagation direction, the second double-layer adiabatic mode converter includes the thirteenth to nineteenth segments connected in sequence, the thirteenth segment is connected in a linear manner, and the initial end waveguide width and the terminal end width are w respectively. m =5.80μm and w n =5.40μm, length L 13 =34.339μm; the fourteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w n =5.40μm and w p =5.10μm, length L 14 =31.724μm; the fifteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w p =5.10μm and w q =4.80μm, length L 15 =32.21μm; the sixteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w q =4.80μm and w u =4.50μm, length L 16 =31.63μm; the seventeenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w u =4.50μm and w v =4.24μm, length L 17 =28.490μm; the eighteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w v =4.24μm and w x =4.00μm, length L 18 =25.048μm; the nineteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w x =4.00μm and w y =3.80μm, length L 19 =20.715μm.

[0012] Further, as a preferred technical solution of the present invention, W0=9μm; h0=1250nm.

[0013] The double-layer adiabatic converter for converting between TE4 mode and TE6 mode described in the present invention has the following technical effects compared with the prior art by adopting the above technical solution:

[0014] (1) The present invention realizes the miniaturization design of the "double-layer" adiabatic mode converter, and achieves high-efficiency (low-loss) conversion between TE4 mode and TE6 mode with the shortest possible length.

[0015] (2) The double-layer adiabatic mode converter proposed in the present invention realizes the design of an ultra-compact device, which can be used for cascading between different functional units in a photonic integrated chip, thereby achieving the design goal of higher integration in the photonic integrated chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the input cross section of the double-layer adiabatic mode converter of the present invention;

[0017] Figure 2 Schematic diagram of the linear connection structure of the double-layer adiabatic mode converter of the present invention;

[0018] Figure 3 The width W of each mode in the double-layer adiabatic mode converter of the present invention is different from the width W of the side ribs. side Schematic diagram of the effective refractive index under ;

[0019] Figure 4 This is a schematic diagram of the connection of the first silicon core of the double-layer adiabatic mode converter of the present invention;

[0020] Figure 5 Schematic diagram of the mode conversion efficiency curve of the present invention;

[0021] The figures are marked as follows: 1. first silicon core; 2. second silicon core; 3. cladding; 4. input end; 5. first double-layer adiabatic mode converter; 6. second double-layer adiabatic mode converter; 7. output end. DETAILED DESCRIPTION

[0022] The present invention will be further explained below in detail with reference to the accompanying drawings so that those skilled in the art can have a deeper understanding of the present invention and be able to implement it. However, the following reference examples are only used to explain the present invention and are not intended to limit the present invention.

[0023] like Figure 1 As shown, a double-layer adiabatic converter for converting between TE4 mode and TE6 mode includes a first silicon core 1, a second silicon core 2 and a cladding 3; the first silicon core 1 is arranged below the second silicon core 2; the cladding 3 is arranged around the first silicon core 1 and the second silicon core 2; the refractive index of the first silicon core 1 and the second silicon core 2 is n Si =3.455; the thickness of the second silicon core 2 is h2 = 200nm, and the width is W = 1μm; the thickness of the first silicon core 1 is h1 = 200nm, and the width is w = 2W side +W, where W sideis the side rib width; the incident beam wavelength is set to 1.55μm; along the beam propagation direction, the first silicon core 1 includes an input end 4, a first double-layer adiabatic mode converter 5, a second double-layer adiabatic mode converter 6 and an output end 7 connected in sequence. The material of the cladding 3 is SiO2 with a refractive index n SiO2 =1.445, width W0, and thickness h0. In this embodiment, W0=9 μm and h0=1250 nm respectively.

[0024] like Figure 2 As shown, the connection method of the first silicon core 1 and the second silicon core 2 with varying widths. If the side rib width is uncertain, the conversion between the specified modes cannot be achieved. For example, in Dai, Y. Tang, and J. E. Bowers, “Mode conversion in tapered submicron silicon ridge optical waveguides,” Opt. Express, vol. 20, no. 12, pp. 13425-13439, May 2012, the width of the input side rib needs to be determined as W. side =3μm, output side rib width W side The conversion between TM0 mode and TE1 mode can only be realized when 0 is 0. The conversion between TE4 mode and TE6 mode is not realized in this document. Other documents also do not see the conversion between TE4 mode and TE6 mode in a double-layer adiabatic mode converter.

[0025] To achieve the conversion between TE4 mode and TE6 mode in a "double-layer" adiabatic mode converter, the first step is to obtain the different modes at different side rib widths W through simulation. side The effective refractive index under Figure 3 As shown in the figure, it can be seen that the side rib width W side = 1.75 μm, there is a first mixed region of TE4 mode and TM1 mode (as shown by the first black dotted circle in the figure), and the side rib width W side = 2.80 μm, there is a second mixed region of TM1 mode and TE6 mode (as indicated by the second black dotted circle in the figure). Therefore, the present invention uses TM1 as a transition mode to achieve the conversion between TE4 mode and TE6 mode.

[0026] like Figure 3 As shown, TM1 is used as a transition mode to realize the conversion transmission between TE4 mode and TE6 mode, and the side rib width W side Change from wide to narrow:

[0027] First, the TE6 mode is converted into the TM1 mode by the first double-layer adiabatic mode converter 5. The input-side rib width W of the first double-layer adiabatic mode converter 5 is side Need to stay away from the second mixing area, that is, satisfy: W side >2.80 μm, the output-side rib width W of the first double-layer adiabatic mode converter 5 side Need to stay away from the second mixing area, that is, satisfy: W side <2.80μm;

[0028] Secondly, the TM1 mode is converted into the TE4 mode by the second double-layer adiabatic mode converter 6. The width W of the input side rib of the second double-layer adiabatic mode converter 6 is side Need to stay away from the first mixing area, that is, satisfy: W side >1.75 μm, the output-side rib width W of the first double-layer adiabatic mode converter 6 side Need to stay away from the second mixing area, that is, satisfy: W side <1.75μm.

[0029] Figure 4 The width of the first silicon core 1 of the double-layer adiabatic mode converter of the present invention is changed: the width of the side rib of the input end of the first double-layer adiabatic mode converter is set to W side =3.6μm, the side rib width at the output end is set to W side = 2.4 μm; the width of the first double-layer adiabatic mode converter input is w1 = 2W side +W=8.2μm, the width of the output end is w2=2W side +W=5.8μm; the side rib width at the input end of the second double-layer adiabatic mode converter is set to W side =2.4μm, side rib width W at the output end side =1.4μm; the width of the second double-layer adiabatic mode converter input is w2 = 2W side +W=5.8μm, the width of the output end is w3=2W side +W=3.8μm. Both the input and output ends are parallel plate waveguides; the widths of the two ends of the input end are w I =w1=8.2μm; the widths of the two ends of the output end are w O = w3 = 3.8 μm. Since the input end 4 and the output end 7 are parallel plate waveguides, their lengths can be selected arbitrarily without restriction.

[0030] Along the propagation direction of the light beam, the first double-layer adiabatic mode converter 5 includes the first to twelfth segments connected in sequence. The first segment is connected in a linear manner, and the initial end waveguide width and the terminal end width are w respectively. a =8.20μm and w b=8.00μm, length L1 = 34.244μm; the second segment is connected in a linear manner, and the initial end waveguide width and the end end width are w b =8.00μm and w c =7.80μm, length L2 = 34.455μm; the third segment is connected in a linear manner, and the initial end waveguide width and the end end width are w c =7.80μm and w d =7.60μm, length L3 = 34.72μm; the fourth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w d =7.60μm and w e =7.40μm, length L4 = 34.967μm; the fifth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w e =7.40μm and w f =7.20μm, length L5 = 35.083μm; the sixth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w f =7.20μm and w g =7.00μm, length L6 = 34.934μm; the seventh segment is connected in a linear manner, and the initial end waveguide width and the end end width are w g =7.00μm and w h =6.80μm, length L7 = 34.391μm; the eighth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w h =6.80μm and w i =6.60μm, length L8 = 33.386μm; the ninth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w i =6.60μm and w j =6.40μm, length L9 = 31.945μm; the tenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w j =6.40μm and w k =6.20μm, length L 10 =30.20 μm; the eleventh segment is connected in a linear manner with a width of w k =6.20μm and w l =6.00μm, length L 11 =28.356μm; the twelfth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w l =6.00μm and w m =5.80μm, length L 12 =26.638μm;

[0031] Along the propagation direction of the light beam, the second double-layer adiabatic mode converter 6 includes the thirteenth to nineteenth segments connected in sequence. The thirteenth segment is connected in a linear manner. The initial end waveguide width and the terminal end width are w respectively. m =5.80μm and w n =5.40μm, length L 13 =34.339μm; the fourteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w n =5.40μm and w p =5.10μm, length L 14 =31.724μm; the fifteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w p =5.10μm and w q =4.80μm, length L 15 =32.21μm; the sixteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w q =4.80μm and w u =4.50μm, length L 16 =31.63μm; the seventeenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w u =4.50μm and w v =4.24μm, length L 17 =28.490μm; the eighteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w v =4.24μm and w x =4.00μm, length L 18 =25.048μm; the nineteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w x =4.00μm and w y =3.80μm, length L 19 =20.715μm.

[0032] With the above layout, when the TE6 mode is input from the input terminal 4, it is converted to the TE4 mode at the output terminal 7, and vice versa.

[0033] The conversion efficiency of the double-layer adiabatic mode converter proposed by the present invention is as follows: Figure 5As shown, the length required for practical applications can be obtained from this figure. As can be seen from the figure, when a transmission efficiency of 96% is to be achieved, the solution of the present invention only requires a length of 86 μm, which is a very compact device size. Therefore, the double-layer adiabatic mode converter proposed in the present invention realizes the design of an ultra-compact device, which can be used for cascading between various functional units in a photonic integrated chip to achieve the design goal of higher integration in the photonic integrated chip. The present invention realizes high-efficiency (low-loss) conversion and transmission in a small size.

[0034] The specific implementation scheme described above further illustrates in detail the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above is only a specific implementation scheme of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by any technician in this field without departing from the concept and principle of the present invention should fall within the scope of protection of the present invention.

Claims

1. A double-layer adiabatic converter for converting between TE4 mode and TE6 mode, characterized in that: The invention comprises a first silicon core (1), a second silicon core (2) and a cladding (3); the first silicon core (1) is arranged below the second silicon core (2); the cladding (3) is arranged around the first silicon core (1) and the second silicon core (2); the refractive index of the first silicon core (1) and the second silicon core (2) are both n Si =3.455; the thickness of the second silicon core (2) is h2 = 200 nm, and the width is W = 1 μm; the thickness of the first silicon core (1) is h1 = 200 nm, and the width is w = 2W side + W, where W side is the side rib width; the wavelength of the incident light beam is set to 1.55 μm; along the propagation direction of the light beam, the first silicon core (1) includes an input end (4), a first double-layer adiabatic mode converter (5), a second double-layer adiabatic mode converter (6) and an output end (7) connected in sequence; the first double-layer adiabatic mode converter (5) converts the TE6 mode into the TM1 mode, and the input end side rib width W of the first double-layer adiabatic mode converter (5) is side > 2.80 μm; width W of the output side rib of the first double-layer adiabatic mode converter (5) side < 2.80 μm; the second double-layer adiabatic mode converter (6) converts the TM1 mode into the TE4 mode; the input-side rib width W of the second double-layer adiabatic mode converter (6) side > 1.75 μm; width W of the output side rib of the second double-layer adiabatic mode converter (6) side < 1.75 μm; Along the propagation direction of the light beam, the first double-layer adiabatic mode converter (5) includes a first segment to a twelfth segment connected in sequence, the first segment is connected in a linear manner, and the initial end waveguide width and the terminal end width are w respectively. a = 8.20 μm and w b = 8.00 μm, length L1 = 34.244 μm; the second segment is connected in a linear manner, and the initial end waveguide width and the end end width are w b = 8.00 μm and w c = 7.80 μm, length L2 = 34.455 μm; the third segment is connected in a linear manner, and the initial end waveguide width and the end end width are w c = 7.80 μm and w d = 7.60 μm, length L3 = 34.72 μm; the fourth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w d = 7.60 μm and w e = 7.40 μm, length L4 = 34.967 μm; the fifth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w e =7.40 μm and w f = 7.20 μm, length L5 = 35.083 μm; the sixth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w f = 7.20 μm and w g = 7.00 μm, length L6 = 34.934 μm; the seventh segment is connected in a linear manner, and the initial end waveguide width and the end end width are w g = 7.00 μm and w h = 6.80 μm, length L7 = 34.391 μm; the eighth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w h = 6.80 μm and w i = 6.60 μm, length L8 = 33.386 μm; the ninth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w i = 6.60 μm and w j = 6.40 μm, length L9 = 31.945 μm; the tenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w j = 6.40 μm and w k = 6.20 μm, length L 10 = 30.20 μm; The eleventh segment is connected in a linear manner with a width of w k = 6.20 μm and w l = 6.00 μm, length L 11 = 28.356 μm; the twelfth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w l = 6.00 μm and w m =5.80 μm, length L 12 = 26.638 μm; Along the propagation direction of the light beam, the second double-layer adiabatic mode converter (6) includes the thirteenth to nineteenth segments connected in sequence, the thirteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w respectively. m = 5.80 μm and w n = 5.40 μm, length L 13 = 34.339 μm; the fourteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w n = 5.40 μm and w p = 5.10 μm, length L 14 = 31.724 μm; the fifteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w p = 5.10 μm and w q = 4.80 μm, length L 15 =32.21 μm; the sixteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w q = 4.80 μm and w u = 4.50 μm, length L 16 = 31.63 μm; the seventeenth segment is connected in a linear manner, and the initial and terminal waveguide widths are w u = 4.50 μm and w v = 4.24 μm, length L 17 = 28.490 μm; the eighteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w v = 4.24 μm and w x = 4.00 μm, length L 18 =25.048 μm; the nineteenth segment is connected in a linear manner, and the initial end waveguide width and the end end width are w x = 4.00 μm and w y = 3.80 μm, length L 19 = 20.715 μm.

2. A double-layer adiabatic converter for converting between TE4 mode and TE6 mode according to claim 1, characterized in that: The material of the cladding (3) is SiO2, with a refractive index n SiO2 = 1.445, width is W0, thickness is h0.

3. The double-layer adiabatic converter for converting between TE4 mode and TE6 mode according to claim 1, characterized in that: The input end (4) and the output end (7) are both parallel plate waveguides; the widths of the two ends of the input end (4) are w I = w1 =8.2 μm; the widths of the two ends of the output end (7) are w O = w3 = 3.8 μm.

4. A double-layer adiabatic converter for converting between TE4 mode and TE6 mode according to claim 3, characterized in that: The side rib width at the input end of the first double-layer adiabatic mode converter (5) is set to W side = 3.6 μm, the side rib width at the output end is set to W side = 2.4 μm; the width of the input end of the first double-layer adiabatic mode converter (5) is w1 = 2W side +W = 8.2 μm, the width of the output end is w2 = 2W side + W = 5.8 μm; the width of the side ribs at the input of the second double-layer adiabatic mode converter (6) is set to W side = 2.4 μm, side rib width W at the output end side = 1.4 μm; the width of the input end of the second double-layer adiabatic mode converter (6) is w2 = 2W side + W = 5.8 μm, the width of the output end is w3 = 2W side + W =3.8 μm.

5. The double-layer adiabatic converter for converting between TE4 mode and TE6 mode according to claim 2, characterized in that: W0= 9 μm;h0 = 1250 nm。

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