A double-layer adiabatic converter for conversion between TE4 and TM1 modes

Abstract

The application belongs to the technical field of integrated optoelectronics, and particularly relates to a double-layer adiabatic converter for converting between TE4 mode and TM1 mode. The application comprises a first silicon core, a second silicon core and a cladding layer; the first silicon core is arranged below the second silicon core; the first silicon core and the second silicon core are both surrounded by the cladding layer; 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 = 200 nm, and the width is W = 1 um; the thickness of the first silicon core is h1 = 200 nm, and the width is w = 2W side + W, wherein W side is the width of the side rib; the wavelength of the incident light beam is set to 1.55 um; along the direction of light beam propagation, the first silicon core comprises an input end, a first adiabatic waveguide, a second adiabatic waveguide, a third adiabatic waveguide, a fourth adiabatic waveguide, a fifth adiabatic waveguide, a sixth adiabatic waveguide, a seventh adiabatic waveguide, an eighth adiabatic waveguide, a ninth adiabatic waveguide, a tenth adiabatic waveguide and an output end which are sequentially connected. The application realizes conversion transmission between TE4 mode and TM1 mode.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of integrated optoelectronic technology, and particularly relates to a double-layer adiabatic converter for converting between TE4 mode and TM1 mode. BACKGROUND

[0002] Photonics integrated chip is the core element of modern optical communication device, which can integrate multiple photonic chips on one chip to realize the integration and cooperation of multiple functions. In future large-scale photonics integrated chip, silicon photonics optical power coupler on silicon-on-insulator (SOI) platform with high refractive index contrast is an ideal candidate device for large-scale photonics integration in optical communication, which is embodied 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 converter in optical waveguide is one of the basic elements of photonics integrated chip, which is usually used for mode conversion between different modes to improve the coupling efficiency between two different cross sections (such as planar optical waveguide and single mode or optical fiber). To realize the conversion between different modes, the most common is the conventional transverse adiabatic mode converter, i.e. the waveguide width changes and the etching depth remains unchanged, and this type of adiabatic mode converter has been studied a lot. While the so-called "double-layer" adiabatic mode converter is rarely reported, which includes two layers of transverse change structure and needs double-layer etching process for processing and manufacturing. Double-layer adiabatic mode converter is used to connect two parts with different etching depths, such as connecting from shallow etched ridge waveguide to deep etched ridge waveguide, which is embodied 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 in this study only realizes the conversion between TM0 mode and TE1 mode, and the conversion between other modes is not realized. Moreover, there is no "double-layer" adiabatic mode converter that can realize the conversion between TE4 mode and TM1 mode in other documents. SUMMARY

[0004] The present application aims to provide a TE4 mode and TM1 mode conversion double-layer adiabatic converter, aiming to obtain a small size, low loss double-layer adiabatic mode converter.

[0005] In order to achieve the above-mentioned application purposes, the technical solutions adopted by the present application are as follows:

[0006] A TE4 mode and TM1 mode conversion double-layer adiabatic converter, comprising a first silicon core, a second silicon core and a cladding layer; the first silicon core is arranged below the second silicon core; the first silicon core and the second silicon core are arranged with a cladding layer around; 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, wherein W side is the side rib width; the wavelength of the incident light beam is set to 1.55μm; along the direction of light beam propagation, the first silicon core comprises an input end, a first adiabatic waveguide, a second adiabatic waveguide, a third adiabatic waveguide, a fourth adiabatic waveguide, a fifth adiabatic waveguide, a sixth adiabatic waveguide, a seventh adiabatic waveguide, an eighth adiabatic waveguide, a ninth adiabatic waveguide, a tenth adiabatic waveguide and an output end connected in sequence; when the TE4 mode is input from the input end, it is converted to TM1 mode output at the output end.

[0007] Further, as a preferred technical solution of the present application, the material of the cladding layer is SiO2, the refractive index n SiO2 =1.445, the width is W0, and the thickness is h0.

[0008] Further, as a preferred technical solution of the present application, the input end and the output end are both parallel plate waveguides; the length of the input end is L I , and the length of the output end is L O , both of which are greater than 0; the side rib width of the input end is set to W side =3.00μm; the side rib width of the output end is set to W side =1.40μm; the width of the input end is w I =7.00μm; the width of the output end is w 12 =3.80μm.

[0009] Further, as a preferred technical scheme of the present application, the initial end waveguide width and the terminal width of the first adiabatic waveguide are w1=7.00 μm and w2=6.60 μm respectively, and the length is L1=38.549 μm; the initial end waveguide width and the terminal width of the second adiabatic waveguide are w2=6.60 μm and w3=6.20 μm respectively, and the length is L2=36.781 μm; the initial end waveguide width and the terminal width of the third adiabatic waveguide are w3=6.20 μm and w4=5.80 μm respectively, and the length is L3=35.29 μm; the initial end waveguide width and the terminal width of the fourth adiabatic waveguide are w4=5.80 μm and w5=5.40 μm respectively, and the length is L4=34.339 μm; the initial end waveguide width and the terminal width of the fifth adiabatic waveguide are w5=5.40 μm and w6=5.10 μm respectively, and the length is L5=31.724 μm; the initial end waveguide width and the terminal width of the sixth adiabatic waveguide are w6=5.10 μm and w7=4.80 μm respectively, and the length is L6=32.21 μm; the initial end waveguide width and the terminal width of the seventh adiabatic waveguide are w7=4.80 μm and w8=4.50 μm respectively, and the length is L7=31.63 μm; the initial end waveguide width and the terminal width of the eighth adiabatic waveguide are w8=4.50 μm and w9=4.24 μm respectively, and the length is L8=28.490 μm; the initial end waveguide width and the terminal width of the ninth adiabatic waveguide are w9=4.24 μm and w 10 =4.00 μm respectively, and the length is L9=25.048 μm; the initial end waveguide width and the terminal width of the tenth adiabatic waveguide are w 10 =4.00 μm and w 11 =3.80 μm respectively, and the length is L 10 =20.715 μm.

[0010] Further, as a preferred technical scheme of the present application, W0=9 μm; h0=1250 nm.

[0011] The double-layer adiabatic converter for converting between TE4 mode and TM1 mode according to the present application has the following technical effects compared with the prior art by adopting the above technical scheme:

[0012] (1) The conversion and transmission between TE4 mode and TM1 mode are realized in the double-layer adiabatic mode converter.

[0013] (2) The miniaturization design of the double-layer adiabatic mode converter is realized, and the high-efficiency (low-loss) conversion between TE4 mode and TM1 mode is realized in the shortest length. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1This is a schematic cross-sectional view of the input end of the double-layer adiabatic mode converter of the present invention;

[0015] Figure 2 This is a schematic diagram of the linear connection structure of the double-layer adiabatic mode converter of the present invention;

[0016] Figure 3 In the double-layer adiabatic mode converter of this invention, the TE4 mode and TM1 mode are at different side rib widths W side A schematic diagram of the effective refractive index;

[0017] Figure 4 This is a schematic diagram showing the connection of the first silicon core of the dual-layer adiabatic mode converter of the present invention.

[0018] Figure 5 This is a schematic diagram of the mode conversion efficiency curve of the present invention;

[0019] The reference numerals in the attached figures are as follows: 1. First silicon core; 2. Second silicon core; 3. Cladding; 4. Input terminal; 5. First adiabatic waveguide; 6. Second adiabatic waveguide; 7. Third adiabatic waveguide; 8. Fourth adiabatic waveguide; 9. Fifth adiabatic waveguide; 10. Sixth adiabatic waveguide; 11. Seventh adiabatic waveguide; 12. Eighth adiabatic waveguide; 13. Ninth adiabatic waveguide; 14. Tenth adiabatic waveguide; 15. Output terminal. Detailed Implementation

[0020] The present invention will be further explained in detail below with reference to the accompanying drawings, so that those skilled in the art can better understand and implement the present invention. However, the following examples are only used to explain the present invention and are not intended to limit the present invention.

[0021] like Figure 1 As shown, a double-layer adiabatic converter for switching between TE4 mode and TM1 mode includes a first silicon core 1, a second silicon core 2, and a cladding 3; the first silicon core 1 is disposed below the second silicon core 2; the cladding 3 is disposed around both the first silicon core 1 and the second silicon core 2; the refractive index of both the first silicon core 1 and the second silicon core 2 is n. Si =3.455; the second silicon core 2 has a thickness of h2 = 200 nm and a width of W = 1 μm; the first silicon core 1 has a thickness of h1 = 200 nm and a width of w = 2W. side +W, where W sideThe width of the side rib is denoted as 1.55 μm. The incident beam wavelength is set to 1.55 μm. Along the beam propagation direction, the first silicon core 1 includes an input terminal 4, a first adiabatic waveguide 5, a second adiabatic waveguide 6, a third adiabatic waveguide 7, a fourth adiabatic waveguide 8, a fifth adiabatic waveguide 9, a sixth adiabatic waveguide 10, a seventh adiabatic waveguide 11, an eighth adiabatic waveguide 12, a ninth adiabatic waveguide 13, a tenth adiabatic waveguide 14, and an output terminal 15 connected in sequence. When the TE4 mode is input from the input terminal 4, it is converted to the TM1 mode output at the output terminal 15.

[0022] The cladding layer 3 is made of SiO2 with a refractive index n SiO2 =1.445, width is W0, thickness is h0. The width and height of cladding 3 are set to W0 = 9μm and h0 = 1250nm, respectively.

[0023] like Figure 2 As shown, this invention illustrates the connection method where the widths of the first silicon core 1 and the second silicon core 2 vary. When the width of the side ribs is uncertain, it is impossible to achieve the conversion between specified modes. For example, in the paper "Mode conversion in tapered submicron silicon ridge optical waveguides," Opt. Express, vol. 20, no. 12, pp. 13425-13439, May 2012, the input side rib width needs to be determined as W. side =3μm, output end side rib width W side The conversion between TM0 and TE1 modes is only possible when the value is 0. The conversion between TE4 and TM1 modes was not implemented in this paper, nor has it been found in other literature to achieve this conversion in a double-insulated mode converter. To achieve the conversion between TE4 and TM1 modes in a double-insulated mode converter, the first step is to obtain the conversion results for these two modes at different side rib widths W through simulation. side The effective refractive index, such as Figure 3 As shown in the figure. It can be seen from this figure that the width W of the side rib... side A mixed region of TE4 and TM1 modes exists around 1.75μm, as shown by the black dashed circle in the figure. Therefore, by appropriately setting the side rib width W at the input and output terminals... side This could potentially enable switching between TE4 and TM1 modes. According to Figure 3 The effective refractive index obtained through simulation determines the width of the side rib at the input end, which is set to W. side =3.00μm, the width of the side ribs at the output end is set to W side= 1.40 μm, and further deduced that the width of the first silicon core 1 at the input end 4 is w = 2W side = 3.80 μm. By this connection, the conversion between TE4 mode and TM1 mode is realized. side = 3.80 μm. By this connection, the conversion between TE4 mode and TM1 mode is realized.

[0024] wherein the input end 4 and the output end 15 are both parallel plate waveguides; the length of the input end 4 is L I and the length of the output end 15 is L O both greater than 0; the side rib width of the input end 4 is set as W side = 3.00 μm; the side rib width of the output end 15 is set as W side = 1.40 μm; the width of the input end 4 is w I = 7.00 μm; and the width of the output end 15 is w 12 = 3.80 μm. The length of the parallel plate waveguide is greater than 0 and can be selected at will, wherein the TE4 mode is input from the input end and converted to TM1 mode at the output end, and vice versa.

[0025] As Figure 4As shown, the initial end waveguide width and the end width of the first adiabatic waveguide 5 are w1=7.00 μm and w2=6.60 μm respectively, and the length needs to reach L1=38.549 μm to meet the adiabatic transmission condition; the initial end waveguide width and the end width of the second adiabatic waveguide 6 are w2=6.60 μm and w3=6.20 μm respectively, and the length needs to reach L2=36.781 μm to meet the adiabatic transmission condition; the initial end waveguide width and the end width of the third adiabatic waveguide 7 are w3=6.20 μm and w4=5.80 μm respectively, and the length needs to reach L3=35.29 μm to meet the adiabatic transmission condition; the initial end waveguide width and the end width of the fourth adiabatic waveguide 8 are w4=5.80 μm and w5=5.40 μm respectively, and the length needs to reach L4=34.339 μm to meet the adiabatic transmission condition; the initial end waveguide width and the end width of the fifth adiabatic waveguide 9 are w5=5.40 μm and w6=5.10 μm respectively, and the length needs to reach L5=31.724 μm to meet the adiabatic transmission condition; the initial end waveguide width and the end width of the sixth adiabatic waveguide 10 are w6=5.10 μm and w7=4.80 μm respectively, and the length needs to reach L6=32.21 μm to meet the adiabatic transmission condition; the initial end waveguide width and the end width of the seventh adiabatic waveguide 11 are w7=4.80 μm and w8=4.50 μm respectively, and the length needs to reach L7=31.63 μm to meet the adiabatic transmission condition; the initial end waveguide width and the end width of the eighth adiabatic waveguide 12 are w8=4.50 μm and w9=4.24 μm respectively, and the length needs to reach L8=28.490 μm to meet the adiabatic transmission condition; the initial end waveguide width and the end width of the ninth adiabatic waveguide 13 are w9=4.24 μm and w 10 =4.00 μm respectively, and the length needs to reach L9=25.048 μm to meet the adiabatic transmission condition; the initial end waveguide width and the end width of the tenth adiabatic waveguide 14 are w 10 =4.00 μm and w 11 =3.80 μm respectively, and the length needs to reach L 10 =20.715 μm to meet the adiabatic transmission condition. Through the above layout, the conversion transmission between the TE4 mode and the TM1 mode can be realized.

[0026] The conversion efficiency of the double-layer adiabatic mode converter designed in the application is as follows Figure 5As shown, the length required in actual application is obtained from the figure. As can be seen from the figure, when a transmission efficiency of 96% is to be achieved, the present application scheme only requires a length of 38.5 μm, which is a very compact device size. Therefore, the double-layer adiabatic mode converter designed by the present application achieves the design of an ultra-compact device, and can be used for cascading between different functional units in a photonic integrated chip, so as to achieve the design goal of higher integration in the photonic integrated chip. Here, a second technical effect is achieved, that is, a small size achieves high-efficiency (low-loss) conversion transmission.

[0027] The above-described specific embodiments further specifically describe the purposes, technical solutions and beneficial effects of the present application. It should be understood that the above-described specific embodiments are merely specific embodiments of the present application, and are not intended to limit the scope of the present application. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present application shall fall within the scope of the present application.

Claims

1. A double-layer adiabatic converter for conversion between TE4 mode and TM1 mode, characterized by, It 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 first silicon core (1) and the second silicon core (2) are both surrounded by the cladding (3); 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=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, wherein W side is the width of the side rib; the wavelength of the incident light beam is set to 1.55 μm; along the direction of the light beam propagation, the first silicon core (1) comprises, in sequence, an input end (4), a first adiabatic waveguide (5), a second adiabatic waveguide (6), a third adiabatic waveguide (7), a fourth adiabatic waveguide (8), a fifth adiabatic waveguide (9), a sixth adiabatic waveguide (10), a seventh adiabatic waveguide (11), an eighth adiabatic waveguide (12), a ninth adiabatic waveguide (13), a tenth adiabatic waveguide (14) and an output end (15); when a TE4 mode is input from the input end (4), it is converted into a TM1 mode and output at the output end (15). The input end (4) and the output end (15) are parallel plate waveguides; the length of the input end (4) is L I and the length of the output end (15) is L O Both are greater than 0; the side rib width of the input end (4) is set as W side = 3.00 μm; the side rib width of the output end (15) is set as W side = 1.40 μm; The width of the input end (4) is w I = 7.00 μm; the width of the output end (15) is w 12 = 3.80 μm; The initial end waveguide width and the terminal width of the first adiabatic waveguide (5) are w1=7.00 μm and w2=6.60 μm respectively, and the length is L1=38.549 μm; the initial end waveguide width and the terminal width of the second adiabatic waveguide (6) are w2=6.60 μm and w3=6.20 μm respectively, and the length is L2=36.781 μm; the initial end waveguide width and the terminal width of the third adiabatic waveguide (7) are w3=6.20 μm and w4=5.80 μm respectively, and the length is L3=35.29 μm; the initial end waveguide width and the terminal width of the fourth adiabatic waveguide (8) are w4=5.80 μm and w5=5.40 μm respectively, and the length is L4=34.339 μm; the initial end waveguide width and the terminal width of the fifth adiabatic waveguide (9) are w5=5.40 μm and w6=5.10 μm respectively, and the length is L5=31.724 μm; the initial end waveguide width and the terminal width of the sixth adiabatic waveguide (10) are w6=5.10 μm and w7=4.80 μm respectively, and the length is L6=32.21 μm; the initial end waveguide width and the terminal width of the seventh adiabatic waveguide (11) are w7=4.80 μm and w8=4.50 μm respectively, and the length is L7=31.63 μm; the initial end waveguide width and the terminal width of the eighth adiabatic waveguide (12) are w8=4.50 μm and w9=4.24 μm respectively, and the length is L8=28.490 μm; the initial end waveguide width and the terminal width of the ninth adiabatic waveguide (13) are w9=4.24 μm and w 10 =4.00 μm respectively, and the length is L9=25.048 μm; the initial end waveguide width and the terminal width of the tenth adiabatic waveguide (14) are w 10 =4.00 μm and w 11 =3.80 μm respectively, and the length is L 10 =20.715 μm.

2. A double-layer adiabatic converter for converting between TE4 and TM1 modes according to claim 1, characterized in that, The material of the cladding layer (3) is SiO2, with a refractive index n SiO2 = 1.445, a width W0, and a thickness h0.

3. A double-layer adiabatic converter for converting between TE4 and TM1 modes according to claim 2, characterized in that, W0= 9 μm; h0= 1250 nm.

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