mode converter

Abstract

The application discloses a mode converter, which is formed by cascading a first mode converter and a second mode converter; a TE0 mode optical signal is transmitted from a first transmission waveguide to the first mode converter; the first mode converter converts the TE0 mode optical signal into a TE1 mode optical signal; since the parity check of the mode before and after the conversion from the TE0 mode to the TE1 mode is opposite, the first mode converter adopts an asymmetric structure to break the parity check; the TE1 mode optical signal is transmitted from a second transmission waveguide to the second mode converter; the second mode converter converts the TE1 mode optical signal into a TE3 mode optical signal; since the parity check of the mode before and after the conversion from the TE1 mode to the TE3 mode is the same, the parity check does not need to be broken, and the second mode converter adopts a symmetric structure; compared with other mode converters, the mode converter with the cascaded structure can realize low-loss mode conversion and improve the conversion efficiency from the TE0 mode to the TE3 mode.

Description

Technical Field

[0001] This invention relates to, but is not limited to, the field of silicon-based photonic integrated chip technology, and particularly to a mode converter. Background Technology

[0002] Mode converters, as one of the fundamental components in future optical communication and optical interconnect technologies, play a crucial role in integrated photonic chip design. Mode multiplexing can utilize different eigenmodes to increase the bandwidth density and spectral efficiency within a single waveguide channel. Mode converters, which convert one eigenmode to other eigenmodes, play a vital role in mode multiplexing. Existing mode converters that convert optical signals from the fundamental mode to higher-order modes suffer from low conversion efficiency when the mode order is greater than 2. Summary of the Invention

[0003] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a mode converter that can improve the conversion efficiency from TE0 mode to TE3 mode.

[0005] This invention provides a mode converter, including a first transmission waveguide, a first mode converter, a second transmission waveguide, a second mode converter, and a third transmission waveguide;

[0006] The first transmission waveguide is used to transmit TEO mode optical signals;

[0007] The first mode converter is used to convert the TE0 mode optical signal into the TE1 mode optical signal. The input terminal of the first mode converter is connected to the output terminal of the first transmission waveguide. The first mode converter is an asymmetric structure waveguide.

[0008] The second transmission waveguide is used to transmit TE1 mode optical signals, and the input end of the second transmission waveguide is connected to the output end of the first mode converter.

[0009] The second mode converter is used to convert the TE1 mode optical signal into the TE3 mode optical signal. The input terminal of the second mode converter is connected to the output terminal of the second transmission waveguide. The second mode converter is a symmetrical waveguide.

[0010] The third transmission waveguide is used to transmit TE3 mode optical signals, and the input end of the third transmission waveguide is connected to the output end of the second mode converter.

[0011] The mode converter provided according to the embodiments of the present invention has at least the following beneficial effects: the mode converter is composed of a first mode converter and a second mode converter cascaded together. The TE0 mode optical signal is transmitted from the first transmission waveguide to the first mode converter, which converts the TE0 mode optical signal into a TE1 mode optical signal. Since the parity check of the modes before and after the TE0 mode to TE1 mode conversion is reversed, the first mode converter adopts an asymmetric structure to break the parity check. The TE1 mode optical signal is transmitted to the second mode converter via the second transmission waveguide, which converts the TE1 mode optical signal into a TE3 mode optical signal. Since the parity check of the modes before and after the TE1 mode to TE3 mode conversion is the same, it is not necessary to break the parity check, and the second mode converter adopts a symmetrical structure. Compared with other mode converters, the cascaded mode converter provided in this embodiment can achieve low-loss mode conversion and improve the conversion efficiency from TE0 mode to TE3 mode.

[0012] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0014] Figure 1 This is a schematic diagram of the overall structure of the mode converter provided in an embodiment of the present invention;

[0015] Figure 2 This is a schematic diagram of the structure of the first transmission waveguide of the mode converter, the first mode converter, and the second transmission waveguide provided in an embodiment of the present invention;

[0016] Figure 3 This is a schematic diagram of the structure of the second transmission waveguide, the second mode converter, and the third transmission waveguide of the mode converter provided in an embodiment of the present invention;

[0017] Figure 4 This is a schematic diagram of the Ey field simulation results of the mode converter provided in this embodiment of the invention;

[0018] Figure 5 This is a schematic diagram of the loss simulation results of the mode converter provided in the embodiment of the present invention. Detailed Implementation

[0019] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0020] In the description of this invention, the use of "first" and "second" is for the purpose of distinguishing technical features only, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0021] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0022] This invention provides a mode converter, which is formed by cascading a first mode converter and a second mode converter. A TE0 mode optical signal is transmitted from a first transmission waveguide to the first mode converter, which converts the TE0 mode optical signal into a TE1 mode optical signal. Since the parity check of the modes before and after the TE0-TE1 conversion is reversed, the first mode converter employs an asymmetric structure to break the parity check. The TE1 mode optical signal is transmitted via a second transmission waveguide to the second mode converter, which converts the TE1 mode optical signal into a TE3 mode optical signal. Since the parity check of the modes before and after the TE1-TE3 conversion is the same, there is no need to break the parity check, and the second mode converter employs a symmetrical structure. Compared to other mode converters, the cascaded mode converter provided in this embodiment can achieve low-loss mode conversion and improve the conversion efficiency from TE0 to TE3.

[0023] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0024] like Figure 1 As shown, Figure 1 This is a schematic diagram of the overall structure of a mode converter provided in one embodiment of this application.

[0025] like Figure 1 As shown, the mode converter 100 includes a first transmission waveguide 110, a first mode converter 120, a second transmission waveguide 130, a second mode converter 140, and a third transmission waveguide 150 connected in sequence.

[0026] The first transmission waveguide 110 is used to transmit TEO mode optical signals;

[0027] The first mode converter 120 is used to convert the TE0 mode optical signal into the TE1 mode optical signal. The input terminal of the first mode converter 120 is connected to the output terminal of the first transmission waveguide 110. The first mode converter 120 is an asymmetric structure waveguide.

[0028] The second transmission waveguide 130 is used to transmit TE1 mode optical signals, and the input end of the second transmission waveguide 130 is connected to the output end of the first mode converter 120.

[0029] The second mode converter 140 is used to convert the TE1 mode optical signal into the TE3 mode optical signal. The input terminal of the second mode converter 140 is connected to the output terminal of the second transmission waveguide 130. The second mode converter 140 is a symmetrical waveguide.

[0030] The third transmission waveguide 150 is used to transmit TE3 mode optical signals, and the input end of the third transmission waveguide 150 is connected to the output end of the second mode converter 140.

[0031] In one embodiment, the first transmission waveguide 110 is a straight waveguide with a width of W0. The TE0 mode optical signal enters the first mode converter 120 through the waveguide structure with a width of W0. It is understood that the output port width of the first transmission waveguide 110 is W0, and the output port of the first transmission waveguide 110 is connected to the input port of the first mode converter 120. Therefore, the input port width of the first mode converter 120 is also initially set to W0.

[0032] In one embodiment, the first mode converter 120 is an asymmetrical tapered waveguide or an asymmetrical wedge waveguide. After the TE0 mode optical signal enters the first mode converter 120 from the input terminal, it gradually becomes a TE1 mode optical signal, and the port width of the first mode converter 120 increases to W1, that is, the port width of the output terminal of the first mode converter 120 is W1, where W1 is greater than W0.

[0033] In one embodiment, the second transmission waveguide 130 is a straight waveguide with a width of W1. The TE1 mode optical signal enters the second mode converter 140 through the waveguide structure with a width of W1. It is understood that the output port width of the second transmission waveguide 130 is W1, and the output port of the second transmission waveguide 130 is connected to the input port of the second mode converter 140. Therefore, the input port width of the second mode converter 140 is also correspondingly set to W1.

[0034] In one embodiment, the second mode converter 140 is a symmetrical tapered waveguide or a symmetrical wedge waveguide. After the TE1 mode optical signal enters the second mode converter 140 from the input terminal, it gradually becomes a TE3 mode optical signal, and the port width of the second mode converter 140 increases to W3, that is, the port width of the output terminal of the second mode converter 140 is W3, where W3 is greater than W1.

[0035] In one embodiment, the third transmission waveguide 150 is a straight waveguide with a width of W3. The TE3 mode optical signal continues to be transmitted through the waveguide structure with a width of W3.

[0036] In such Figure 1 In the illustrated embodiment, the mode converter 100 is cascaded from a first mode converter 120 and a second mode converter 140. The TE0 mode optical signal is transmitted from the first transmission waveguide 110 to the first mode converter 120, which converts the TE0 mode optical signal into a TE1 mode optical signal. Since the parity check of the modes before and after the TE0-TE1 conversion is reversed, the first mode converter 120 employs an asymmetric structure to break the parity check. The TE1 mode optical signal is transmitted via the second transmission waveguide 130 to the second mode converter 140, which converts the TE1 mode optical signal into a TE3 mode optical signal. Since the parity check of the modes before and after the TE1-TE3 conversion is the same, there is no need to break the parity check, and the second mode converter 140 employs a symmetrical structure. Compared to other mode converters, the cascaded mode converter provided in this embodiment, by combining different mode converters, achieves the conversion of the TE0 mode optical signal into a TE3 mode optical signal, enabling low-loss mode conversion and improving the conversion efficiency from TE0 to TE3.

[0037] It is understandable that, theoretically, the cascaded structure of this embodiment can realize the conversion of optical signals from any mode from TE0 to TEn; however, the conversion between TE0 mode optical signals and other modes of optical signals requires redesigning the structure.

[0038] In one embodiment, the port width of the output terminal of the first mode converter 120 is greater than the port width of the output terminal of the first transmission waveguide 110. The width of the first transmission waveguide 110 is designed as W0, which is 0.5μm, meaning the port width of the output terminal of the first transmission waveguide 110 is also W0. The output terminal of the first transmission waveguide 110 is connected to the input terminal of the first mode converter 120, meaning the port width of the input terminal of the first mode converter 120 is also W0. After the TE0 mode optical signal enters the first mode converter 120 from its input terminal, it gradually becomes a TE1 mode optical signal, and the port width of the first mode converter 120 increases to W1, which is 1.2μm, meaning the port width of the output terminal of the first mode converter 120 is W1. Wherein, W1 is greater than W0, meaning the port width of the output terminal of the first mode converter 120 is greater than the port width of the output terminal of the first transmission waveguide 110.

[0039] In one embodiment, the port width of the output terminal of the second mode converter 140 is greater than the port width of the output terminal of the second transmission waveguide 130. The width of the second transmission waveguide 130 is designed as W1, which is 1.2 μm, meaning the port width of the output terminal of the second transmission waveguide 130 is also W1. The output terminal of the second transmission waveguide 130 is connected to the input terminal of the second mode converter 140, meaning the port width of the input terminal of the second mode converter 140 is also W1. After the TE1 mode optical signal enters the second mode converter 140 from its input terminal, it gradually transforms into a TE3 mode optical signal, and the port width of the second mode converter 140 increases to W3, which is 1.8 μm, meaning the port width of the output terminal of the second mode converter 140 is W3, where W3 is greater than W1, i.e., the port width of the output terminal of the second mode converter 140 is greater than the port width of the output terminal of the second transmission waveguide 130.

[0040] In one embodiment, the first transmission waveguide 110, the first mode converter 120, the second transmission waveguide 130, the second mode converter 140, and the third transmission waveguide 150 are silicon waveguides. The height of the silicon waveguide is 220 nm, which refers to the etching thickness. The etching thickness of the first transmission waveguide 110, the first mode converter 120, the second transmission waveguide 130, the second mode converter 140, and the third transmission waveguide 150 is 220 nm during the etching process.

[0041] In one embodiment, the first transmission waveguide 110, the first mode converter 120, the second transmission waveguide 130, the second mode converter 140, and the third transmission waveguide 150 are covered by a silicon dioxide overcladding.

[0042] In one embodiment, the first mode converter 120 and the second mode converter 140 are adiabatic, slowly varying structures.

[0043] As will be understood by those skilled in the art, adiabatic gradual change refers to a relatively slow change in device size, thereby achieving the effect of thermal insulation (i.e., no loss or extremely low loss). Therefore, both the first mode converter 120 and the second mode converter 140 are adiabatic gradual change structures, specifically meaning that the width values ​​of the first mode converter 120 and the second mode converter 140 change slowly along the length direction.

[0044] In one embodiment, the length and width change rates of the first mode converter 120 and the second mode converter 140 are calculated using a particle swarm optimization (PSO) algorithm. PSO is an evolutionary computation technique that finds the optimal solution through cooperation and information sharing among individuals within a swarm. In this embodiment, the optimization approach involves first setting initial values ​​for the widths and lengths of the first and second mode converters 120 and 140, then gradually optimizing the structure using the PSO algorithm to find the optimal solution. Interpolation points are used to allow for slow structural changes, and finally, simulation verification yields the waveguide structure with minimum loss.

[0045] Since optical signals propagate in waveguides, different structures may excite different optical modes for transmission, and the generation of unnecessary optical modes can lead to energy loss. By inputting a specific optical mode signal in the simulation and optimizing the structure of the mode converter, the output power of the target optical mode can be maximized, i.e., the loss minimized, thus achieving ultra-high conversion efficiency. Therefore, by using a particle swarm optimization algorithm to calculate the length and width change rates of the first mode converter 120 and the second mode converter 140, unnecessary mode hybridization in the structures of the first mode converter 120 and the second mode converter 140 can be avoided, achieving a low-loss, adiabatic structure, thereby reducing waveguide loss and improving mode conversion efficiency.

[0046] In one embodiment, the length and width variation rates of the first mode converter 120 and the second mode converter 140 are obtained through parameter search using a neural network algorithm. Using a neural network algorithm to obtain the length and width variation rates of the first mode converter 120 and the second mode converter 140 can avoid unnecessary mode hybridization in the structures of the first mode converter 120 and the second mode converter 140, achieving a low-loss thermal insulation structure, thereby reducing waveguide loss and improving mode conversion efficiency.

[0047] like Figure 2 As shown, Figure 2 This is a schematic diagram of the structure of the first transmission waveguide 110, the first mode converter 120, and the second transmission waveguide 130 of the mode converter 100 provided in this embodiment of the invention. This part of the structure mainly realizes the conversion of TE0 mode optical signals into TE1 mode optical signals; as shown Figure 3 As shown, Figure 3 This is a schematic diagram of the structure of the second transmission waveguide 130, the second mode converter 140, and the third transmission waveguide 150 of the mode converter 100 provided in this embodiment of the invention. This part of the structure mainly realizes the conversion of TE1 mode optical signals into TE3 mode optical signals; this embodiment achieves this by... Figure 2 and Figure 3 The two parts are cascaded together to form a structure like Figure 1 The mode converter 100 shown operates as follows: a TE0 mode optical signal enters from the input of the first transmission waveguide 110, is converted into a TE1 mode optical signal by the first mode converter 120, and then transmitted to the second mode converter 140 for the TE1 mode optical signal via the second transmission waveguide 130. The second mode converter 140 converts the TE1 mode optical signal into a TE3 mode optical signal, which is then output from the third transmission waveguide 150, completing the conversion from TE0 to TE3 mode. This invention can utilize a particle swarm optimization algorithm to optimize the structure of the mode converter 100, dividing the device into multiple segments and using interpolation to optimize the device's shape and structural parameters. Ultimately, this ensures that the components of the higher-order modes reach the same phase after passing through different effective lengths, achieving the conversion between the base film and the higher-order modes. Furthermore, this invention can also use a neural network algorithm to search for parameters to obtain the optimal structural parameters of the mode converter 100.

[0048] Existing mode conversion technologies include phase matching, beam shaping, and coherent scattering. Many mode conversion devices have achieved good performance in mode conversion, but challenges remain. For example, devices based on tapered directional couplers and asymmetric Y-junction multi-channel branched waveguides are typically large in size, while asymmetric directional couplers are sensitive to manufacturing tolerances. Other devices based on grating couplers, such as photonic crystals, often require high manufacturing resolution due to the presence of subwavelength or hyperfine features. Therefore, achieving mode conversion while simultaneously balancing conversion efficiency, device size, required manufacturing resolution, and manufacturing tolerance remains difficult. Compared to existing mode converters, the mode converter for mode order conversion based on a single waveguide design proposed in this invention, through optimized device structure and combination of different mode converters, achieves efficient conversion between TE0 and TE3 modes. It boasts advantages such as high conversion efficiency, large operating bandwidth, large process tolerance, and ease of fabrication, making it highly valuable for applications in silicon-based photonic integrated chips.

[0049] like Figure 4 and Figure 5 As shown, Figure 4 This is a schematic diagram of the Ey field simulation results of the mode converter 100 provided in this embodiment of the invention. Figure 5 yes Figure 5 This is a schematic diagram of the loss simulation results of the mode converter provided in this embodiment of the invention. The simulation results show that the mode converter 100 provided in this embodiment can achieve high-efficiency mode conversion over a wide wavelength range, thereby achieving lower loss and greater bandwidth.

[0050] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A mode converter characterized by, include: The first transmission waveguide is used to transmit TEO mode optical signals; The first mode converter is used to convert the TE0 mode optical signal into the TE1 mode optical signal. The input terminal of the first mode converter is connected to the output terminal of the first transmission waveguide. The first mode converter is an asymmetric structure waveguide. The second transmission waveguide is used to transmit TE1 mode optical signals, and the input end of the second transmission waveguide is connected to the output end of the first mode converter. The second mode converter is used to convert the TE1 mode optical signal into the TE3 mode optical signal. The input terminal of the second mode converter is connected to the output terminal of the second transmission waveguide. The second mode converter is a symmetrical waveguide. The third transmission waveguide is used to transmit TE3 mode optical signals, and the input end of the third transmission waveguide is connected to the output end of the second mode converter.

2. The mode converter of claim 1, wherein, The first mode converter is a tapered waveguide or a wedge waveguide.

3. The mode converter of claim 1, wherein, The second mode converter is a tapered waveguide or a wedge waveguide.

4. The mode converter of claim 1, wherein, The port width of the output terminal of the first mode converter is greater than the port width of the output terminal of the first transmission waveguide.

5. The mode converter of claim 1, wherein, The port width of the output terminal of the second mode converter is greater than the port width of the output terminal of the second transmission waveguide.

6. The mode converter of claim 1, wherein, The first transmission waveguide, the first mode converter, the second transmission waveguide, the second mode converter, and the third transmission waveguide are silicon waveguides.

7. The mode converter of claim 1, wherein, The first transmission waveguide, the first mode converter, the second transmission waveguide, the second mode converter, and the third transmission waveguide are covered by a silicon dioxide overcladding.

8. The mode converter of claim 1, wherein, The first mode converter and the second mode converter are adiabatic, slowly varying structures.

9. The mode converter of claim 1, wherein, The length and width change rates of the first mode converter and the second mode converter were calculated using a particle swarm optimization algorithm.

10. The mode converter of claim 1, wherein, The length and width change rates of the first mode converter and the length and width change rates of the second mode converter are obtained by parameter search using a neural network algorithm.

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