A few-mode waveguide optical switch based on a total internal reflection structure and a preparation method thereof

Abstract

A few-mode waveguide optical switch based on a total internal reflection structure and a preparation method thereof belong to the technical field of planar optical waveguide devices. It is composed of a silicon wafer substrate, a polymer lower cladding, a strip-shaped polymer optical waveguide core layer, a polymer upper cladding and a heating electrode. The core layer is composed of an input few-mode straight waveguide, an input bent waveguide, an input tapered waveguide, an input multimode straight waveguide, a first output multimode straight waveguide, a second output multimode straight waveguide, a first output tapered waveguide, a second output tapered waveguide, a first output bent waveguide, a second output bent waveguide, a first output few-mode straight waveguide and a second output few-mode straight waveguide; the second output few-mode straight waveguide is on the extension line of the input few-mode straight waveguide, and the first output few-mode straight waveguide and the second output few-mode straight waveguide are arranged in parallel; before and after heating the heating electrode, the signal light is output from the first output few-mode straight waveguide or from the second output few-mode straight waveguide, so as to realize the function of the few-mode waveguide optical switch based on the total internal reflection structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of planar optical waveguide devices, and particularly relates to a few-mode waveguide optical switch based on a total internal reflection structure and a preparation method thereof. Background Art

[0002] Light is currently the most ideal carrier in communication systems. Optical communication technology not only has the advantages of fast transmission speed, large transmission capacity, and good confidentiality, but also can effectively improve the communication capacity of optical communication through technologies such as wavelength division multiplexing, polarization division multiplexing, and time division multiplexing. However, due to the influence of the Shannon limit, traditional single-mode optical fibers still have limitations. To overcome the bottleneck of single-mode fiber communication, researchers have proposed mode division multiplexing technology, which uses multiple mutually orthogonal spatial modes to simultaneously transmit information, thereby doubling the transmission capacity of the communication system. To meet the requirements of large-capacity communication systems, current photonic devices are rapidly developing in the direction of simple device preparation process, low cost, small device size, multiple supported optical modes, low driving power consumption, and fast response speed.

[0003] As a core component of an optical communication system, an optical switch is the basic unit for realizing optical switching and can be used to realize the dynamic routing of optical signals between various channels. In addition, an optical switch can also realize automatic protection switching and network monitoring functions in an optical network and plays an irreplaceable role in an optical communication network. Among them, an optical switch based on a planar optical waveguide structure has the advantages of small size, easy integration, and low insertion loss, and can modulate the signal light through the electro-optic effect or thermo-optic effect, etc., so as to realize the switching function of the optical signal at different output ports. There are various types of materials for preparing waveguide-type optical switches. Among them, polymer materials have received extensive attention due to their large thermo-optic coefficient, and the refractive index difference between the optical waveguide core layer and the cladding of polymer materials is small, so that the device size can be well compatible with the optical fiber system. The optical waveguide manufacturing process based on polymer materials is simple and low-cost.

[0004] However, most traditional waveguide-type optical switches can only regulate single-mode signals or realize the conversion between the fundamental mode and high-order modes, and are sensitive to different transmission modes, which severely limits the further improvement of the transmission capacity of optical communication. Total internal reflection is a basic device structure and is also a relatively easy-to-implement optical switch scheme, which has important application value in the fields of optical communication and on-chip optical interconnection. Its modulation principle is to change the refractive index of the waveguide under the heating electrode through the thermo-optic effect or electro-optic effect, etc. When not modulated, the signal light directly passes through. When the switch is modulated, the signal light undergoes total internal reflection at the waveguide intersection and outputs from the other port, thus realizing the switching function of the output ports of multiple optical modes. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a few-mode waveguide optical switch based on a total internal reflection structure that can process multiple optical modes and a preparation method thereof.

[0006] The present invention introduces a total internal reflection structure to achieve insensitive regulation of multiple modes. Through the thermo-optic effect, the refractive index of the material in a specific region is changed, so as to achieve total internal reflection of multiple-mode signal light during waveguide transmission, and change the propagation path of the optical signal. This device structure has the advantages of polarization insensitivity, large process tolerance, wavelength insensitivity, small volume, etc. At the same time, the preparation method proposed by the present invention is relatively simple, only requiring some common semiconductor devices and conventional manufacturing processes, without complex and expensive process equipment and difficult preparation techniques, with low production cost and high efficiency, and is suitable for mass production of practical few-mode waveguide optical switches. The present invention makes full use of the advantages of polymer materials, such as a wide variety of types, large thermo-optic coefficient, and low cost. The preparation process adopted by the present invention is simple, easy to integrate, and can be mass-produced, so it has important practical application value.

[0007] The present invention uses a silicon wafer as the substrate, polymer materials as the lower cladding and upper cladding of the optical waveguide, and a polymer material with a relatively large refractive index as the core layer of the optical waveguide. The polymer material used to make the core layer of the optical waveguide has a large thermo-optic coefficient.

[0008] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0009] As shown in Figure 1 (a) and 1(b), a few-mode waveguide optical switch based on a total internal reflection structure, along the light propagation direction from left to right, sequentially consists of an input few-mode straight waveguide 1 (capable of transmitting E 11 、E 12 、E 21mode), input bending waveguide 2, input tapered waveguide 3, input multimode straight waveguide 4 (the function of the multimode waveguide is to increase the mode field to reduce the crosstalk at the waveguide intersection), first output multimode straight waveguide 5, second output multimode straight waveguide 6, first output tapered waveguide 7, second output tapered waveguide 8, first output bending waveguide 9, second output bending waveguide 10, first output few-mode straight waveguide 11, second output few-mode straight waveguide 12, and heating electrode 13 with electrode pins and electrode leads; the input few-mode straight waveguide 1, the first output few-mode straight waveguide 11, and the second output few-mode straight waveguide 12 have the same shape and size, and their length a1 is equal, which is 0.5 - 5 mm; the input bending waveguide 2, the first output bending waveguide 9, and the second output bending waveguide 10 have the same shape and size, and their length a2 is equal, which is 0.5 - 4 mm; the input tapered waveguide 3, the first output tapered waveguide 7, and the second output tapered waveguide 8 have the same shape and size, and their length a3 is equal, which is 1 - 5 mm; the input multimode straight waveguide 4, the first output multimode straight waveguide 5, and the second output multimode straight waveguide 6 have the same shape and size, and their length a4 is equal, which is 0.2 - 3 mm;

[0010] The second output few-mode straight waveguide 12 is on the extension line of the input few-mode straight waveguide 1. The first output few-mode straight waveguide 11 and the second output few-mode straight waveguide 12 are arranged in parallel. The input multimode straight waveguide 4 and the first output multimode straight waveguide 5 are on the same straight line; the termination position of the input multimode straight waveguide 4, the starting position of the first output multimode straight waveguide 5, and the starting position of the second output multimode straight waveguide 6 are connected together; the angle between the central axis of the input few-mode straight waveguide 1 and the central axis of the input tapered waveguide 3, the angle between the central axis of the input few-mode straight waveguide 1 and the central axis of the input multimode straight waveguide 4, the angle between the central axis of the first output few-mode straight waveguide 11 and the central axis of the first output multimode straight waveguide 5, the angle between the central axis of the first output few-mode straight waveguide 11 and the central axis of the first output tapered waveguide 7, the angle between the central axis of the second output few-mode straight waveguide 12 and the central axis of the second output multimode straight waveguide 6, and the angle between the central axis of the second output few-mode straight waveguide 12 and the central axis of the second output tapered waveguide 8, θ, are equal, which is 1 - 10°; the bending angles θ of the input bending waveguide 2, the first output bending waveguide 9, and the second output bending waveguide 10 are equal, which is 1 - 10°. The angle between the first output multimode straight waveguide 5 and the second output multimode straight waveguide 6 is 2θ;

[0011] The widths w1 of the input single-mode straight waveguide 1, the input bent waveguide 2, the first output bent waveguide 9, the second output bent waveguide 10, the first output single-mode straight waveguide 11, and the second output single-mode straight waveguide 12 are equal, ranging from 5 to 15 μm; the starting width of the input tapered waveguide 3, and the terminating widths of the first output tapered waveguide 7 and the second output tapered waveguide 8 are equal, ranging from 5 to 15 μm; the widths w2 of the input multimode straight waveguide 4, the first output multimode straight waveguide 5, and the second output multimode straight waveguide 6 are equal, ranging from 7 to 50 μm, and the terminating width of the input tapered waveguide 3, and the starting widths of the first output tapered waveguide 7 and the second output tapered waveguide 8 are equal, ranging from 7 to 50 μm;

[0012] As shown in Figure 2 the attached Figure 1 figure (which is the cross-sectional view at the position of A-A' in

[0013] ), it is the cross-sectional view at the connection position of the input multimode straight waveguide 4, the first output multimode straight waveguide 5, and the second output multimode straight waveguide 6 (the width at the connection is the width w2 of the input multimode straight waveguide 4, the first output multimode straight waveguide 5, and the second output multimode straight waveguide 6), which is composed of a silicon substrate 31, a polymer lower cladding 32 prepared on the silicon substrate 31, a strip-shaped polymer optical waveguide core layer 33 prepared on the polymer lower cladding 32, and a polymer upper cladding 34 prepared on the optical waveguide core layer 33 and the polymer lower cladding 32. On the polymer upper cladding 34 at the connection position of the first output multimode straight waveguide 5 and the second output multimode straight waveguide 6, a heating electrode 13 with electrode pins and electrode leads is prepared (the material is selected from Al, Au, or Cr). The heating electrode 13 is parallel to the input single-mode straight waveguide 1, with a length a5 of 0.5 to 5 mm and a width w3 of 5 to 20 μm; the horizontal distance w4 from the central axis of the heating electrode 13 to the connection of the first output multimode straight waveguide 5 and the second output multimode straight waveguide 6 is 1 to 30 μm.The input signal light is input from the input few-mode straight waveguide 1, enters the input tapered waveguide 3 through the input bent waveguide 2, and then enters the input multimode straight waveguide 4 through the transition of the input tapered waveguide 3; when the heating electrode 13 is not heated, the signal light is input into the first output multimode straight waveguide 5, and the power of the signal light input into the first output multimode straight waveguide 5 is the same as that of the input signal light, and is output from the first output few-mode straight waveguide 11 through the first output tapered waveguide 7 and the first output bent waveguide 9; when the heating electrode 13 is heated, due to the thermo-optic effect, the refractive index of the polymer optical waveguide core layer directly below the heating electrode changes. Since the polymer material with a negative thermo-optic coefficient is selected for the optical waveguide core layer, when the optical waveguide is heated, the refractive index of the optical waveguide core layer decreases, and the optical signal cannot be directly input into the first output multimode straight waveguide 5, but undergoes total internal reflection at the front interface of the refractive index reduction region, and thus enters the second output multimode straight waveguide 6; the power of the signal light input into the second output multimode straight waveguide 6 is the same as that of the input signal light, and is output from the second output few-mode straight waveguide 12 through the second output tapered waveguide 8 and the second output bent waveguide 10, thereby realizing the function of a few-mode waveguide optical switch based on the total internal reflection structure.

[0014] The thickness of the silicon wafer substrate 31 is 0.5 - 1.5 mm, the thickness of the polymer lower cladding 32 is 4 - 14 μm, the thickness of the polymer optical waveguide core layer 33 is 3 - 13 μm, the thickness of the polymer upper cladding 34 located above the polymer lower cladding 32 is 5 - 25 μm, and the thickness of the heating electrode 13 is 50 - 300 nm.

[0015] A kind of few-mode waveguide optical switch based on the total internal reflection structure described in the present invention, its preparation process flow is shown in the appendix Figure 3 , and the specific steps are as follows:

[0016] A: Cleaning treatment of the silicon wafer substrate 31

[0017] The silicon wafer substrate is ultrasonically cleaned with acetone and ethanol for 5 - 20 minutes respectively, then rinsed with deionized water, dried with nitrogen, and then plasma cleaned for 1 - 10 minutes, and stored in a clean petri dish in a sealed manner;

[0018] B: Preparation of the polymer optical waveguide lower cladding

[0019] The polymer undercladding material (a series of organic polymer materials with good transparency including polymethyl methacrylate (PMMA), polyimide (PI), polycarbonate (PC), polyester (PET), polystyrene (PS), EpoClad, etc.) is spin-coated on the cleaned silicon wafer substrate 31 by spin coating. The spin coating speed is 1000 - 4000 revolutions per minute, and then it is heated at 90°C - 150°C for 5 - 20 minutes, and then exposed as a whole under ultraviolet light with a wavelength of 300 - 400 nm for 5 - 20 seconds, and then heated at 90°C - 150°C for 20 - 60 minutes to obtain a polymer undercladding 32 with a thickness of 4 - 14 μm;

[0020] C: Preparation of the polymer optical waveguide core layer

[0021] The polymer optical waveguide core layer material (the optical waveguide core layer is a series of wet-etchable ultraviolet negative photoresist materials including EpoCore, SU-8 2002, SU-8 2005, and the refractive index of the optical waveguide core layer material is higher than that of the polymer cladding material) is spin-coated on the polymer undercladding at a speed of 1000 - 3000 revolutions per minute; then the prepared polymer thin film is pre-baked and heated at 80°C - 140°C for 3 - 20 minutes, and then cooled to 50°C - 80°C; the polymer thin film is lithographed, and alignment lithography is carried out under ultraviolet light with a wavelength of 300 - 400 nm. The waveguide mask has a structure complementary to the optical waveguide core layer to be prepared (such as Figure 1 shown), and the exposure time is 3 - 30 seconds, so that the optical waveguide core layer materials in the input / output few-mode straight waveguide region, curved waveguide region, tapered waveguide region, and multimode straight waveguide region of the device to be prepared are exposed to ultraviolet light; after lithography, it is heated at 70°C - 130°C for 3 - 30 minutes and cooled to 20°C - 30°C; then development is carried out. First, it is wet-etched in the developer corresponding to the optical waveguide core layer material for 10 - 60 seconds to remove the non-optical waveguide core layer structure that is not exposed, and then it is respectively placed in isopropyl alcohol solution and deionized water to wash away the residual optical waveguide core layer material and developer, and finally dried with nitrogen; after development, post-baking and hardening are carried out, and it is heated at 120°C - 160°C for 30 - 60 minutes to obtain an optical waveguide core layer 33 with a strip structure and a thickness of 3 - 13 μm;

[0022] D: Preparation of the polymer optical waveguide upper cladding

[0023] The polymer upper cladding material (the same as the polymer lower cladding material, which is a series of organic polymer materials with good transparency including polymethyl methacrylate (PMMA), polyimide (PI), polycarbonate (PC), polyester (PET), polystyrene (PS), EpoClad, etc.) is spin-coated on the optical waveguide core layer 33 and the polymer lower cladding 32 by a spin-coating process. The spin-coating speed is 600 - 3000 revolutions per minute, and then it is heated at 90°C - 150°C for 5 - 20 minutes, and then exposed integrally under ultraviolet light with a wavelength of 300 - 400 nm for 5 - 30 seconds, and then heated at 90°C - 150°C for 20 - 60 minutes to obtain a polymer upper cladding 34 with a thickness of 5 - 25 μm (the thickness of the polymer upper cladding above the polymer lower cladding 32);

[0024] E: Preparation of Al heating electrode

[0025] A metal thin film (Al, Au or Cr) with a thickness of 50 - 300 nm is evaporated on the polymer upper cladding 34 by an evaporation process, and then a positive photoresist BP212 is spin-coated on the metal thin film at a speed of 2000 - 4000 revolutions per minute; then pre-baked at 70°C - 110°C for 10 - 30 minutes, and then cooled to 40°C - 70°C to obtain a BP212 thin film with a thickness of 0.5 - 2.5 μm; alignment lithography is carried out. The mask has the same structure as the heating electrode to be prepared (as Figure 1 shown), and exposed under ultraviolet light with a wavelength of 300 - 400 nm for 1.5 - 5.5 seconds to expose the photoresist BP212 thin film in the area other than the heating electrode and its electrode leads; then put it into a NaOH solution with a mass concentration of 3 - 10‰ for 10 - 60 seconds to remove the exposed photoresist, and then rinse it with deionized water and dry it with nitrogen; heated at 80°C - 120°C for 10 - 30 minutes, and then cooled to 20°C - 30°C; finally, the metal electrode is developed, that is, put it into a NaOH solution with a mass concentration of 3 - 10‰ for 2 - 10 minutes to remove the metal thin film in the area other than the heating electrode (including the electrode leads and electrode wires), rinse it repeatedly with deionized water and dry it with nitrogen, and finally put the sample into ethanol for 5 - 10 seconds to wash away the unexposed photoresist BP212 thin film on the heating electrode, then rinse it with deionized water and dry it with nitrogen, so as to obtain the few-mode waveguide optical switch based on the total internal reflection structure of the present invention.

[0026] Compared with the existing device structures and preparation technologies, the beneficial effects of the present invention are as follows: The waveguide-type few-mode optical switch of the present invention combines the advantages of the simple total internal reflection structure and easy realization of the switching function of multiple optical modes and the large thermo-optic coefficient of organic polymer materials. By designing and optimizing the dimensions of each part of the total internal reflection structure, the switching of E 11 、E 12 、E21 The switching functions of three optical modes; in addition, the use of polymer materials makes the device preparation process relatively simple, only requiring conventional processes such as spin coating, photolithography, and wet etching, and has low production costs, high efficiency, is easy to mass-produce, and can be applied in practice. More importantly, the polymer material has a relatively large thermo-optic coefficient, which can effectively reduce the power consumption of the device. Brief Description of the Drawings

[0027] Figure 1 (a): Schematic three-dimensional structure diagram of the few-mode waveguide optical switch based on the total internal reflection structure of the present invention;

[0028] Figure 1 (b): Schematic planar structure diagram of the few-mode waveguide optical switch based on the total internal reflection structure of the present invention;

[0029] Figure 2 : Figure 1 Cross-sectional structure diagram at the A-A' position in;

[0030] Figure 3 : Process flow chart for the preparation of the few-mode waveguide optical switch based on the total internal reflection structure;

[0031] Figure 4 (a): When the few-mode waveguide optical switch based on the total internal reflection structure has no modulation, simulation diagram of the optical field distribution and simulation diagram of the optical field transmission of the input E 11 mode;

[0032] Figure 4 (b): When the few-mode waveguide optical switch based on the total internal reflection structure modulates the heating electrode, simulation diagram of the optical field distribution and simulation diagram of the optical field transmission of the input E 11 mode;

[0033] Figure 5 (a): When the few-mode waveguide optical switch based on the total internal reflection structure has no modulation, simulation diagram of the optical field distribution and simulation diagram of the optical field transmission of the input E 12 mode;

[0034] Figure 5 (b): When the few-mode waveguide optical switch based on the total internal reflection structure modulates the heating electrode, simulation diagram of the optical field distribution and simulation diagram of the optical field transmission of the input E 12 mode;

[0035] Figure 6 (a): When the few-mode waveguide optical switch based on the total internal reflection structure has no modulation, simulation diagram of the optical field distribution and simulation diagram of the optical field transmission of the input E 21 mode;

[0036] Figure 6(b): When modulating the heating electrode of the few-mode waveguide optical switch based on the total internal reflection structure, the simulated optical field distribution diagram and the simulated optical field transmission diagram of the input E 21 mode;

[0037] Figure 7 : The curve of the normalized output power of the two output ports of the few-mode waveguide optical switch based on the total internal reflection structure varying with the modulation temperature of the heating electrode;

[0038] Figure 8 (a): When the few-mode waveguide optical switch based on the total internal reflection structure is at ΔT = 0K and ΔT = 100K, and the input is the optical signal of E 11 mode, the output curves of the two output ports varying with the wavelength;

[0039] Figure 8 (b): When the few-mode waveguide optical switch based on the total internal reflection structure is at ΔT = 0K and ΔT = 100K, and the input is the optical signal of E 12 mode, the output curves of the two output ports varying with the wavelength;

[0040] Figure 8 (c): When the few-mode waveguide optical switch based on the total internal reflection structure is at ΔT = 0K and ΔT = 100K, and the input is the optical signal of E 21 mode, the output curves of the two output ports varying with the wavelength;

[0041] Figure 9 (a): The microscope plan view of the heating electrode of the few-mode waveguide optical switch based on the total internal reflection structure;

[0042] Figure 9 (b): The microscope plan view of the multimode straight waveguide part of the few-mode waveguide optical switch based on the total internal reflection structure;

[0043] Figure 9 (c): The microscope cross-sectional view of the input few-mode straight waveguide 1 of the few-mode waveguide optical switch based on the total internal reflection structure;

[0044] As Figure 1 (a) and Figure 1 (b) show, the three-dimensional structure schematic diagram and the plane structure schematic diagram of the few-mode waveguide optical switch based on the total internal reflection structure. The names of each component are: input few-mode straight waveguide 1, input curved waveguide 2, input tapered waveguide 3, input multimode straight waveguide 4, first output multimode straight waveguide 5, first output multimode straight waveguide 6, first output tapered waveguide 7, second output tapered waveguide 8, first output curved waveguide 9, second output curved waveguide 10, first output few-mode straight waveguide 11, second output few-mode straight waveguide 12, heating electrode 13.

[0045] As Figure 2 shown, it isFigure 1 Cross-sectional schematic diagram at the A-A' position. The names of each component are: silicon wafer substrate 31, polymer lower cladding 32, polymer optical waveguide core layer 33, polymer upper cladding 34, and Al heating electrode 13.

[0046] As Figure 3 shown, 31 in the figure is the silicon substrate, 32 is the polymer lower cladding prepared by the spin coating process, 33 is the optical waveguide core layer prepared by the spin coating, photolithography, and wet etching processes, 34 is the polymer upper cladding prepared by the spin coating process, and 13 is the Al heating electrode.

[0047] As Figure 4 (a) shows the simulated light field distribution diagram and the simulated light field transmission diagram when inputting the E 11 mode. During the simulation process, we selected the materials and waveguide dimensions used in Example 1. It can be seen that without modulation, the signal light is output from the first output few-mode straight waveguide 11;

[0048] As Figure 4 (b) shows the simulated light field distribution diagram and the simulated light field transmission diagram when modulating the heating electrode and inputting the E 11 mode. During the simulation process, we selected the materials and waveguide dimensions used in Example 1. It can be seen that when modulation is applied, the signal light is output from the second output few-mode straight waveguide 12;

[0049] As Figure 5 (a) shows the simulated light field distribution diagram and the simulated light field transmission diagram when inputting the E 12 mode. During the simulation process, we selected the materials and waveguide dimensions used in Example 1. It can be seen that without modulation, the signal light is output from the first output few-mode straight waveguide 11;

[0050] As Figure 5 (b) shows the simulated light field distribution diagram and the simulated light field transmission diagram when modulating the heating electrode and inputting the E 12 mode. During the simulation process, we selected the materials and waveguide dimensions used in Example 1. It can be seen that when modulation is applied, the signal light is output from the second output few-mode straight waveguide 12;

[0051] As Figure 6 (a) shows the simulated light field distribution diagram and the simulated light field transmission diagram when inputting the E 21 mode. During the simulation process, we selected the materials and waveguide dimensions used in Example 1. It can be seen that without modulation, the signal light is output from the first output few-mode straight waveguide 11;

[0052] As Figure 6(b) shows the simulated optical field distribution and optical field transmission diagrams when modulating the heating electrode. During the simulation, we selected the materials and waveguide dimensions used in Example 1. It can be seen that under modulation, the signal light is output from the second output few-mode straight waveguide 12; 21 When the input is the E

[0053] mode, as shown in Figure 7 we selected the materials and waveguide dimensions used in Example 1. For the few-mode waveguide optical switch based on the total internal reflection structure, when the input is the E 11 mode, E 12 mode, and E 21 mode, the curves of the normalized output power at the two output ports versus the modulation temperature of the heating electrode are shown. It can be seen that when the modulation temperature increases, the switching of the output ports can be achieved for all three signal lights;

[0054] Figure 8 (a): For the few-mode waveguide optical switch based on the total internal reflection structure, when ΔT = 0K and ΔT = 100K, and the input is the optical signal of the E 11 mode, the curves of the output at the two output ports versus the wavelength are shown. It can be seen that the output is insensitive to the wavelength. When ΔT = 0K, almost all of the optical signal is output from the O1 port. When ΔT = 100K, almost all of the optical signal is output from the O2 port;

[0055] Figure 8 (b): For the few-mode waveguide optical switch based on the total internal reflection structure, when ΔT = 0K and ΔT = 100K, and the input is the optical signal of the E 12 mode, the curves of the output at the two output ports versus the wavelength are shown. It can be seen that the output is insensitive to the wavelength. When ΔT = 0K, almost all of the optical signal is output from the O1 port. When ΔT = 100K, almost all of the optical signal is output from the O2 port;

[0056] Figure 8 (c): For the few-mode waveguide optical switch based on the total internal reflection structure, when ΔT = 0K and ΔT = 100K, and the input is the optical signal of the E 21 mode, the curves of the output at the two output ports versus the wavelength are shown. It can be seen that the output is insensitive to the wavelength. When ΔT = 0K, almost all of the optical signal is output from the O1 port. When ΔT = 100K, almost all of the optical signal is output from the O2 port;

[0057] Figure 9 (a): Microscopic plan view of the heating electrode part of the few-mode waveguide optical switch based on the total internal reflection structure. During the experiment, we selected the materials and waveguide dimensions used in Example 1. It can be seen from the microscopic view that the heating electrode has a good morphology and the electrode structure can concentrate the heat in the modulation area;

[0058] Figure 9 (b): Microscope plan view of the multimode waveguide region of the few-mode waveguide optical switch based on the total internal reflection structure. During the experiment, we selected the materials and waveguide dimensions used in Example 1. It can be seen from the microscope image that the waveguide morphology is good and the dimensions are basically the same as those selected in Example 1;

[0059] Figure 9 (c): Microscope cross-sectional view of the input few-mode straight waveguide 1 of the few-mode waveguide optical switch based on the total internal reflection structure. During the experiment, we selected the materials and waveguide dimensions used in Example 1. It can be seen from the microscope image that the waveguide morphology is good and the dimensions are basically the same as those selected in Example 1. Specific implementation mode

[0060] Example 1

[0061] The present invention will be further described below with reference to the accompanying drawings and examples.

[0062] The structure of the example is as Figure 1 (a) shown. The input few-mode straight waveguide 1, the first output few-mode straight waveguide 11, and the second output few-mode straight waveguide 12 have the same shape and size, and their length a1 is equal to 1 mm; the input bent waveguide 2, the first output bent waveguide 9, and the second output bent waveguide 10 have the same shape and size, and their length a2 is equal to 1.5 mm; the input tapered waveguide 3, the first output tapered waveguide 7, and the second output tapered waveguide 8 have the same shape and size, and their length a3 is equal to 1.7 mm; the input multimode straight waveguide 4, the first output multimode straight waveguide 5, and the second output multimode straight waveguide 6 have the same shape and size, and their length a4 is equal to 0.65 mm; the heating electrode 13 with electrode pins and electrode leads, the heating electrode is parallel to the input few-mode straight waveguide 1, and its length a5 is 1.3 mm;

[0063] The widths w1 of the input few-mode straight waveguide 1, the input bent waveguide 2, the first output bent waveguide 9, the second output bent waveguide 10, the first output few-mode straight waveguide 11, and the second output few-mode straight waveguide 12 are equal to 8 μm; the starting width of the input tapered waveguide 3, the termination widths of the first output tapered waveguide 7 and the second output tapered waveguide 8 are equal to 8 μm; the widths w2 of the input multimode straight waveguide 4, the first output multimode straight waveguide 5, and the second output multimode straight waveguide 6 are equal to 34 μm, and the termination width of the input tapered waveguide 3, the starting widths of the first output tapered waveguide 7 and the second output tapered waveguide 8 are equal to 34 μm;

[0064] The width w3 of the heating electrode 13 is 12 μm, and the horizontal distance w4 from the central axis of the heating electrode 13 to the center position of the connection between the input multimode straight waveguide 4 and the first output multimode straight waveguide 5 is 17 μm;

[0065] The second output few-mode straight waveguide 12 is on the extension line of the input few-mode straight waveguide 1. The first output few-mode straight waveguide 11 and the second output few-mode straight waveguide 12 are arranged in parallel. The input multimode straight waveguide 4 and the first output multimode straight waveguide 5 are on the same straight line. The termination position of the input multimode straight waveguide 4, the starting position of the first output multimode straight waveguide 5, and the starting position of the second output multimode straight waveguide 6 are connected together. The included angle between the central axis of the input few-mode straight waveguide 1 and the central axis of the input tapered waveguide 3, the included angle between the central axis of the input few-mode straight waveguide 1 and the central axis of the input multimode straight waveguide 4, the included angle between the central axis of the first output few-mode straight waveguide 11 and the central axis of the first output multimode straight waveguide 5, the included angle between the central axis of the first output few-mode straight waveguide 11 and the central axis of the first output tapered waveguide 7, the included angle between the central axis of the second output few-mode straight waveguide 12 and the central axis of the second output multimode straight waveguide 6, and the included angle between the central axis of the second output few-mode straight waveguide 12 and the central axis of the second output tapered waveguide 8 are all equal to θ, which is 4.5°. The bending angles of the input bent waveguide 2, the first output bent waveguide 9, and the second output bent waveguide 10 are all equal to θ, which is 4.5°. The included angle between the first output multimode straight waveguide 5 and the second output multimode straight waveguide 6 is 2*θ, which is 9°.

[0066] As shown in the Figure 2 accompanying Figure 1 figure (the cross-sectional view at the A-A' position in

[0067] it), the few-mode waveguide optical switch based on the total internal reflection structure is the cross-sectional view at the connection of the input multimode straight waveguide 4, the first output multimode straight waveguide 5, and the second output multimode straight waveguide 6. It consists of a silicon wafer substrate 31, a polymer lower cladding 32 prepared on the silicon wafer substrate 31, a strip-shaped optical waveguide core layer 33 prepared on the polymer lower cladding 32, a polymer upper cladding 34 prepared on the optical waveguide core layer 33 and the polymer lower cladding 32, and a heating electrode 13 prepared on the polymer upper cladding 34. The heating electrode material is selected as Al.

[0068] The input signal light enters from the input few-mode straight waveguide 1, enters the input tapered waveguide 3 through the input curved waveguide 2, and transitions into the input multimode straight waveguide 4 through the input tapered waveguide 3; when the heating electrode 13 is not heated, the signal light enters the first output multimode straight waveguide 5, and the signal light power entering the first output multimode straight waveguide 5 is the same as the input signal light power, and is output from the first output few-mode straight waveguide 11 through the first output tapered waveguide 7 and the first output curved waveguide 9; when the heating electrode 13 is heated, due to the thermo-optic effect, the refractive index of the polymer optical waveguide core layer directly below the heating electrode changes. Since the polymer material with a negative thermo-optic coefficient is selected for the optical waveguide core layer, when the optical waveguide is heated, the refractive index of the optical waveguide core layer decreases, and the optical signal cannot directly enter the first output multimode straight waveguide 5, but undergoes total internal reflection at the front interface of the refractive index reduction region, and thus enters the second output multimode straight waveguide 6; the signal light power entering the second output multimode straight waveguide 6 is the same as the input signal light power, and is output from the second output few-mode straight waveguide 12 through the second output tapered waveguide 8 and the second output curved waveguide 10.

[0069] As shown in the appendix Figure 4 (a), when the input is the E 11 mode and the heating electrode is not modulated, the E 11 mode signal light enters from the input few-mode straight waveguide 1, enters the input tapered waveguide 3 through the input curved waveguide 2, and transitions into the input multimode straight waveguide 4 through the input tapered waveguide 3. When the heating electrode 13 does not heat the switch, the signal light enters the first output multimode straight waveguide 5 and is directly output from the first output few-mode straight waveguide 11 through the first output tapered waveguide 7 and the first output curved waveguide 9.

[0070] As shown in the appendix Figure 4 (b), when the input is the E 11 mode and the heating electrode is modulated, the E 11 mode signal light enters from the input few-mode straight waveguide 1, enters the input tapered waveguide 3 through the input curved waveguide 2, and transitions into the input multimode straight waveguide 4 through the input tapered waveguide 3. When the heating electrode 13 heats the switch, the refractive index of the waveguide below the electrode changes. Therefore, the signal light no longer directly enters the first output multimode straight waveguide 1, but undergoes total reflection at the multimode waveguide intersection and enters the second output multimode straight waveguide 6, and is directly output from the second output few-mode straight waveguide 12 through the second output tapered waveguide 8 and the second output curved waveguide 10.

[0071] As shown in the appendix Figure 5 (a), when the input is the E 12 mode and the heating electrode is not modulated, the E 12The mode signal light is input from the input few-mode straight waveguide 1, enters the input tapered waveguide 3 through the input bent waveguide 2, and transitions into the input multimode straight waveguide 4 through the input tapered waveguide 3. When the heating electrode 13 does not heat the switch, the signal light is input into the first output multimode straight waveguide 5 and directly output from the first output few-mode straight waveguide 11 through the first output tapered waveguide 7 and the first output bent waveguide 9.

[0072] As shown in Figure 5 (b), when the input is the E 12 mode and the heating electrode is modulated, the E 12 mode signal light is input from the input few-mode straight waveguide 1, enters the input tapered waveguide 3 through the input bent waveguide 2, and transitions into the input multimode straight waveguide 4 through the input tapered waveguide 3. When the heating electrode 13 heats the switch, the refractive index of the waveguide under the electrode changes. Therefore, the signal light no longer directly enters the first output multimode straight waveguide 1, but undergoes total internal reflection at the multimode waveguide intersection and is input into the second output multimode straight waveguide 6, and is directly output from the second output few-mode straight waveguide 12 through the second output tapered waveguide 8 and the second output bent waveguide 10.

[0073] As shown in Figure 6 (a), when the input is the E 21 mode and the heating electrode is not modulated, the E 21 mode signal light is input from the input few-mode straight waveguide 1, enters the input tapered waveguide 3 through the input bent waveguide 2, and transitions into the input multimode straight waveguide 4 through the input tapered waveguide 3. When the heating electrode 13 does not heat the switch, the signal light is input into the first output multimode straight waveguide 5 and directly output from the first output few-mode straight waveguide 11 through the first output tapered waveguide 7 and the first output bent waveguide 9.

[0074] As shown in Figure 6 (b), when the input is the E 21 mode and the heating electrode is modulated, the E 21 mode signal light is input from the input few-mode straight waveguide 1, enters the input tapered waveguide 3 through the input bent waveguide 2, and transitions into the input multimode straight waveguide 4 through the input tapered waveguide 3. When the heating electrode 13 heats the switch, the refractive index of the waveguide under the electrode changes. Therefore, the signal light no longer directly enters the first output multimode straight waveguide 1, but undergoes total internal reflection at the multimode waveguide intersection and is input into the second output multimode straight waveguide 6, and is directly output from the second output few-mode straight waveguide 12 through the second output tapered waveguide 8 and the second output bent waveguide 10.

[0075] As Figure 7 shown, for the few-mode waveguide optical switch based on the total internal reflection structure, the input E11 Mode, E 12 Mode, E 21 In the case of the

[0076] As Figure 8 (a) shows, for the few-mode waveguide optical switch based on the total internal reflection structure, the output curves of the two output ports versus wavelength when the input is the optical signal of 11 mode. It can be seen that the output of this few-mode waveguide optical switch based on the total internal reflection structure is insensitive to wavelength changes. When ΔT = 0K, almost all of the optical signal is output from the O1 port. When ΔT = 100K, almost all of the optical signal is output from the O2 port. In the wavelength range of 1520nm - 1620nm, the extinction ratio is greater than 48dB;

[0077] As Figure 8 (b) shows, for the few-mode waveguide optical switch based on the total internal reflection structure, the output curves of the two output ports versus wavelength when the input is the optical signal of 12 mode. It can be seen that the output of this few-mode waveguide optical switch based on the total internal reflection structure is insensitive to wavelength changes. When ΔT = 0K, almost all of the optical signal is output from the O1 port. When ΔT = 100K, almost all of the optical signal is output from the O2 port. In the wavelength range of 1520nm - 1620nm, the extinction ratio is greater than 54dB;

[0078] As Figure 8 (c) shows, for the few-mode waveguide optical switch based on the total internal reflection structure, the output curves of the two output ports versus wavelength when the input is the optical signal of 21 mode. It can be seen that the output of this few-mode waveguide optical switch based on the total internal reflection structure is insensitive to wavelength changes. When ΔT = 0K, almost all of the optical signal is output from the O1 port. When ΔT = 100K, almost all of the optical signal is output from the O2 port. In the wavelength range of 1520nm - 1620nm, the extinction ratio is greater than 43dB;

[0079] Example 2

[0080] Cleaning treatment of the silicon wafer substrate: Ultrasonically clean the silicon wafer substrate with acetone and ethanol for 10 minutes respectively, then rinse it thoroughly with deionized water, dry it with nitrogen, and then perform plasma cleaning for 5 minutes. After that, put it into a clean petri dish and seal it for storage.

[0081] Preparation of the polymer optical waveguide lower cladding 32 by spin coating: Spin coat the polymer lower cladding material EpoClad on the cleaned silicon wafer substrate by spin coating. The spin coating speed is 2800 revolutions per minute, and then heat it at 120 °C for 10 minutes. Expose the polymer thin film, expose it as a whole under ultraviolet light with a wavelength of 365 nm for 10 seconds, and then heat it at 120 °C for 40 minutes. The thickness of the prepared polymer lower cladding is 6 μm.

[0082] Preparation of the polymer optical waveguide core layer 33 including input / output few-mode straight waveguides, bent waveguides, tapered waveguides, and multimode straight waveguides by spin coating, photolithography, and wet etching processes: Spin coat the core layer material EpoCore on the sample with the polymer lower cladding prepared, and the speed is 1600 revolutions per minute. The thickness of the polymer core layer thin film is 9 μm. Pre-bake the prepared polymer thin film, heat it at 90 °C for 5 minutes, and then cool it down to 65 °C. Perform photolithography on the polymer thin film, perform alignment photolithography under ultraviolet light with a wavelength of 356 nm. The waveguide mask is the structure of the few-mode waveguide optical switch based on the total internal reflection structure to be prepared (as Figure 1 shown), and the exposure time is 6 seconds. After photolithography, perform mid-bake, heat it at 85 °C for 10 minutes, and then cool it down to 25 °C. Then develop the sample. First, wet etch it in the developer corresponding to the optical waveguide core layer material for 40 seconds to remove the non-optical waveguide core layer structure that is not exposed. Then, put it into isopropyl alcohol solution and deionized water respectively to wash away the residual optical waveguide core layer material and developer, and finally dry it with nitrogen. After development, perform post-bake and harden the film on the sample, heat it at 120 °C for 40 minutes. In this way, a strip-shaped optical waveguide core layer is prepared, and the length and width of the optical waveguide core layer are the same as the simulation results.

[0083] Preparation of the polymer optical waveguide upper cladding 34 by spin coating: Spin coat the polymer upper cladding material EpoClad on the sample, and the spin coating speed is 1000 revolutions per minute. Then heat it at 120 °C for 10 minutes. Expose the polymer thin film, expose it as a whole under ultraviolet light with a wavelength of 365 nm for 10 seconds, and then heat it at 120 °C for 40 minutes. The thickness of the prepared polymer upper cladding is 15 μm (the upper cladding thickness above the upper surface of the optical waveguide lower cladding).

[0084] The Al heating electrode 13 is prepared by evaporation coating, spin coating, photolithography, and wet etching processes: an Al thin film with a thickness of 150 nm is evaporated on the cladding of the polymer optical waveguide, and then a positive photoresist BP212 is spin-coated on the Al film at a rotation speed of 2500 revolutions per minute; the photoresist BP212 thin film is pre-baked at 87 °C for 20 minutes and then cooled to 50 °C, and the thickness of the obtained BP212 thin film is 1.5 μm; alignment photolithography is carried out, and the mask is the structure of the heating electrode to be prepared (as Figure 1 shown), and it is exposed to ultraviolet light with a wavelength of 365 nm for 2 seconds, and the exposure makes the photoresist BP212 thin film in the area other than the modulation arm electrode and its electrode pins; then the sample is placed in a NaOH solution with a mass concentration of 5‰ for 30 seconds to remove the exposed photoresist, and then rinsed with deionized water and dried with nitrogen; the sample is heated at 95 °C for 10 minutes and then cooled to 25 °C; finally, the Al electrode is developed, that is, the sample is placed in a NaOH solution with a mass concentration of 5‰ for 3 minutes to remove the Al film part in the area other than the heating electrode and its electrode pins, rinsed repeatedly with deionized water and dried with nitrogen, and finally the sample is placed in ethanol for 5 seconds to wash off the unexposed photoresist BP212 thin film on the Al electrode, then rinsed with deionized water and dried with nitrogen, and the length of the prepared heating electrode is 1.3 mm and the width is 12 μm.

[0085] In this way, a few-mode waveguide optical switch based on the total internal reflection structure that meets the requirements is prepared. It should be noted that the specific implementation manners are only representative examples given to help readers understand. Obviously, the technical solutions of the present invention are not limited to such specific statements and embodiments, and there can be many variations. For example, waveguides such as lithium niobate, silicon, and silicon nitride can be used to replace the polymer material in the present invention. Those skilled in the art, based on what is clearly disclosed in the present invention or obtained without any objection according to the written description of the document, various other variations and combinations that do not depart from the essence of the present invention all fall within the scope of protection of this patent

Claims

1. A few-mode waveguide optical switch based on a total internal reflection structure, characterized in that: From bottom to top, it consists of a silicon wafer substrate (31), a polymer lower cladding (32) prepared on the silicon wafer substrate (31), a strip-shaped polymer optical waveguide core layer (33) prepared on the polymer lower cladding (32), a polymer upper cladding (34) prepared on the polymer optical waveguide core layer (33) and the polymer lower cladding (32), and a heating electrode (13) with electrode pins and electrode leads prepared on the polymer upper cladding (34); along the light propagation direction, the polymer optical waveguide core layer (33) consists of an input single-mode straight waveguide (1), an input bent waveguide (2), an input tapered waveguide (3), an input multimode straight waveguide (4), a first output multimode straight waveguide (5), a second output multimode straight waveguide (6), a first output tapered waveguide (7), a second output tapered waveguide (8), a first output bent waveguide (9), a second output bent waveguide (10), a first output single-mode straight waveguide (11), and a second output single-mode straight waveguide (12); the input single-mode straight waveguide (1), the first output single-mode straight waveguide (11), and the second output single-mode straight waveguide (12) have the same shape and size, the input bent waveguide (2), the first output bent waveguide (9), and the second output bent waveguide (10) have the same shape and size, the input tapered waveguide (3), the first output tapered waveguide (7), and the second output tapered waveguide (8) have the same shape and size, and the input multimode straight waveguide (4), the first output multimode straight waveguide (5), and the second output multimode straight waveguide (6) have the same shape and size; the second output single-mode straight waveguide (12) is on the extension line of the input single-mode straight waveguide (1), the first output single-mode straight waveguide (11) and the second output single-mode straight waveguide (12) are arranged in parallel, and the input multimode straight waveguide (4) and the first output multimode straight waveguide (5) are on the same straight line; the termination position of the input multimode straight waveguide (4), the starting position of the first output multimode straight waveguide (5), and the starting position of the second output multimode straight waveguide (6) are connected together; the heating electrode (13) is prepared above the polymer upper cladding (34) at the connection position of the first output multimode straight waveguide (5) and the second output multimode straight waveguide (6), and the heating electrode (13) is parallel to the input single-mode straight waveguide (1); the angles between the central axis of the input single-mode straight waveguide (1) and the central axis of the input tapered waveguide (3), between the central axis of the input single-mode straight waveguide (1) and the central axis of the input multimode straight waveguide (4), between the central axis of the first output single-mode straight waveguide (11) and the central axis of the first output multimode straight waveguide (5), between the central axis of the first output single-mode straight waveguide (11) and the central axis of the first output tapered waveguide (7), between the central axis of the second output single-mode straight waveguide (12) and the central axis of the second output multimode straight waveguide (6), and between the central axis of the second output single-mode straight waveguide (12) and the central axis of the second output tapered waveguide (8) are equal;The bending angles θ of the input bending waveguide (2), the first output bending waveguide (9), and the second output bending waveguide (10) are equal, and the included angle between the first output multimode straight waveguide (5) and the second output multimode straight waveguide (6) is 2θ.

2. The multimode waveguide optical switch based on the total internal reflection structure according to claim 1, characterized in that: The lengths a1 of the input single-mode straight waveguide (1), the first output single-mode straight waveguide (11), and the second output single-mode straight waveguide (12) are equal, ranging from 0.5 to 5 mm; the lengths a2 of the input curved waveguide (2), the first output curved waveguide (9), and the second output curved waveguide (10) are equal, ranging from 0.5 to 4 mm; the lengths a3 of the input tapered waveguide (3), the first output tapered waveguide (7), and the second output tapered waveguide (8) are equal, ranging from 1 to 5 mm; the lengths a4 of the input multimode straight waveguide (4), the first output multimode straight waveguide (5), and the second output multimode straight waveguide (6) are equal, ranging from 0.2 to 3 mm; the widths w1 of the input single-mode straight waveguide (1), the input curved waveguide (2), the first output curved waveguide (9), the second output curved waveguide (10), the first output single-mode straight waveguide (11), and the second output single-mode straight waveguide (12) are equal, ranging from 5 to 15 μm; the starting width of the input tapered waveguide (3), the ending widths of the first output tapered waveguide (7) and the second output tapered waveguide (8) are equal, ranging from 5 to 15 μm; the widths w2 of the input multimode straight waveguide (4), the first output multimode straight waveguide (5), and the second output multimode straight waveguide (6) are equal, ranging from 7 to 50 μm; the ending width of the input tapered waveguide (3), the starting widths of the first output tapered waveguide (7) and the second output tapered waveguide (8) are equal, ranging from 7 to 50 μm; the length a5 of the heating electrode (13) is from 0.5 to 5 mm, the width w3 is from 5 to 20 μm, and the horizontal distance w4 from the central axis of the heating electrode (13) to the connection of the first output multimode straight waveguide (5) and the second output multimode straight waveguide (6) is from 1 to 30 μm; θ is from 1 to 10°.

3. The few-mode waveguide optical switch based on the total internal reflection structure according to claim 1, wherein: The materials of the polymer upper and lower claddings are polymethyl methacrylate, polyimide, polycarbonate, polyester, polystyrene, or EpoClad, and the material of the polymer optical waveguide core layer is EpoCore, SU-8 2002, or SU-8 2005, whose refractive index is higher than that of the polymer cladding material; the material of the heating electrode (13) is Al, Au, or Cr.

4. The few-mode waveguide optical switch based on a total internal reflection structure according to claim 3, characterized in that: The input signal light enters through the input few-mode straight waveguide (1), and enters the input tapered waveguide (3) through the input bent waveguide (2), and then enters the input multi-mode straight waveguide (4) through the transition of the input tapered waveguide (3); when the heating electrode (13) is not heated, the signal light enters the first output multi-mode straight waveguide (5), and the power of the signal light entering the first output multi-mode straight waveguide (5) is the same as that of the input signal light, and it is output from the first output few-mode straight waveguide (11) through the first output tapered waveguide (7) and the first output bent waveguide (9); when the heating electrode (13) is heated, the refractive index of the polymer optical waveguide core layer (33) directly below the heating electrode (13) changes, and the refractive index of the optical waveguide core layer decreases. The optical signal undergoes total internal reflection at the front interface of the refractive index reduction region, and thus enters the second output multi-mode straight waveguide (6); the power of the signal light entering the second output multi-mode straight waveguide (6) is the same as that of the input signal light, and it is output from the second output few-mode straight waveguide (12) through the second output tapered waveguide (8) and the second output bent waveguide (10), thereby realizing the function of a few-mode waveguide optical switch based on the total internal reflection structure.

5. The few-mode waveguide optical switch based on the total internal reflection structure according to claim 1, characterized in that: The thickness of the silicon wafer substrate (31) is 0.5 - 1.5 mm, the thickness of the polymer lower cladding (32) is 4 - 14 μm, the thickness of the polymer optical waveguide core layer (33) is 3 - 13 μm, the thickness of the polymer upper cladding (34) located above the polymer lower cladding (32) is 5 - 25 μm, and the thickness of the heating electrode (13) is 50 - 300 nm.

6. A preparation method for a few-mode waveguide optical switch based on the total internal reflection structure, the steps are as follows: A: Cleaning treatment of the silicon wafer substrate (31) The silicon wafer substrate is ultrasonically cleaned with acetone and ethanol for 5 - 20 minutes respectively, then rinsed with deionized water, dried with nitrogen, and then plasma cleaned for 1 - 10 minutes, and placed in a clean petri dish and sealed for storage; B: Preparation of the polymer optical waveguide lower cladding The polymer lower cladding material is spin-coated on the cleaned silicon wafer substrate (31) by the spin-coating process, the spin-coating speed is 1000 - 4000 revolutions per minute, then heated at 90°C - 150°C for 5 - 20 minutes, and then integrally exposed to ultraviolet light with a wavelength of 300 - 400 nm for 5 - 20 seconds, and then heated at 90°C - 150°C for 20 - 60 minutes to obtain the polymer lower cladding (32); C: Preparation of the polymer optical waveguide core layer The polymer optical waveguide core layer material is spin-coated on the polymer undercladding (32) by a spin-coating process at a rotational speed of 1000 to 3000 revolutions per minute; then the prepared polymer thin film is pre-baked, heated at a temperature of 80°C to 140°C for 3 to 20 minutes, and then cooled to 50°C to 80°C; the polymer thin film is lithographed, alignment lithography is carried out under ultraviolet light with a wavelength of 300 to 400 nm, the waveguide mask has a structure complementary to the optical waveguide core layer to be prepared, and the exposure time is 3 to 30 seconds, so that the optical waveguide core layer materials in the input / output few-mode straight waveguide region, curved waveguide region, tapered waveguide region, and multimode straight waveguide region of the device to be prepared are exposed to ultraviolet light; after lithography, it is heated at a temperature of 70°C to 130°C for 3 to 30 minutes and cooled to 20°C to 30°C; then development is carried out, first wet etching for 10 to 60 seconds in the developer corresponding to the optical waveguide core layer material to remove the unexposed non-optical waveguide core layer structure, then respectively placed in isopropyl alcohol solution and deionized water to wash away the residual optical waveguide core layer material and developer, and finally dried with nitrogen; After development, post-baking and hardening are carried out, and heated at 120°C - 160°C for 30 - 60 minutes to obtain the strip-shaped optical waveguide core layer (33); D: Preparation of the polymer optical waveguide upper cladding The polymer upper cladding material is spin-coated on the optical waveguide core layer (33) and the polymer lower cladding (32) by a spin-coating process at a spin-coating speed of 600 to 3000 revolutions per minute, and then heated at 90°C to 150°C for 5 to 20 minutes, and then integrally exposed to ultraviolet light with a wavelength of 300 to 400 nm for 5 to 30 seconds, and then heated at 90°C to 150°C for 20 to 60 minutes to obtain the polymer upper cladding (34). E: Preparation of the Al heating electrode A metal thin film is evaporated on the polymer upper cladding (34) by an evaporation process, and then a positive photoresist BP212 is spin-coated on the metal thin film at a speed of 2000 to 4000 revolutions per minute. Then pre-baked at a temperature of 70°C to 110°C for 10 to 30 minutes, and then cooled to 40°C to 70°C to obtain a BP212 thin film with a thickness of 0.5 to 2.5 μm; alignment lithography is performed, and the mask has the same structure as the heating electrode (13) with electrode pins and electrode leads to be prepared. It is exposed to ultraviolet light with a wavelength of 300 to 400 nm for 1.5 to 5.5 seconds to expose the photoresist BP212 thin film in the area other than the heating electrode; then it is placed in a NaOH solution with a mass concentration of 3 to 10‰ for 10 to 60 seconds to remove the exposed photoresist, and then rinsed with deionized water and dried with nitrogen; heated at a temperature of 80°C to 120°C for 10 to 30 minutes, and then cooled to 20°C to 30°C; finally, the metal electrode is developed, that is, placed in a NaOH solution with a mass concentration of 3 to 10‰ for 2 to 10 minutes to remove the metal thin film in the area other than the heating electrode, repeatedly rinsed with deionized water and dried with nitrogen, and finally the sample is placed in ethanol for 5 to 10 seconds to wash off the unexposed photoresist BP212 thin film on the heating electrode, then rinsed with deionized water and dried with nitrogen, so as to obtain a few-mode waveguide optical switch based on the total internal reflection structure.

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