Single-port input / output multi-state adjustable waveguide mode converter and preparation method thereof

Abstract

The invention provides a single-port input / output multi-state adjustable waveguide mode converter and a preparation method thereof, and belongs to the technical field of on-chip silicon-based polymer hybrid integrated waveguide mode converters. According to the invention, a double-layer MZI parallel combination structure is adopted, independent electrodes are configured at specific positions of interference arms, and corresponding modulation signals are applied, so that accurate regulation and control of an input light field are realized. When E00-mode signal light is input, the structure can dynamically realize the conversion function of three modes of E00 / E01 / E10 on the premise of keeping single-port output, and the mode conversion efficiency reaches 95%. And the device is compatible with a standard silicon-based CMOS (Complementary Metal-Oxide-Semiconductor Transistor) process, is beneficial to reducing the manufacturing cost and promoting large-scale integrated application, is suitable for the fields of a high-capacity mode division multiplexing system and multi-dimensional optical signal processing, and can meet the urgent requirements of modern optical communication on high-integration-level, reconfigurable operation and low-cost devices.

Description

Technical Field

[0001] This invention relates to the field of on-chip silicon-based polymer hybrid integrated waveguide mode converter technology, and in particular to a single-port input / output multi-state tunable waveguide mode converter and its fabrication method. Background Technology

[0002] As communication technology increasingly becomes a key pillar of social development, on-chip photonic integrated devices (OSIPs) integrate multiple components such as lasers, modulators, waveguides, and detectors onto a single chip. This combines the large-scale integration advantages of CMOS technology with the high bandwidth, low power consumption, and anti-interference characteristics of optical signals, effectively improving data transmission rates and providing an indispensable technological path for the development of data centers and high-performance computing. However, with the continuous growth of communication demands, traditional single-mode waveguide structures are insufficient to meet the requirements of ultra-high-density integration, restricting the functional expansion of chip-level photonic devices. Mode Division Multiplexing (MDM) technology utilizes different spatial modes in a waveguide as independent transmission channels to simultaneously transmit multiple signals on the same wavelength, effectively improving the transmission capacity of communication systems. A MDM system consists of several key components, including mode converters, mode multiplexers, few-mode fibers, and mode demultiplexers. Among these, the mode converter, as the core component of the MDM system, enables energy exchange between the fundamental mode and higher-order modes.

[0003] Optical waveguide mode converters can be broadly classified into single-port and multi-port output types based on their output port configurations. Common structures for single-port output mode converters include asymmetric directional couplers, Mach-Zehnder interferometers (MZI), Bragg gratings, and tapered structures. An asymmetric directional coupler consists of two parallel waveguides. By controlling parameters such as the waveguide spacing, length, and refractive index, coupling and mode conversion of the optical signal between the two waveguides in the coupling region are achieved. MZI mode converters achieve mode conversion by controlling the dimensions of the two interferometer arms and adjusting the optical path difference between the two different paths. Bragg grating mode converters introduce periodic refractive index variations in the waveguide. By satisfying the phase matching conditions between different modes, the intensity and phase of the input signal light change, thereby achieving the transfer of optical energy between different modes. Tapered structure mode converters employ a longitudinally non-uniform coupling design. By optimizing the tapered port structure, they achieve few-mode to multi-mode conversion. However, for the aforementioned single-port output mode converters, once the device structure is determined, they can only achieve single-mode to single-mode conversion. For complex mode-division multiplexing systems that need to process multiple modes simultaneously, their function is relatively limited. Multi-port output mode converters can distribute a single input optical signal to multiple output ports and simultaneously achieve mode conversion. For example, related technologies have designed Y-branch waveguide structures to achieve single-port E11 input to dual-port E21 and E22 mode output. However, only one mode conversion can be achieved simultaneously among multiple output ports. Another example is an adjustable 7-port mode coupler disclosed in related technologies, which can achieve TE0 mode to TE1 or TE2 mode conversion. However, the multi-port output waveguide structure is large in size, which is not conducive to high-density integration, and the parallel ports will generate mode crosstalk problems during transmission.

[0004] Therefore, although progress has been made in the research of single-port and multi-port output mode couplers, single-port mode couplers mostly focus on specific mode conversions, achieving limited performance. While multi-port mode couplers can achieve multi-mode output, their complex structure and problems such as crosstalk and uneven energy distribution exist. Therefore, in the field of on-chip photonic integration technology, there is still a lack of waveguide mode converters that can integrate single-port output, flexible multi-mode tunability, and compact structure. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a single-port input / output multi-state tunable waveguide mode converter and its fabrication method. The multi-state tunable waveguide mode converter of this invention adopts a dual-layer MZI parallel combination structure, which can dynamically achieve E while maintaining single-port output. 00 / E 01 / E 10 Three-mode switching function.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a single-port input / output multi-state tunable waveguide mode converter, comprising a substrate layer, a first cladding layer, a second cladding layer and a third cladding layer stacked sequentially, and a double-layer MZI core layer, wherein the double-layer MZI core layer comprises a first MZI core layer and a second MZI core layer, and the double-layer MZI core layer is a single-port input and single-port output waveguide structure; The first MZI core layer is embedded in the second cladding layer, and the second cladding layer and the first MZI core layer have the same thickness; the second MZI core layer is embedded in the third cladding layer, and the third cladding layer and the second MZI core layer have the same thickness. An MZI structure is nested on the interference arm of the first MZI core layer and the second MZI core layer, respectively. The first MZI core layer includes a first core layer first interferometric arm waveguide, a first core layer second interferometric arm waveguide, and a first core layer third interferometric arm waveguide, with the first core layer second interferometric arm waveguide and the first core layer third interferometric arm waveguide located in a nested MZI structure; the second MZI core layer includes a second core layer first interferometric arm waveguide, a second core layer second interferometric arm waveguide, and a second core layer third interferometric arm waveguide, with the second core layer second interferometric arm waveguide and the second core layer third interferometric arm waveguide located in a nested MZI structure; A first partial electrode is provided above at least one of the first core layer first interferometric arm waveguide and the second core layer first interferometric arm waveguide. The first partial electrode is disposed on the surface of the second cladding layer. A second partial electrode is provided on the surface of at least two of the first core layer second interferometric arm waveguide, the first core layer third interferometric arm waveguide, the second core layer second interferometric arm waveguide and the second core layer third interferometric arm waveguide. At least one second partial electrode is provided above the first core layer second interferometric arm waveguide and the first core layer third interferometric arm waveguide. The second partial electrode is disposed on the surface of the third cladding layer.

[0007] Preferably, a first portion of electrodes is provided above both the first core layer first interferometer waveguide and the second core layer first interferometer waveguide.

[0008] Preferably, the surfaces of two of the first core layer second interferometer waveguide, the first core layer third interferometer waveguide, the second core layer second interferometer waveguide, and the second core layer third interferometer waveguide are provided with second part electrodes.

[0009] Preferably, the first MZI core layer and the second MZI core layer have the same material and refractive index.

[0010] Preferably, the materials of the first MZI core layer and the second MZI core layer are Si, Si3N4, SU-8 series photoresist, NR series photoresist, AZ series photoresist or EPOCore photoresist.

[0011] Preferably, the thickness of the first interferometric arm waveguide in the first core layer is 2~24μm and the width is 2~20μm, and the thickness of the second interferometric arm waveguide and the width of the third interferometric arm waveguide in the first core layer are independently 2~24μm and independently 1~10μm. The thickness of the first interferometer waveguide in the second core layer is 2~24μm and the width is 2~20μm. The thickness of the second interferometer waveguide in the second core layer and the width of the third interferometer waveguide in the second core layer are independently 2~24μm and independently 1~10μm.

[0012] Preferably, the thickness of the first part of the electrode is 100~300nm and the width is 5~30μm, and the thickness of the second part of the electrode is 100~300nm and the width is 3~15μm.

[0013] Preferably, the thickness of the first coating layer is 2~24μm, the thickness of the second coating layer is 2~24μm, and the thickness of the third coating layer is 1~10μm.

[0014] Preferably, the materials of the first cladding layer, the second cladding layer, and the third cladding layer independently include one or more of SiO2, polymethyl methacrylate, polystyrene, EpoClad, hydrogel, polydimethylsiloxane, and the NOA series.

[0015] This invention also provides a method for fabricating the single-port input / output multi-state tunable waveguide mode converter described in the above technical solution, comprising the following steps: The first MZI core layer is formed by sequentially coating the surface of the substrate with a first MZI core layer material, performing first photolithography, first exposure, and first development. A first cladding material is coated around the first MZI core layer to form the first cladding layer; The second MZI core layer is formed by sequentially coating the surface of the first cladding layer with the second MZI core layer material, performing the second photolithography, the second exposure, and the second development. A second cladding material is coated around the second MZI core layer to form the second cladding layer; A first metal thin film is deposited on the surface of the second cladding layer, and then a third photolithography, a third exposure and a third development are sequentially performed on the surface of the first metal thin film to form the electrode in the first MZI core layer. Then, a third cladding material is coated on the surface of the obtained sample to form the third cladding layer. A second metal thin film is deposited on the surface of the third cladding layer, and then a fourth photolithography, a fourth exposure, and a fourth development are performed sequentially on the surface of the second metal thin film to form the electrode in the second MZI core layer, thereby obtaining the single-port input / output multi-state tunable waveguide mode converter.

[0016] This invention provides a single-port input / output multi-state tunable waveguide mode converter, comprising a substrate layer, a first cladding layer, a second cladding layer, and a third cladding layer stacked sequentially, and a dual-layer MZI core layer. The dual-layer MZI core layer includes a first MZI core layer and a second MZI core layer, and is a single-port input, single-port output waveguide structure. The first MZI core layer is embedded in the second cladding layer, and the second cladding layer and the first MZI core layer have the same thickness. The second MZI core layer is embedded in the third cladding layer, and the third cladding layer and the second MZI core layer have the same thickness. An MZI structure is nested on the interferometer arms of the first and second MZI core layers. The first MZI core layer includes a first core layer first interferometer arm waveguide, a first core layer second interferometer arm waveguide, and a first core layer third interferometer arm waveguide, which are located within the nested MZI structures. The second MZI core layer includes a second core layer first interferometer waveguide, a second core layer second interferometer waveguide, and a second core layer third interferometer waveguide, which are located in a nested MZI structure. A first partial electrode is provided above at least one of the first core layer first interferometer waveguide and the second core layer first interferometer waveguide. The first partial electrode is located on the surface of the second cladding layer. A second partial electrode is provided on the surface of at least two of the first core layer second interferometer waveguide, the first core layer third interferometer waveguide, the second core layer second interferometer waveguide, and the second core layer third interferometer waveguide. At least one second partial electrode is provided above the first core layer second interferometer waveguide and the first core layer third interferometer waveguide. The second partial electrode is located on the surface of the third cladding layer.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a dual-layer MZI parallel combination structure, achieving precise control of the input optical field by configuring independent electrodes at specific positions on the interferometer arms and applying corresponding modulation signals. When the input E 00 When the mode signal is in operation, this structure can dynamically achieve E while maintaining single-port output. 00 / E 01 / E 10 The three mode switching functions offer the following specific benefits: 1. The device structure employs a single-port input / output MZI waveguide to achieve fundamental mode and multi-mode switching: This invention uses a parallel MZI combination structure, and by configuring independent electrodes at specific positions on the interferometer arms and applying corresponding modulation signals, it achieves precise control of the input optical field. When the input E 00 When the mode signal is in operation, this structure can dynamically achieve E while maintaining single-port output. 00 / E 01 / E 10 The three-mode conversion function overcomes the limitations of single-port devices having limited functionality and multi-port output devices experiencing mode crosstalk. This design enables single-port devices to have multi-mode processing capabilities, making them suitable for mode-division multiplexing systems that require flexible configuration and improving the multi-dimensional signal processing capabilities of optical communication systems.

[0018] 2. In terms of device performance, independent electrode control enables efficient multi-mode switching: This invention configures independent electrode structures in the MZI interferometer arm regions. By applying matched electrical modulation signals to different electrodes, the phase change of the optical signal within each interferometer arm can be precisely controlled, thereby achieving crosstalk-free switching between the three modes. The mode conversion efficiency of this device is consistently greater than 95%, improving the transmission distance and data transmission reliability of the optical communication system.

[0019] This invention also provides a method for fabricating the single-port input / output multi-mode tunable waveguide mode converter, which is compatible with standard CMOS manufacturing processes and has the advantages of high integration and low cost. All structures of the device in this invention, including waveguides and electrodes, can be fabricated using standard silicon photonics CMOS processes, which simplifies the fabrication process and reduces mass production costs. The dual-layer parallel structure design realizes multi-mode control functions within a limited chip area, improves the integration of the device, and can effectively meet the urgent needs of modern optical communication systems for multi-dimensional signal processing, high-density integration, reconfigurable operation, and low-cost devices. Attached Figure Description

[0020] Figure 1 The diagram shows the structure of the single-port input / output multi-state tunable waveguide mode converter, where (a) is a three-dimensional structure diagram; (b) is a cross-sectional view of the input end; (c) is a cross-sectional view of the first and second electrodes; and (d) is a cross-sectional view of the third and fourth electrodes. Figure 2 Flowchart of the fabrication process of the first and second MZI core layers for a single-port input / output multi-state tunable waveguide mode converter; Figure 3 The fabrication flowchart of the first, second, third, and fourth electrodes of a single-port input / output multi-state tunable waveguide mode converter is shown. Figure 4The image shows an optical micrograph of the single-port input / output multi-state tunable waveguide mode converter fabricated in Example 1. In (a), the micrograph shows the structure of the first core layer input straight waveguide 301, the first core layer first curved waveguide 302, the first core layer first interferometer waveguide 303, the second core layer input straight waveguide 401, the second core layer first curved waveguide 402, and the second core layer first interferometer waveguide 403. Figure 4 (b) is a structural diagram of the first core layer first interferometric arm waveguide 303, the first core layer second curved waveguide 304, the first core layer third curved waveguide 305, the first core layer second interferometric arm waveguide 306, the first core layer third interferometric arm waveguide 307, the second core layer first interferometric arm waveguide 403, the second core layer second curved waveguide 404, the second core layer third curved waveguide 405, the second core layer second interferometric arm waveguide 406, and the second core layer third interferometric arm waveguide 407. Figure 5 For E 00 -E 00 E 00 -E 01 E 00 -E 10 The curves showing the normalized mode conversion efficiency as a function of the widths of input waveguides 301 and 401; Figure 6 For E 00 -E 00 E 00 -E 01 E 00 -E 10 The curves showing the normalized mode conversion efficiency as a function of the heights of input waveguides 301 and 401; Figure 7 When the electrode is applied, E 00 -E 00 Transmission path diagram of the mode; Figure 8 When the first electrode or the second electrode is adjusted, E 00 -E 01 Transmission path diagram of the mode; Figure 9 When the third and fourth electrodes are simultaneously controlled, E 00 -E 10 Transmission path diagram of the mode; In the diagram, 100 represents the substrate layer, 101 the first substrate layer, 102 the second substrate layer, 200 the cladding layer (201 being the first cladding layer, 202 the second cladding layer, 203 the third cladding layer), and 300 the first MZI core layer (301 the input straight waveguide, 302 the first bent waveguide, 303 the first interferometer waveguide, 304 the second bent waveguide, 305 the third bent waveguide, 306 the second interferometer waveguide, 307 the third interferometer waveguide, 308 the fourth bent waveguide, 309 the fifth bent waveguide, 310 the first output waveguide, and 311 the sixth bent waveguide. 312 is the second output waveguide of the first core layer, 400 is the second MZI core layer, wherein 401 is the input straight waveguide of the second core layer, 402 is the first curved waveguide of the second core layer, 403 is the first interferometer waveguide of the second core layer, 404 is the second curved waveguide of the second core layer, 405 is the third curved waveguide of the second core layer, 406 is the second interferometer waveguide of the second core layer, 407 is the third interferometer waveguide of the second core layer, 408 is the fourth curved waveguide of the second core layer, 409 is the fifth curved waveguide of the second core layer, 410 is the first output waveguide of the second core layer, 411 is the sixth curved waveguide of the second core layer, 412 is the second output waveguide of the second core layer, 501 is the first electrode, 502 is the second electrode, 503 is the third electrode, and 504 is the fourth electrode. Detailed Implementation

[0021] This invention provides a single-port input / output multi-state tunable waveguide mode converter, comprising a substrate layer, a first cladding layer, a second cladding layer and a third cladding layer stacked sequentially, and a double-layer MZI core layer, wherein the double-layer MZI core layer comprises a first MZI core layer and a second MZI core layer, and the double-layer MZI core layer is a single-port input and single-port output waveguide structure; The first MZI core layer is embedded in the second cladding layer, and the second cladding layer and the first MZI core layer have the same thickness; the second MZI core layer is embedded in the third cladding layer, and the third cladding layer and the second MZI core layer have the same thickness. An MZI structure is nested on the interference arm of the first MZI core layer and the second MZI core layer, respectively. The first MZI core layer includes a first core layer first interferometric arm waveguide, a first core layer second interferometric arm waveguide, and a first core layer third interferometric arm waveguide, with the first core layer second interferometric arm waveguide and the first core layer third interferometric arm waveguide located in a nested MZI structure; the second MZI core layer includes a second core layer first interferometric arm waveguide, a second core layer second interferometric arm waveguide, and a second core layer third interferometric arm waveguide, with the second core layer second interferometric arm waveguide and the second core layer third interferometric arm waveguide located in a nested MZI structure; A first partial electrode is provided above at least one of the first core layer first interferometric arm waveguide and the second core layer first interferometric arm waveguide. The first partial electrode is disposed on the surface of the second cladding layer. A second partial electrode is provided on the surface of at least two of the first core layer second interferometric arm waveguide, the first core layer third interferometric arm waveguide, the second core layer second interferometric arm waveguide and the second core layer third interferometric arm waveguide. At least one second partial electrode is provided above the first core layer second interferometric arm waveguide and the first core layer third interferometric arm waveguide. The second partial electrode is disposed on the surface of the third cladding layer.

[0022] Figure 1 The diagram shows the structure of the single-port input / output multi-state tunable waveguide mode converter, where (a) is a three-dimensional structure diagram; (b) is a cross-sectional view of the input end; (c) is a cross-sectional view of the first and second electrodes; and (d) is a cross-sectional view of the third and fourth electrodes. In the diagram, 100 represents the substrate layer, 101 the first substrate layer, 102 the second substrate layer, 200 the cladding layer (201 being the first cladding layer, 202 the second cladding layer, 203 the third cladding layer), and 300 the first MZI core layer (301 the input straight waveguide, 302 the first bent waveguide, 303 the first interferometer waveguide, 304 the second bent waveguide, 305 the third bent waveguide, 306 the second interferometer waveguide, 307 the third interferometer waveguide, 308 the fourth bent waveguide, 309 the fifth bent waveguide, 310 the first output waveguide, and 311 the sixth bent waveguide. 312 is the second output waveguide of the first core layer, 400 is the second MZI core layer, wherein 401 is the input straight waveguide of the second core layer, 402 is the first curved waveguide of the second core layer, 403 is the first interferometer waveguide of the second core layer, 404 is the second curved waveguide of the second core layer, 405 is the third curved waveguide of the second core layer, 406 is the second interferometer waveguide of the second core layer, 407 is the third interferometer waveguide of the second core layer, 408 is the fourth curved waveguide of the second core layer, 409 is the fifth curved waveguide of the second core layer, 410 is the first output waveguide of the second core layer, 411 is the sixth curved waveguide of the second core layer, 412 is the second output waveguide of the second core layer, 501 is the first electrode, 502 is the second electrode, 503 is the third electrode, and 504 is the fourth electrode.

[0023] In this invention, the substrate layer 100 preferably includes a first substrate layer 101 and a second substrate layer 102 from bottom to top, and a double-layer MZI core structure is provided above the second substrate layer 102.

[0024] In this invention, the material of the first substrate layer 101 preferably includes a Si-based SiO2 wafer.

[0025] In this invention, the thickness of the first substrate layer 101 is preferably 0.5~1mm.

[0026] In this invention, the material of the second substrate layer 102 preferably includes one or more of SiO2, polymethyl methacrylate (PMMA), polystyrene (PS), EpoClad, hydrogel, polydimethylsiloxane (PDMS), and NOA series.

[0027] In this invention, the thickness of the second substrate layer 102 is preferably 3~20μm, specifically 5μm.

[0028] In this invention, the double-layer MZI core layer includes a first MZI core layer 300 and a second MZI core layer 400.

[0029] In this invention, the first MZI core layer 300 preferably includes, from left to right, a first core layer input straight waveguide 301, a first core layer first bent waveguide 302, a first core layer first interference arm waveguide 303, a first core layer second bent waveguide 304, a first core layer third bent waveguide 305, a first core layer second interference arm waveguide 306, a first core layer third interference arm waveguide 307, a first core layer fourth bent waveguide 308, a first core layer fifth bent waveguide 309, a first core layer first output waveguide 310, a first core layer sixth bent waveguide 311, and a first core layer second output waveguide 312.

[0030] In this invention, the second MZI core layer 400 preferably includes, from left to right, a second core layer input straight waveguide 401, a second core layer first bent waveguide 402, a second core layer first interference arm waveguide 403, a second core layer second bent waveguide 404, a second core layer third bent waveguide 405, a second core layer second interference arm waveguide 406, a second core layer third interference arm waveguide 407, a second core layer fourth bent waveguide 408, a second core layer fifth bent waveguide 409, a second core layer first output waveguide 410, a second core layer sixth bent waveguide 411, and a second core layer second output waveguide 412.

[0031] In this invention, a first electrode is preferably provided above the first core layer first interferometer waveguide 303 and the second core layer first interferometer waveguide 403, that is, a first electrode 501 is provided above the first core layer first interferometer waveguide 303 and a second electrode 502 is provided above the second core layer first interferometer waveguide 403.

[0032] In this invention, the surfaces of two of the first core layer second interferometer waveguide 306, the first core layer third interferometer waveguide 307, the second core layer second interferometer waveguide 406, and the second core layer third interferometer waveguide 407 are preferably provided with second part electrodes, that is, a third electrode 503 is provided above the first core layer third interferometer waveguide 307, and a fourth electrode 504 is provided above the second core layer third interferometer waveguide 407.

[0033] In this invention, there must be at least two electrodes on the first core layer second interferometer waveguide 306, the first core layer third interferometer waveguide 307, the second core layer second interferometer waveguide 406, and the second core layer third interferometer waveguide 407. At least one electrode is located on the first core layer second interferometer waveguide 306 and the first core layer third interferometer waveguide 307, and at least one electrode is located on the second core layer second interferometer waveguide 406 and the second core layer third interferometer waveguide 407. When adjusting, the adjustment must be "simultaneous" and "symmetrical". "Simultaneous" means that one electrode on the first core layer second interferometer waveguide 306 and the first core layer third interferometer waveguide 307 and one electrode on the second core layer second interferometer waveguide 406 and the second core layer third interferometer waveguide 407 are adjusted at the same time, such as adjusting 503 and 504 at the same time. "Symmetrical" means that either 503 and 504 are adjusted at the same time, or the other two interferometer arms without electrodes are adjusted at the same time.

[0034] In this invention, the materials and refractive indices of the first MZI core layer 300 and the second MZI core layer 400 are preferably the same.

[0035] In this invention, the materials of the first MZI core layer 300 and the second MZI core layer 400 are preferably Si, Si3N4, SU-8 series photoresist, NR series photoresist, AZ series photoresist or EPOCore photoresist.

[0036] In this invention, the thickness of the first core layer first interferometric arm waveguide 303 is preferably 2~24μm, specifically 4μm, and the width is preferably 2~20μm, specifically 6μm. The thickness of the first core layer second interferometric arm waveguide 306 and the first core layer third interferometric arm waveguide 307 is independently preferably 2~24μm, and the width is independently preferably 1~10μm. The thickness of the second core layer first interferometric arm waveguide 403 is preferably 2~24μm, specifically 4μm, and the width is preferably 2~20μm, specifically 3μm. The thickness of the second core layer second interferometric arm waveguide 406 and the second core layer third interferometric arm waveguide 407 is independently preferably 2~24μm, specifically 4μm, and the width is independently preferably 1~10μm, specifically 3μm.

[0037] In this invention, the thickness of the first core layer input straight waveguide 301, the first core layer first bent waveguide 302, the first core layer first output waveguide 310, the first core layer sixth bent waveguide 311, and the first core layer second output waveguide 312 is preferably 2~24μm, specifically 4μm, and the width is preferably 2~20μm, specifically 6μm. The thickness of the first core layer second bent waveguide 304, the first core layer third bent waveguide 305, the first core layer fourth bent waveguide 308, and the first core layer fifth bent waveguide 309 is independently preferably 2~24μm, specifically 4μm, and the width is independently preferably 1~10μm, specifically 3μm.

[0038] In this invention, the widths of the first core layer second curved waveguide 304, the first core layer third curved waveguide 305, the first core layer second interference arm waveguide 306, the first core layer third interference arm waveguide 307, the first core layer fourth curved waveguide 308, and the first core layer fifth curved waveguide 309 are half of the other waveguides in the first MZI core layer 300, while the thicknesses remain consistent.

[0039] In this invention, the width and thickness of each waveguide in the second MZI core layer 400 are the same as those of each waveguide in the first MZI core layer 300.

[0040] In this invention, the materials of the first and second partial electrodes independently include one or more of Au, Al, and graphene.

[0041] In this invention, the thickness of the first part of the electrode is preferably 100~300nm, specifically 100nm, and the width is preferably 5~30μm, specifically 10μm. The thickness of the second part of the electrode is preferably 100~300nm, specifically 100nm, and the width is preferably 3~15μm, specifically 6μm.

[0042] In this invention, the thickness of the first electrode 501 and the second electrode 502 is preferably 100~300nm, specifically 100nm, and the width is preferably 5~30μm, specifically 10μm. The thickness of the third electrode 503 and the fourth electrode 504 is preferably 100~300nm, specifically 100nm, and the width is preferably 3~15μm, specifically 6μm.

[0043] In this invention, the thickness of the first cladding layer 201 is preferably 2~24μm, specifically 4μm; the thickness of the second cladding layer 202 is preferably 2~24μm, specifically 4μm; and the thickness of the third cladding layer 203 is preferably 1~10μm, specifically 3μm.

[0044] In this invention, the materials of the first cladding layer, the second cladding layer, and the third cladding layer preferably include one or more of the following: SiO2, polymethyl methacrylate (PMMA), polystyrene (PS), EpoClad, hydrogel, polydimethylsiloxane (PDMS), and NOA series.

[0045] This invention also provides a method for fabricating the single-port input / output multi-state tunable waveguide mode converter described in the above technical solution, comprising the following steps: The first MZI core layer is formed by sequentially coating the surface of the substrate with a first MZI core layer material, performing first photolithography, first exposure, and first development. A first cladding material is coated around the first MZI core layer to form the first cladding layer; The second MZI core layer is formed by sequentially coating the surface of the first cladding layer with the second MZI core layer material, performing the second photolithography, the second exposure, and the second development. A second cladding material is coated around the second MZI core layer to form the second cladding layer; A first metal thin film is deposited on the surface of the second cladding layer, and then a third photolithography, a third exposure and a third development are sequentially performed on the surface of the first metal thin film to form the electrode in the first MZI core layer. Then, a third cladding material is coated on the surface of the obtained sample to form the third cladding layer. A second metal thin film is deposited on the surface of the third cladding layer, and then a fourth photolithography, a fourth exposure, and a fourth development are performed sequentially on the surface of the second metal thin film to form the electrode in the second MZI core layer, thereby obtaining the single-port input / output multi-state tunable waveguide mode converter.

[0046] In this invention, the first MZI core layer is formed by sequentially coating the surface of the substrate with a first MZI core layer material, performing a first photolithography, a first exposure, and a first development.

[0047] Figure 2 The fabrication flowchart of the first and second MZI core layers for a single-port input / output multi-state tunable waveguide mode converter is shown.

[0048] Preferably, the surface of the first substrate layer 101 is cleaned to remove solid impurities and soluble contaminants, and then dried with a nitrogen stream. A second substrate solution material is uniformly dropped onto the surface of the first substrate layer 102, and a spin coater is started to perform a spin coating operation, forming a polymer film of uniform thickness and a smooth surface, namely the second substrate layer 102. After the spin coating is completed, the sample is dried to obtain the substrate layer with stable structure and good performance.

[0049] In this invention, the spin coating preferably includes pre-spinning and spin coating in sequence. The pre-spinning is preferably performed at a low speed of 400-1000 rpm (specifically 600 rpm) for 5-10 seconds, using centrifugal force to initially cover the surface of the first substrate layer 101 with the second substrate solution material. The spin coating process preferably involves rapidly increasing the rotation speed to 1000-3000 rpm (specifically 2000 rpm) and maintaining it for 30-60 seconds to form a film of uniform thickness.

[0050] In this invention, the drying temperature is preferably 90~160℃, specifically 120℃, and the drying time is preferably 25~40min, specifically 30min.

[0051] In this invention, the drying is preferably carried out in a dryer.

[0052] The present invention preferably involves taking the first MZI core layer material and uniformly coating it (preferably spin coating, preferably including sequential pre-spinning and spin coating, wherein the pre-spinning is performed at a low speed of 500-800 rpm for 5-10 seconds, and the spin coating is preferably performed by rapidly increasing the speed to 1500-5500 rpm and maintaining it for 30-60 seconds) at the center of the substrate layer 100, starting the spin coater to form a polymer film of uniform thickness, and then performing pre-baking: after spin coating, the sample with the polymer film is transferred to a hot plate for processing to remove most of the solvent in the polymer film and to allow the film to initially cure. The pre-baking is preferably performed by gradient heating, preferably... First, preheat at a lower temperature of 65-75℃ for 5-15 minutes. Then, raise the temperature to 95-105℃ and hold for 15-35 minutes (specifically 25 minutes). This preheating process avoids the violent evaporation of solvent during rapid heating, which could lead to the formation of numerous micro-defects. Then, perform the first photolithography: After the sample cools to room temperature, place it on the sample stage of the photolithography machine. Align and place the mask with the first MZI core layer pattern above the photoresist. Start the photolithography machine to perform the first exposure on the photoresist. The exposure light source for the first photolithography is preferably 365nm ultraviolet light, and the exposure intensity is preferably 150-200 mJ / cm². 2 Specifically, it can be 180mJ / cm 2The exposure time is preferably 3-20 seconds, specifically 5 seconds, followed by post-baking: After the first exposure, the sample is transferred to a hot plate for further processing. The post-baking is preferably performed by first baking on a hot plate at 75-95℃ (specifically 85℃) for 5-15 minutes, then increasing the temperature to 95-140℃ and heating for 15-35 minutes (specifically 25 minutes), followed by the first development: After the post-baking, the sample is immersed in the developing solution to form a photolithographic pattern corresponding to the mask pattern. The first development time is preferably 1-2 minutes. After the first development, the sample surface is preferably rinsed with deionized water to remove residual developing solution, followed by hardening: The sample is placed in an oven for hardening treatment to further solidify the photoresist. The hardening temperature is preferably 120-160℃, specifically 130℃, and the time is preferably 15-30 minutes.

[0053] After forming the first MZI core layer, the present invention coats the first cladding material around the first MZI core layer to form the first cladding layer.

[0054] In this invention, the coating is preferably spin coating, which preferably includes pre-spinning and spin coating in sequence. The pre-spinning is preferably performed at a low speed of 500-800 rpm for 5-10 seconds, and the spin coating is preferably performed at a speed of 1000-6000 rpm, specifically 3500 rpm, and maintained for 20-60 seconds.

[0055] After the coating is completed, the resulting sample is preferably placed on a hot plate and heated to dry, and then naturally cooled to room temperature after heating. In this invention, the heating and drying is preferably carried out by first heating at 70~95℃ for 5~15 minutes, and then raising the temperature to 100~130℃ (specifically 120℃) for curing for 30 minutes.

[0056] After the first cladding layer is formed, the present invention sequentially coats the surface of the first cladding layer with a second MZI core layer material, performs a second photolithography, a second exposure, and a second development to form the second MZI core layer.

[0057] The present invention preferably performs the same patterning process as the first MZI core layer, that is, the steps of coating the second MZI core layer material, the second photolithography, the second exposure and the second development are preferably the same as those for preparing the first MZI core layer. The mask used in the patterning process is specifically designed to define the structure of the second MZI core layer.

[0058] After forming the second MZI core layer, the present invention coats the second MZI core layer with a second cladding material to form the second cladding layer. In the present invention, the parameters for forming the second cladding layer are preferably the same as those for forming the first cladding layer, and will not be repeated here.

[0059] After the coating is completed, the resulting sample is preferably placed on a hot plate and heated to dry, and then naturally cooled to room temperature after heating. In this invention, the heating and drying is preferably carried out by first heating at 70~95℃ for 5~15 minutes, and then raising the temperature to 100~130℃ (specifically 120℃) for curing for 30 minutes.

[0060] After forming the second cladding, the present invention deposits a first metal thin film on the surface of the second cladding, and then performs a third photolithography, a third exposure, and a third development sequentially on the surface of the first metal thin film to form the electrode in the first MZI core layer. Then, a third cladding material is coated on the surface of the obtained sample to form the third cladding; a second metal thin film is deposited on the surface of the third cladding, and then a fourth photolithography, a fourth exposure, and a fourth development sequentially are performed on the surface of the second metal thin film to form the electrode in the second MZI core layer, thereby obtaining the single-port input / output multi-state tunable waveguide mode converter.

[0061] Figure 3 This is a flowchart illustrating the fabrication process of the first, second, third, and fourth electrodes of a single-port input / output multi-state tunable waveguide mode converter.

[0062] This invention preferably utilizes vacuum evaporation technology to form a first metal film over the entire surface of the second cladding layer. Preferably, BP212 positive photoresist is applied to the first metal film, and then cured by pre-baking. The pre-baking temperature is preferably 95-105°C, and the heating time is preferably 5-15 minutes. Then, the third photolithography is performed: alignment exposure is performed using a mask that defines the electrode geometry (the exposure wavelength is preferably 365-405 nm, and the exposure energy is preferably 100-150 mJ / cm²). 2 Specifically, it can be 180mJ / cm 2 The exposure time is preferably 3-10s, followed by a post-baking process to promote the full completion of the photochemical reaction. The post-baking temperature is preferably 110-120℃ and the time is preferably 5-20min. Then, a third development is performed: excess photoresist and its metal film are removed using a developing solution to form the electrode pattern. The third development time is preferably 45-75s. Finally, a cleaning process is preferably performed: residual BP212 photoresist mask on the pattern is thoroughly removed by soaking in an organic solvent to complete the patterning of the first and third electrodes.

[0063] In this invention, the parameters of the vacuum evaporation technology preferably include: cavity vacuum degree 1.0 × 10⁻⁶. -5 ~1.0×10 -6 Pa, deposition rate 0.2~0.5 nm / s, specifically 0.3 nm / s.

[0064] In this invention, the thickness of the first metal thin film is preferably 100~300 nm.

[0065] In this invention, the spin coating speed of the BP212 positive photoresist is preferably 2500~4000 rpm, specifically 3000 rpm, and the spin coating time is preferably 30~60s.

[0066] After forming the electrodes in the first MZI core layer, the present invention coats the obtained sample with a third cladding material, places it on a hot plate for heating and drying, and then allows it to cool naturally to room temperature after heating to form the third cladding layer. In the present invention, the parameters for forming the third cladding layer are preferably the same as those for forming the first cladding layer, and will not be repeated here.

[0067] The present invention preferably utilizes vacuum evaporation technology to deposit the second metal film on the surface of the third cladding layer, then preferably spin-coates BP212 positive photoresist and cures it through pre-baking, and then performs the fourth photolithography: using a mask that defines the electrode geometry for alignment and exposure, followed by post-baking to promote the full completion of the photochemical reaction, and then performs the fourth development: using a developer to remove excess photoresist and its metal film to form the electrode pattern, and finally preferably performs cleaning: using an organic solvent to thoroughly remove the residual BP212 photoresist mask on the pattern, completing the patterning of the third and fourth electrodes.

[0068] In this invention, the preparation parameters of the third and fourth electrodes are preferably the same as those of the first and second electrodes, and will not be repeated here.

[0069] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0070] Example 1 Preparation such as Figure 1 The single-port input / output multi-state tunable waveguide mode converter shown includes a substrate layer 100, an upper cladding layer 200, a first MZI core layer 300, a second MZI core layer 400, and electrodes. The first MZI core layer 300 and the second MZI core layer 400 together form a dual-layer MZI core layer structure with single-port input and single-port output.

[0071] The substrate 100 includes, from bottom to top, a first substrate 101 and a second substrate 102; A first MZI core layer 300 is disposed above the second substrate layer 102. The structure, from left to right, includes a first core layer input straight waveguide 301, a first core layer first bent waveguide 302, a first core layer first interference arm waveguide 303, a first core layer second bent waveguide 304, a first core layer third bent waveguide 305, a first core layer second interference arm waveguide 306, a first core layer third interference arm waveguide 307, a first core layer fourth bent waveguide 308, a first core layer fifth bent waveguide 309, a first core layer first output waveguide 310, a first core layer sixth bent waveguide 311, and a first core layer second output waveguide 312. A second MZI core layer 400 is provided above the first MZI core layer 300. The structure from left to right includes the second core layer input straight waveguide 401, the second core layer first bent waveguide 402, the second core layer first interference arm waveguide 403, the second core layer second bent waveguide 404, the second core layer third bent waveguide 405, the second core layer second interference arm waveguide 406, the second core layer third interference arm waveguide 407, the second core layer fourth bent waveguide 408, the second core layer fifth bent waveguide 409, the second core layer first output waveguide 410, the second core layer sixth bent waveguide 411, and the second core layer second output waveguide 412. The electrodes include a first electrode 501, a second electrode 502, a third electrode 503, and a fourth electrode 504. The first electrode 501 is provided above the first interference arm 303 of the first core layer in the first MZI core layer. The second electrode 502 is provided above the first interference arm 403 of the second core layer in the second MZI core layer. The third electrode 503 is provided above the third interference arm 307 of the first core layer in the first MZI core layer. The fourth electrode 504 is provided above the third interference arm 406 of the second core layer in the second MZI core layer. The cladding 200 includes a first cladding 201, a second cladding 202, and a third cladding 203. The first cladding 201 is provided around the first MZI core layer 300, and the second cladding 202 is provided around the second MZI core layer 400. A first electrode 501, a third electrode 503, and a third cladding 203 are provided above the second cladding 202. A second electrode 502 and a fourth electrode 504 are provided on the third cladding 203.

[0072] The first substrate layer 101 is a Si-based SiO2 wafer, the second substrate layer 102 is PMMA, the first MZI core layer 300 is made of SU-8 series photoresist, the second MZI core layer 400 is made of SU-8 series photoresist, the upper cladding layer 200 is made of PMMA, and the electrode material is made of Al.

[0073] The first MZI core layer 300 and the second MZI core layer 400 have the same material and refractive index.

[0074] The thickness of the second substrate layer 102 is 5 μm. The thickness of the first core layer 300 input straight waveguide 301, the first core layer first bent waveguide 302, the first core layer first interference arm waveguide 303, the first core layer first output waveguide 310, the first core layer sixth bent waveguide 311 and the first core layer second output waveguide 312 is 4 μm and the width is 6 μm. The thickness of the first core layer second bent waveguide 304, the first core layer third bent waveguide 305, the first core layer second interference arm waveguide 306, the first core layer third interference arm waveguide 307, the first core layer fourth bent waveguide 308 and the first core layer fifth bent waveguide 309 is 4 μm and the width is 3 μm.

[0075] The horizontal distance from the end of the first curved waveguide 302 in the first core layer to the end of the input straight waveguide 301 in the first core layer is 30 μm, and the optical transmission distance is 2000 μm. The horizontal distance from the ends of the second curved waveguide 304 and the third curved waveguide 305 in the first core layer to the end of the first interference arm waveguide 303 in the first core layer is 20 μm, and the optical transmission distance is 1500 μm. The horizontal distance from the beginning of the fourth curved waveguide 308 and the fifth curved waveguide 309 in the first core layer to the beginning of the first output waveguide 310 in the first core layer is 20 μm, and the optical transmission distance is 1500 μm.

[0076] The width, thickness, and structure of each waveguide in the second MZI core layer 400 are consistent with those in the first MZI core layer 300.

[0077] The first electrode 501 and the second electrode 502 have a thickness of 100 nm and a width of 10 μm, while the third electrode 503 and the fourth electrode 504 have a thickness of 100 nm and a width of 6 μm.

[0078] The thickness of the first cladding layer 201 is the same as the thickness of the first MZI core layer 300, which is 4 μm. The thickness of the second cladding layer 202 is the same as the thickness of the second MZI core layer 400, which is 4 μm. The thickness of the third cladding layer is 3 μm.

[0079] The preparation method includes the following steps: S1. Preparation of the second substrate layer 102: The surface of the first substrate layer 101 is cleaned to remove solid impurities and soluble contaminants, and then dried with nitrogen gas. The second substrate PMMA polymer material is uniformly dropped onto the surface of the first substrate layer 101, and a spin coater is started to perform a spin coating operation, forming a PMMA polymer film of uniform thickness and a smooth surface. After spin coating, the sample is transferred to a dryer to obtain a substrate structure with stable structure and good performance.

[0080] The spin coating process consists of two steps: pre-spinning and spin coating. Pre-spinning involves rotating at a low speed of 600 rpm for 10 seconds, using centrifugal force to initially cover the surface of the first substrate layer with the coating solution. The spin coating process increases the rotation speed to 2000 rpm and maintains this speed for 30 seconds, forming a film of uniform thickness.

[0081] The drying process involves heating at 120℃ for 30 minutes.

[0082] S2. Preparation of the first MZI core layer 300: Specifically includes spin coating, pre-baking, photolithography, post-baking, development and hardening.

[0083] The spin coating process involves taking the first MZI core layer SU-8 series photoresist material, uniformly dropping it onto the center of the sample in step S1, and starting the spin coater to form a polymer film of uniform thickness.

[0084] In the spin coating process, the pre-spreading agent is rotated at a low speed of 800 rpm for 10 seconds, and the spinning speed is increased to 3000 rpm and maintained for 20 seconds.

[0085] Pre-baking involves transferring the sample containing SU-8 series photoresist to a hot plate for pre-baking treatment, which removes most of the solvent in the SU-8 series photoresist and allows the film to be initially cured.

[0086] During the pre-baking process, the temperature is first preheated at a lower temperature of 75°C for 15 minutes, and then the temperature is raised to 95°C and held for 25 minutes.

[0087] The photolithography process involves placing the sample on the stage of the photolithography machine after it has cooled to room temperature. A mask with the first MZI core layer 300 pattern is then aligned and placed above the sample, and the photolithography machine is started to expose the photoresist.

[0088] In the photolithography process, 365nm ultraviolet light is used as the exposure light source, with an exposure intensity of 180mJ / cm. 2 The exposure time is 5 seconds.

[0089] The post-baking process involves transferring the sample back onto a hot plate for further baking. The heating process begins with preheating at a lower temperature of 85°C for 15 minutes, followed by raising the temperature to 95°C and holding it for 25 minutes.

[0090] The development process involves immersing the sample in the developing solution to form a photolithographic pattern corresponding to the pattern on the photomask. After development, the sample surface is rinsed with deionized water to remove any residual developing solution.

[0091] The development time is 1 minute.

[0092] The hardening process involves placing the sample in an oven for hardening treatment to further solidify the photoresist. The hardening temperature is 130℃, and the time is 30 minutes.

[0093] S3. Preparation of the first coating layer 201: Spin-coat the first coating layer PMMA polymer material onto the sample in step S2, place the spin-coated sample on a hot plate to heat and dry, and slowly cool to room temperature after heating is completed.

[0094] The spin coating conditions are as follows: pre-spread the adhesive at a low speed of 800 rpm for 10 seconds, then increase the speed to 3500 rpm and maintain it for 20 seconds.

[0095] In the drying process, the material is first heated at 95°C for 15 minutes, and then heated at 120°C for 30 minutes to fully cure it.

[0096] S4. Preparation of the second MZI core layer 400: On the sample that has completed step S3, perform a graphical process that is exactly the same as S2.

[0097] The process conditions for spin coating, pre-baking, exposure, post-baking, and development are consistent with those in step S2.

[0098] The mask used in the graphical process has a pattern specifically designed to define the structure of the second MZI core layer 400.

[0099] S5. Preparation of the second coating layer 202: Spin-coat the sample in step S4 with the second coating layer PMMA polymer material, place the spin-coated sample on a hot plate and heat to dry, and then slowly cool to room temperature after heating is completed.

[0100] The spin coating and drying conditions in step S5 are the same as those in S3.

[0101] S6. Preparation of the first electrode 501 and the third electrode 503: The preparation process includes vapor deposition, spin coating, pre-baking, photolithography, post-baking, development and removal of photoresist.

[0102] The vapor deposition process utilizes vacuum vapor deposition technology to form a thin metal film on the sample. In vacuum vapor deposition technology, the vacuum level in the chamber should be maintained at 1.0 × 10⁻⁶. -5 The deposition rate is on the order of Pa, with a deposition rate of 0.3 nm / s and a metal layer thickness of 100 nm.

[0103] The spin coating and pre-baking process involves applying BP212 positive photoresist onto a metal film and then pre-baking it to cure. During spin coating of the BP212 positive photoresist, the spin coater speed is 3000 rpm, and the spin coating time is 30 seconds. The pre-baking temperature is 95℃, and the heating time is 15 minutes.

[0104] The photolithography and post-baking processes involve alignment and exposure using a mask that defines the electrode geometry, followed by post-baking to promote the full completion of the photochemical reaction. The exposure wavelength in the photolithography process is 365 nm, and the exposure energy is 180 mJ / cm². 2The exposure time was 3 seconds. The post-baking temperature was 120℃ and the post-baking time was 20 minutes.

[0105] Development involves using a developing solution to remove excess photoresist and its metal film, forming the electrode pattern. The development time is 60 seconds.

[0106] The photoresist removal process involves soaking the image to completely remove any remaining BP212 photoresist mask from the pattern, thus completing the patterning of the entire electrode.

[0107] S7. Preparation of the third coating layer 203: Spin-coating the third coating layer PMMA polymer material onto the sample in step S6, with the process flow being consistent with S5.

[0108] S8. Preparation of the second electrode 502 and the fourth electrode 504: The process steps include evaporating a metal thin film, spin-coating BP212, pre-baking, photolithography, post-baking, development, and cleaning to remove residual BP212. The process flow is consistent with S6.

[0109] Figure 4 The image shows an optical micrograph of the single-port input / output multi-state tunable waveguide mode converter fabricated in Example 1. The optical microscope used was model NJF-120A. Figure 4 Figure (a) shows the structure of the first core layer input straight waveguide 301, the first core layer first curved waveguide 302, the first core layer first interferometer waveguide 303, the second core layer input straight waveguide 401, the second core layer first curved waveguide 402, and the second core layer first interferometer waveguide 403. Figure 4 (b) is a structural diagram of the first core layer first interfering arm waveguide 303, the first core layer second curved waveguide 304, the first core layer third curved waveguide 305, the first core layer second interfering arm waveguide 306, the first core layer third interfering arm waveguide 307, the second core layer first interfering arm waveguide 403, the second core layer second curved waveguide 404, the second core layer third curved waveguide 405, the second core layer second interfering arm waveguide 406, and the second core layer third interfering arm waveguide 407.

[0110] Test Example 1 E 00 -E 00 / E 00 -E 01 / E 00 -E 10 Mode Conversion Efficiency Analysis 1. Testing Method This invention tested the performance of a single-port input / output multi-state tunable waveguide mode converter based on thermo-optical effect according to this embodiment. The performance of E was analyzed using the finite-differential beam propagation method (FD-BPM). 00 -E 00 E 00 -E 01and E 00 -E 10 The conversion efficiency of the three modes. The fundamental mode (E) is set in the communication band (1550nm) in the simulation environment. 00 The input excitation is used as the signal. By applying an external modulation signal and using a mode field monitor, the output optical power of each mode at ports 312 and 412 of the second output waveguide is calculated, and the mode conversion efficiency is calculated as shown in Formula 1: Formula 1, Where P in (E 00 ) indicates input E 00 Mode optical power, P out (E 00 ), P out (E 01 ) and P out (E 10 ) represent the optical power of each mode at the output end.

[0111] 2. Test Results Figure 5 Curve E represents the effect of the waveguide widths of the first core layer input straight waveguide 301 and the second core layer input straight waveguide 401 on the mode conversion efficiency. 00 The mode conversion efficiency (E) calculated without applying a control signal. 00 -E 00 (pattern), curve E 01 To control the mode conversion efficiency (E) when using the first or second electrode 00 -E 01 ), curve E 10 To simultaneously control the mode switching efficiency (E) of the third and fourth electrodes 00 -E 10 E 00 -E 00 The overall mode conversion efficiency is greater than E. 00 -E 01 and E 00 -E 10 When the waveguide widths of the first core layer input straight waveguide 301 and the second core layer input straight waveguide 401 are 5.5 μm, E 00 E 01 and E 10 The mode conversion efficiencies of the three modes are 98.9%, 95.0% and 96.1%, respectively, indicating that the device has a high tolerance for experimental fabrication errors. Figure 6 This indicates the effect of the waveguide thickness of the first core layer input straight waveguide 301 and the second core layer input straight waveguide 401 on the mode conversion efficiency. When the waveguide thickness of the first core layer input straight waveguide 301 and the second core layer input straight waveguide 401 is 4μm, E00 E 01 and E 10 The mode conversion efficiencies of the three modes are 99.0%, 95.5%, and 95.0%, respectively.

[0112] Test Example 2 E 00 -E 00 / E 00 -E 01 / E 00 -E 10 Transmission path analysis of the mode 1. Testing Method This invention analyzes the optical transmission process of a single-port input / output multi-state tunable waveguide mode converter based on the thermo-optical effect in this embodiment. The test method is based on mode coupling theory and utilizes an external modulation method based on the thermo-optical effect. When two optical waveguide modes achieve phase matching, the optical power can be efficiently transferred periodically between modes. A fundamental mode Gaussian light source is configured at the input end, and a power monitoring surface is set up in the optical propagation direction using a mode power monitor to monitor E. 00 E 01 and E 10 The optical power of the mode.

[0113] 2. Test Results Figure 7 E represents 00 During mode input, the normalized optical power detected in the second MZI core layer 400 is as follows: After the output light passes through the second core layer input straight waveguide 401 and the second core layer first bent waveguide 402, the light energy in the second core layer first interferometer waveguide 403 decreases to 0.495. The light energy in the second core layer second interferometer waveguide 406 and the second core layer third interferometer waveguide 407 decreases to 0.22, and the light energy in the second core layer first output waveguide 410 increases to 0.49. After being summarized by all waveguides, an E of 0.965 is detected in the second core layer second output waveguide 412. 00 Mode signal light. Figure 8 This indicates that when the first electrode 501 is adjusted, the normalized optical power detected in the second MZI core layer 400 is obtained, and the E in the second output waveguide 312 of the first core layer and the second output waveguide 412 of the second core layer is also detected. 01 The energy of the mode signal light is 0.95. Figure 9 This indicates the normalized optical power detected in the second MZI core layer 400 when the third electrode 503 and the fourth electrode 504 are simultaneously controlled, and the E in the second output waveguide 312 of the first core layer and the second output waveguide 412 of the second core layer are also monitored. 10 The energy of the mode signal light is 0.955.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A single-port input / output multi-state tunable waveguide mode converter, characterized in that, It includes a substrate layer, a first cladding layer, a second cladding layer and a third cladding layer stacked in sequence, and also includes a double-layer MZI core layer, which includes a first MZI core layer and a second MZI core layer, and the double-layer MZI core layer is a single-port input and single-port output waveguide structure. The first MZI core layer is embedded in the second cladding layer, and the second cladding layer and the first MZI core layer have the same thickness; the second MZI core layer is embedded in the third cladding layer, and the third cladding layer and the second MZI core layer have the same thickness. An MZI structure is nested on the interference arm of the first MZI core layer and the second MZI core layer, respectively. The first MZI core layer includes a first core layer first interferometric arm waveguide, a first core layer second interferometric arm waveguide, and a first core layer third interferometric arm waveguide, with the first core layer second interferometric arm waveguide and the first core layer third interferometric arm waveguide located in a nested MZI structure; the second MZI core layer includes a second core layer first interferometric arm waveguide, a second core layer second interferometric arm waveguide, and a second core layer third interferometric arm waveguide, with the second core layer second interferometric arm waveguide and the second core layer third interferometric arm waveguide located in a nested MZI structure; A first partial electrode is provided above at least one of the first core layer first interferometric arm waveguide and the second core layer first interferometric arm waveguide. The first partial electrode is disposed on the surface of the second cladding layer. A second partial electrode is provided on the surface of at least two of the first core layer second interferometric arm waveguide, the first core layer third interferometric arm waveguide, the second core layer second interferometric arm waveguide and the second core layer third interferometric arm waveguide. At least one second partial electrode is provided above the first core layer second interferometric arm waveguide and the first core layer third interferometric arm waveguide. The second partial electrode is disposed on the surface of the third cladding layer.

2. The multi-state tunable waveguide mode converter according to claim 1, characterized in that, A first portion of electrodes is provided above both the first core layer first interferometer waveguide and the second core layer first interferometer waveguide.

3. The multi-state tunable waveguide mode converter according to claim 1, characterized in that, Two of the first core layer second interferometric arm waveguide, the first core layer third interferometric arm waveguide, the second core layer second interferometric arm waveguide, and the second core layer third interferometric arm waveguide have second part electrodes on their surfaces.

4. The multi-state tunable waveguide mode converter according to claim 1, characterized in that, The first MZI core layer and the second MZI core layer have the same material and refractive index.

5. The multi-state tunable waveguide mode converter according to claim 1, characterized in that, The materials of the first MZI core layer and the second MZI core layer are Si, Si3N4, SU-8 series photoresist, NR series photoresist, AZ series photoresist or EPOCore photoresist.

6. The multi-state tunable waveguide mode converter according to claim 1, characterized in that, The first core layer first interferometric arm waveguide has a thickness of 2~24μm and a width of 2~20μm. The first core layer second interferometric arm waveguide and the first core layer third interferometric arm waveguide have independent thicknesses of 2~24μm and independent widths of 1~10μm. The thickness of the first interferometer waveguide in the second core layer is 2~24μm and the width is 2~20μm. The thickness of the second interferometer waveguide in the second core layer and the width of the third interferometer waveguide in the second core layer are independently 2~24μm and independently 1~10μm.

7. The multi-state tunable waveguide mode converter according to claim 1 or 6, characterized in that, The first part of the electrode has a thickness of 100~300nm and a width of 5~30μm, and the second part of the electrode has a thickness of 100~300nm and a width of 3~15μm.

8. The multi-state tunable waveguide mode converter according to claim 1 or 6, characterized in that, The thickness of the first cladding layer is 2~24μm, the thickness of the second cladding layer is 2~24μm, and the thickness of the third cladding layer is 1~10μm.

9. The multi-state tunable waveguide mode converter according to claim 1, characterized in that, The materials of the first cladding layer, the second cladding layer, and the third cladding layer independently include one or more of SiO2, polymethyl methacrylate, polystyrene, EpoClad, hydrogel, polydimethylsiloxane, and the NOA series.

10. A method for fabricating a single-port input / output multi-state tunable waveguide mode converter according to any one of claims 1 to 9, characterized in that, Includes the following steps: The first MZI core layer is formed by sequentially coating the surface of the substrate with a first MZI core layer material, performing first photolithography, first exposure, and first development. A first cladding material is coated around the first MZI core layer to form the first cladding layer; The second MZI core layer is formed by sequentially coating the surface of the first cladding layer with the second MZI core layer material, performing the second photolithography, the second exposure, and the second development. A second cladding material is coated around the second MZI core layer to form the second cladding layer; A first metal thin film is deposited on the surface of the second cladding layer, and then a third photolithography, a third exposure and a third development are sequentially performed on the surface of the first metal thin film to form the electrode in the first MZI core layer. Then, a third cladding material is coated on the surface of the obtained sample to form the third cladding layer. A second metal thin film is deposited on the surface of the third cladding layer, and then a fourth photolithography, a fourth exposure, and a fourth development are performed sequentially on the surface of the second metal thin film to form the electrode in the second MZI core layer, thereby obtaining the single-port input / output multi-state tunable waveguide mode converter.

Images