A silica multifunctional mode processor based on a cascaded multimode interferometer

Abstract

A kind of silica multifunctional mode processor based on cascaded multimode interferometer belongs to silica integrated optics technical field.It is successively composed of silicon substrate, silica lower cladding, germanium-doped silica core layer, silica upper cladding, and the core layer is covered in the upper cladding;The core layer is composed of three unit modules of first mode converter, mode filter and second mode converter, and the structure and size of the first mode converter and the second mode converter are completely same;The mode converter is composed of 1x3Y branch waveguide, 1x2Y branch waveguide, 4x4 multimode interferometer, 2x1 branch combiner and 3x1Y branch combiner.The device has 12 kinds of basic working states, and through different combinations of basic working states, the input TE0, TE1, TE2 and TE3 four mode signals can be processed with five different functions of high-pass filter, low-pass filter, band-pass filter, band-stop filter and mode conversion.

Description

Technical Field

[0001] This invention belongs to the field of silicon dioxide integrated optical technology, specifically relating to a silicon dioxide multifunctional mode processor based on a cascaded multimode interferometer. Background Technology

[0002] Currently, people's demands for communication are increasing, and communication technology is advancing at an ever-accelerating pace. In optical communication networks, mode-division multiplexing (MDD) technology plays a crucial role, multiplexing and demultiplexing multiple modes of optical signals to improve the transmission efficiency and system capacity of optical communication systems. However, in MMD systems, different types of processing are required for the optical modes, such as mode filtering and mode conversion. Therefore, in the field of optical communication, by modulating and processing the optical mode signals in waveguides, multiple functions can be achieved, effectively improving the performance and flexibility of optical communication systems. Such multi-functional mode processing devices have significant application value.

[0003] The multi-functional mode processor primarily processes different modes of optical signals. Its main functions include high-pass filtering, low-pass filtering, band-pass filtering, band-stop filtering, and mode conversion. High-pass filtering removes low-order modes while allowing higher-order modes to pass; low-pass filtering removes high-order modes while allowing low-order modes to pass; band-pass filtering allows intermediate-order modes to pass; band-stop filtering removes intermediate-order modes while allowing both high- and low-order modes to pass; and mode conversion converts any input optical mode of any order into a target mode of any order at the device's output through a mode matching process. This improves the flexibility of the communication system, increases the system's optical transmission efficiency, and expands the system bandwidth.

[0004] The performance metrics of a multi-mode processor mainly include insertion loss, operating bandwidth, and inter-mode crosstalk. For a multi-mode processor, low inter-mode crosstalk is required while maintaining low loss and high bandwidth to achieve ideal performance. Multi-mode processors can be implemented using different materials. Among them, silicon dioxide has advantages such as mature manufacturing processes, large process tolerance, and low optical loss, which can meet the performance requirements of multi-mode processors. Summary of the Invention

[0005] The purpose of this invention is to provide a silicon dioxide multifunctional mode processor based on a cascaded multimode interferometer, which can be used in a mode-division multiplexing system. This device can perform high-pass filtering, low-pass filtering, band-pass filtering, band-stop filtering, and mode conversion on four input modes: TE0, TE1, TE2, and TE3. The device employs an active structure, using four electrodes to thermo-optically modulate the modulation arm, changing the phase of the optical signal in the modulation arm waveguide to achieve control over the optical signal mode.

[0006] The silicon dioxide multifunctional mode processor based on a cascaded multimode interferometer described in this invention comprises, from bottom to top, a silicon substrate, a silicon dioxide lower cladding layer, a germanium-doped silicon dioxide core layer, and a silicon dioxide upper cladding layer, with the core layer encapsulated within the upper cladding layer, as shown below. Figure 1 As shown in (a).

[0007] like Figure 2 As shown in (a), along the optical transmission direction, the core layer of this multi-functional mode processor consists of three unit modules: a first mode converter, a mode filter, and a second mode converter. The first and second mode converters have identical structures and dimensions, as shown in (a). Figure 2 (b) Figure 2 As shown in (d).

[0008] The first mode converter consists of a first 1×3 Y-branch waveguide (Ⅰ), a first 1×2 Y-branch waveguide (Ⅱ), a first 4×4 multimode interferometer (Ⅲ), a first 2×1 branch combiner (Ⅳ), and a first 3×1 Y-branch combiner (Ⅴ), as follows: Figure 2 As shown in (b), the following are respectively: first input straight waveguide 1, first straight waveguide 2, second straight waveguide 3, third straight waveguide 4, first curved waveguide 5, second curved waveguide 6, third curved waveguide 7, fourth curved waveguide 8, fourth straight waveguide 9, fifth straight waveguide 10, sixth straight waveguide 11, seventh straight waveguide 12, fifth curved waveguide 13, sixth curved waveguide 14, seventh curved waveguide 15, eighth curved waveguide 16, first input tapered waveguide 17, second input tapered waveguide 18, third input tapered waveguide 19, fourth input tapered waveguide 20, first 4×4 multimode interferometer (Ⅲ), first output tapered waveguide 21, second output tapered waveguide 22, third output tapered waveguide 23, fourth output tapered waveguide 24, ninth curved waveguide 25, tenth curved waveguide 26, eleventh curved waveguide 27, twelfth curved waveguide 28, eighth straight waveguide 29, and first output straight waveguide 30, wherein the first input... Straight waveguide 1, first straight waveguide 2, second straight waveguide 3, and third straight waveguide 4 constitute the first 1×3 Y-branch waveguide (Ⅰ); second straight waveguide 3, second curved waveguide 6, and third curved waveguide 7 constitute the first 1×2 Y-branch waveguide (Ⅱ); first input tapered waveguide 17, second input tapered waveguide 18, third input tapered waveguide 19, and fourth input tapered waveguide 20 are the four input terminals of the first 4×4 multimode interferometer (Ⅲ); and the first output tapered waveguide... 21. The second output tapered waveguide 22, the third output tapered waveguide 23, and the fourth output tapered waveguide 24 are the four output terminals of the first 4×4 multimode interferometer (Ⅲ); the tenth curved waveguide 26, the eleventh curved waveguide 27, and the eighth straight waveguide 29 constitute the first 2×1 Y branch combiner (Ⅳ); the ninth curved waveguide 25, the eighth straight waveguide 29, the twelfth curved waveguide 28, and the first output straight waveguide 30 constitute the first 3×1 Y branch combiner (Ⅴ).

[0009] The first input straight waveguide 1 has a width of W1 = 16 μm, which can accommodate four modes: TE0, TE1, TE2, and TE3. After passing through the first 1×3 Y-branch waveguide (Ⅰ), the first input straight waveguide 1 is divided into a second straight waveguide 3 with a width of W2 = 8 μm, a first straight waveguide 2 with a width of W4 = 4 μm, and a third straight waveguide 4. After passing through the first 1×2 Y-branch waveguide (Ⅱ), the second straight waveguide 3 is divided into a second curved waveguide 6 with a width of W3 = 4 μm and a third curved waveguide 7. The first curved waveguide 5, the fourth straight waveguide 9, and the fifth curved waveguide 13, which are connected to the first straight waveguide 2 in sequence, have the same width of W4 = 4 μm. The widths of the connected fourth curved waveguide 8, seventh straight waveguide 12, and eighth curved waveguide 16 are equal, W4 = 4 μm. The widths of the fifth straight waveguide 10 and sixth curved waveguide 14, which are sequentially connected to the second curved waveguide 6, are equal, W3 = 4 μm. The widths of the sixth straight waveguide 11 and seventh curved waveguide 15, which are sequentially connected to the third curved waveguide 7, are equal, W3 = 4 μm. The fourth straight waveguide 9 and fifth straight waveguide 10 are phase-shifting waveguides. A first heating electrode 31 and a second heating electrode 32 are respectively disposed on the silicon dioxide cladding corresponding to their positions. The lengths of the fourth straight waveguide 9, fifth straight waveguide 10, first heating electrode 31, and second heating electrode 32 are equal, L. PS =3000μm, the widths of the first heating electrode 31 and the second heating electrode 32 are equal, W PS =21μm; Air isolation grooves penetrating the upper silicon dioxide cladding, the lower silicon dioxide cladding, and a portion of the silicon substrate are provided on both sides of the first heating electrode 31 and the second heating electrode 32. The width of the air isolation grooves is 35μm and the length is 3000μm, as shown below. Figure 1As shown in (b); the first input tapered waveguide 17 and the first output tapered waveguide 21, the second input tapered waveguide 18 and the second output tapered waveguide 22, the third input tapered waveguide 19 and the third output tapered waveguide 23, the fourth input tapered waveguide 20 and the fourth output tapered waveguide 24 are symmetrical about the first 4×4 multimode interferometer (Ⅲ). The first straight waveguide 2 and the third straight waveguide 4, the first curved waveguide 5 and the fourth curved waveguide 8, the second curved waveguide 6 and the third curved waveguide 7, the fourth straight waveguide 9 and the seventh straight waveguide 12, the fifth straight waveguide 10 and the sixth straight waveguide 11, the fifth curved waveguide 13 and the eighth curved waveguide 16, the sixth curved waveguide 14 and the seventh curved waveguide 15, the ninth curved waveguide 25 and the twelfth curved waveguide 28. The tenth curved waveguide 26 and the eleventh curved waveguide 27 are vertically symmetrical structures; the waveguide widths of the first input tapered waveguide 17 and the fourth input tapered waveguide 20 both increase linearly from W4 = 4 μm to W5 = 8 μm; the waveguide widths of the second input tapered waveguide 18 and the third input tapered waveguide 19 increase linearly from W3 = 4 μm to W6 = 9.6 μm; the width of the 4×4 multimode interferometer (Ⅲ) is W7 = 62 μm, and its length is L1 = 7740 μm (except for the multimode interferometer, the heating electrode, and the phase-shifting region waveguide below the heating electrode, which have length requirements, the other waveguides only serve a connecting function and their lengths are not specifically required); the waveguide widths of the first output tapered waveguide 21 and the fourth output tapered waveguide 24 decrease linearly from W5 = 8 μm. As small as W4 = 4 μm, the waveguide widths of the second output tapered waveguide 22 and the third output tapered waveguide 23 linearly decrease from W6 = 9.6 μm to W3 = 4 μm. The distance between the center of symmetry of the first input tapered waveguide 17, the fourth input tapered waveguide 20, the first output tapered waveguide 21, and the fourth output tapered waveguide 24 and the center of symmetry of the 4×4 multimode interferometer (Ⅲ) is X2 = 24 μm. The distance between the center of symmetry of the second input tapered waveguide 18, the third input tapered waveguide 19, the second output tapered waveguide 22, and the third output tapered waveguide 23 and the center of symmetry of the 4×4 multimode interferometer (Ⅲ) is X1 = 9.4 μm. The fifth curved waveguide 13, the sixth curved waveguide 14, the seventh curved waveguide 15, and the eighth curved waveguide 16 respectively The first input tapered waveguide 17, the second input tapered waveguide 18, the third input tapered waveguide 19, and the fourth input tapered waveguide 20 are connected to a 4×4 multimode interferometer (Ⅲ); the first output tapered waveguide 21, the second output tapered waveguide 22, the third output tapered waveguide 23, and the fourth output tapered waveguide 24 are connected to the ninth curved waveguide 25, the tenth curved waveguide 26, the eleventh curved waveguide 27, and the twelfth curved waveguide 28, respectively; the widths of the tenth curved waveguide 26 and the eleventh curved waveguide 27 are equal, W3 = 4 μm, the width of the eighth straight waveguide 29 is W2 = 8 μm, the widths of the ninth curved waveguide 25 and the twelfth curved waveguide 28 are equal, W4 = 4 μm, and the width of the first output straight waveguide 30 is W8 = 16 μm.

[0010] The structure of the mode filter is as follows Figure 2 As shown in (c), the waveguide consists of an input tapered waveguide 33, a thirteenth curved waveguide 34, a ninth straight waveguide 35, a fourteenth curved waveguide 36, and an output tapered waveguide 37 connected in sequence. The width of the ninth straight waveguide (35) is W9 = 6 μm; the width of the input tapered waveguide 33 decreases linearly from W8 = 16 μm to W9 = 6 μm; the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are all equal at W9 = 6 μm; and the width of the output tapered waveguide 37 increases linearly from W9 = 6 μm to W9 = 6 μm. 10 =16μm.

[0011] The second mode converter consists of a second 1×3 Y-branch waveguide (VI), a second 1×2 Y-branch waveguide (VII), a second 4×4 multimode interferometer (VIII), a second 2×1 Y-branch combiner (IX), and a second 3×1 Y-branch combiner (X), as follows: Figure 2As shown in (d), these are the second input straight waveguide 38, the tenth straight waveguide 39, the eleventh straight waveguide 40, the twelfth straight waveguide 41, the fifteenth curved waveguide 42, the sixteenth curved waveguide 43, the seventeenth curved waveguide 44, the eighteenth curved waveguide 45, the thirteenth straight waveguide 46, the fourteenth straight waveguide 47, the fifteenth straight waveguide 48, the sixteenth straight waveguide 49, the nineteenth curved waveguide 50, the twentieth curved waveguide 51, the twenty-first curved waveguide 52, the twenty-second curved waveguide 53, and the... 54. Five-input tapered waveguide; 55. Sixth-input tapered waveguide; 56. Seventh-input tapered waveguide; 57. Eighth-input tapered waveguide; Second 4×4 multimode interferometer (VIII); Fifth-output tapered waveguide; 58. Sixth-output tapered waveguide; 59. Seventh-output tapered waveguide; 60. Eighth-output tapered waveguide; 61. Twenty-third curved waveguide; 62. Twenty-fourth curved waveguide; 63. Twenty-fifth curved waveguide; 64. Twenty-sixth curved waveguide; 65. Seventeenth straight waveguide; 66. Second output straight waveguide; 67. In the second input straight waveguide 38, the tenth straight waveguide 39, the eleventh straight waveguide 40, and the twelfth straight waveguide 41 constitute the second 1×3 Y-branch waveguide (VI). The eleventh straight waveguide 40, the sixteenth curved waveguide 43, and the seventeenth curved waveguide 44 constitute the second 1×2 Y-branch waveguide (VII). The fifth input tapered waveguide 54, the sixth input tapered waveguide 55, the seventh input tapered waveguide 56, and the eighth input tapered waveguide 57 are the four input terminals of the second 4×4 multimode interferometer (VIII). Output tapered waveguide 58, sixth output tapered waveguide 59, seventh output tapered waveguide 60, and eighth output tapered waveguide 61 are the four output terminals of the second 4×4 multimode interferometer (VIII); twenty-fourth curved waveguide 63, twenty-fifth curved waveguide 64, and seventeenth straight waveguide 66 constitute the second 2×1 Y branch combiner (IX); twenty-third curved waveguide 62, seventeenth straight waveguide 66, twenty-sixth curved waveguide 65, and second output straight waveguide 67 constitute the second 3×1 Y branch combiner (X).

[0012] All straight waveguides or extensions of straight waveguides in the three unit modules—the first mode converter, the mode filter, and the second mode converter—are set to be parallel.

[0013] The width of the second input straight waveguide 38 is W. 10 =16μm, capable of accommodating four modes: TE0, TE1, TE2, and TE3. After passing through the second 1×3Y branch waveguide (VI), the second input straight waveguide is divided into 38 sections with a width of W. 11 Eleventh direct waveguide 40 with a width of 8μm and a diameter of W 13 The tenth straight waveguide 39 and the twelfth straight waveguide 41 have a width of 4μm; after passing through the second 1×2Y branch waveguide (VII), the eleventh straight waveguide 40 is divided into two branches with a width of W. 12The sixteenth curved waveguide 43 and the seventeenth curved waveguide 44, with a width of 4 μm, and the fifteenth curved waveguide 42, the thirteenth straight waveguide 46, and the nineteenth curved waveguide 50, which are sequentially connected to the tenth straight waveguide 39, have the same width of W. 13 =4μm, and the widths of the eighteenth curved waveguide 45, the sixteenth straight waveguide 49, and the twenty-second curved waveguide 53, which are sequentially connected to the twelfth straight waveguide 41, are equal to W. 13 =4μm, and the width of the fourteenth straight waveguide 47 and the twentieth curved waveguide 51, which are sequentially connected to the sixteenth curved waveguide 43, is equal to W. 12 =4μm, and the width of the fifteenth straight waveguide 48 and the twenty-first bent waveguide 52, which are sequentially connected to the seventeenth bent waveguide 44, is equal to W. 12 =4μm; The thirteenth straight waveguide 46 and the fourteenth straight waveguide 47 are phase-shifting region waveguides. A third heating electrode 68 and a fourth heating electrode 69 are respectively disposed on the silicon dioxide cladding corresponding to their positions. The lengths of the thirteenth straight waveguide 46, the fourteenth straight waveguide 47, the third heating electrode 68, and the fourth heating electrode 69 are equal and L. PS =3000μm, the widths of the third heating electrode 68 and the fourth heating electrode 69 are equal, W PS =21μm, and on both sides of the third heating electrode 68 and the fourth heating electrode 69, there are air isolation grooves that penetrate the upper silicon dioxide cladding, the lower silicon dioxide cladding, and a portion of the silicon substrate. The width of the air isolation groove is 35μm and the length is 3000μm. Figure 1 As shown in (b); the fifth input tapered waveguide 54 and the fifth output tapered waveguide 58, the sixth input tapered waveguide 55 and the sixth output tapered waveguide 59, the seventh input tapered waveguide 56 and the seventh output tapered waveguide 60, the eighth input tapered waveguide 57 and the eighth output tapered waveguide 61 are symmetrical about the second 4×4 multimode interferometer (VⅢ), and the tenth straight waveguide 39 and the twelfth straight waveguide 41, the fifteenth curved waveguide 42 and the eighteenth curved waveguide 45, the sixteenth curved waveguide 43 and the... The seventeenth curved waveguide 44, the thirteenth straight waveguide 46, the sixteenth straight waveguide 49, the fourteenth straight waveguide 47, the fifteenth straight waveguide 48, the nineteenth curved waveguide 50, the twenty-second curved waveguide 53, the twentieth curved waveguide 51, the twenty-first curved waveguide 52, the twenty-third curved waveguide 62, the twenty-sixth curved waveguide 65, the twenty-fourth curved waveguide 63, and the twenty-fifth curved waveguide 64 are vertically symmetrical; the waveguide widths of the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 are from W... 13 =4μm linearly increased to W 14 =8μm, the waveguide widths of the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 are from W 12 =4μm linearly increased to W 15 = 9.6 μm; the width of the second 4×4 multimode interferometer (VIII) is W16 =62μm, length L2=7740μm (except for the multimode interferometer, heating electrode, and the phase-shifting waveguide below the heating electrode, which have length requirements, the other waveguides only serve a connecting function and their lengths have no specific requirements); the waveguide widths of the fifth output tapered waveguide 58 and the eighth output tapered waveguide 61 are from W 14 =8μm linearly decreased to W 13 =4μm, the waveguide widths of the sixth output tapered waveguide 59 and the seventh output tapered waveguide 60 are from W 15 = 9.6 μm linearly decreased to W 12 =4μm; the distance between the center of symmetry of the fifth input tapered waveguide 54, the eighth input tapered waveguide 57, the fifth output tapered waveguide 58, and the eighth output tapered waveguide 61 and the center of symmetry of the 4×4 multimode interferometer (VIII) is X4 = 24μm; the distance between the center of symmetry of the sixth input tapered waveguide 55, the seventh input tapered waveguide 56, the sixth output tapered waveguide 59, and the seventh output tapered waveguide 60 and the center of symmetry of the 4×4 multimode interferometer (VIII) is X3 = 9.4μm; the distance between the center of symmetry of the nineteenth curved waveguide 50, the twentieth curved waveguide 51, the twenty-first curved waveguide 52, and the twenty-second curved waveguide 53 is connected to the 4×4 multimode interferometer (VIII) via the fifth input tapered waveguide 54, the sixth input tapered waveguide 55, the seventh input tapered waveguide 56, and the eighth input tapered waveguide 57, respectively; the 4×4 multimode interferometer (VIII) is connected to the twenty-third curved waveguide 62, the twenty-fourth curved waveguide 63, the twenty-fifth curved waveguide 64, and the twenty-sixth curved waveguide 65 via the fifth output tapered waveguide 58, the sixth output tapered waveguide 59, the seventh output tapered waveguide 60, and the eighth output tapered waveguide 61, respectively; the twenty-fourth curved waveguide 63 and the twenty-fifth curved waveguide 64 have the same width, W. 12 =4μm, the width of the seventeenth straight waveguide 66 is W 11 =8μm, the width of the twenty-third curved waveguide 62 and the twenty-sixth curved waveguide 65 is W 13 =4μm, the width of the second output straight waveguide 67 is W 17 =16μm. Attached Figure Description

[0014] Figure 1 This is a cross-sectional schematic diagram of the multi-functional mode processor structure; where, Figure 1 (a) is a cross-sectional structural diagram of the non-phase-shifting region; Figure 1 (b) is a cross-sectional structural diagram of the phase-shifting region;

[0015] Figure 2 This is a top view of the multi-functional processor chip; where, Figure 2 (a) is a schematic diagram of the overall structure of the multi-functional mode processor core layer; Figure 2 (b) is a schematic diagram of the first mode converter; Figure 2 (c) is a schematic diagram of the mode filter structure; Figure 2 (d) is a schematic diagram of the second mode converter;

[0016] Figure 3 The graph shows the effective refractive index of different modes of a silicon dioxide waveguide as a function of waveguide width.

[0017] Figure 4 (a)~ Figure 4 (l) are the optical signal phase diagrams at various positions of the device core layer under twelve basic operating states;

[0018] Figure 5 (a)~ Figure 5 (l) are the simulated optical field diagrams of the device under twelve basic operating conditions;

[0019] Figure 6 This is a flowchart of the device fabrication process. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0021] Example 1

[0022] See appendix Figure 1 The multi-functional processor consists of a substrate, a lower cladding layer, a core layer, an upper cladding layer, and electrodes, arranged from bottom to top. Except for its lower surface, the core layer is entirely covered by the upper cladding layer, and both the core layer and the upper cladding layer are located above the lower cladding layer. Both the lower and upper cladding layers are made of silicon dioxide with a refractive index of 1.4447, while the core layer is made of germanium-doped silicon dioxide with a refractive index of 1.4741. The thickness of each core layer is 4 μm.

[0023] See appendix Figure 2 The core layer of the multi-functional mode processor, along the direction of light transmission, consists of three unit modules: a first mode converter, a mode filter, and a second mode converter. The first and second mode converters have identical structures and dimensions. The first mode converter is as follows: Figure 2 As shown in (b), it can be divided into three parts; the first part includes a first 1×3Y branch waveguide (Ⅰ), a first 1×2Y branch waveguide (Ⅱ), a first heating electrode 31, and a second heating electrode 32; the second part is a first 4×4 multimode interferometer (Ⅲ); the third part is a first 2×1Y branch combiner (Ⅳ) and a first 3×1Y branch combiner (Ⅴ). The mode filter is as follows... Figure 2 As shown in (c), it consists of an input tapered waveguide 33, a thirteenth curved waveguide 34, a ninth straight waveguide 35, a fourteenth curved waveguide 36, and an output tapered waveguide 37. The second mode converter is as follows: Figure 2As shown in (d), it can be divided into three parts; the first part is the second 1×3Y branch waveguide (VI), the second 1×2Y branch waveguide (VII), the third heating electrode 68, and the fourth heating electrode 69; the second part is the second 4×4 multimode interferometer (VIII); the third part is the second 2×1Y branch combiner (IX) and the second 3×1Y branch combiner (X).

[0024] Example 2

[0025] The dimensional parameters of each part of the core waveguide are determined, with the core waveguide height fixed at 4μm. The first mode converter supports four modes at its input: TE0, TE1, TE2, and TE4. Figure 3 The effective refractive index of different modes of silicon dioxide waveguides varies with the waveguide width. The width of the first input straight waveguide 1 is set to W1 = 16μm. The optical signal exists in the TE0 mode in the first straight waveguide 2, the third straight waveguide 4, the fourth straight waveguide 9, the fifth straight waveguide 10, the sixth straight waveguide 11 and the seventh straight waveguide 12. The widths of the first straight waveguide 2, the third straight waveguide 4, the fourth straight waveguide 9, the fifth straight waveguide 10, the sixth straight waveguide 11, and the seventh straight waveguide 12 are all equal, W3 = 4 μm. The optical signal exists in TE0 mode in the first curved waveguide 5, the second curved waveguide 6, the third curved waveguide 7, the fourth curved waveguide 8, the fifth curved waveguide 13, the sixth curved waveguide 14, the seventh curved waveguide 15, and the eighth curved waveguide 16. The widths of the first curved waveguide 5, the second curved waveguide 6, the third curved waveguide 7, the fourth curved waveguide 8, the fifth curved waveguide 13, the sixth curved waveguide 14, the seventh curved waveguide 15, and the eighth curved waveguide 16 are all equal, W3 = 4 μm. The width of the second straight waveguide 3 is W2 = 8 μm. Modulation electrodes 31 and 32 are located above the fourth straight waveguide 9 and the fifth straight waveguide 10, respectively.

[0026] The width of the first 4×4 multimode interferometer (Ⅲ) was determined to be W7 = 62 μm and the length to be L1 = 7740 μm by the beam propagation method. The distance between the center of the first input tapered waveguide 17, the fourth input tapered waveguide 20, the first output tapered waveguide 21, and the fourth output tapered waveguide 24 and the center of the 4×4 multimode interferometer (Ⅲ) was X2 = 24 μm. The distance between the center of the second input tapered waveguide 18, the third input tapered waveguide 19, the second output tapered waveguide 22, and the third output tapered waveguide 23 and the center of the 4×4 multimode interferometer (Ⅲ) was X1 = 9.4 μm.

[0027] The optical signals in the ninth curved waveguide 25, the tenth curved waveguide 26, the eleventh curved waveguide 27, and the twelfth curved waveguide 28 are all in TE0 mode. The length of the above series of curved waveguides is W3 = 4 μm. The width of the eighth straight waveguide 29 is W2 = 8 μm, and the width of the first output straight waveguide 30 is W8 = 16 μm.

[0028] Mode filter, according to Figure 3 The effective refractive index of different modes of the silicon dioxide waveguide varies with the waveguide width. The width of the input tapered waveguide 33 is linearly decreased from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are all equal at W9 = 6 μm. The width of the output tapered waveguide 37 linearly increases from W9 = 6 μm to W9 = 6 μm. 10 =16μm, only supports TE0 and TE1 modes for transmission.

[0029] The second-mode converter supports four input modes: TE0, TE1, TE2, and TE4. Figure 3 The effective refractive index of different modes in a silicon dioxide waveguide varies with the waveguide width. The width of the second input straight waveguide 38 is set to W. 10 =16μm, the optical signal exists in TE0 mode in the tenth straight waveguide 39, the twelfth straight waveguide 41, the thirteenth straight waveguide 46, the fourteenth straight waveguide 47, the fifteenth straight waveguide 48, and the sixteenth straight waveguide 49. The widths of the tenth straight waveguide 39, the twelfth straight waveguide 41, the thirteenth straight waveguide 46, the fourteenth straight waveguide 47, the fifteenth straight waveguide 48, and the sixteenth straight waveguide 49 are equal to W. 12 =4μm, the optical signal exists in TE0 mode in the fifteenth curved waveguide 42, sixteenth curved waveguide 43, seventeenth curved waveguide 44, eighteenth curved waveguide 45, nineteenth curved waveguide 50, twentieth curved waveguide 51, twenty-first curved waveguide 52, and twenty-second curved waveguide 53. The widths of the fifteenth curved waveguide 42, sixteenth curved waveguide 43, seventeenth curved waveguide 44, eighteenth curved waveguide 45, nineteenth curved waveguide 50, twentieth curved waveguide 51, twenty-first curved waveguide 52, and twenty-second curved waveguide 53 are equal and W. 12 =4μm, the eleventh direct waveguide has a width of 40W. 11 =8μm. Modulation electrodes 68 and 69 are located above the thirteenth straight waveguide 46 and the fourteenth straight waveguide 47, respectively.

[0030] The width W of the second 4×4 multimode interferometer (VIII) was determined using the beam propagation method. 16 =62μm, length L2=7740μm, the center of the fifth input tapered waveguide 54, the eighth input tapered waveguide 57, the fifth output tapered waveguide 58, and the eighth output tapered waveguide 61 is X4=24μm away from the center of the 4×4 multimode interferometer (VIII), and the center of the sixth input tapered waveguide 55, the seventh input tapered waveguide 56, the sixth output tapered waveguide 59, and the seventh output tapered waveguide 60 is X3=9.4μm away from the center of the 4×4 multimode interferometer (VIII).

[0031] The optical signals in the twenty-third curved waveguide 62, the twenty-fourth curved waveguide 63, the twenty-fifth curved waveguide 64, and the twenty-sixth curved waveguide 65 are all in TE0 mode. The widths of the twenty-third curved waveguide 62, the twenty-fourth curved waveguide 63, the twenty-fifth curved waveguide 64, and the twenty-sixth curved waveguide 65 are equal, with a width of W. 12 =4μm, the width of the seventeenth straight waveguide 66 is W 11 =8μm, the width of the second output straight waveguide 67 is W 17 =16μm.

[0032] Example 3

[0033] The following is in conjunction with the appendix Figure 6 The specific preparation method of the present invention is illustrated below, with the following steps:

[0034] 1. Silicon substrate cleaning: Select a silicon wafer with a thickness of 0.6mm as the substrate. First, clean the silicon wafer with acetone to remove organic impurities on the surface of the silicon wafer; then clean the silicon wafer with ethanol to remove the acetone residue on the surface of the silicon wafer in the previous step; finally, clean the silicon wafer with deionized water to remove the ethanol residue on the surface of the silicon wafer, and then dry the silicon wafer to remove the residual moisture on the surface.

[0035] 2. Deposition of the silicon dioxide lower cladding layer: The refractive index of the silicon dioxide lower cladding layer is 1.4447. It is deposited by wet thermal oxidation method. The temperature is maintained at 1000 degrees Celsius during deposition. The substrate temperature, reaction ratio and reaction time are controlled to grow a silicon dioxide lower cladding layer with a thickness of 10 μm on the silicon substrate cleaned in step 1.

[0036] 3. Deposition of germanium-doped silicon dioxide layer: The refractive index of the germanium-doped silicon dioxide layer is 1.4741. Plasma-enhanced chemical vapor deposition is used to deposit the germanium-doped silicon dioxide layer on the surface of the silicon dioxide undercoat. During the deposition process, the flow rate of the reactive gas GeCl4 is 32 sccm, the flow rate of the reactive gas SiH4 is 20 sccm, the flow rate of the reactive gas N2O is 40 sccm, and the substrate temperature is 200℃. By controlling the reaction time and chemical mechanical polishing, a germanium-doped silicon dioxide layer with a thickness of 4 μm and a refractive index of 1.4741 is deposited on the surface of the silicon dioxide undercoat with a refractive index of 1.4447 in step 2.

[0037] 4. Growth of polycrystalline silicon mask layer: Using hot filament chemical vapor deposition, the gas pressure in the chamber is controlled at 1 Pa, the substrate temperature is controlled at 200℃, and the reaction ratio of SiH4 and H2, V(H2) / (V(SiH4)+V(H2)) is 98.4%, to grow a 1μm thick polycrystalline silicon mask layer on the surface of germanium-doped silicon dioxide layer.

[0038] 5. Etching polysilicon: Spin-coat UV-curable photoresist onto the surface of the polysilicon mask layer grown in step 4. Remove the exposed photoresist using UV lithography and wet development. Control the gas flow rates of SF6, CHF3, and O2 to 25 sccm, 50 sccm, and 35 sccm, respectively, and remove the unprotected polysilicon mask layer using reactive ion etching. Then remove the photoresist from the surface of the polysilicon mask layer to obtain a polysilicon mask layer with the same core structure as the required fabrication layer.

[0039] 6. Etching the silicon dioxide core layer: Using the reactive ion etching method in step 5, the exposed germanium-doped silicon dioxide layer is etched and bombarded with fluorine ions under the same conditions to obtain the germanium-doped silicon dioxide core layer with the desired structure.

[0040] 7. Remove the polysilicon mask layer: Remove the polysilicon mask layer remaining from step 6 using a 15% KOH aqueous solution;

[0041] 8. Deposit silicon dioxide upper cladding: The same process as in step 3 is used to deposit a silicon dioxide upper cladding on the surface of the germanium-doped silicon dioxide core layer and the silicon dioxide lower cladding. The thickness of the silicon dioxide upper cladding is controlled to be 15 μm using chemical mechanical polishing, and the refractive index of the silicon dioxide upper cladding is 1.4447.

[0042] 9. Metal thin film deposition: A 300nm thick aluminum metal thin film is deposited on the upper surface of the device by metal evaporation in the previous step;

[0043] 10. Electrode fabrication: UV-curable photoresist is spin-coated onto a metal film. Photolithography and wet development are used to remove the photoresist exposed to UV light. The aluminum metal film without photoresist protection is then etched with a 0.5% NaOH solution. The remaining photoresist is then exposed and developed to complete the electrode fabrication.

[0044] 11. Etching Air Isolation Grooves: UV-curable photoresist is spin-coated onto the electrodes and silicon dioxide cladding. The photoresist exposed to UV light is removed using an air isolation groove mask photolithography and wet development. The gas flow rates of SF6, CHF3, and O2 are controlled at 25 sccm, 50 sccm, and 35 sccm, respectively. The silicon dioxide cladding without photoresist mask protection is removed using reactive ion etching. Then, excess photoresist on the surface of the silicon dioxide cladding is removed. An air isolation groove with a depth of 35 μm is formed on both sides of the metal electrodes, penetrating the silicon dioxide cladding, the silicon dioxide lower cladding, and a portion of the silicon substrate, thereby fabricating the silicon dioxide multi-functional mode processor based on a cascaded multimode interferometer.

[0045] Example 4

[0046] The working principle of this multi-functional processor is as follows:

[0047] Under different input and control conditions, this multi-functional mode processor has twelve operating states: State 1: When a TE0 mode optical signal is input, output a TE0 mode optical signal; State 2: When a TE1 mode optical signal is input, output a TE1 mode optical signal; State 3: When a TE2 mode optical signal is input, output a TE2 mode optical signal; State 4: When a TE3 mode optical signal is input, output a TE3 mode optical signal; State 5: When a TE0 mode optical signal is input, output a TE3 mode optical signal; State 6: When a TE3 mode optical signal is input, output a TE0 mode optical signal; State 7: When a TE1 mode optical signal is input, output a TE2 mode optical signal; State 8: When a TE2 mode optical signal is input, output a TE1 mode optical signal; State 9: The input TE0 mode optical signal is blocked, and no optical signal is output; State 10: The input TE1 mode optical signal is blocked, and no optical signal is output; State 11: The input TE2 mode optical signal is blocked, and no optical signal is output; State 12: The input TE3 mode optical signal is blocked, and no optical signal is output. The working principle of each operating state is as follows:

[0048] The working principle of state 1 is as follows Figure 4As shown in (a), the TE0 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the second straight waveguide 3 but does not enter the first straight waveguide 2 or the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is divided into two TE0 mode optical signals by the second curved waveguide 6 and the third curved waveguide 7, both with a phase of π. The optical signal in the second curved waveguide 6 travels along the fifth straight waveguide 10 and the sixth curved waveguide 14 to reach the second input tapered waveguide 18. The optical signal in the third curved waveguide 7 travels along the sixth straight waveguide 11 and the seventh curved waveguide 15 to reach the third input tapered waveguide 19. The phase of the optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 is π (the fifth straight waveguide 10 is a phase-shifting waveguide. At this time, the electrode 32 above the fifth straight waveguide 10 is not in working condition, and the optical signal does not produce a phase change after passing through the fifth straight waveguide 10. Therefore, the phase of the optical signal at the second input tapered waveguide 18 is π+0=π). The optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signals are output from the second output tapered waveguide 22 and the third output tapered waveguide 23, and then pass through the tenth curved waveguide 26 and the eleventh curved waveguide 27 respectively to enter the eighth straight waveguide 29. They continue to be transmitted to the first output straight waveguide 30 and are coupled into the TE0 mode with a phase of -(1 / 2)π. The optical signals enter the input tapered waveguide 33 of the mode filter in the TE0 mode and reach the output tapered waveguide 37 along the thirteenth curved waveguide 34, the ninth straight waveguide 35 and the fourteenth curved waveguide 36. The width of the input tapered waveguide 33 decreases linearly from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are all equal, W9 = 6 μm. This width only allows optical signals in TE0 and TE1 modes to transmit smoothly. Therefore, the optical signal in TE0 mode can reach the output tapered waveguide 37. The optical signal continues to enter the second input straight waveguide 38 of the mode filter in TE0 mode with a phase of π. Then, the optical signal enters the eleventh straight waveguide 40, but does not enter the tenth straight waveguide 39 or the twelfth straight waveguide 41. After entering the eleventh straight waveguide 40, the optical signal is split into two TE modes by the sixteenth curved waveguide 43 and the seventeenth curved waveguide 44. The optical signal in mode 0 has a phase of π. The optical signal in the sixteenth curved waveguide 43 travels along the fourteenth straight waveguide 47 and the twentieth curved waveguide 51 to reach the sixth input tapered waveguide 55. The optical signal in the seventeenth curved waveguide 44 travels along the fifteenth straight waveguide 48 and the twenty-first curved waveguide 52 to reach the seventh input tapered waveguide 56. The phase of the optical signal in the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 is π. (The fourteenth straight waveguide 47 is a phase-shifting waveguide. At this time, the electrode 69 above the fourteenth straight waveguide 47 is not in working state. The optical signal does not produce a phase change after passing through the fourteenth straight waveguide 47. Therefore, at the sixth input tapered waveguide 55, the phase of the optical signal is π + 0 = π).The optical signals in the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 enter the 4×4 multimode interferometer (VIII). According to the self-image principle of the multimode interferometer, the optical signals are output in the sixth output tapered waveguide 59 and the seventh output tapered waveguide 60, and then pass through the twenty-fourth curved waveguide 63 and the twenty-fifth curved waveguide 64 respectively, enter the seventeenth straight waveguide 66, continue to be transmitted to the second output straight waveguide 67, and are coupled into the TE0 mode with a phase of -(1 / 2)π.

[0049] The working principle of state 2 is as follows Figure 4As shown in (b), the TE1 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the first straight waveguide 2 and the third straight waveguide 4, but does not enter the second straight waveguide 3. The optical signal is divided into two TE0 mode optical signals in the first straight waveguide 2 and the third straight waveguide 4, with phases of π and 0, respectively. The optical signal in the first straight waveguide 2 travels along the first curved waveguide 5, the fourth straight waveguide 9, and the fifth curved waveguide 13 to reach the first input tapered waveguide 17. The optical signal in the third straight waveguide 4 travels along the fourth curved waveguide 8, the seventh straight waveguide 12, and the eighth curved waveguide 16 to reach the fourth input tapered waveguide 20. The phases of the optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 are π and 0, respectively (the fourth straight waveguide 9 is a phase-shifting waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is not in working condition, and the optical signal does not produce a phase change after passing through the fourth straight waveguide 9. Therefore, the phase of the optical signal at the first input tapered waveguide 17 is π + 0 = π). The optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signals are output from the first output tapered waveguide 21 and the fourth output tapered waveguide 24, and then pass through the ninth curved waveguide 25 and the twelfth curved waveguide 28 respectively to merge into the first output straight waveguide 30 and couple into the TE1 mode with a phase of (1 / 4)π. The optical signals enter the input tapered waveguide 33 of the mode filter in the TE1 mode, and reach the output tapered waveguide 37 along the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36. The width of the input tapered waveguide 33 decreases linearly from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are all equal, W9 = 6 μm. This width only allows the optical signals in TE0 and TE1 modes to transmit smoothly. Therefore, the optical signal in TE1 mode can reach the output tapered waveguide 37. The optical signal continues to enter the second input straight waveguide 38 of the mode filter in TE1 mode with a phase of π. Then, the optical signal enters the tenth straight waveguide 39 and the twelfth straight waveguide 41, but does not enter the eleventh straight waveguide 40. The optical signal is evenly split into two TE0 mode optical signals in the tenth straight waveguide 39 and the twelfth straight waveguide 41, with phases of π and 0, respectively. The optical signal in the tenth straight waveguide 39 travels along the fifteenth curved waveguide 42, the thirteenth straight waveguide 46, and the nineteenth curved waveguide 50 to reach the fifth input tapered waveguide 54. The optical signal in the twelfth straight waveguide 41 travels along the eighteenth curved waveguide 45, the sixteenth straight waveguide 49, and the twenty-second curved waveguide 53 to reach the eighth input tapered waveguide 57. The phases of the optical signals in the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 are π and 0, respectively. (The thirteenth straight waveguide 46 is a phase-shifting waveguide. At this time, the electrode 68 above the thirteenth straight waveguide 46 is not in operation, and the optical signal does not undergo a phase change after passing through the thirteenth straight waveguide 46. Therefore, the phase of the optical signal at the fifth input tapered waveguide 54 is π + 0 = π).The optical signals in the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 enter the 4×4 multimode interferometer (VIII). According to the self-image principle of the multimode interferometer, the optical signals are output in the fifth output tapered waveguide 58 and the eighth output tapered waveguide 61, and then pass through the twenty-third curved waveguide 62 and the twenty-sixth curved waveguide 65 respectively, and enter the second output straight waveguide 67, and are coupled into the TE1 mode with a phase of (1 / 4)π.

[0050] The working principle of state 3 is as follows Figure 4As shown in (c), the TE2 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the first straight waveguide 2 and the third straight waveguide 4, but not the second straight waveguide 3. The optical signal is evenly split into two TE0 mode optical signals in the first straight waveguide 2 and the third straight waveguide 4, both with a phase of (7 / 4)π. The optical signal in the first straight waveguide 2 travels along the first curved waveguide 5, the fourth straight waveguide 9, and the fifth curved waveguide 13 to reach the first input tapered waveguide 17. The optical signal in the third straight waveguide 4 travels along the fourth curved waveguide 9... Waveguide 8, the seventh straight waveguide 12, and the eighth curved waveguide 16 reach the fourth input tapered waveguide 20. The phases of the optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 are (3 / 4)π and (7 / 4)π, respectively. (The fourth straight waveguide 9 is a phase-shifting waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is in working condition. The optical signal undergoes a phase change of -π after passing through the fourth straight waveguide 9. Therefore, the phase of the optical signal at the first input tapered waveguide 17 is (7 / 4)π - π = (3 / 4)π). The optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signals are output from the first output tapered waveguide 21 and the fourth output tapered waveguide 24, and then pass through the ninth curved waveguide 25 and the twelfth curved waveguide 28 respectively to merge into the first output straight waveguide 30 and couple into the TE1 mode with a phase of (1 / 2)π. The optical signals enter the input tapered waveguide 33 of the mode filter in the TE1 mode, and reach the output tapered waveguide 37 along the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36.The width of the input tapered waveguide 33 decreases linearly from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are all equal, W9 = 6 μm. This width only allows the optical signals of TE0 and TE1 modes to transmit smoothly. Therefore, the optical signal of TE1 mode can reach the output tapered waveguide 37. The optical signal continues to enter the second input straight waveguide 38 of the mode filter in TE1 mode with a phase of π. Then the optical signal enters the tenth straight waveguide 39 and the twelfth straight waveguide 41, but does not enter the eleventh straight waveguide 40. The optical signal is evenly split into two TE0 mode optical signals in the tenth straight waveguide 39 and the twelfth straight waveguide 41, with phases of π and 0, respectively. The optical signal in the tenth straight waveguide 39 travels along the fifteenth curved waveguide 42, the thirteenth straight waveguide 46, and the nineteenth curved waveguide 50 to reach the fifth input tapered waveguide 54. The optical signal in the twelfth straight waveguide 41 travels along the eighteenth curved waveguide 45, the sixteenth straight waveguide 49, and the twenty-second curved waveguide 53 to reach the eighth input tapered waveguide 57. The phase of the optical signals in the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 is 0 (the thirteenth straight waveguide 46 is a phase-shifting waveguide, and the electrode 68 above the thirteenth straight waveguide 46 is in working condition. The optical signal undergoes a -π phase change after passing through the thirteenth straight waveguide 46, so the phase of the optical signal at the fifth input tapered waveguide 54 is π-π=0). The optical signals in the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 enter the 4×4 multimode interferometer (VIII). According to the self-image principle of the multimode interferometer, the optical signals are output in the fifth output tapered waveguide 58 and the eighth output tapered waveguide 61, and then enter the second output straight waveguide 67 through the twenty-third curved waveguide 62 and the twenty-sixth curved waveguide 65 respectively, and are coupled into the TE2 mode with a phase of (5 / 4)π.

[0051] The working principle of state 4 is as follows Figure 4As shown in (d), the TE3 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the second straight waveguide 3, but not the first straight waveguide 2 or the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is split into two TE0 mode optical signals by the second curved waveguide 6 and the third curved waveguide 7, with phases of (1 / 4)π and (5 / 4)π respectively. The optical signal in the second curved waveguide 6 travels along the fifth straight waveguide 10 and the sixth curved waveguide 14 to reach the second input tapered waveguide 18. The third curved waveguide 18... The optical signal in waveguide 7 travels along the sixth straight waveguide 11 and the seventh curved waveguide 15 to the third input tapered waveguide 19. The phase of the optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 is (5 / 4)π (the fifth straight waveguide 10 is a phase-shifting waveguide. At this time, the electrode 32 above the fifth straight waveguide 10 is in working condition. The optical signal undergoes a π phase change after passing through the fifth straight waveguide 10. Therefore, the phase of the optical signal at the second input tapered waveguide 18 is (1 / 4)π + π = (5 / 4)π). The optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signals are output from the second output tapered waveguide 22 and the third output tapered waveguide 23, and then pass through the tenth curved waveguide 26 and the eleventh curved waveguide 27 respectively to merge into the eighth straight waveguide 29. They continue to be transmitted to the first output straight waveguide 30 and are coupled into TE0 mode with a phase of (1 / 2)π. The optical signals enter the input tapered waveguide 33 of the mode filter in TE0 mode and reach the output tapered waveguide 37 along the thirteenth curved waveguide 34, the ninth straight waveguide 35 and the fourteenth curved waveguide 36.The width of the input tapered waveguide 33 decreases linearly from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are all equal, W9 = 6 μm. This width only allows optical signals in TE0 and TE1 modes to transmit smoothly. Therefore, the optical signal in TE0 mode can reach the output tapered waveguide 37. The optical signal continues to enter the second input straight waveguide 38 of the mode filter in TE0 mode with a phase of π. Then, the optical signal enters the eleventh straight waveguide 40, but does not enter the tenth straight waveguide 39 or the twelfth straight waveguide 41. After entering the eleventh straight waveguide 40, the optical signal is split into two TE0 modes by the sixteenth curved waveguide 43 and the seventeenth curved waveguide 44. The optical signals in the mode all have a phase of π. The optical signal in the sixteenth curved waveguide 43 travels along the fourteenth straight waveguide 47 and the twentieth curved waveguide 51 to reach the sixth input tapered waveguide 55. The optical signal in the seventeenth curved waveguide 44 travels along the fifteenth straight waveguide 48 and the twenty-first curved waveguide 52 to reach the seventh input tapered waveguide 56. The phases of the optical signals in the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 are 0 and π, respectively (the fourteenth straight waveguide 47 is a phase-shifting waveguide. At this time, the electrode 69 above the fourteenth straight waveguide 47 is in working condition. The optical signal undergoes a phase change of -π after passing through the fourteenth straight waveguide 47. Therefore, the phase of the optical signal at the sixth input tapered waveguide 55 is π-π=0). The optical signals in the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 enter the 4×4 multimode interferometer (VIII). According to the self-image principle of the multimode interferometer, the optical signals are output in the sixth output tapered waveguide 59 and the seventh output tapered waveguide 60, and then pass through the twenty-fourth curved waveguide 63 and the twenty-fifth curved waveguide 64 respectively to enter the seventeenth straight waveguide 66, and continue to be transmitted to the second output straight waveguide 67, where they are coupled into the TE3 mode with a phase of (1 / 4)π.

[0052] The working principle of state 5 is as follows Figure 4As shown in (e), the TE0 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the second straight waveguide 3 but does not enter the first straight waveguide 2 or the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is divided into two TE0 mode optical signals by the second curved waveguide 6 and the third curved waveguide 7, both with a phase of π. The optical signal in the second curved waveguide 6 travels along the fifth straight waveguide 10 and the sixth curved waveguide 14 to reach the second input tapered waveguide 18. The optical signal in the third curved waveguide 7 travels along the sixth straight waveguide 11 and the seventh curved waveguide 15 to reach the third input tapered waveguide 19. The phase of the optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 is π (the fifth straight waveguide 10 is a phase-shifting waveguide. At this time, the electrode 32 above the fifth straight waveguide 10 is not in working condition, and the optical signal does not produce a phase change after passing through the fifth straight waveguide 10. Therefore, the phase of the optical signal at the second input tapered waveguide 18 is π+0=π). The optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signals are output from the second output tapered waveguide 22 and the third output tapered waveguide 23, and then pass through the tenth curved waveguide 26 and the eleventh curved waveguide 27 respectively to merge into the eighth straight waveguide 29. They continue to be transmitted to the first output straight waveguide 30 and are coupled into the TE0 mode with a phase of -(1 / 2)π. The optical signals enter the input tapered waveguide 33 of the mode filter in the TE0 mode and reach the output tapered waveguide 37 along the thirteenth curved waveguide 34, the ninth straight waveguide 35 and the fourteenth curved waveguide 36. The width of the input tapered waveguide 33 decreases linearly from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are all equal, W9 = 6 μm. This width only allows optical signals in TE0 and TE1 modes to transmit smoothly. Therefore, the optical signal in TE0 mode can reach the output tapered waveguide 37. The optical signal continues to enter the second input straight waveguide 38 of the mode filter in TE0 mode with a phase of π. Then, the optical signal enters the eleventh straight waveguide 40, but does not enter the tenth straight waveguide 39 or the twelfth straight waveguide 41. After entering the eleventh straight waveguide 40, the optical signal is split into two TE0 modes by the sixteenth curved waveguide 43 and the seventeenth curved waveguide 44. The optical signals in the mode all have a phase of π. The optical signal in the sixteenth curved waveguide 43 travels along the fourteenth straight waveguide 47 and the twentieth curved waveguide 51 to reach the sixth input tapered waveguide 55. The optical signal in the seventeenth curved waveguide 44 travels along the fifteenth straight waveguide 48 and the twenty-first curved waveguide 52 to reach the seventh input tapered waveguide 56. The phases of the optical signals in the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 are 0 and π, respectively (the fourteenth straight waveguide 47 is a phase-shifting waveguide. At this time, the electrode 69 above the fourteenth straight waveguide 47 is in working condition. After the optical signal passes through the fourteenth straight waveguide 47, it produces a phase change of -π. Therefore, the phase of the optical signal at the sixth input tapered waveguide 55 is π-π=0).The optical signals in the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 enter the 4×4 multimode interferometer (VIII). According to the self-image principle of the multimode interferometer, the optical signals are output in the sixth output tapered waveguide 59 and the seventh output tapered waveguide 60, and then pass through the twenty-fourth curved waveguide 63 and the twenty-fifth curved waveguide 64 respectively to enter the seventeenth straight waveguide 66, and continue to be transmitted to the second output straight waveguide 67, where they are coupled into the TE3 mode with a phase of (1 / 4)π.

[0053] The working principle of state 6 is as follows Figure 4As shown in (f), the TE3 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the second straight waveguide 3, but not the first straight waveguide 2 or the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is split into two TE0 mode optical signals by the second curved waveguide 6 and the third curved waveguide 7, with phases of (1 / 4)π and (5 / 4)π respectively. The optical signal in the second curved waveguide 6 travels along the fifth straight waveguide 10 and the sixth curved waveguide 14 to reach the second input tapered waveguide 18. The third curved waveguide 7... The optical signal in the curved waveguide 7 travels along the sixth straight waveguide 11 and the seventh curved waveguide 15 to reach the third input tapered waveguide 19; the phase of the optical signal in the second input tapered waveguide 18 and the third input tapered waveguide 19 is (5 / 4)π (the fifth straight waveguide 10 is a phase-shifting waveguide, and the electrode 32 above the fifth straight waveguide 10 is in working condition. The optical signal undergoes a phase change of π after passing through the fifth straight waveguide 10, so the phase of the optical signal at the second input tapered waveguide 18 is (1 / 4)π + π = (5 / 4)π). The optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signals are output from the second output tapered waveguide 22 and the third output tapered waveguide 23, and then pass through the tenth curved waveguide 26 and the eleventh curved waveguide 27 respectively, enter the eighth straight waveguide 29, continue to be transmitted to the first output straight waveguide 30, and are coupled into the TE0 mode with a phase of (1 / 2)π. The optical signals enter the input tapered waveguide 33 of the mode filter in the TE0 mode, and reach the output tapered waveguide 37 along the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36.The width of the input tapered waveguide 33 decreases linearly from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal, W9 = 6 μm. This width only allows the transmission of TE0 and TE1 mode optical signals. Therefore, the TE0 mode optical signal can reach the output tapered waveguide 37. The optical signal continues to enter the second input straight waveguide 38 of the mode filter in TE0 mode with a phase of π. Then, the optical signal enters the eleventh straight waveguide 40, but does not enter the tenth straight waveguide 39 or the twelfth straight waveguide 41. After entering the eleventh straight waveguide 40, the optical signal is split into two TE modes by the sixteenth curved waveguide 43 and the seventeenth curved waveguide 44. The optical signal in mode 0 has a phase of π. The optical signal in the sixteenth curved waveguide 43 travels along the fourteenth straight waveguide 47 and the twentieth curved waveguide 51 to the sixth input tapered waveguide 55. The optical signal in the seventeenth curved waveguide 44 travels along the fifteenth straight waveguide 48 and the twenty-first curved waveguide 52 to the seventh input tapered waveguide 56. The phase of the optical signal in the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 is π. (The fourteenth straight waveguide 47 is a phase-shifting waveguide. At this time, the electrode 69 above the fourteenth straight waveguide 47 is not in working state. The optical signal does not produce a phase change after passing through the fourteenth straight waveguide 47. Therefore, the phase of the optical signal at the sixth input tapered waveguide 55 is π + 0 = π.) The optical signals in the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 enter the 4×4 multimode interferometer (VIII). According to the self-image principle of the multimode interferometer, the optical signals are output from the sixth output tapered waveguide 59 and the seventh output tapered waveguide 60, and then pass through the twenty-fourth curved waveguide 63 and the twenty-fifth curved waveguide 64 respectively to merge into the seventeenth straight waveguide 66. They continue to be transmitted to the second output straight waveguide 67 and are coupled into the TE0 mode with a phase of -(1 / 2)π.

[0054] The working principle of state 7 is as follows Figure 4As shown in (g), the TE1 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the first straight waveguide 2 and the third straight waveguide 4, but does not enter the second straight waveguide 3. The optical signal is divided into two TE0 mode optical signals in the first straight waveguide 2 and the third straight waveguide 4, with phases of π and 0, respectively. The optical signal in the first straight waveguide 2 travels along the first curved waveguide 5, the fourth straight waveguide 9, and the fifth curved waveguide 13 to reach the first input tapered waveguide 17. The optical signal in the third straight waveguide 4 travels along the fourth curved waveguide 8, the seventh straight waveguide 12, and the eighth curved waveguide 16 to reach the fourth input tapered waveguide 20. The phases of the optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 are π and 0, respectively (the fourth straight waveguide 9 is a phase-shifting waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is not in working state, and the optical signal does not produce a phase change after passing through the fourth straight waveguide 9. Therefore, the phase of the optical signal at the first input tapered waveguide 17 is π + 0 = π). The optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signals are output from the first output tapered waveguide 21 and the fourth output tapered waveguide 24, and then converge into the first output straight waveguide 30 through the ninth curved waveguide 25 and the twelfth curved waveguide 28 respectively, and are coupled into the TE1 mode with a phase of (1 / 4)π. The optical signals enter the input tapered waveguide 33 of the mode filter in the TE1 mode, and reach the output tapered waveguide 37 along the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36. The width of the input tapered waveguide 33 decreases linearly from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal, W9 = 6 μm. This waveguide width only supports TE0 and TE1 mode optical signal transmission. Therefore, the TE1 mode optical signal can reach the output tapered waveguide 37. The optical signal continues to enter the second input straight waveguide 38 of the mode filter in TE1 mode with a phase of π. Then, the optical signal enters the tenth straight waveguide 39 and the twelfth straight waveguide 41, but does not enter the eleventh straight waveguide 40. The optical signal is evenly split into two TE0 mode optical signals in the tenth straight waveguide 39 and the twelfth straight waveguide 41, with phases of π and 0, respectively. The optical signal in the tenth straight waveguide 39 travels along the fifteenth curved waveguide 42, the thirteenth straight waveguide 46, and the nineteenth curved waveguide 50 to reach the fifth input tapered waveguide 54. The optical signal in the twelfth straight waveguide 41 travels along the eighteenth curved waveguide 45, the sixteenth straight waveguide 49, and the twenty-second curved waveguide 53 to reach the eighth input tapered waveguide 57. The phase of the optical signals in the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 is 0 (the thirteenth straight waveguide 46 is a phase-shifting waveguide, and the electrode 68 above the thirteenth straight waveguide 46 is in working condition. The optical signal undergoes a -π phase change after passing through the thirteenth straight waveguide 46. Therefore, the phase of the optical signal at the fifth input tapered waveguide 54 is π-π=0).The optical signals in the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 enter the 4×4 multimode interferometer (VIII). According to the self-image principle of the multimode interferometer, the optical signals are output from the fifth output tapered waveguide 58 and the eighth output tapered waveguide 61, and then pass through the twenty-third curved waveguide 62 and the twenty-sixth curved waveguide 65 respectively to merge into the second output straight waveguide 67, and are coupled into the TE2 mode with a phase of (5 / 4)π.

[0055] The working principle of state 8 is as follows Figure 4As shown in (h), the TE2 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the first straight waveguide 2 and the third straight waveguide 4, but not the second straight waveguide 3. The optical signal is evenly split into two TE0 mode optical signals in the first straight waveguide 2 and the third straight waveguide 4, both with a phase of (7 / 4)π. The optical signal in the first straight waveguide 2 travels along the first curved waveguide 5, the fourth straight waveguide 9, and the fifth curved waveguide 13 to reach the first input tapered waveguide 17. The optical signal in the third straight waveguide 4 travels along the fourth... The curved waveguide 8, the seventh straight waveguide 12, and the eighth curved waveguide 16 reach the fourth input tapered waveguide 20. The phases of the optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 are (3 / 4)π and (7 / 4)π, respectively. (The fourth straight waveguide 9 is a phase-shifting waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is in working condition. The optical signal generates a -π phase change after passing through the fourth straight waveguide 9. Therefore, the phase of the optical signal at the first input tapered waveguide 17 is (7 / 4)π-π=(3 / 4)π). The optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signals are output from the first output tapered waveguide 21 and the fourth output tapered waveguide 24, and then pass through the ninth curved waveguide 25 and the twelfth curved waveguide 28 respectively, and enter the first output straight waveguide 30, and are coupled into the TE1 mode with a phase of (1 / 2)π. The optical signals enter the input tapered waveguide 33 of the mode filter in the TE1 mode, and reach the output tapered waveguide 37 along the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36.The width of the input tapered waveguide 33 decreases linearly from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal, W9 = 6 μm. This width only supports TE0 and TE1 mode optical signal transmission. Therefore, the TE1 mode optical signal can reach the output tapered waveguide 37. The optical signal continues to enter the second input straight waveguide 38 of the mode filter in TE1 mode with a phase of π. Then, the optical signal enters the tenth straight waveguide 39 and the twelfth straight waveguide 41, but does not enter the eleventh straight waveguide 40. The optical signal is evenly split into two TE0 mode optical signals in the tenth straight waveguide 39 and the twelfth straight waveguide 41, with phases of π and 0, respectively. The optical signal in the 10th straight waveguide 39 travels along the 15th curved waveguide 42, the 13th straight waveguide 46, and the 19th curved waveguide 50 to reach the 5th input tapered waveguide 54. The optical signal in the 12th straight waveguide 41 travels along the 18th curved waveguide 45, the 16th straight waveguide 49, and the 22nd curved waveguide 53 to reach the 8th input tapered waveguide 57. The phases of the optical signals in the 5th input tapered waveguide 54 and the 8th input tapered waveguide 57 are π and 0, respectively. (The 13th straight waveguide 46 is a phase-shifting waveguide. At this time, the electrode 68 above the 13th straight waveguide 46 is not in working condition. The optical signal does not undergo a phase change after passing through the 13th straight waveguide 46. Therefore, the phase of the optical signal at the 5th input tapered waveguide 54 is π + 0 = π). The optical signals in the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 enter the 4×4 multimode interferometer (VIII). According to the self-image principle of the multimode interferometer, the optical signals are output in the fifth output tapered waveguide 58 and the eighth output tapered waveguide 61, and then pass through the twenty-third curved waveguide 62 and the twenty-sixth curved waveguide 65 respectively to merge into the second output straight waveguide 67 and couple into the TE1 mode with a phase of (1 / 4)π.

[0056] The working principle of state 9 is as follows: Figure 4As shown in (i), the TE0 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the second straight waveguide 3 but does not enter the first straight waveguide 2 or the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is divided into two TE0 mode optical signals by the second curved waveguide 6 and the third curved waveguide 7, both with a phase of π. The optical signal in the second curved waveguide 6 travels along the fifth straight waveguide 10 and the sixth curved waveguide 14 to reach the second input tapered waveguide 18. The optical signal in the third curved waveguide 7 travels along the sixth straight waveguide 11 and the seventh curved waveguide 15 to reach the third input tapered waveguide 19. The phases of the optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 are 0 and π, respectively (the fifth straight waveguide 10 is a phase-shifting waveguide. At this time, the electrode 32 above the fifth straight waveguide 10 is in working condition. The optical signal undergoes a phase change of -π after passing through the fifth straight waveguide 10. Therefore, the phase of the optical signal at the second input tapered waveguide 18 is π-π=0). The optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signal is output from the second output tapered waveguide 22 and the third output tapered waveguide 23, and then passes through the tenth curved waveguide 26 and the eleventh curved waveguide 27 respectively before converging into the eighth straight waveguide 29. It continues to propagate to the first output straight waveguide 30 and is coupled into TE3 mode with a phase of (1 / 4)π. The optical signal enters the input tapered waveguide 33 of the mode filter in TE3 mode. The width of the input tapered waveguide 33 decreases linearly from W8 = 16μm to W9 = 6μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal, W9 = 6μm. This width only allows the optical signals of TE0 mode and TE1 mode to transmit smoothly. Therefore, the optical signal of TE3 mode is blocked and cannot continue to transmit.

[0057] The working principle of state 10 is as follows: Figure 4As shown in (j), the TE1 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the first straight waveguide 2 and the third straight waveguide 4, but does not enter the second straight waveguide 3. The optical signal is divided into two TE0 mode optical signals in the first straight waveguide 2 and the third straight waveguide 4, with phases of π and 0, respectively. The optical signal in the first straight waveguide 2 travels along the first curved waveguide 5, the fourth straight waveguide 9, and the fifth curved waveguide 13 to reach the first input tapered waveguide 17. The optical signal in the third straight waveguide 4 travels along the fourth curved waveguide 8, the seventh straight waveguide 12, and the eighth curved waveguide 16 to reach the fourth input tapered waveguide 20. The phases of the optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 are both 0 (the fourth straight waveguide 9 is a phase-shifting waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is in working condition. The optical signal undergoes a phase change of -π after passing through the fourth straight waveguide 9. Therefore, the phase of the optical signal at the first input tapered waveguide 17 is π-π=0). The optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signals are output from the first output tapered waveguide 21 and the fourth output tapered waveguide 24, and then pass through the ninth curved waveguide 25 and the twelfth curved waveguide 28 respectively before converging into the first output straight waveguide 30 and coupling into the TE2 mode with a phase of (5 / 4)π. The optical signals enter the input tapered waveguide 33 of the mode filter in the TE2 mode. The width of the input tapered waveguide 33 decreases linearly from W8 = 16μm to W9 = 6μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal, W9 = 6μm. This width only supports the transmission of TE0 and TE1 mode optical signals. Therefore, the TE2 mode optical signal is blocked, and the optical signal cannot continue to be transmitted.

[0058] The working principle of state 11 is as follows: Figure 4As shown in (k), the TE2 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the first straight waveguide 2 and the third straight waveguide 4, but not the second straight waveguide 3. The optical signal is evenly split into two TE0 mode optical signals in the first straight waveguide 2 and the third straight waveguide 4, both with a phase of (7 / 4)π. The optical signal in the first straight waveguide 2 travels along the first curved waveguide 5, the fourth straight waveguide 9, and the fifth curved waveguide 13 to reach the first input tapered waveguide 17. The optical signal in the third straight waveguide 4 travels along... The optical signal reaches the fourth input tapered waveguide 20 via the fourth curved waveguide 8, the seventh straight waveguide 12, and the eighth curved waveguide 16. The phase of the optical signal in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 is (7 / 4)π (the fourth straight waveguide 9 is a phase-shifting waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is not in working state, and the optical signal does not produce a phase change after passing through the fourth straight waveguide 9. Therefore, the phase of the optical signal at the first input tapered waveguide 17 is (7 / 4)π + 0 = (7 / 4)π). Optical signals from the first input tapered waveguide 17 and the fourth input tapered waveguide 20 enter a 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signal is output from the first output tapered waveguide 21 and the fourth output tapered waveguide 24, and then passes through the ninth curved waveguide 25 and the twelfth curved waveguide 28 respectively, entering the first output straight waveguide 30 and coupling into the TE2 mode with a phase of (1 / 4)π. The optical signal enters the input tapered waveguide 33 of the mode filter in the TE2 mode. The width of the input tapered waveguide 33 decreases linearly from W8 = 16μm to W9 = 6μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal, W9 = 6μm. This width only supports the transmission of TE0 and TE1 mode optical signals. Therefore, the TE2 mode optical signal is blocked, and the optical signal cannot continue to be transmitted.

[0059] The working principle of state 12 is as follows Figure 4As shown in (l), the TE3 mode optical signal enters the first input straight waveguide 1 with an initial phase of π. Then, the optical signal enters the second straight waveguide 3, but not the first straight waveguide 2 or the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is divided into two TE0 mode optical signals by the second curved waveguide 6 and the third curved waveguide 7, with phases of (1 / 4)π and (5 / 4)π respectively. The optical signal in the second curved waveguide 6 travels along the fifth straight waveguide 10 and the sixth curved waveguide 14 to reach the second input tapered waveguide 18. The optical signal in the third curved waveguide 7... The optical signal travels along the sixth straight waveguide 11 and the seventh curved waveguide 15 to the third input tapered waveguide 19. The phases of the optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 are (1 / 4)π and (5 / 4)π, respectively. (The fifth straight waveguide 10 is a phase-shifting waveguide. At this time, the electrode 32 above the fifth straight waveguide 10 is not in working condition. The optical signal does not undergo a phase change after passing through the fifth straight waveguide 10. Therefore, the phase of the optical signal at the second input tapered waveguide 18 is (1 / 4)π + 0 = (1 / 4)π). The optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 enter the 4×4 multimode interferometer (Ⅲ). According to the self-image principle of the multimode interferometer, the optical signal is output from the second output tapered waveguide 22 and the third output tapered waveguide 23, and then passes through the tenth curved waveguide 26 and the eleventh curved waveguide 27 respectively before converging into the eighth straight waveguide 29. It continues to transmit and reaches the first output straight waveguide 30, where it is coupled into TE3 mode with a phase of 0. The optical signal enters the input tapered waveguide 33 of the mode filter in TE3 mode. The width of the input tapered waveguide 33 decreases linearly from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal, W9 = 6 μm. This width only supports the transmission of TE0 and TE1 mode optical signals. Therefore, the TE3 mode optical signal is blocked and cannot continue to transmit.

[0060] Example 5

[0061] The multi-functional mode processor with twelve basic states based on Embodiment 4 can be divided into five functional modules: a high-pass filter module, a low-pass filter module, a band-pass filter module, a band-stop filter module, and a mode conversion module. Each functional module includes several sub-functions. The functional modules are described below, along with the operating states of each electrode under each function:

[0062] High-pass filter module:

[0063] Function 1 (TE3 passes smoothly, TE2, TE1, TE0 are blocked): For TE3 to pass smoothly, electrode 32 and electrode 69 must be in the "ON" state. The states of electrodes 31 and 68 have no effect on the device function. For TE2 to be blocked, electrode 31 must be in the "OFF" state. The states of electrodes 32, 68, and 69 have no effect on the device function. For TE1 to be blocked, electrode 31 must be in the "ON" state. The states of electrodes 32, 68, and 69 have no effect on the device function. For TE0 to be blocked, electrode 32 must be in the "ON" state. The states of electrodes 31, 68, and 69 have no effect on the device function.

[0064] Function 2 (TE3 and TE2 pass smoothly, TE1 and TE0 are blocked): For TE3 to pass smoothly, electrode 32 and electrode 69 must be in the "ON" state. The states of electrodes 31 and 68 have no effect on the device function. For TE2 to pass smoothly, electrode 31 and electrode 68 must be in the "ON" state. The states of electrodes 32 and 69 have no effect on the device function. For TE1 to be blocked, electrode 31 must be in the "ON" state. The states of electrodes 32, 68, and 69 have no effect on the device function. For TE0 to be blocked, electrode 32 must be in the "ON" state. The states of electrodes 31, 68, and 69 have no effect on the device function.

[0065] Function 3 (TE3, TE2, TE1 pass smoothly, TE0 is blocked): For TE3 to pass smoothly, electrode 32 and electrode 69 must be in the "ON" state. The states of electrodes 31 and 68 have no effect on the device function. For TE2 to pass smoothly, electrode 31 and electrode 68 must be in the "ON" state. The states of electrodes 32 and 69 have no effect on the device function. For TE1 to pass smoothly, electrode 31 and electrode 68 must be in the "OFF" state. The states of electrodes 32 and 69 have no effect on the device function. For TE0 to be blocked, electrode 32 must be in the "ON" state. The states of electrodes 31, 68, and 69 have no effect on the device function.

[0066] Low-pass filter module:

[0067] Function 1 (TE3, TE2, and TE1 are blocked, TE0 passes smoothly): For TE3 to be blocked, electrode 32 must be in the "OFF" state; the states of electrodes 31, 68, and 69 have no effect on the device function. For TE2 to be blocked, electrode 31 must be in the "OFF" state; the states of electrodes 32, 68, and 69 have no effect on the device function. For TE1 to be blocked, electrode 31 must be in the "ON" state; the states of electrodes 32, 68, and 69 have no effect on the device function. For TE0 to pass smoothly, electrode 32 must be in the "OFF" state; electrode 69 must be in the "OFF" state; the states of electrodes 31 and 68 have no effect on the device function.

[0068] Function 2 (TE3 and TE2 are blocked, TE1 and TE0 pass smoothly): For TE3 to be blocked, electrode 32 must be in the "OFF" state. The states of electrodes 31, 68, and 69 have no effect on the device function. For TE2 to be blocked, electrode 31 must be in the "OFF" state. The states of electrodes 32, 68, and 69 have no effect on the device function. For TE1 to pass smoothly, electrode 31 must be in the "OFF" state. Electrode 68 must be in the "OFF" state. The states of electrodes 32 and 69 have no effect on the device function. For TE0 to pass smoothly, electrode 32 must be in the "OFF" state. Electrode 69 must be in the "OFF" state. The states of electrodes 31 and 68 have no effect on the device function.

[0069] Function 3 (TE3 blocked, TE2, TE1, TE0 pass smoothly): For TE3 to be blocked, electrode 32 must be in the "OFF" state. The states of electrodes 31, 68, and 69 have no effect on the device function. For TE2 to pass smoothly, electrode 31 must be in the "ON" state. Electrode 68 must be in the "ON" state. The states of electrodes 32 and 69 have no effect on the device function. For TE1 to pass smoothly, electrode 31 must be in the "OFF" state. Electrode 68 must be in the "OFF" state. The states of electrodes 32 and 69 have no effect on the device function. For TE0 to pass smoothly, electrode 32 must be in the "OFF" state. Electrode 69 must be in the "OFF" state. The states of electrodes 31 and 68 have no effect on the device function.

[0070] Bandpass filter module:

[0071] Function 1 (TE3 blocked, TE2 passes smoothly, TE1 and TE0 blocked): TE3 being blocked requires electrode 32 to be in the "OFF" state; the states of electrodes 31, 68, and 69 have no effect on the device function. TE2 passing smoothly requires electrode 31 to be in the "ON" state; electrode 68 to be in the "ON" state; the states of electrodes 32 and 69 have no effect on the device function. TE1 being blocked requires electrode 31 to be in the "ON" state; the states of electrodes 32, 68, and 69 have no effect on the device function. TE0 being blocked requires electrode 32 to be in the "ON" state; the states of electrodes 31, 68, and 69 have no effect on the device function.

[0072] Function 2 (TE3 and TE2 blocked, TE1 passes smoothly, TE0 blocked): For TE3 to be blocked, electrode 32 must be in the "OFF" state. The states of electrodes 31, 68, and 69 have no effect on the device function. For TE2 to be blocked, electrode 31 must be in the "OFF" state. The states of electrodes 32, 68, and 69 have no effect on the device function. For TE1 to pass smoothly, electrode 31 must be in the "OFF" state. Electrode 68 must be in the "OFF" state. The states of electrodes 32 and 69 have no effect on the device function. For TE0 to be blocked, electrode 32 must be in the "ON" state. The states of electrodes 31, 68, and 69 have no effect on the device function.

[0073] Function 3 (TE3 blocked, TE2 and TE1 pass smoothly, TE0 blocked): For TE3 to be blocked, electrode 32 must be in the "OFF" state. The states of electrodes 31, 68, and 69 have no effect on the device function. For TE2 to pass smoothly, electrode 31 must be in the "ON" state. Electrode 68 must be in the "ON" state. The states of electrodes 32 and 69 have no effect on the device function. For TE1 to pass smoothly, electrode 31 must be in the "OFF" state. Electrode 68 must be in the "OFF" state. The states of electrodes 32 and 69 have no effect on the device function. For TE0 to be blocked, electrode 32 must be in the "ON" state. The states of electrodes 31, 68, and 69 have no effect on the device function.

[0074] Band-stop filter module:

[0075] Function 1 (TE3 passes smoothly, TE2 is blocked, TE1 and TE0 pass smoothly): For TE3 to pass smoothly, electrode 32 and electrode 69 must be in the "ON" state. The states of electrodes 31 and 68 have no effect on the device function. For TE2 to be blocked, electrode 31 must be in the "OFF" state. The states of electrodes 32, 68, and 69 have no effect on the device function. For TE1 to pass smoothly, electrode 31 and electrode 68 must be in the "OFF" state. The states of electrodes 32 and 69 have no effect on the device function. For TE0 to pass smoothly, electrode 32 and electrode 69 must be in the "OFF" state. The states of electrodes 31 and 68 have no effect on the device function.

[0076] Function 2 (TE3 and TE2 pass successfully, TE1 is blocked, TE0 pass successfully): For TE3 to pass successfully, electrode 32 and electrode 69 must be in the "ON" state. The states of electrodes 31 and 68 have no effect on the device function. For TE2 to pass successfully, electrode 31 and electrode 68 must be in the "ON" state. The states of electrodes 32 and 69 have no effect on the device function. For TE1 to be blocked, electrode 31 must be in the "ON" state. The states of electrodes 32, 68, and 69 have no effect on the device function. For TE0 to pass successfully, electrode 32 and electrode 69 must be in the "OFF" state. The states of electrodes 31 and 68 have no effect on the device function.

[0077] Function 3 (TE3 passes smoothly, TE2 and TE1 are blocked, TE0 passes smoothly): For TE3 to pass smoothly, electrode 32 and electrode 69 must be in the "ON" state. The states of electrodes 31 and 68 have no effect on the device function. For TE2 to be blocked, electrode 31 must be in the "OFF" state. The states of electrodes 32, 68, and 69 have no effect on the device function. For TE1 to be blocked, electrode 31 must be in the "ON" state. The states of electrodes 32, 68, and 69 have no effect on the device function. For TE0 to pass smoothly, electrode 32 must be in the "OFF" state. The states of electrodes 31 and 68 have no effect on the device function.

[0078] Mode conversion function module:

[0079] Function 1 (TE0 mode to TE3 mode conversion) requires electrode 32 to be in the "OFF" state, electrode 69 to be in the "ON" state, and the states of electrodes 31 and 68 have no effect on the device function.

[0080] Function 2 (TE3 mode to TE0 mode) requires electrode 32 to be in the "ON" state, electrode 69 to be in the "OFF" state, and the states of electrodes 31 and 68 have no effect on the device function.

[0081] Function 3 (TE1 mode to TE2 mode conversion) requires electrode 31 to be in the "OFF" state, electrode 68 to be in the "ON" state, and the states of electrodes 32 and 69 have no effect on the device function.

[0082] Function 4 (TE2 mode to TE1 mode conversion) requires electrode 31 to be in the "ON" state, electrode 68 to be in the "OFF" state, and the states of electrodes 32 and 69 have no effect on the device function.

[0083] The simulation results for the twelve basic states of the device are as follows: Figure 5 As shown in (a)-5(l), insertion loss is an important indicator for measuring device performance, and its calculation formula is: IL=-10×lg(P out / P in ), where P in P represents the efficiency of the device input. out IL represents the efficiency at the device's output terminal, and is the device's insertion loss.

[0084] When the device inputs TE0 mode and outputs TE0 mode, the simulation results are as follows: Figure 5 As shown in (a), the efficiency of the multi-function mode processor output is 90.21% at this time, and the insertion loss is calculated to be 0.45dB.

[0085] When the device inputs TE1 mode and outputs TE1 mode, the simulation results are as follows: Figure 5 As shown in (b), the efficiency of the multi-function mode processor output is 90.43% at this time, and the insertion loss is calculated to be 0.44dB.

[0086] When the device is in TE2 input mode and TE2 output mode, the simulation results are as follows: Figure 5 As shown in (c), the efficiency of the multi-function mode processor output is 89.30% at this time, and the insertion loss is calculated to be 0.49dB.

[0087] When the device inputs TE3 mode and outputs TE3 mode, the simulation results are as follows: Figure 5 As shown in (d), the efficiency of the multi-function mode processor output is 91.70% at this time, and the insertion loss is calculated to be 0.38dB.

[0088] When the device inputs in TE0 mode and outputs in TE3 mode, the simulation results are as follows: Figure 5As shown in (e), the efficiency of the multi-function mode processor output is 91.51% at this time, and the insertion loss is calculated to be 0.39dB.

[0089] When the device inputs in TE3 mode and outputs in TE0 mode, the simulation results are as follows: Figure 5 As shown in (f), the efficiency of the multi-function mode processor output is 90.40% at this time, and the insertion loss is calculated to be 0.44dB.

[0090] When the device inputs in TE1 mode and outputs in TE2 mode, the simulation results are as follows: Figure 5 As shown in (g), the efficiency of the multi-function mode processor output is 89.93% at this time, and the insertion loss is calculated to be 0.46dB.

[0091] When the device inputs in TE2 mode and outputs in TE1 mode, the simulation results are as follows: Figure 5 As shown in (h), the efficiency of the multi-function mode processor output is 89.80% at this time, and the insertion loss is calculated to be 0.47dB.

[0092] When the device input TE0 mode is blocked, the simulation results are as follows: Figure 5 As shown in (i), the efficiency of the multi-function mode processor output is 0.00063% at this time, and the insertion loss is calculated to be 52.0dB.

[0093] When the device input TE1 mode is blocked, the simulation results are as follows: Figure 5 As shown in (j), the efficiency of the multi-function mode processor output is 0.004% at this time, and the calculated insertion loss is 43.97dB;

[0094] When the device input TE2 mode is blocked, the simulation results are as follows: Figure 5 As shown in (k), the efficiency of the multi-function mode processor output is 0.00051% at this time, and the insertion loss is calculated to be 52.92dB.

[0095] When the device input TE3 mode is blocked, the simulation results are as follows: Figure 5 As shown in (l), the efficiency of the multi-function mode processor output is 0.00023% at this time, and the calculated insertion loss is 56.38dB.

Claims

1. A silica multi-functional mode processor based on a cascaded multimode interferometer, characterized by: From bottom to top, it consists of a silicon substrate, a silicon dioxide lower cladding layer, a germanium-doped silicon dioxide core layer, and a silicon dioxide upper cladding layer, with the core layer encased within the upper cladding layer; along the light transmission direction, the core layer consists of three unit modules: a first mode converter, a mode filter, and a second mode converter, with the first mode converter and the second mode converter having identical structures and dimensions. The first mode converter consists of a first 1×3Y branch waveguide (Ⅰ), a first 1×2Y branch waveguide (Ⅱ), a first 4×4 multimode interferometer (Ⅲ), a first 2×1 branch combiner (Ⅳ), and a first 3×1Y branch combiner (Ⅴ). The first input straight waveguide (1), the first straight waveguide (2), the second straight waveguide (3), and the third straight waveguide (4) constitute the first 1×3Y branch waveguide (Ⅰ). The second straight waveguide (3), the second curved waveguide (6), and the third curved waveguide (7) constitute the first 1×2Y branch waveguide (Ⅱ). The first input tapered waveguide (17), the second input tapered waveguide (18), and the third input tapered waveguide (19) are also included. The fourth input tapered waveguide (20) is the four input terminals of the first 4×4 multimode interferometer (Ⅲ); the first output tapered waveguide (21), the second output tapered waveguide (22), the third output tapered waveguide (23), and the fourth output tapered waveguide (24) are the four output terminals of the first 4×4 multimode interferometer (Ⅲ); the tenth curved waveguide (26), the eleventh curved waveguide (27), and the eighth straight waveguide (29) constitute the first 2×1Y branch combiner (Ⅳ); the ninth curved waveguide (25), the eighth straight waveguide (29), the twelfth curved waveguide (28), and the first output straight waveguide (30) constitute the first 3×1Y branch combiner (Ⅴ). The width of the first input straight waveguide (1) is W1 = 16 μm, which can accommodate the transmission of four modes: TE0, TE1, TE2, and TE3. After passing through the first 1×3Y branch waveguide (Ⅰ), the first input straight waveguide (1) is divided into a second straight waveguide (3) with a width of W2 = 8 μm, a first straight waveguide (2) with a width of W4 = 4 μm, and a third straight waveguide (4). After passing through the first 1×2Y branch waveguide (Ⅱ), the second straight waveguide (3) is divided into a second curved waveguide (6) with a width of W3 = 4 μm and a third curved waveguide (7). The first curved waveguide (5), the fourth straight waveguide (9), and the fifth curved waveguide (13) connected to the first straight waveguide (2) in sequence have the same width of W4 = 4 μm. The third straight waveguide (4) is connected to the third straight waveguide (4) in sequence. The widths of the fourth curved waveguide (8), the seventh straight waveguide (12), and the eighth curved waveguide (16) are equal, W4 = 4 μm. The widths of the fifth straight waveguide (10) and the sixth curved waveguide (14), which are sequentially connected to the second curved waveguide (6), are equal, W3 = 4 μm. The widths of the sixth straight waveguide (11) and the seventh curved waveguide (15), which are sequentially connected to the third curved waveguide (7), are equal, W3 = 4 μm. The fourth straight waveguide (9) and the fifth straight waveguide (10) are phase-shifting waveguides. A first heating electrode (31) and a second heating electrode (32) are respectively disposed on the silicon dioxide cladding corresponding to their positions. The lengths of the fourth straight waveguide (9), the fifth straight waveguide (10), the first heating electrode (31), and the second heating electrode (32) are equal, L. PS =3000μm, the widths of the first heating electrode (31) and the second heating electrode (32) are equal to W. PS =21μm; air isolation grooves penetrating the upper silicon dioxide cladding, the lower silicon dioxide cladding, and a portion of the silicon substrate are provided on both sides of the first heating electrode (31) and the second heating electrode (32); the width of the 4×4 multimode interferometer (Ⅲ) is W7 = 62μm and the length is L1 = 7740μm; the fifth bent waveguide (13), the sixth bent waveguide (14), the seventh bent waveguide (15), and the eighth bent waveguide (16) are respectively connected to the 4×4 multimode interferometer (Ⅲ) through the first input tapered waveguide (17), the second input tapered waveguide (18), the third input tapered waveguide (19), and the fourth input tapered waveguide (20); the first The first output tapered waveguide (21), the second output tapered waveguide (22), the third output tapered waveguide (23), and the fourth output tapered waveguide (24) are connected to the ninth curved waveguide (25), the tenth curved waveguide (26), the eleventh curved waveguide (27), and the twelfth curved waveguide (28), respectively. The widths of the tenth curved waveguide (26) and the eleventh curved waveguide (27) are equal, with a width of W3 = 4 μm. The width of the eighth straight waveguide (29) is W2 = 8 μm. The widths of the ninth curved waveguide (25) and the twelfth curved waveguide (28) are equal, with a width of W4 = 4 μm. The width of the first output straight waveguide (30) is W8 = 16 μm. The mode filter consists of an input tapered waveguide (33), a thirteenth curved waveguide (34), a ninth straight waveguide (35), a fourteenth curved waveguide (36), and an output tapered waveguide (37) connected in sequence; the width of the ninth straight waveguide (35) is W9 = 6 μm; The second mode converter consists of a second 1×3Y branch waveguide (VI), a second 1×2Y branch waveguide (VII), a second 4×4 multimode interferometer (VIII), a second 2×1Y branch combiner (IX), and a second 3×1Y branch combiner (X); the second input straight waveguide (38), the tenth straight waveguide (39), the eleventh straight waveguide (40), and the twelfth straight waveguide (41) constitute the second 1×3Y branch waveguide (VI); the eleventh straight waveguide (40) and the sixteenth curved waveguide (43) and the seventeenth curved waveguide (44) constitute the second 1×2Y branch waveguide (VII); the fifth input tapered waveguide (54), the sixth input tapered waveguide (55), and the seventh input tapered waveguide (56) constitute the second 1×2Y branch waveguide (VII). 56) and the eighth input tapered waveguide (57) are the four input terminals of the second 4×4 multimode interferometer (VIII); the fifth output tapered waveguide (58), the sixth output tapered waveguide (59), the seventh output tapered waveguide (60), and the eighth output tapered waveguide (61) are the four output terminals of the second 4×4 multimode interferometer (VIII); the twenty-fourth curved waveguide (63), the twenty-fifth curved waveguide (64), and the seventeenth straight waveguide (66) constitute the second 2×1Y branch combiner (IX); the twenty-third curved waveguide (62), the seventeenth straight waveguide (66), the twenty-sixth curved waveguide (65), and the second output straight waveguide (67) constitute the second 3×1Y branch combiner (X); The width of the second input straight waveguide (38) is W 10 =16μm, which can accommodate four modes of transmission: TE0, TE1, TE2, and TE3. After passing through the second 1×3Y branch waveguide (VI), the second input straight waveguide (38) is divided into two parts with a width of W. 11 An eleventh direct waveguide (40) with a width of 8 μm and a width of W 13 =4μm, the tenth straight waveguide (39) and the twelfth straight waveguide (41); then through the second 1×2Y branch waveguide (VII), the eleventh straight waveguide (40) is divided into two sections with a width of W. 12 The sixteenth curved waveguide (43) and the seventeenth curved waveguide (44) are 4 μm wide; the fifteenth curved waveguide (42), the thirteenth straight waveguide (46), and the nineteenth curved waveguide (50), which are connected in sequence to the tenth straight waveguide (39), have the same width W. 13 =4μm, and the widths of the eighteenth curved waveguide (45), the sixteenth straight waveguide (49), and the twenty-second curved waveguide (53), which are sequentially connected to the twelfth straight waveguide (41), are equal to W. 13 =4μm, and the width of the fourteenth straight waveguide (47) and the twentieth curved waveguide (51), which are sequentially connected to the sixteenth curved waveguide (43), is equal to W. 12 =4μm, and the width of the fifteenth straight waveguide (48) and the twenty-first curved waveguide (52), which are sequentially connected to the seventeenth curved waveguide (44), is equal to W. 12 =4μm; The thirteenth straight waveguide (46) and the fourteenth straight waveguide (47) are phase-shifting waveguides. A third heating electrode (68) and a fourth heating electrode (69) are respectively disposed on the silicon dioxide cladding corresponding to their positions. The lengths of the thirteenth straight waveguide (46), the fourteenth straight waveguide (47), the third heating electrode (68), and the fourth heating electrode (69) are equal and are L. PS =3000μm, the widths of the third heating electrode (68) and the fourth heating electrode (69) are equal, W PS =21μm, with air isolation grooves penetrating the upper silicon dioxide cladding, the lower silicon dioxide cladding, and a portion of the silicon substrate on both sides of the third heating electrode (68) and the fourth heating electrode (69); the width of the second 4×4 multimode interferometer (VIII) is W. 16 =62μm, length L2=7740μm; the nineteenth curved waveguide (50), twentieth curved waveguide (51), twenty-first curved waveguide (52), and twenty-second curved waveguide (53) are connected to the 4×4 multimode interferometer (VIII) through the fifth input tapered waveguide (54), sixth input tapered waveguide (55), seventh input tapered waveguide (56), and eighth input tapered waveguide (57), respectively; the 4×4 multimode interferometer (VIII) is connected to the twenty-third curved waveguide (62), twenty-fourth curved waveguide (63), twenty-fifth curved waveguide (64), and twenty-sixth curved waveguide (65) through the fifth output tapered waveguide (58), sixth output tapered waveguide (59), seventh output tapered waveguide (60), and eighth output tapered waveguide (61), respectively; the width of the twenty-fourth curved waveguide (63) and the twenty-fifth curved waveguide (64) is equal to W. 12 =4μm, the width of the seventeenth straight waveguide (66) is W 11 =8μm, the width of the twenty-third curved waveguide (62) and the twenty-sixth curved waveguide (65) is W 13 =4μm, the width of the second output straight waveguide (67) is W 17 =16μm.

2. The silicon dioxide multi-functional mode processor based on a cascaded multimode interferometer as described in claim 1, characterized in that: The waveguide widths of the first input tapered waveguide (17) and the fourth input tapered waveguide (20) are linearly increased from W4 = 4 μm to W5 = 8 μm; the waveguide widths of the second input tapered waveguide (18) and the third input tapered waveguide (19) are linearly increased from W3 = 4 μm to W6 = 9.6 μm; the waveguide widths of the first output tapered waveguide (21) and the fourth output tapered waveguide (24) are linearly decreased from W5 = 8 μm to W4 = 4 μm, and the waveguide widths of the second output tapered waveguide (22) and the third output tapered waveguide (23) are linearly decreased from W6 = 9.6 μm to W3 = 4 μm; the first input tapered waveguide (17), the fourth input tapered waveguide (20), and the first output tapered waveguide (24) are linearly increased from W5 = 8 μm to W4 = 4 μm. 21) The distance between the center of symmetry of the fourth output tapered waveguide (24) and the center of symmetry of the 4×4 multimode interferometer (Ⅲ) is X2 = 24 μm. The distance between the center of symmetry of the second input tapered waveguide (18), the third input tapered waveguide (19), the second output tapered waveguide (22), and the third output tapered waveguide (23) and the center of symmetry of the 4×4 multimode interferometer (Ⅲ) is X1 = 9.4 μm. The width of the input tapered waveguide (33) decreases linearly from W8 = 16 μm to W9 = 6 μm. The widths of the thirteenth curved waveguide (34), the ninth straight waveguide (35), and the fourteenth curved waveguide (36) are equal at W9 = 6 μm. The width of the output tapered waveguide (37) increases linearly from W9 = 6 μm to W9 = 6 μm. 10 =16μm; the waveguide widths of the fifth input tapered waveguide (54) and the eighth input tapered waveguide (57) are from W 13 =4μm linearly increased to W 14 =8μm, the waveguide widths of the sixth input tapered waveguide (55) and the seventh input tapered waveguide (56) are from W 12 =4μm linearly increased to W 15 = 9.6μm; the waveguide widths of the fifth output tapered waveguide (58) and the eighth output tapered waveguide (61) are from W 14 =8μm linearly decreased to W 13 =4μm, the waveguide widths of the sixth output tapered waveguide (59) and the seventh output tapered waveguide (60) are from W 15 = 9.6 μm linearly decreased to W 12 =4μm; the distance between the center of symmetry of the fifth input tapered waveguide (54), the eighth input tapered waveguide (57), the fifth output tapered waveguide (58), and the eighth output tapered waveguide (61) and the center of symmetry of the 4×4 multimode interferometer (VIII) is X4 = 24μm; the distance between the center of symmetry of the sixth input tapered waveguide (55), the seventh input tapered waveguide (56), the sixth output tapered waveguide (59), and the seventh output tapered waveguide (60) and the center of symmetry of the 4×4 multimode interferometer (VIII) is X3 = 9.4μm.

3. A silica multi-functional mode processor based on a cascaded multimode interferometer as claimed in claim 1, characterized in that: The first input tapered waveguide (17) and the first output tapered waveguide (21), the second input tapered waveguide (18) and the second output tapered waveguide (22), the third input tapered waveguide (19) and the third output tapered waveguide (23), the fourth input tapered waveguide (20) and the fourth output tapered waveguide (24) are symmetrical about the first 4×4 multimode interferometer (Ⅲ). The first straight waveguide (2) and the third straight waveguide (4), the first curved waveguide (5) and the fourth curved waveguide (8), the second The curved waveguide (6) and the third curved waveguide (7), the fourth straight waveguide (9) and the seventh straight waveguide (12), the fifth straight waveguide (10) and the sixth straight waveguide (11), the fifth curved waveguide (13) and the eighth curved waveguide (16), the sixth curved waveguide (14) and the seventh curved waveguide (15), the ninth curved waveguide (25) and the twelfth curved waveguide (28), the tenth curved waveguide (26) and the eleventh curved waveguide (27) are vertically symmetrical structures; the fifth input tapered waveguide (54) and The fifth output tapered waveguide (58), the sixth input tapered waveguide (55), the sixth output tapered waveguide (59), the seventh input tapered waveguide (56), the seventh output tapered waveguide (60), the eighth input tapered waveguide (57), and the eighth output tapered waveguide (61) are symmetrical structures about the second 4×4 multimode interferometer (VⅢ), and the tenth straight waveguide (39) and the twelfth straight waveguide (41), the fifteenth curved waveguide (42) and the eighteenth curved waveguide (45), the sixteenth curved waveguide (46) and the twelfth curved waveguide (41) are symmetrical structures about the second 4×4 multimode interferometer (VⅢ), and the twelfth straight waveguide (39) and the twelfth curved ... the twelfth straight waveguide (39) and the twelfth straight waveguide (41), the fifteenth curved waveguide (42) and the eighteenth curved waveguide (45), the sixteenth curved waveguide (46) and the twelfth curved waveguide (41) are symmetrical structures about the second 4×4 multimode interferometer (VⅢ). 43) is symmetrical with the seventeenth curved waveguide (44), the thirteenth straight waveguide (46) and the sixteenth straight waveguide (49), the fourteenth straight waveguide (47) and the fifteenth straight waveguide (48), the nineteenth curved waveguide (50) and the twenty-second curved waveguide (53), the twentieth curved waveguide (51) and the twenty-first curved waveguide (52), the twenty-third curved waveguide (62) and the twenty-sixth curved waveguide (65), and the twenty-fourth curved waveguide (63) and the twenty-fifth curved waveguide (64).

4. A silica multi-functional mode processor based on a cascaded multi-mode interferometer of claim 1, characterized by: All straight waveguides or extensions of straight waveguides in the three unit modules—the first mode converter, the mode filter, and the second mode converter—are set to be parallel.

5. A silica multi-functional mode processor based on a cascaded multi-mode interferometer of claim 1, characterized by: Under different input and control conditions, this multi-functional mode processor has twelve operating states, namely: State (1): When a TE0 mode optical signal is input, output a TE0 mode optical signal; State (2): When a TE1 mode optical signal is input, output a TE1 mode optical signal; State (3): When a TE2 mode optical signal is input, output a TE2 mode optical signal; State (4): When a TE3 mode optical signal is input, output a TE3 mode optical signal; State (5): When a TE0 mode optical signal is input, output a TE3 mode optical signal; State (6): When a TE0 mode optical signal is input, output a TE3 mode optical signal; State (7): When a TE0 mode optical signal is input, output a TE3 mode optical signal; State (8): When a TE0 mode optical signal is input, output a TE3 mode optical signal; State (9): When a TE0 mode optical signal is input, output a TE3 mode optical signal; State (10): When a TE0 mode optical signal is input, output a TE0 mode optical signal. In the case of a 3-mode optical signal, the output is a TE0 mode optical signal; State (7): In the case of an input TE1 mode optical signal, the output is a TE2 mode optical signal; State (8): In the case of an input TE2 mode optical signal, the output is a TE1 mode optical signal; State (9): The input TE0 mode optical signal is blocked, and there is no optical signal output; State (10): The input TE1 mode optical signal is blocked, and there is no optical signal output; State (11): The input TE2 mode optical signal is blocked, and there is no optical signal output; State (12): The input TE3 mode optical signal is blocked, and there is no optical signal output.

Images