Silicon dioxide multifunctional mode processor based on cascade multimode interference device

Abstract

The invention discloses a silicon dioxide multifunctional mode processor based on a cascade multimode interference device, and belongs to the technical field of silicon dioxide integrated optics. The silicon-based germanium-doped silicon dioxide thin film transistor is composed of a silicon substrate, a silicon dioxide lower cladding, a germanium-doped silicon dioxide core layer and a silicon dioxide upper cladding in sequence, wherein the core layer is coated in the upper cladding; the core layer is composed of three unit modules, namely a first mode converter, a mode filter and a second mode converter, and the first mode converter and the second mode converter are identical in structure and size; the mode converter is composed of a 1 * 3Y branch waveguide, a 1 * 2Y branch waveguide, a 4 * 4 multimode interference device, a 2 * 1 branch combiner and a 3 * 1Y branch combiner. The device has 12 basic working states, and through different combinations of the basic working states, five different function processing such as high-pass filtering, low-pass filtering, band-pass filtering, band-stop filtering and mode conversion can be carried out on input four mode signals of TE0, TE1, TE2 and TE3.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon dioxide integrated optics, and in particular relates to a silicon dioxide multifunctional mode processor based on a cascaded multimode interferometer. Background Art

[0002] At present, people's demand for communication is getting higher and higher, and the progress of communication technology is also getting faster and faster. In optical communication networks, mode division multiplexing technology plays a vital role. It can multiplex and demultiplex multiple modes of optical signals to improve the transmission efficiency and system capacity of optical communication systems. In mode division multiplexing systems, different types of processing are required for the modes of light, such as mode filtering, mode conversion, etc. Therefore, in the field of optical communications, by modulating and processing the optical mode signals in the waveguide, multiple functions can be realized, effectively improving the performance and flexibility of the optical communication system. This type of multifunctional mode processing device has important application value.

[0003] The multifunctional mode processor mainly processes different modes of optical signals, and its main functions include high-pass filtering, low-pass filtering, band-pass filtering, band-stop filtering and mode conversion. The high-pass filtering function means that the device can filter out low-order modes and allow high-order modes to pass normally; low-pass filtering can filter out high-order modes and allow low-order modes to pass smoothly; band-pass filtering allows modes in the middle order to pass smoothly; band-stop filtering can filter out middle-order modes and allow high-order and low-order modes to pass smoothly; mode conversion can convert any order of input optical mode into any order target mode at the output end of the device through the mode matching process, thereby improving the flexibility of the communication system, improving the system optical transmission efficiency, and increasing the system bandwidth.

[0004] The performance indicators of the multifunctional mode processor mainly include insertion loss, working bandwidth, and inter-mode crosstalk. For the multifunctional mode processor, it should have low inter-mode crosstalk while maintaining low loss and large bandwidth to obtain ideal performance. The multifunctional mode processor can be realized using different materials. Among them, silicon dioxide material has the advantages of mature manufacturing process, large process tolerance and low optical loss, which can meet the indicator requirements of the multifunctional mode processor. Summary of the invention

[0005] The purpose of the present 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. 0 TE 1 TE 2 and TE 3The four modes are high-pass filtering, low-pass filtering, band-pass filtering, band-stop filtering and mode conversion processing. The device adopts an active structure, and uses four electrodes to perform thermo-optical control on the modulation arm to change the phase of the optical signal in the modulation arm waveguide to achieve the control of the optical signal mode.

[0006] The silicon dioxide multifunctional mode processor based on cascaded multimode interferometer described in the present invention is composed of a silicon substrate, a silicon dioxide lower cladding layer, a germanium-doped silicon dioxide core layer, and a silicon dioxide upper cladding layer from bottom to top, wherein the core layer is coated in the upper cladding layer. Figure 1 (a) shown.

[0007] like Figure 2 As shown in (a), along the light transmission direction, the core layer of the multifunctional mode processor is composed of three unit modules: a first mode converter, a mode filter, and a second mode converter. The structures and sizes of the first mode converter and the second mode converter are exactly the same. Figure 2 (b) Figure 2 (d) as shown.

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

[0009] The width of the first input straight waveguide 1 is W 1 =16μm, can accommodate TE 0 TE 1 TE 2 TE 3 After the four modes are transmitted through the first 1×3Y branch waveguide (Ⅰ), the first input straight waveguide 1 is divided into a width of W 2 = 8 μm second straight waveguide 3, width W 4 =4μm first straight waveguide 2 and third straight waveguide 4; then through the first 1×2Y branch waveguide (Ⅱ), the second straight waveguide 3 is divided into a width of W 3 =4μm second curved waveguide 6 and third curved waveguide 7; the first curved waveguide 5, the fourth straight waveguide 9, and the fifth curved waveguide 13 connected in sequence to the first straight waveguide 2 are equal to W 4 =4 μm, the widths of the fourth curved waveguide 8, the seventh straight waveguide 12 and the eighth curved waveguide 16 connected in sequence to the third straight waveguide 4 are equal to W4 =4 μm, the fifth straight waveguide 10 and the sixth curved waveguide 14 connected in sequence to the second curved waveguide 6 have the same width as W 3 =4 μm, the sixth straight waveguide 11 and the seventh curved waveguide 15 connected in sequence to the third curved waveguide 7 have the same width as W 3 =4μm; the fourth straight waveguide 9 and the fifth straight waveguide 10 are phase-shift waveguides, and the first heating electrode 31 and the second heating electrode 32 are respectively arranged on the silicon dioxide upper cladding corresponding to their positions, and 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 to L PS =3000 μm, the width of the first heating electrode 31 and the second heating electrode 32 are equal to W PS =21μm; on both sides of the first heating electrode 31 and the second heating electrode 32, there are air isolation grooves penetrating the silicon dioxide upper cladding, the silicon dioxide lower cladding and a portion of the silicon substrate, the air isolation groove has a width of 35μm and a length of 3000μm, such as Figure 1 (b) as shown; 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 front-to-back symmetrical structures with respect to 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 top-to-bottom symmetrical structures; the waveguide widths of the first input tapered waveguide 17 and the fourth input tapered waveguide 20 are both represented by W 4 =4μm linearly increases to W 5 = 8 μm; the waveguide width of the second input tapered waveguide 18 and the third input tapered waveguide 19 is from W 3 =4μm linearly increases to W 6 =9.6μm; the width of the 4×4 multimode interferometer (III) is W 7 =62μm, length is L 1 =7740 μm (except for the multi-mode interferometer, the heating electrode, and the phase shift region waveguide length under the heating electrode, the remaining waveguides only play a connecting role and have no specific length requirements); the waveguide width of the first output tapered waveguide 21 and the fourth output tapered waveguide 24 is from W 5 =8μm linearly reduced to W 4=4 μm, the waveguide widths of the second output tapered waveguide 22 and the third output tapered waveguide 23 are from W 6 =9.6μm linearly decreases to W 3 =4 μm, the distance between the symmetry center of the first input tapered waveguide 17, the fourth input tapered waveguide 20, the first output tapered waveguide 21, the fourth output tapered waveguide 24 and the symmetry center of the 4×4 multimode interferometer (III) is X 2 =24 μm, the distance between the symmetry center of the second input tapered waveguide 18, the third input tapered waveguide 19, the second output tapered waveguide 22, the third output tapered waveguide 23 and the symmetry center of the 4×4 multimode interferometer (III) is X 1 =9.4 μm; the fifth curved waveguide 13, the sixth curved waveguide 14, the seventh curved waveguide 15, and the eighth curved waveguide 16 are 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 respectively; 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 to W 3 =4 μm, the width of the eighth straight waveguide 29 is W 2 =8 μm, the width of the ninth curved waveguide 25 and the twelfth curved waveguide 28 are equal to W 4 =4μm, the width of the first output straight waveguide 30 is W 8 =16μm.

[0010] The structure of the mode filter is as follows Figure 2 As shown in (c), the input tapered waveguide 33, the thirteenth curved waveguide 34, the ninth straight waveguide 35, the fourteenth curved waveguide 36 and the output tapered waveguide 37 are connected in sequence. The width W of the ninth straight waveguide (35) is 9 =6μm; the width of the input tapered waveguide 33 is from W 8 =16μm linearly reduced to W 9 =6 μm, the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal to W 9 = 6 μm, the width of the output tapered waveguide 37 is from W 9 =6μm linearly increases to W 10 =16μm.

[0011] The second mode converter is composed 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), such as Figure 2 4, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110 a fifth input tapered waveguide 54, a sixth input tapered waveguide 55, a seventh input tapered waveguide 56, an eighth input tapered waveguide 57, a second 4×4 multimode interferometer (VIII), a fifth output tapered waveguide 58, a sixth output tapered waveguide 59, a seventh output tapered waveguide 60, an eighth output tapered waveguide 61, a twenty-third curved waveguide 62, a twenty-fourth curved waveguide 63, a twenty-fifth curved waveguide 64, a twenty-sixth curved waveguide 65, a seventeenth straight waveguide 66 and a second output straight waveguide 67, wherein In the embodiment, the second input straight waveguide 38, the tenth straight waveguide 39, the eleventh straight waveguide 40, and the twelfth straight waveguide 41 constitute a second 1×3Y branch waveguide (VI), the eleventh straight waveguide 40 and the sixteenth curved waveguide 43 and the seventeenth curved waveguide 44 constitute a second 1×2Y 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 four input ends of the second 4×4 multimode interferometer (VIII), and 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 four input ends of the second 4×4 multimode interferometer (VIII). The 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 ends 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), and 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).

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

[0013] The width of the second input straight waveguide 38 is W 10 =16μm, can accommodate TE 0 TE 1 TE 2 TE 3 After the four modes are transmitted through the second 1×3Y branch waveguide (VI), the second input straight waveguide 38 is divided into a width of W 11 = 8 μm, the eleventh straight waveguide 40, the width is W 13= 4μm tenth straight waveguide 39 and twelfth straight waveguide 41; then through the second 1×2Y branch waveguide (VII), the eleventh straight waveguide 40 is divided into a width of W 12 = 4 μm of the sixteenth curved waveguide 43 and the seventeenth curved waveguide 44; the fifteenth curved waveguide 42, the thirteenth straight waveguide 46 and the nineteenth curved waveguide 50 connected in sequence to the tenth straight waveguide 39 have the same width as W 13 =4 μm, the widths of the eighteenth curved waveguide 45, the sixteenth straight waveguide 49 and the twenty-second curved waveguide 53 sequentially connected to the twelfth straight waveguide 41 are equal to W 13 =4 μm, the width of the fourteenth straight waveguide 47 and the twentieth curved waveguide 51 connected in sequence to the sixteenth curved waveguide 43 are equal to W 12 =4 μm, the width of the fifteenth straight waveguide 48 and the twenty-first curved waveguide 52 sequentially connected to the seventeenth curved waveguide 44 are equal to W 12 =4μm; the thirteenth straight waveguide 46 and the fourteenth straight waveguide 47 are phase-shift waveguides, and the third heating electrode 68 and the fourth heating electrode 69 are respectively arranged on the silicon dioxide upper cladding corresponding to their positions, and 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 to L PS =3000 μm, the width of the third heating electrode 68 and the fourth heating electrode 69 are equal to W PS =21μm, and air isolation grooves penetrating the silicon dioxide upper cladding, the silicon dioxide lower cladding and a portion of the silicon substrate are provided on both sides of the third heating electrode 68 and the fourth heating electrode 69, and the width of the air isolation groove is 35μm and the length is 3000μm. Figure 1 (b); the fifth input tapered waveguide 54 and the fifth input 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 front-to-back symmetrical structures with respect to 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 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, the twenty-fourth curved waveguide 63 and the twenty-fifth curved waveguide 64 are vertically symmetrical structures; the waveguide widths of the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 are from W to W. 13 =4μm linearly increases to W 14= 8 μm, the waveguide widths of the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 are from W 12 =4μm linearly increases to W 15 =9.6μm; the width of the second 4×4 multimode interferometer (VIII) is W 16 =62μm, length is L 2 =7740 μm (except for the multi-mode interferometer, the heating electrode, and the phase shift region waveguide length under the heating electrode, the remaining waveguides only play a connecting role and have no specific length requirements); the waveguide width of the fifth output tapered waveguide 58 and the eighth output tapered waveguide 61 is from W 14 =8μm linearly reduced to W 13 =4 μm, the waveguide widths of the sixth output tapered waveguide 59 and the seventh output tapered waveguide 60 are from W 15 =9.6μm linearly reduced to W 12 =4μm; the distance between the symmetry 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 and the symmetry center of the 4×4 multimode interferometer (VIII) is X 4 = 24 μm; the distance between the symmetry 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 and the symmetry center of the 4×4 multimode interferometer (VIII) is X 3 =9.4 μm; the nineteenth curved waveguide 50, the twentieth curved waveguide 51, the twenty-first curved waveguide 52, and the twenty-second curved waveguide 53 are connected to the 4×4 multimode interferometer (VIII) through 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 through 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 width of the twenty-fourth curved waveguide 63 and the twenty-fifth curved waveguide 64 is equal to W 12 =4 μm, the width of the seventeenth straight waveguide 66 is W 11 =8 μm, 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the cross-section of the multi-function mode processor structure; wherein, Figure 1 (a) is the cross-sectional structure diagram of the non-phase shifting region; Figure 1 (b) is a cross-sectional structural diagram of the phase shift region;

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

[0016] Figure 3 is a graph showing the effective refractive index of different modes of a silica waveguide changing with the waveguide width;

[0017] Figure 4 (a)~ Figure 4 (l) Phase diagrams of optical signals at various positions of the device core layer under twelve basic working conditions;

[0018] Figure 5 (a)~ Figure 5 (l) Simulated light field diagrams of the device under twelve basic working states;

[0019] Figure 6 The device preparation process flow chart is shown in FIG. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below through specific implementations in conjunction with the accompanying drawings.

[0021] Example 1

[0022] See attached Figure 1 The multifunctional mode processor is composed of substrate, lower cladding, core layer, upper cladding and electrode from bottom to top. Except for the lower surface, the rest of the core layer is covered by the upper cladding. The core layer and the upper cladding are both located above the lower cladding. The lower cladding and the upper cladding are made of silicon dioxide with a refractive index of 1.4447. The core layer is made of germanium-doped silicon dioxide with a refractive index of 1.4741. The thickness of the core layer is 4μm.

[0023] See attached Figure 2 The core layer of the multifunctional mode processor is along the transmission direction of light and is composed of three unit modules: a first mode converter, a mode filter, and a second mode converter. The structures and sizes of the first mode converter and the second mode converter are exactly the same. Figure 2As shown in (b), it can be divided into three parts; the first part includes the first 1×3Y branch waveguide (Ⅰ), the first 1×2Y branch waveguide (Ⅱ) and the first heating electrode 31 and the second heating electrode 32; the second part is the first 4×4 multimode interferometer (Ⅲ); the third part is the first 2×1Y branch combiner (Ⅳ) and the first 3×1Y branch combiner (Ⅴ). The mode filter is as follows Figure 2 As shown in (c), it is composed 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 shown in FIG. Figure 2 As 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) and the third heating electrode 68 and the fourth heating electrode 69; the second part is the second 4×4 multi-mode 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] Determine the size parameters of each part of the core waveguide. The core waveguide height is fixed at 4μm. The first mode converter, the input end can support TE 0 TE 1 TE 2 and TE 4 Four modes, according to Figure 3 The effective refractive index of different modes of silica waveguide varies with the waveguide width. The width of the first input straight waveguide 1 is set to W. 1 =16 μm, the optical signal is transmitted 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 at TE 0 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 equal to W. 3 =4 μm, the optical signal is transmitted 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 at TE 0 The mode exists, and 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 equal to W. 3 =4μm, the width of the second straight waveguide 3 is W 2 =8 μm. The modulation electrode 31 and the modulation electrode 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) is determined by the beam propagation method to be W 7 =62μm, length is L 1 =7740 μm, the distance between the center of the first input tapered waveguide 17, the fourth input tapered waveguide 20, the first output tapered waveguide 21, the fourth output tapered waveguide 24 and the center of the 4×4 multimode interferometer (III) is X 2 = 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, the third output tapered waveguide 23 and the center of the 4×4 multimode interferometer (III) is X 1 =9.4μm.

[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 TE 0 mode, the length of the above series of curved waveguides is W 3 =4μm, the width of the eighth straight waveguide 29 is W 2 =8μm, the width of the first output straight waveguide 30 is W 8 =16μm.

[0028] Mode filter, according to Figure 3 The effective refractive index of different modes in the silica waveguide varies with the waveguide width. The width of the input tapered waveguide 33 is set from W 8 =16μm linearly reduced to W 9 =6 μm, the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35 and the fourteenth curved waveguide 36 are equal to W 9 = 6 μm, the width of the output tapered waveguide 37 is from W 9 =6μm linearly increases to W 10 =16μm, only supports TE 0 TE 1 Mode transfer.

[0029] The second mode converter can support TE 0 TE 1 TE 2 and TE 4 Four modes of transmission, according to Figure 3 The effective refractive index of different modes in the silica waveguide varies with the waveguide width. The width of the second input straight waveguide 38 is set to W. 10 =16 μm, the optical signal is transmitted 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 at TE 0The mode exists, and 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 =4 μm, the optical signal is transmitted in the fifteenth curved waveguide 42, the sixteenth curved waveguide 43, the seventeenth curved waveguide 44, the eighteenth curved waveguide 45, the nineteenth curved waveguide 50, the twentieth curved waveguide 51, the twenty-first curved waveguide 52 and the twenty-second curved waveguide 53 at TE 0 The mode exists, and the widths of the fifteenth curved waveguide 42, the sixteenth curved waveguide 43, the seventeenth curved waveguide 44, the eighteenth curved waveguide 45, the nineteenth curved waveguide 50, the twentieth curved waveguide 51, the twenty-first curved waveguide 52 and the twenty-second curved waveguide 53 are equal to W. 12 =4μm, the width of the eleventh straight waveguide 40 is W 11 =8 μm. The modulation electrode 68 and the modulation electrode 69 are located above the thirteenth straight waveguide 46 and the fourteenth straight waveguide 47 respectively.

[0030] The width of the second 4×4 multimode interferometer (VIII) is determined by the beam propagation method to be W. 16 =62μm, length is L 2 =7740 μm, the distance between the center of the fifth input tapered waveguide 54, the eighth input tapered waveguide 57, the fifth output tapered waveguide 58, the eighth output tapered waveguide 61 and the center of the 4×4 multimode interferometer (VIII) is X 4 =24 μm, the distance between the center of the sixth input tapered waveguide 55, the seventh input tapered waveguide 56, the sixth output tapered waveguide 59, the seventh output tapered waveguide 60 and the center of the 4×4 multimode interferometer (VIII) is X 3 =9.4μm.

[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 TE 0 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 to W 12 =4 μm, the width of the seventeenth straight waveguide 66 is W 11 = 8 μm, the width of the second output straight waveguide 67 is W 17 =16μm.

[0032] Example 3

[0033] The following is combined with Figure 6 The specific preparation method of the present invention is demonstrated, and the steps are as follows:

[0034] 1. Silicon substrate cleaning: Use a 0.6mm thick silicon wafer 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 remaining on the surface of the silicon wafer in the previous step. Finally, clean the silicon wafer with deionized water to remove the ethanol remaining on the surface of the silicon wafer. Then, dry the silicon wafer to remove the residual moisture on the surface.

[0035] 2. Deposition of silica lower cladding: The refractive index of the silica lower cladding is 1.4447. It is deposited by wet thermal oxidation method. The temperature is kept at 1000 degrees Celsius during deposition. The substrate temperature, reaction ratio and reaction time are controlled. A 10 μm thick silica lower cladding is grown on the cleaned silicon substrate 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. The germanium-doped silicon dioxide layer is deposited on the surface of the silicon dioxide lower cladding layer by plasma enhanced chemical vapor deposition. During the deposition process, the reaction gas GeCl 4 The flow rate is 32sccm, the reaction gas SiH 4 The flow rate is 20 sccm, the reaction gas N 2 The O flow rate is 40 sccm, the substrate temperature is 200°C, and 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 lower cladding layer with a refractive index of 1.4447 in the second step;

[0037] 4. Growth of polysilicon mask layer: Using hot wire chemical vapor deposition method, control the pressure in the chamber to 1Pa, substrate temperature to 200℃, SiH 4 and H 2 The reaction ratio V(H 2 ) / (V(SiH 4 )+V(H 2 )) is 98.4%, and a 1 μm thick polysilicon mask layer is grown on the surface of the germanium-doped silicon dioxide layer;

[0038] 5. Etching polysilicon: Spin-coat the surface of the polysilicon mask layer grown in step 4 with UV-curable photoresist, and remove the exposed photoresist using UV lithography and wet development; control SF 6 , CHF 3 , O 2 The gas flow rates are 25 sccm, 50 sccm, and 35 sccm respectively, and the polysilicon mask layer without photoresist protection is removed by reactive ion etching; then the photoresist on the surface of the polysilicon mask layer is removed to obtain a polysilicon mask layer with the same structure as the core layer to be prepared;

[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 corroded and bombarded with fluorine ions under the same conditions to obtain a germanium-doped silicon dioxide core layer of the desired structure;

[0040] 7. Removing the polysilicon mask layer: Use a 15% by mass KOH aqueous solution to remove the polysilicon mask layer remaining in step 6;

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

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

[0043] 10. Electrode preparation: Spin-coat UV-curable photoresist on the metal film, use electrode mask photolithography and wet development to remove the photoresist exposed to UV light, and then use 0.5% by mass NaOH solution to etch the aluminum metal film without photoresist protection; then expose and develop the remaining photoresist to complete the preparation of the electrode;

[0044] 11. Etching air isolation groove: Spin-coat UV-curable photoresist on the electrode and the silicon dioxide upper cladding, use the air isolation groove mask to photolithography, and wet development to remove the photoresist exposed to UV light; control SF 6 , CHF 3 , O 2 The gas flow rates are 25sccm, 50sccm, and 35sccm respectively. The silicon dioxide cladding without photoresist mask protection is removed by reactive ion etching, and then the excess photoresist on the surface of the silicon dioxide upper cladding is removed, and an air isolation groove with a depth of 35μm is formed on both sides of the metal electrode, penetrating the silicon dioxide upper cladding, the silicon dioxide lower cladding and a part of the silicon substrate, thereby preparing the silicon dioxide multifunctional mode processor based on the cascaded multimode interferometer.

[0045] Example 4

[0046] The multi-function mode processor works as follows:

[0047] Under different input and control conditions, the multifunctional mode processor has twelve working states, namely: State 1: Input TE 0 In the case of mode optical signal, the output TE 0 Mode optical signal; State 2: Input TE 1 In the case of mode optical signal, the output TE 1Mode optical signal; State 3: Input TE 2 In the case of mode optical signal, the output TE 2 Mode optical signal; State 4: Input TE 3 In the case of mode optical signal, the output TE 3 Mode optical signal; State 5: Input TE 0 In the case of mode optical signal, the output TE 3 Mode optical signal; State 6: Input TE 3 In the case of mode optical signal, the output TE 0 Mode optical signal; State 7: Input TE 1 In the case of mode optical signal, the output TE 2 Mode optical signal; State 8: Input TE 2 In the case of mode optical signal, the output TE 1 Mode optical signal; State 9: Input TE 0 The mode optical signal is blocked and no optical signal is output; State 10: Input TE 1 The mode optical signal is blocked and no optical signal is output; State 11: Input TE 2 The mode optical signal is blocked and no optical signal is output; State 12: Input TE 3 The mode optical signal is blocked and no optical signal is output. The working principle of each working state is as follows:

[0048] The working principle of state 1 is as follows Figure 4 As shown in (a), TE 0 The optical signal of the mode enters the first input straight waveguide 1 with an initial phase of π, and then enters the second straight waveguide 3 without entering the first straight waveguide 2 and the third straight waveguide 4; after entering the second straight waveguide 3, the optical signal is evenly divided into two TE 0The phases of the optical signals in the mode are all π; the optical signals in the second curved waveguide 6 reach the second input tapered waveguide 18 along the fifth straight waveguide 10 and the sixth curved waveguide 14; the optical signals in the third curved waveguide 7 reach the third input tapered waveguide 19 along the sixth straight waveguide 11 and the seventh curved waveguide 15; the phases of the optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 are all π (the fifth straight waveguide 10 is a phase-shifting zone waveguide, at which time the electrode 32 above the fifth straight waveguide 10 is not in a working state, and the optical signal does not produce a phase change after passing through the fifth straight waveguide 10, so 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-imaging 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 respectively pass through the tenth curved waveguide 26 and the eleventh curved waveguide 27 to enter the eighth straight waveguide 29, and continue to transmit to the first output straight waveguide 30, and couple into TE 0 mode, the phase is -(1 / 2)π; the optical signal is TE 0 The mode enters the input tapered waveguide 33 of the mode filter and reaches 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=16μm to W9=6μm, and the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal to W9=6μm. This width only allows TE 0 Mode and TE 1 The optical signal of the mode is transmitted smoothly, so TE 0 The optical signal of the TE mode can reach the output tapered waveguide 37; the optical signal continues to 0 The mode enters the second input straight waveguide 38 of the mode filter with a phase of π. Then the optical signal enters the eleventh straight waveguide 40, but does not enter the tenth straight waveguide 39 and the twelfth straight waveguide 41. After entering the eleventh straight waveguide 40, the optical signal is evenly divided into two TE by the sixteenth curved waveguide 43 and the seventeenth curved waveguide 44. 0The phases of the optical signals in the mode are all π, the optical signals in the sixteenth curved waveguide 43 reach the sixth input tapered waveguide 55 along the fourteenth straight waveguide 47 and the twentieth curved waveguide 51, the optical signals in the seventeenth curved waveguide 44 reach the seventh input tapered waveguide 56 along the fifteenth straight waveguide 48 and the twenty-first curved waveguide 52, the phases of the optical signals in the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 are all π (the fourteenth straight waveguide 47 is a phase shift zone waveguide, at this time the electrode 69 above the fourteenth straight waveguide 47 is not in a 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-imaging 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, and enter the seventeenth straight waveguide 66, and continue to be transmitted to the second output straight waveguide 67, and are coupled to form TE 0 mode, with a phase of -(1 / 2)π.

[0049] State 2 works like this Figure 4 As shown in (b), TE 1 The optical signal of the mode enters the first input straight waveguide 1 with an initial phase of π, and then 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 evenly divided into two TE 0 The phases of the optical signal of the mode are π and 0 respectively. The optical signal in the first straight waveguide 2 reaches the first input tapered waveguide 17 along the first curved waveguide 5, the fourth straight waveguide 9 and the fifth curved waveguide 13. The optical signal in the third straight waveguide 4 reaches the fourth input tapered waveguide 20 along the fourth curved waveguide 8, the seventh straight waveguide 12 and the eighth curved waveguide 16. 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 shift zone waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is not in a working state. 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-imaging 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 enter the first output straight waveguide 30 and couple into TE 1 mode, the phase is (1 / 4)π; the optical signal is TE 1The mode enters the input tapered waveguide 33 of the mode filter and reaches 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=16μm to W9=6μm, and the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal to W9=6μm. This width only allows TE 0 Mode and TE 1 The optical signal of the mode is transmitted smoothly, so TE 1 The optical signal of the TE mode can reach the output tapered waveguide 37; the optical signal continues to 1 The mode enters the second input straight waveguide 38 of the mode filter with a phase of π, and then the optical signal enters the tenth straight waveguide 39 and the twelfth straight waveguide 41, and does not enter the eleventh straight waveguide 40. The optical signal is evenly divided into two TE 0 The phases of the optical signal of the mode are π and 0 respectively. The optical signal in the tenth straight waveguide 39 reaches the fifth input tapered waveguide 54 along the fifteenth curved waveguide 42, the thirteenth straight waveguide 46 and the nineteenth curved waveguide 50. The optical signal in the twelfth straight waveguide 41 reaches the eighth input tapered waveguide 57 along the eighteenth curved waveguide 45, the sixteenth straight waveguide 49 and the twenty-second curved waveguide 53. 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 shift zone waveguide. At this time, the electrode 68 above the thirteenth straight waveguide 46 is not in a working state. The optical signal does not produce 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-imaging 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, enter the second output straight waveguide 67, and couple to form TE 1 mode, the phase is (1 / 4)π.

[0050] State 3 works like this Figure 4 As shown in (c), TE 2 The 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 evenly divided into two TE 0The phases of the mode optical signals are all (7 / 4)π. The optical signal in the first straight waveguide 2 reaches the first input tapered waveguide 17 along the first curved waveguide 5, the fourth straight waveguide 9, and the fifth curved waveguide 13. The optical signal in the third straight waveguide 4 reaches the fourth input tapered waveguide 20 along the fourth curved waveguide 8, the seventh straight waveguide 12, and the eighth curved waveguide 16. 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 shift zone waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is in a working state. The optical signal produces 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-imaging 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 enter the first output straight waveguide 30 and couple into TE 1 mode, the phase is (1 / 2)π; the optical signal is TE 1 The mode enters the input tapered waveguide 33 of the mode filter and reaches 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=16μm to W9=6μm, and the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal to W9=6μm. This width only allows TE 0 Mode and TE 1 The optical signal of the mode is transmitted smoothly, so TE 1 The optical signal of the TE mode can reach the output tapered waveguide 37; the optical signal continues to 1 The mode enters the second input straight waveguide 38 of the mode filter with a phase of π, and then the optical signal enters the tenth straight waveguide 39 and the twelfth straight waveguide 41, and does not enter the eleventh straight waveguide 40. The optical signal is evenly divided into two TE 0The phases of the mode optical signal are π and 0 respectively. The optical signal in the tenth straight waveguide 39 reaches the fifth input tapered waveguide 54 along the fifteenth curved waveguide 42, the thirteenth straight waveguide 46 and the nineteenth curved waveguide 50. The optical signal in the twelfth straight waveguide 41 reaches the eighth input tapered waveguide 57 along the eighteenth curved waveguide 45, the sixteenth straight waveguide 49 and the twenty-second curved waveguide 53. The phases of the optical signals in the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 are both 0 (the thirteenth straight waveguide 46 is a phase shift zone waveguide. At this time, the electrode 68 above the thirteenth straight waveguide 46 is in a working state. The optical signal produces a phase change of -π 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-imaging 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 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 to form TE 2 mode, the phase is (5 / 4)π.

[0051] State 4 works like this Figure 4 As shown in (d), TE 3 The mode optical signal enters the first input straight waveguide 1, with an initial phase of π, and then enters the second straight waveguide 3, without entering the first straight waveguide 2 and the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is evenly divided into two TE 0 The phases of the mode optical signals are (1 / 4)π and (5 / 4)π respectively. The optical signal in the second curved waveguide 6 reaches the second input tapered waveguide 18 along the fifth straight waveguide 10 and the sixth curved waveguide 14. The optical signal in the third curved waveguide 7 reaches the third input tapered waveguide 19 along the sixth straight waveguide 11 and the seventh curved waveguide 15. The phases of the optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 are both (5 / 4)π (the fifth straight waveguide 10 is a phase shift zone waveguide. At this time, the electrode 32 above the fifth straight waveguide 10 is in a working state. The optical signal produces 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 (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-imaging 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 respectively pass through the tenth curved waveguide 26 and the eleventh curved waveguide 27 to enter the eighth straight waveguide 29, and continue to transmit backward to reach the first output straight waveguide 30 and couple into TE 0 mode, the phase is (1 / 2)π; the optical signal is TE 0The mode enters the input tapered waveguide 33 of the mode filter and reaches 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=16μm to W9=6μm, and the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal to W9=6μm. This width only allows TE 0 Mode and TE 1 The optical signal of the mode is transmitted smoothly, so TE 0 The optical signal of the TE mode can reach the output tapered waveguide 37; the optical signal continues to 0 The mode enters the second input straight waveguide 38 of the mode filter with a phase of π. Then the optical signal enters the eleventh straight waveguide 40, but does not enter the tenth straight waveguide 39 and the twelfth straight waveguide 41. After entering the eleventh straight waveguide 40, the optical signal is evenly divided into two TE by the sixteenth curved waveguide 43 and the seventeenth curved waveguide 44. 0 The phases of the optical signals of the mode are all π, the optical signal in the sixteenth curved waveguide 43 reaches the sixth input tapered waveguide 55 along the fourteenth straight waveguide 47 and the twentieth curved waveguide 51, the optical signal in the seventeenth curved waveguide 44 reaches the seventh input tapered waveguide 56 along the fifteenth straight waveguide 48 and the twenty-first curved waveguide 52, 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 shift zone waveguide, at this time the electrode 69 above the fourteenth straight waveguide 47 is in a working state, the optical signal produces a phase change of -π after passing through the fourteenth straight waveguide 47, so 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-imaging 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 to enter the seventeenth straight waveguide 66, and continue to be transmitted to the second output straight waveguide 67, and are coupled to form TE 3 mode, the phase is (1 / 4)π.

[0052] State 5 works like this Figure 4 As shown in (e), TE 0 The optical signal of the mode enters the first input straight waveguide 1 with an initial phase of π, and then enters the second straight waveguide 3 without entering the first straight waveguide 2 and the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is evenly divided into two TE 0The phase of the optical signal of the mode is π. The optical signal in the second curved waveguide 6 reaches the second input tapered waveguide 18 along the fifth straight waveguide 10 and the sixth curved waveguide 14. The optical signal in the third curved waveguide 7 reaches the third input tapered waveguide 19 along the sixth straight waveguide 11 and the seventh curved waveguide 15. The phases of the optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 are both π (the fifth straight waveguide 10 is a phase-shifting zone waveguide. At this time, the electrode 32 above the fifth straight waveguide 10 is not in a working state. 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-imaging 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 respectively pass through the tenth curved waveguide 26 and the eleventh curved waveguide 27 to enter the eighth straight waveguide 29, and continue to transmit backward to reach the first output straight waveguide 30 and couple into TE 0 mode, the phase is -(1 / 2)π; the optical signal is TE 0 The mode enters the input tapered waveguide 33 of the mode filter and reaches 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=16μm to W9=6μm, and the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal to W9=6μm. This width only allows TE 0 Mode and TE 1 The optical signal of the mode is transmitted smoothly, so TE 0 The optical signal of the TE mode can reach the output tapered waveguide 37; the optical signal continues to 0 The mode enters the second input straight waveguide 38 of the mode filter with a phase of π. Then the optical signal enters the eleventh straight waveguide 40, but does not enter the tenth straight waveguide 39 and the twelfth straight waveguide 41. After entering the eleventh straight waveguide 40, the optical signal is evenly divided into two TE by the sixteenth curved waveguide 43 and the seventeenth curved waveguide 44. 0The phases of the mode optical signals are all π. The optical signal in the sixteenth curved waveguide 43 reaches the sixth input tapered waveguide 55 along the fourteenth straight waveguide 47 and the twentieth curved waveguide 51. The optical signal in the seventeenth curved waveguide 44 reaches the seventh input tapered waveguide 56 along the fifteenth straight waveguide 48 and the twenty-first curved waveguide 52. 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 shift zone waveguide. At this time, the electrode 69 above the fourteenth straight waveguide 47 is in a working state. The optical signal generates 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-imaging 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 to enter the seventeenth straight waveguide 66, and continue to be transmitted to the second output straight waveguide 67, and are coupled to form TE 3 mode, the phase is (1 / 4)π.

[0053] State 6 works like this Figure 4 As shown in (f), TE 3 The optical signal of the mode enters the first input straight waveguide 1 with an initial phase of π, and then enters the second straight waveguide 3 without entering the first straight waveguide 2 and the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is evenly divided into two TE 0 The phases of the optical signals of the modes are (1 / 4)π and (5 / 4)π respectively; the optical signal in the second curved waveguide 6 reaches the second input tapered waveguide 18 along the fifth straight waveguide 10 and the sixth curved waveguide 14; the optical signal in the third curved waveguide 7 reaches the third input tapered waveguide 19 along the sixth straight waveguide 11 and the seventh curved waveguide 15; the phases of the optical signals in the second input tapered waveguide 18 and the third input tapered waveguide 19 are both (5 / 4)π (the fifth straight waveguide 10 is a phase shift zone waveguide, at this time the electrode 32 above the fifth straight waveguide 10 is in a working state, and the optical signal produces 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-imaging 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, and enter the eighth straight waveguide 29, and continue to be transmitted to the first output straight waveguide 30, and are coupled to form TE 0 mode, the phase is (1 / 2)π; the optical signal is TE 0The mode enters the input tapered waveguide 33 of the mode filter and reaches 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=16μm to W9=6μm, and the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal to W9=6μm. This width only allows TE 0 Mode and TE 1 mode optical signal transmission, so TE 0 mode optical signal can reach the output tapered waveguide 37; the optical signal continues to TE 0 The mode enters the second input straight waveguide 38 of the mode filter with a phase of π. Then the optical signal enters the eleventh straight waveguide 40, but does not enter the tenth straight waveguide 39 and the twelfth straight waveguide 41. After entering the eleventh straight waveguide 40, the optical signal is evenly divided into two TE by the sixteenth curved waveguide 43 and the seventeenth curved waveguide 44. 0 The phases of the mode optical signals are all π. The optical signal in the sixteenth curved waveguide 43 reaches the sixth input tapered waveguide 55 along the fourteenth straight waveguide 47 and the twentieth curved waveguide 51. The optical signal in the seventeenth curved waveguide 44 reaches the seventh input tapered waveguide 56 along the fifteenth straight waveguide 48 and the twenty-first curved waveguide 52. The phases of the optical signals in the sixth input tapered waveguide 55 and the seventh input tapered waveguide 56 are all π (the fourteenth straight waveguide 47 is a phase shift zone waveguide. At this time, the electrode 69 above the fourteenth straight waveguide 47 is not in a 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-imaging 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 respectively pass through the twenty-fourth curved waveguide 63 and the twenty-fifth curved waveguide 64 to merge into the seventeenth straight waveguide 66, and then continue to be transmitted to the second output straight waveguide 67, and coupled to form TE 0 mode, with a phase of -(1 / 2)π.

[0054] State 7 works like this Figure 4 As shown in (g), TE 1 The optical signal of the mode enters the first input straight waveguide 1 with an initial phase of π, and then 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 evenly divided into two TE 0The phases of the optical signal of the mode are π and 0 respectively. The optical signal in the first straight waveguide 2 reaches the first input tapered waveguide 17 along the first curved waveguide 5, the fourth straight waveguide 9 and the fifth curved waveguide 13. The optical signal in the third straight waveguide 4 reaches the fourth input tapered waveguide 20 along the fourth curved waveguide 8, the seventh straight waveguide 12 and the eighth curved waveguide 16. 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 shift zone waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is not in a working state. 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-imaging 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 respectively pass through the ninth curved waveguide 25 and the twelfth curved waveguide 28 to enter the first output straight waveguide 30, and are coupled to form TE 1 mode, the phase is (1 / 4)π; the optical signal is TE 1 The mode enters the input tapered waveguide 33 of the mode filter, and reaches 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=16μm to W9=6μm, and the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal to W9=6μm. This waveguide width only supports TE 0 Mode and TE 1 mode optical signal transmission, therefore, TE 1 mode optical signal can reach the output tapered waveguide 37; the optical signal continues to TE 1 The mode enters the second input straight waveguide 38 of the mode filter with a phase of π, and then the optical signal enters the tenth straight waveguide 39 and the twelfth straight waveguide 41, and does not enter the eleventh straight waveguide 40. The optical signal is evenly divided into two TE 0The phases of the optical signals of the mode are π and 0 respectively. The optical signal in the tenth straight waveguide 39 reaches the fifth input tapered waveguide 54 along the fifteenth curved waveguide 42, the thirteenth straight waveguide 46 and the nineteenth curved waveguide 50. The optical signal in the twelfth straight waveguide 41 reaches the eighth input tapered waveguide 57 along the eighteenth curved waveguide 45, the sixteenth straight waveguide 49 and the twenty-second curved waveguide 53. The phases of the optical signals in the fifth input tapered waveguide 54 and the eighth input tapered waveguide 57 are both 0 (the thirteenth straight waveguide 46 is a phase shift zone waveguide. At this time, the electrode 68 above the thirteenth straight waveguide 46 is in a working state. The optical signal produces a phase change of -π 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-imaging 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 respectively pass through the twenty-third curved waveguide 62 and the twenty-sixth curved waveguide 65 to enter the second output straight waveguide 67, and are coupled to form TE 2 mode, the phase is (5 / 4)π.

[0055] State 8 works like this Figure 4 As shown in (h), TE 2 The optical signal of the mode enters the first input straight waveguide 1 with an initial phase of π, and then 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 evenly divided into two TE 0 The phases of the optical signals of the mode are all (7 / 4)π. The optical signals in the first straight waveguide 2 reach the first input tapered waveguide 17 along the first curved waveguide 5, the fourth straight waveguide 9 and the fifth curved waveguide 13. The optical signals in the third straight waveguide 4 reach the fourth input tapered waveguide 20 along the fourth curved waveguide 8, the seventh straight waveguide 12 and the eighth curved waveguide 16. 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 shift zone waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is in a working state. The optical signal produces 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-imaging 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 to form TE 1 mode, the phase is (1 / 2)π; the optical signal is TE 1The mode enters the input tapered waveguide 33 of the mode filter, and reaches 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=16μm to W9=6μm, and the widths of the thirteenth curved waveguide 34, the ninth straight waveguide 35, and the fourteenth curved waveguide 36 are equal to W9=6μm, which only supports TE 0 Mode and TE 1 mode optical signal transmission, therefore, TE 1 mode optical signal can reach the output tapered waveguide 37; the optical signal continues to TE 1 The mode enters the second input straight waveguide 38 of the mode filter with a phase of π, and then the optical signal enters the tenth straight waveguide 39 and the twelfth straight waveguide 41, and does not enter the eleventh straight waveguide 40. The optical signal is evenly divided into two TE 0 The phases of the optical signal of the mode are π and 0 respectively. The optical signal in the tenth straight waveguide 39 reaches the fifth input tapered waveguide 54 along the fifteenth curved waveguide 42, the thirteenth straight waveguide 46 and the nineteenth curved waveguide 50. The optical signal in the twelfth straight waveguide 41 reaches the eighth input tapered waveguide 57 along the eighteenth curved waveguide 45, the sixteenth straight waveguide 49 and the twenty-second curved waveguide 53. 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 shift zone waveguide. At this time, the electrode 68 above the thirteenth straight waveguide 46 is not in a working state. The optical signal does not produce 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-imaging 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 respectively pass through the twenty-third curved waveguide 62 and the twenty-sixth curved waveguide 65 to enter the second output straight waveguide 67 and couple into TE 1 mode, the phase is (1 / 4)π.

[0056] State 9 works like this Figure 4 As shown in (i), TE 0 The optical signal of the mode enters the first input straight waveguide 1 with an initial phase of π, and then enters the second straight waveguide 3 without entering the first straight waveguide 2 and the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is evenly divided into two TE 0The phases of the optical signals in the mode are all π, the optical signals in the second curved waveguide 6 reach the second input tapered waveguide 18 along the fifth straight waveguide 10 and the sixth curved waveguide 14, the optical signals in the third curved waveguide 7 reach the third input tapered waveguide 19 along the sixth straight waveguide 11 and the seventh curved waveguide 15, 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 shift zone waveguide, at this time the electrode 32 above the fifth straight waveguide 10 is in a working state, the optical signal produces 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 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-imaging 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 respectively pass through the tenth curved waveguide 26 and the eleventh curved waveguide 27 to enter the eighth straight waveguide 29, and continue to transmit backward to reach the first output straight waveguide 30 and couple into TE 3 mode, the phase is (1 / 4)π; the optical signal is TE 3 The mode enters the input tapered waveguide 33 of the mode filter. 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 to W9 = 6 μm. This width only allows TE 0 Mode and TE 1 The optical signal of the mode is transmitted smoothly, so TE 3 The optical signal of the mode is blocked and cannot be transmitted further.

[0057] State 10 works like this Figure 4 As shown in (j), TE 1 The 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 evenly divided into two TE 0The phases of the optical signals of the mode are π and 0 respectively. The optical signal in the first straight waveguide 2 reaches the first input tapered waveguide 17 along the first curved waveguide 5, the fourth straight waveguide 9 and the fifth curved waveguide 13. The optical signal in the third straight waveguide 4 reaches the fourth input tapered waveguide 20 along the fourth curved waveguide 8, the seventh straight waveguide 12 and the eighth curved waveguide 16. 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 shift zone waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is in a working state. The optical signal produces 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-imaging 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 enter the first output straight waveguide 30 and couple into TE 2 mode, the phase is (5 / 4)π; the optical signal is TE 2 The mode enters the input tapered waveguide 33 of the mode filter. 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 to W9=6μm, which only supports TE 0 Mode and TE 1 mode optical signal transmission, so TE 2 The mode optical signal is blocked and the optical signal cannot be transmitted any further.

[0058] State 11 works like this Figure 4 As shown in (k), TE 2 The 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 evenly divided into two TE 0The phases of the optical signals of the mode are all (7 / 4)π. The optical signals in the first straight waveguide 2 reach the first input tapered waveguide 17 along the first curved waveguide 5, the fourth straight waveguide 9, and the fifth curved waveguide 13. The optical signals in the third straight waveguide 4 reach the fourth input tapered waveguide 20 along the fourth curved waveguide 8, the seventh straight waveguide 12, and the eighth curved waveguide 16. The phases of the optical signals in the first input tapered waveguide 17 and the fourth input tapered waveguide 20 are all (7 / 4)π (the fourth straight waveguide 9 is a phase shift zone waveguide. At this time, the electrode 31 above the fourth straight waveguide 9 is not in a working state. 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). 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-imaging 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 to form TE 2 mode, the phase is (1 / 4)π; the optical signal is TE 2 The mode enters the input tapered waveguide 33 of the mode filter. 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 to W9=6μm, which only supports TE 0 Mode and TE 1 mode optical signal transmission, therefore, TE 2 The mode optical signal is blocked and the optical signal cannot continue to be transmitted.

[0059] State 12 works like this Figure 4 As shown in (l), TE 3 The mode optical signal enters the first input straight waveguide 1, with an initial phase of π, and then enters the second straight waveguide 3, without entering the first straight waveguide 2 and the third straight waveguide 4. After entering the second straight waveguide 3, the optical signal is evenly divided into two TE 0The phases of the optical signal of the mode are (1 / 4)π and (5 / 4)π respectively. The optical signal in the second curved waveguide 6 reaches the second input tapered waveguide 18 along the fifth straight waveguide 10 and the sixth curved waveguide 14. The optical signal in the third curved waveguide 7 reaches the third input tapered waveguide 19 along the sixth straight waveguide 11 and the seventh curved waveguide 15. 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 shift zone waveguide. At this time, the electrode 32 above the fifth straight waveguide 10 is not in a working state. 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 (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-imaging 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 respectively pass through the tenth curved waveguide 26 and the eleventh curved waveguide 27 to enter the eighth straight waveguide 29, and continue to transmit to the first output straight waveguide 30, and couple to form TE 3 mode, the phase is 0; the optical signal is TE 3 The mode enters the input tapered waveguide 33 of the mode filter. 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 to W9=6μm, which only supports TE 0 Mode and TE 1 mode optical signal transmission, therefore, TE 3 The mode optical signal is blocked and the optical signal cannot continue to be transmitted.

[0060] Example 5

[0061] The multifunctional mode processor of the twelve basic states based on the fourth embodiment can be divided into five functional modules, namely, a high-pass filtering functional module, a low-pass filtering functional module, a band-pass filtering functional module, a band-stop filtering functional module and a mode conversion functional module. Each functional module includes several subdivided functions. The functional modules are introduced as follows, and the working state of each electrode under each function is explained:

[0062] High-pass filter function module:

[0063] Function 1 (TE 3 Successfully passed,TE 2 TE 1 TE 0 is blocked), TE 3 For smooth passage, electrode 32 must be in the "ON" state, electrode 69 must be in the "ON" state, and the states of electrode 31 and electrode 68 have no effect on the device function; TE2 The blocked electrode 31 is in the "OFF" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 1 The blocked electrode 31 is in the "ON" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 0 The blocked electrode 32 is in the "ON" state, and the states of the electrodes 31, 68, and 69 have no effect on the function of the device.

[0064] Function 2 (TE 3 TE 2 Successfully passed,TE 1 TE 0 is blocked), TE 3 For smooth passage, electrode 32 must be in the "ON" state, electrode 69 must be in the "ON" state, and the states of electrode 31 and electrode 68 must have no effect on the device function; TE 2 For smooth passage, electrode 31 must be in the "ON" state, electrode 68 must be in the "ON" state, and the states of electrode 32 and electrode 69 have no effect on the device function; TE 1 The blocked electrode 31 is in the "ON" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 0 The blocked electrode 32 is in the "ON" state, and the states of the electrodes 31, 68, and 69 have no effect on the function of the device.

[0065] Function 3 (TE 3 TE 2 TE 1 Successfully passed,TE 0 is blocked), TE 3 For smooth passage, electrode 32 must be in the "ON" state, electrode 69 must be in the "ON" state, and the states of electrode 31 and electrode 68 have no effect on the device function; TE 2 For smooth passage, electrode 31 must be in the "ON" state, electrode 68 must be in the "ON" state, and the states of electrode 32 and electrode 69 have no effect on the device function; TE 1 For smooth passage, electrode 31 must be in the "OFF" state, electrode 68 must be in the "OFF" state, and the states of electrode 32 and electrode 69 must have no effect on the device function; TE 0 The blocked electrode 32 is in the "ON" state, and the states of the electrodes 31, 68, and 69 have no effect on the function of the device.

[0066] Low-pass filter function module:

[0067] Function 1 (TE 3 TE 2 TE 1Blocked, TE 0 Successfully passed), TE 3 The blocked electrode 32 is in the "OFF" state, and the states of the electrodes 31, 68, and 69 have no effect on the device function; TE 2 The blocked electrode 31 is in the "OFF" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 1 The blocked electrode 31 is in the "ON" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 0 For smooth passage, electrode 32 must be in the "OFF" state, electrode 69 must be in the "OFF" state, and the states of electrode 31 and electrode 68 must have no effect on the function of the device.

[0068] Function 2 (TE 3 TE 2 Blocked, TE 1 TE 0 Successfully passed), TE 3 The blocked electrode 32 is in the "OFF" state, and the states of the electrodes 31, 68, and 69 have no effect on the device function; TE 2 The blocked electrode 31 is in the "OFF" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 1 For smooth passage, electrode 31 must be in the "OFF" state, electrode 68 must be in the "OFF" state, and the states of electrode 32 and electrode 69 must have no effect on the device function; TE 0 For smooth passage, electrode 32 must be in the "OFF" state, electrode 69 must be in the "OFF" state, and the states of electrode 31 and electrode 68 must have no effect on the function of the device.

[0069] Function 3 (TE 3 Blocked, TE 2 TE 1 TE 0 Successfully passed), TE 3 The blocked electrode 32 is in the "OFF" state, and the states of the electrodes 31, 68, and 69 have no effect on the device function; TE 2 For smooth passage, electrode 31 must be in the "ON" state, electrode 68 must be in the "ON" state, and the states of electrode 32 and electrode 69 have no effect on the device function; TE 1 For smooth passage, electrode 31 must be in the "OFF" state, electrode 68 must be in the "OFF" state, and the states of electrode 32 and electrode 69 must have no effect on the device function; TE 0 For smooth passage, electrode 32 must be in the "OFF" state, electrode 69 must be in the "OFF" state, and the states of electrode 31 and electrode 68 must have no effect on the function of the device.

[0070] Bandpass filter function module:

[0071] Function 1 (TE 3 Blocked, TE 2 Successfully passed,TE 1 TE 0 is blocked), TE 3 The blocked electrode 32 is in the "OFF" state, and the states of the electrodes 31, 68, and 69 have no effect on the device function; TE 2 For smooth passage, electrode 31 must be in the "ON" state, electrode 68 must be in the "ON" state, and the states of electrode 32 and electrode 69 have no effect on the device function; TE 1 The blocked electrode 31 is in the "ON" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 0 The blocked electrode 32 is in the "ON" state, and the states of the electrodes 31, 68, and 69 have no effect on the function of the device.

[0072] Function 2 (TE 3 TE 2 Blocked, TE 1 Successfully passed,TE 0 is blocked), TE 3 The blocked electrode 32 is in the "OFF" state, and the states of the electrodes 31, 68, and 69 have no effect on the device function; TE 2 The blocked electrode 31 is in the "OFF" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 1 For smooth passage, electrode 31 must be in the "OFF" state, electrode 68 must be in the "OFF" state, and the states of electrode 32 and electrode 69 must have no effect on the device function; TE 0 The blocked electrode 32 is in the "ON" state, and the states of the electrodes 31, 68, and 69 have no effect on the function of the device.

[0073] Function 3 (TE 3 Blocked, TE 2 TE 1 Successfully passed,TE 0 is blocked), TE 3 The blocked electrode 32 is in the "OFF" state, and the states of the electrodes 31, 68, and 69 have no effect on the device function; TE 2 For smooth passage, electrode 31 must be in the "ON" state, electrode 68 must be in the "ON" state, and the states of electrode 32 and electrode 69 have no effect on the device function; TE 1For smooth passage, electrode 31 must be in the "OFF" state, electrode 68 must be in the "OFF" state, and the states of electrode 32 and electrode 69 must have no effect on the device function; TE 0 The blocked electrode 32 is in the "ON" state, and the states of the electrodes 31, 68, and 69 have no effect on the function of the device.

[0074] Band-stop filter function module:

[0075] Function 1 (TE 3 Successfully passed,TE 2 Blocked, TE 1 TE 0 Successfully passed), TE 3 For smooth passage, electrode 32 must be in the "ON" state, electrode 69 must be in the "ON" state, and the states of electrode 31 and electrode 68 have no effect on the device function; TE 2 The blocked electrode 31 is in the "OFF" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 1 For smooth passage, electrode 31 must be in the "OFF" state, electrode 68 must be in the "OFF" state, and the states of electrode 32 and electrode 69 must have no effect on the device function; TE 0 For smooth passage, electrode 32 must be in the "OFF" state, electrode 69 must be in the "OFF" state, and the states of electrode 31 and electrode 68 must have no effect on the function of the device.

[0076] Function 2 (TE 3 TE 2 Successfully passed,TE 1 Blocked, TE 0 Successfully passed), TE 3 For smooth passage, electrode 32 must be in the "ON" state, electrode 69 must be in the "ON" state, and the states of electrode 31 and electrode 68 have no effect on the device function; TE 2 For smooth passage, electrode 31 must be in the "ON" state, electrode 68 must be in the "ON" state, and the states of electrode 32 and electrode 69 have no effect on the device function; TE 1 The blocked electrode 31 is in the "ON" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 0 For smooth passage, electrode 32 must be in the "OFF" state, electrode 69 must be in the "OFF" state, and the states of electrode 31 and electrode 68 must have no effect on the function of the device.

[0077] Function 3 (TE 3 Successfully passed,TE 2 TE 1 Blocked, TE 0 Successfully passed), TE3 For smooth passage, electrode 32 must be in the "ON" state, electrode 69 must be in the "ON" state, and the states of electrode 31 and electrode 68 have no effect on the device function; TE 2 The blocked electrode 31 is in the "OFF" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 1 The blocked electrode 31 is in the "ON" state, and the states of the electrodes 32, 68, and 69 have no effect on the device function; TE 0 For smooth passage, electrode 32 must be in the "OFF" state, electrode 69 must be in the "OFF" state, and the states of electrode 31 and electrode 68 must have no effect on the function of the device.

[0078] Mode conversion function module:

[0079] Function 1 (TE 0 Mode conversion to TE 3 Mode), electrode 32 needs to be in the "OFF" state, electrode 69 needs to be in the "ON" state, and the states of electrode 31 and electrode 68 have no effect on the function of the device;

[0080] Function 2 (TE 3 Mode conversion to TE 0 Mode), electrode 32 is in the "ON" state, electrode 69 is in the "OFF" state, and the states of electrode 31 and electrode 68 have no effect on the function of the device;

[0081] Function 3 (TE 1 Mode conversion to TE 2 Mode), electrode 31 needs to be in the "OFF" state, electrode 68 needs to be in the "ON" state, and the states of electrode 32 and electrode 69 have no effect on the function of the device;

[0082] Function 4 (TE 2 Mode conversion to TE 1 Mode), electrode 31 needs to be in the "ON" state, electrode 68 needs to be in the "OFF" state, and the states of electrode 32 and electrode 69 have no effect on the function of the device;

[0083] The simulation results of 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 is the efficiency at the input of the device, P out is the efficiency at the output of the device, and IL is the insertion loss of the device.

[0084] When the device input TE 0 Mode, output TE0 In this 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% and the calculated insertion loss is 0.45 dB;

[0085] When the device input TE 1 Mode, output TE 1 In this 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% and the calculated insertion loss is 0.44 dB.

[0086] When the device input TE 2 Mode, output TE 2 In this mode, the simulation results are as follows: Figure 5 As shown in (c), the efficiency of the multi-function mode processor output end is 89.30% at this time, and the calculated insertion loss is 0.49dB;

[0087] When the device input TE 3 Mode, output TE 3 In this mode, the simulation results are as follows: Figure 5 As shown in (d), the efficiency of the multi-function mode processor output end is 91.70% at this time, and the calculated insertion loss is 0.38dB;

[0088] When the device input TE 0 Mode, output TE 3 In this mode, the simulation results are as follows: Figure 5 As shown in (e), the efficiency of the multi-function mode processor output end is 91.51% at this time, and the calculated insertion loss is 0.39 dB;

[0089] When the device input TE 3 Mode, output TE 0 In this mode, the simulation results are as follows: Figure 5 As shown in (f), the efficiency of the multi-function mode processor output end is 90.40% at this time, and the calculated insertion loss is 0.44dB;

[0090] When the device input TE 1 Mode, output TE 2 In this mode, the simulation results are as follows: Figure 5 As shown in (g), the efficiency of the multi-function mode processor output end is 89.93% at this time, and the calculated insertion loss is 0.46dB;

[0091] When the device input TE 2 Mode, output TE 1 In this mode, the simulation results are as follows: Figure 5As shown in (h), the efficiency of the multi-function mode processor output end is 89.80% at this time, and the calculated insertion loss is 0.47dB;

[0092] When the device input TE 0 When the mode is blocked, the simulation results are as follows Figure 5 As shown in (i), the efficiency of the multi-function mode processor output end is 0.00063% at this time, and the calculated insertion loss is 52.0 dB;

[0093] When the device input TE 1 When the mode is blocked, the simulation results are as follows Figure 5 As shown in (j), the efficiency of the multi-function mode processor output end is 0.004% at this time, and the calculated insertion loss is 43.97dB;

[0094] When the device input TE 2 When the mode is blocked, the simulation results are as follows Figure 5 As shown in (k), the efficiency of the multi-function mode processor output end is 0.00051% at this time, and the calculated insertion loss is 52.92dB;

[0095] When the device input TE 3 When the mode is blocked, the simulation results are as follows Figure 5 As shown in (l), at this time, the efficiency of the multi-function mode processor output end is 0.00023%, and the calculated insertion loss is 56.38dB.

Claims

1. A silicon dioxide multifunctional mode processor based on cascaded multimode interferometer, characterized in that: From bottom to top, it is composed of a silicon substrate, a silicon dioxide lower cladding, a germanium-doped silicon dioxide core layer and a silicon dioxide upper cladding layer, and the core layer is coated in the upper cladding layer; along the light transmission direction, the core layer is composed of three unit modules: a first mode converter, a mode filter and a second mode converter, and the structures and sizes of the first mode converter and the second mode converter are exactly the same; The first mode converter is composed 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) and 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) , the fourth input tapered waveguide (20) is the four input ends 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 ends 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 a first 2×1Y branch combiner (IV), and the ninth curved waveguide (25), the eighth straight waveguide (29), the twelfth curved waveguide (28), and the first output straight waveguide (30) constitute a 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 in sequence to the first straight waveguide (2) have the same width of W4=4 μm. The first curved waveguide (6), the fourth straight waveguide (9) and the fifth curved waveguide (13) connected in sequence to the third straight waveguide (4) have the same width of W4=4 μm. The widths of the four curved waveguides (8), the seventh straight waveguide (12) and the eighth curved waveguide (16) are equal, namely, W4=4 μm; the widths of the fifth straight waveguide (10) and the sixth curved waveguide (14) connected in sequence to the second curved waveguide (6) are equal, namely, W3=4 μm; the widths of the sixth straight waveguide (11) and the seventh curved waveguide (15) connected in sequence to the third curved waveguide (7) are equal, namely, W3=4 μm; the fourth straight waveguide (9) and the fifth straight waveguide (10) are phase shift zone waveguides, and a first heating electrode (31) and a second heating electrode (32) are respectively arranged on the silicon dioxide upper cladding layer corresponding to the positions thereof; 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, namely, L PS =3000 μm, the width of the first heating electrode (31) and the second heating electrode (32) are equal to W PS =21 μm; air isolation grooves penetrating the silicon dioxide upper cladding, the silicon dioxide lower 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=62 μm, and the length is L1=7740 μm; the fifth curved waveguide (13), the sixth curved waveguide (14), the seventh curved waveguide (15), and the eighth curved waveguide (16) are 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), respectively; 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 respectively connected to the ninth curved waveguide (25), the tenth curved waveguide (26), the eleventh curved waveguide (27) and the twelfth curved waveguide (28); the widths of the tenth curved waveguide (26) and the eleventh curved waveguide (27) are equal, that is, 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, that is, W4=4 μm; and the width of the first output straight waveguide (30) is W8=16 μm; The mode filter is composed 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 W9 of the ninth straight waveguide (35) is 6 μm; The second mode converter is composed 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 ( The second 4×4 multimode interferometer (VIII) is a 4-port branch combiner (IX) comprising a 24-way curved waveguide (63), a 25-way curved waveguide (64), and a 17-way straight waveguide (66). The 23-way curved waveguide (62), the 17-way straight waveguide (66), the 26-way curved waveguide (65), and the second output straight waveguide (67) are configured as a 24-way curved waveguide (63), a 25-way curved waveguide (64), and a 17-way straight waveguide (66). The second 2×1Y branch combiner (IX) is a 4-port branch combiner (IX). The second 4×4 multimode interferometer (VIII) is a 4-port branch combiner (IX). The width of the second input straight waveguide (38) is W 10 =16μm, which can accommodate the transmission of four modes: TE0, TE1, TE2, and TE3. After passing through the second 1×3Y branch waveguide (VI), the second input straight waveguide (38) is divided into a second straight waveguide with a width of W. 11 = 8 μm, the eleventh straight waveguide (40) has a width of W 13 =4μm, the tenth straight waveguide (39) and the twelfth straight waveguide (41); and then through the second 1×2Y branch waveguide (VII), the eleventh straight waveguide (40) is divided into a width of W 12 =4 μm; the widths of the fifteenth curved waveguide (42), the thirteenth straight waveguide (46) and the nineteenth curved waveguide (50) connected in sequence to the tenth straight waveguide (39) are equal to W 13 =4 μm, the widths of the eighteenth curved waveguide (45), the sixteenth straight waveguide (49) and the twenty-second curved waveguide (53) sequentially connected to the twelfth straight waveguide (41) are equal to W 13 =4 μm, the widths of the fourteenth straight waveguide (47) and the twentieth curved waveguide (51) sequentially connected to the sixteenth curved waveguide (43) are equal to W 12 =4 μm, the widths of the fifteenth straight waveguide (48) and the twenty-first curved waveguide (52) sequentially connected to the seventeenth curved waveguide (44) are equal to W 12 =4 μm; the thirteenth straight waveguide (46) and the fourteenth straight waveguide (47) are phase shift region waveguides, and a third heating electrode (68) and a fourth heating electrode (69) are respectively arranged on the silicon dioxide upper cladding corresponding to their positions, and 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 to L PS =3000 μm, the width of the third heating electrode (68) and the fourth heating electrode (69) are equal to W PS =21 μm, and air isolation grooves penetrating the silicon dioxide upper cladding, the silicon dioxide lower cladding and a portion of the silicon substrate are provided 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 =62 μm, and the length is L2=7740 μm; the nineteenth curved waveguide (50), the twentieth curved waveguide (51), the twenty-first curved waveguide (52), and the twenty-second curved waveguide (53) are connected to the 4×4 multimode interferometer (VIII) through 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) through 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 widths of the twenty-fourth curved waveguide (63) and the twenty-fifth curved waveguide (64) are equal to W 12 =4 μm, the width of the seventeenth straight waveguide (66) is W 11 = 8 μm, the width of the twenty-third curved waveguide (62) and the twenty-sixth curved waveguide (65) is W 13 =4 μm, the width of the second output straight waveguide (67) is W 17 =16μm.

2. The silicon dioxide multifunctional mode processor based on cascaded multimode interferometer according to claim 1, characterized in that: The waveguide widths of the first input tapered waveguide (17) and the fourth input tapered waveguide (20) both increase linearly from W4=4μm to W5=8μm; the waveguide widths of the second input tapered waveguide (18) and the third input tapered waveguide (19) increase linearly from W3=4μm to W6=9.6μm; the waveguide widths of the first output tapered waveguide (21) and the fourth output tapered waveguide (24) decrease linearly from W5=8μm to W4=4μm, and the waveguide widths of the second output tapered waveguide (22) and the third output tapered waveguide (23) decrease linearly from W6=9.6μm to W3=4μm; the first input tapered waveguide (17), the fourth input tapered waveguide (20), the first output tapered waveguide ( 21), the distance between the symmetry center of the fourth output tapered waveguide (24) and the symmetry center of the 4×4 multimode interferometer (III) is X2=24μm, the distance between the symmetry 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 symmetry center of the 4×4 multimode interferometer (III) is X1=9.4μm; 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 to W9=6μm, and the width of the output tapered waveguide (37) increases linearly from W9=6μm to W9=6μm. 10 =16 μm; the waveguide width of the fifth input tapered waveguide (54) and the eighth input tapered waveguide (57) is from W 13 =4μm linearly increases to W 14 = 8 μm, the waveguide widths of the sixth input tapered waveguide (55) and the seventh input tapered waveguide (56) are from W 12 =4μm linearly increases to W 15 =9.6 μm; the waveguide width of the fifth output tapered waveguide (58) and the eighth output tapered waveguide (61) is from W 14 =8μm linearly reduced to W 13 =4 μm, the waveguide widths of the sixth output tapered waveguide (59) and the seventh output tapered waveguide (60) are increased from W 15 =9.6μm linearly reduced to W 12 =4 μm; the distance between the symmetry 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) and the symmetry center of the 4×4 multimode interferometer (VIII) is X4=24 μm; the distance between the symmetry 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) and the symmetry center of the 4×4 multimode interferometer (VIII) is X3=9.4 μm.

3. The silicon dioxide multifunctional mode processor based on cascaded multimode interferometer according to 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 front-to-back symmetrical structures with respect to 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), and the tenth curved waveguide (26) and the eleventh curved waveguide (27) are vertically symmetrical structures; the fifth input tapered waveguide (54) and The fifth input 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 structures with respect to 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 ( The structure of the curved waveguide (43) and 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) are symmetrical.

4. The silicon dioxide multifunctional mode processor based on cascaded multimode interferometer according to claim 1, characterized in that: All straight waveguides or extensions of the straight waveguides in the three unit modules of the first mode converter, the mode filter and the second mode converter are arranged in parallel.

5. The silicon dioxide multifunctional mode processor based on cascaded multimode interferometer according to claim 1, characterized in that: Under different input and control conditions, the multifunctional mode processor has twelve working states, namely, state (1): when a TE0 mode optical signal is input, a TE0 mode optical signal is output; state (2): when a TE1 mode optical signal is input, a TE1 mode optical signal is output; state (3): when a TE2 mode optical signal is input, a TE2 mode optical signal is output; state (4): when a TE3 mode optical signal is input, a TE3 mode optical signal is output; state (5): when a TE0 mode optical signal is input, a TE3 mode optical signal is output; state (6): when a TE is input, a TE In the case of a TE3 mode optical signal, a TE0 mode optical signal is output; in state (7): when a TE1 mode optical signal is input, a TE2 mode optical signal is output; in state (8): when a TE2 mode optical signal is input, a TE1 mode optical signal is output; in state (9): the input TE0 mode optical signal is blocked, and no optical signal is output; in state (10): the input TE1 mode optical signal is blocked, and no optical signal is output; in state (11): the input TE2 mode optical signal is blocked, and no optical signal is output; in state (12): the input TE3 mode optical signal is blocked, and no optical signal is output.

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