Wavelength-mode hybrid multiplexer based on cascaded multimode interference device structure

Abstract

The invention discloses a wavelength-mode hybrid multiplexer based on a cascade multimode interference device structure, and belongs to the technical field of silicon dioxide integrated optics. The silicon substrate, the silicon dioxide lower wrapping layer, the germanium-doped silicon dioxide core layer and the silicon dioxide upper wrapping layer are sequentially arranged from bottom to top, the germanium-doped silicon dioxide core layer and the upper wrapping layer are jointly located on the lower wrapping layer, and the core layer is wrapped in the upper wrapping layer; the germanium-doped silicon dioxide core layer is composed of a 1 * 2 Y branch waveguide, an optical phase modulator, a 2 * 2 multimode interference device, a first 1 * 2 multimode interference device, a second 1 * 2 multimode interference device, a first 1 * 1 multimode interference device and a second 1 * 1 multimode interference device, and the wavelength-mode hybrid multiplexer adopts a passive structure; through an optical phase modulator on a modulation arm waveguide and a self-mapping principle of a multimode interference device structure, multiplexing and demultiplexing of four kinds of input signals TE0 and TE1 under the wavelength of 1550 nm and TE0 and TE1 under the wavelength of 1620 nm can be realized.

Description

Technical Field

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

[0002] At present, due to the rapid development of information technology, people have higher and higher requirements on the communication capacity of optical communication systems. In optical communication networks, the capacity of communication systems can be improved by multiplexing and demultiplexing technologies. Generally speaking, multiplexing technologies include mode division multiplexing, wavelength division multiplexing, polarization multiplexing, time division multiplexing, etc. Mode division multiplexing technology is a technology that couples optical signals of different modes (fundamental mode, first-order mode, second-order mode, etc.) at the input end through a mode division multiplexer into the same waveguide for transmission, and wavelength division multiplexing technology is a technology that couples optical signals of different wavelengths (optical signals of different wavelengths can carry different information) at the input end through a wavelength division multiplexer into the same waveguide for transmission.

[0003] Research shows that single mode division multiplexing technology, wavelength division multiplexing technology and polarization multiplexing technology are difficult to meet people's demand for ultra-high capacity of optical communication systems. Therefore, in this context, a new multiplexing technology, namely wavelength-mode hybrid multiplexing technology, has emerged. This hybrid multiplexing technology is achieved by combining wavelength division multiplexing technology with mode division multiplexing technology. For a wavelength-mode hybrid multiplexer, it can multiplex and demultiplex several wavelength signals and several mode signals at the same time. This new combination can greatly improve the capacity and transmission efficiency of the communication system.

[0004] The performance indicators of wavelength-mode hybrid multiplexers mainly include insertion loss, inter-mode crosstalk, working bandwidth, etc. For wavelength-mode hybrid multiplexers, these performance indicators need to be balanced and good. Under the premise of ensuring that the device has low loss and wide bandwidth, there is also low inter-mode crosstalk, which can better realize the multiplexing and demultiplexing of mixed signals of different wavelengths and modes, and improve the system capacity and transmission efficiency of the device. Silica materials have mature manufacturing processes, high process tolerances, and low losses, which can meet the design requirements of wavelength-mode hybrid multiplexers. Summary of the invention

[0005] The present invention aims to provide a wavelength-mode hybrid multiplexer based on a cascaded multimode interferometer structure for a wavelength division and mode division hybrid multiplexing system. The wavelength-mode hybrid multiplexer adopts a passive structure and can modulate the input TE at a wavelength of 1550nm through the optical phase modulator on the modulation arm waveguide and the self-imaging principle of the multimode interferometer structure. 0 TE 1 and TE at 1620nm 0 TE 1 Four signals are multiplexed and demultiplexed.

[0006] like Figure 1 As shown, the wavelength-mode hybrid multiplexer based on the cascaded multimode interferometer structure for a wavelength division and mode division hybrid multiplexing system described in the present invention is composed of a silicon substrate, a silica lower cladding, a germanium-doped silica core layer and a silica upper cladding, from bottom to top, the germanium-doped silica core layer and the upper cladding are located together on the lower cladding, and the core layer is coated in the upper cladding; the germanium-doped silica core layer is composed of a 1×2 Y-branch waveguide I, an optical phase modulator, a 2×2 multimode interferometer II, a first 1×2 multimode interferometer III, a second 1×2 multimode interferometer IV, a first 1×1 multimode interferometer V and a second 1×1 multimode interferometer VI.

[0007] like Figure 2As shown, along the transmission direction of light, the germanium-doped silica core layer consists of an input straight waveguide 1, a first curved waveguide 2 and a second curved waveguide 3 with the same structure and size, a first straight waveguide 4, a first tapered waveguide 5, a second tapered waveguide 6, a second straight waveguide 7, a third straight waveguide 8, a third tapered waveguide 9 and a fourth tapered waveguide 10 with the same structure and size, a 2×2 multimode interferometer II, a fifth tapered waveguide 11 and a sixth tapered waveguide 12 with the same structure and size, a first 1×2 multimode interferometer III and a second 1×2 multimode interferometer IV with the same structure and size, a seventh tapered waveguide 13 and a tenth tapered waveguide 16 with the same structure and size, an eighth tapered waveguide 14 and a ninth tapered waveguide 15 with the same structure and size, The invention comprises a first 1×1 multimode interferometer V and a second 1×1 multimode interferometer VI having the same structure and size, a fourth straight waveguide 17 and a fifth straight waveguide 18 having the same structure and size, an eleventh tapered waveguide 19 and a twelfth tapered waveguide 20 having the same structure and size, a third curved waveguide 21 and a fourth curved waveguide 22 having the same structure and size, a thirteenth tapered waveguide 23, a fourteenth tapered waveguide 24, a fifteenth tapered waveguide 25 and a sixteenth tapered waveguide 26 having the same structure and size, and a first output straight waveguide 27, a second output straight waveguide 28, a third output straight waveguide 29 and a fourth output straight waveguide 30 having the same structure and size; wherein the input straight waveguide 1, the first curved waveguide 2 and the second curved waveguide 3 constitute The first straight waveguide 4, the first tapered waveguide 5, the second tapered waveguide 6 and the second straight waveguide 7 are connected in sequence to form an optical phase modulator. The first curved waveguide 2 is connected to the optical phase modulator. The second curved waveguide 3, the third straight waveguide 8 and the fourth tapered waveguide 10 are connected in sequence. The third tapered waveguide 9 and the fourth tapered waveguide 10 are two input ends of the 2×2 multimode interferometer II. The fifth tapered waveguide 11 and the sixth tapered waveguide 12 are two output ends of the 2×2 multimode interferometer II. The fifth tapered waveguide 11 is also the input end of the first 1×2 multimode interferometer III. The seventh tapered waveguide 13 and the eighth tapered waveguide 14 are two output ends of the first 1×2 multimode interferometer III. The eighth tapered waveguide 14 is connected to the optical phase modulator. The first tapered waveguide 14, the fourth straight waveguide 17, the fourteenth tapered waveguide 24 and the second output straight waveguide 28 are connected in sequence; the sixth tapered waveguide 12 is also the input end of the second 1×2 multimode interferometer IV, the ninth tapered waveguide 15 and the tenth tapered waveguide 16 are the two output ends of the second 1×2 multimode interferometer IV, the ninth tapered waveguide 15, the fifth straight waveguide 18, the fifteenth tapered waveguide 25 and the third output straight waveguide 29 are connected in sequence; the seventh tapered waveguide 13 is the input end of the first 1×1 multimode interferometer V, the eleventh tapered waveguide 19 is the output end of the first 1×1 multimode interferometer V, the eleventh tapered waveguide 19, the third curved waveguide 21, the thirteenth tapered waveguide 23 and the first output straight waveguide 27 are connected in sequence;The tenth tapered waveguide 16 is the input end of the second 1×1 multimode interferometer VI, the twelfth tapered waveguide 20 is the output end of the second 1×1 multimode interferometer VI, and the twelfth tapered waveguide 20, the fourth curved waveguide 22, the sixteenth tapered waveguide 26 and the fourth output straight waveguide 30 are connected in sequence; the first curved waveguide 2 and the second curved waveguide 3, the third tapered waveguide 9 and the fourth tapered waveguide 10, the fifth tapered waveguide 11 and the sixth tapered waveguide 12, the first 1×2 multimode interferometer III and the second 1×2 multimode interferometer IV, the seventh tapered waveguide 13 and the tenth tapered waveguide 16, the eighth tapered waveguide 14 and the ninth tapered waveguide 15, the first 1×1 multimode interferometer V and the second 1×1 multimode interferometer VI, the fourth straight waveguide 17 and the fifth straight waveguide 18, the third curved waveguide 21 and the fourth curved waveguide 22, the first output straight waveguide 23 and the fourth output The straight waveguide 26, the second output straight waveguide 24 and the third output straight waveguide 25, the first output straight waveguide 27 and the fourth output straight waveguide 30, the second output straight waveguide 28 and the third output straight waveguide 29 are symmetrical structures about the input straight waveguide 1 and its extension line; one side edge of the 2×2 multimode interferometer II, the outer edge of the fifth tapered waveguide 11, the outer edge of the first 1×2 multimode interferometer III, the outer edge of the seventh tapered waveguide 13, and the outer edge of the first 1×1 multimode interferometer V are on the same straight line; the other side edge of the 2×2 multimode interferometer II, the outer edge of the sixth tapered waveguide 12, the outer edge of the second 1×2 multimode interferometer IV, the outer edge of the tenth tapered waveguide 16, and the outer edge of the second 1×1 multimode interferometer VI are on the same straight line; all straight waveguides or extension lines of straight waveguides are set to be parallel. Except for the waveguides with marked lengths, the remaining waveguides only serve as connections, and there is no specific requirement for the length. The input straight waveguide 1 is used as the input end of the wavelength-mode hybrid multiplexer, and the first output straight waveguide 27, the second output straight waveguide 28, the third output straight waveguide 29 and the fourth output straight waveguide 30 are used as the Output 1, Output 2, Output 3 and Output 4 ends of the wavelength-mode hybrid multiplexer respectively. ;

[0008] The width of the input straight waveguide 1 is W 1 =8μm, can accommodate TE 0 TE 1 The two modes are transmitted. After passing through the 1×2 Y-branch waveguide I, the input straight waveguide 1 is divided into a width of W 2 =4 μm for the first curved waveguide 2 and the second curved waveguide 3; the width of the first straight waveguide 4 and the second straight waveguide 7 is W 2 =4μm, the width of the first tapered waveguide 5 is from W 2 =4μm linearly increases to W 3 =5μm, the width of the second tapered waveguide 6 is from W 3 =5μm linearly reduced to W 2=4 μm, the lengths of the first tapered waveguide 5 and the second tapered waveguide 6 are both L 1 = 200 μm, the width of the third straight waveguide 8 is W 2 =4μm; the width of the third tapered waveguide 9 and the fourth tapered waveguide 10 is from W 2 =4μm linearly increases to W 4 =6μm, the distance between the symmetry center of the third tapered waveguide 9 and the fourth tapered waveguide 10 and the symmetry center of the 2×2 multimode interferometer II is X 1 =22μm; the width of 2×2 multimode interferometer II is W 5 =50μm, length is L 2 =4945μm; the fifth tapered waveguide 11 and the sixth tapered waveguide 12 are right-angled trapezoidal structures, and the width of the fifth tapered waveguide 11 and the sixth tapered waveguide 12 is from W 6 =23μm linearly reduced to W 7 =20μm, length is L 3 =500μm; the width of the first 1×2 multimode interferometer III and the second 1×2 multimode interferometer IV is W 7 =20μm, length is L 4 = 1445 μm; the seventh tapered waveguide 13 and the tenth tapered waveguide 16 are right-angled trapezoidal structures, and the width of the seventh tapered waveguide 13 and the tenth tapered waveguide 16 is from W 9 =12μm linearly reduced to W 10 =10μm, length is L 6 = 200 μm; the width of the eighth tapered waveguide 14 and the ninth tapered waveguide 15 is from W 8 =6μm linearly reduced to W 11 =2μm, length is L 6 =200 μm; the width of the first 1×1 multimode interferometer V and the second 1×1 multimode interferometer VI is W 10 =10μm, length is L 5 =915μm; the width of the fourth straight waveguide 17 and the fifth straight waveguide 18 is W 11 =2μm; the width of the eleventh tapered waveguide 19 and the twelfth tapered waveguide 20 is from W 12 =4μm linearly reduced to W 13 =2 μm; the width W of the third curved waveguide 21 and the fourth curved waveguide 22 13 = 2 μm; the width of the thirteenth tapered waveguide 23, the fourteenth tapered waveguide 24, the fifteenth tapered waveguide 25 and the sixteenth tapered waveguide 26 is from W 13 =2μm linearly increases to W 14 =4μm; the width of the first output straight waveguide 27, the second output straight waveguide 28, the third output straight waveguide 29 and the fourth output straight waveguide 30 is W 14 =4μm;

[0009] The working principle of the wavelength-mode hybrid multiplexer is as follows:

[0010] TE 0 The optical signal of the mode (including 1550nm and 1620nm) enters the input straight waveguide 1 and is evenly divided into two TE 0 The optical signal of the first curved waveguide 2 reaches the third tapered waveguide 9 along the first straight waveguide 4, the first tapered waveguide 5, the second tapered waveguide 6, and the second straight waveguide 7, and the optical signal of the second curved waveguide 3 reaches the fourth tapered waveguide 10 along the third straight waveguide 8; the first straight waveguide 4, the first tapered waveguide 5, the second tapered waveguide 6, and the second straight waveguide 7 constitute an optical phase modulator. According to the optical waveguide theory, the changes in the width and length of the first tapered waveguide 5 and the second tapered waveguide 6 can affect the changes in the phase of the optical signal in the waveguide. Therefore, when the optical signal passes through the optical phase modulator, a phase change will occur, and the TE input to the straight waveguide 1 will be 0 The two TE 0 When the optical signal of the mode reaches the third tapered waveguide 9 and the fourth tapered waveguide 10, there is a phase difference of 1 / 2π, such as Figure 4 As shown in (a), the two TEs in the third tapered waveguide 9 and the fourth tapered waveguide 10 0 The optical signal of the mode enters the 2×2 multimode interferometer II, and according to the self-imaging principle, the optical signal is output from the sixth tapered waveguide 12; the optical signal continues to be transmitted to the second 1×2 multimode interferometer IV. Since the self-imaging period of the 1550nm wavelength signal is longer, the 1550nm optical signal is output from the ninth tapered waveguide 15 after passing through the second 1×2 multimode interferometer IV, and then continues to reach the third output tapered waveguide 29 along the fifth straight waveguide 18 and the fifteenth tapered waveguide 25; since the self-imaging period of the 1620nm wavelength signal is less than the self-imaging period of the 1550nm wavelength signal, the 1620nm optical signal is output from the tenth tapered waveguide 16 after passing through the second 1×2 multimode interferometer IV, and then continues to reach the fourth output straight waveguide 30 along the second 1×1 multimode interferometer VI, the twelfth tapered waveguide 20, the fourth curved waveguide 22, and the sixteenth tapered waveguide 26.

[0011] TE 1 The optical signal of the mode (including 1550nm and 1620nm) enters the input straight waveguide 1 and is evenly divided into two TE 0The optical signal of the first curved waveguide 2 reaches the third tapered waveguide 9 along the first straight waveguide 4, the first tapered waveguide 5, the second tapered waveguide 6, and the second straight waveguide 7, and the optical signal of the second curved waveguide 3 reaches the fourth tapered waveguide 10 along the third straight waveguide 8; the first straight waveguide 4, the first tapered waveguide 5, the second tapered waveguide 6, and the second straight waveguide 7 constitute an optical phase modulator. According to the optical waveguide theory, the change in the width and length of the first tapered waveguide 5 and the second tapered waveguide 6 can affect the change in the phase of the optical signal in the waveguide. Therefore, when the optical signal passes through, a phase change will occur, and the TE input to the straight waveguide 1 1 The two TE 0 When the optical signal of the mode reaches the third tapered waveguide 9 and the fourth tapered waveguide 10, it has a phase difference of -1 / 2π, such as Figure 4 As shown in (b), the two TEs in the third tapered waveguide 9 and the fourth tapered waveguide 10 0 The optical signal of the mode enters the 2×2 multimode interferometer II, and according to the self-imaging principle, the optical signal is output from the fifth tapered waveguide 11; the optical signal continues to be transmitted to the first 1×2 multimode interferometer III. Since the self-imaging period of the 1550nm wavelength signal is longer, the 1550nm optical signal is output from the eighth tapered waveguide 14 through the first 1×2 multimode interferometer III, and then continues to reach the second output tapered waveguide 28 along the fourth straight waveguide 17 and the fourteenth tapered waveguide 24; since the self-imaging period of the 1620nm wavelength signal is less than the self-imaging period of the 1550nm wavelength signal, the 1620nm optical signal is output from the seventh tapered waveguide 13 through the first 1×2 multimode interferometer III, and then reaches the first output straight waveguide 27 along the first 1×1 multimode interferometer V, the eleventh tapered waveguide 19, the third curved waveguide 21, and the thirteenth tapered waveguide 23.

[0012] TE 0 When the 1550nm wavelength signal is input in the TE mode, the optical signal is output at the Output 3 port; 0 When the 1620nm wavelength signal is input in the TE mode, the optical signal is output at the Output 4 port; 1 When the 1550nm wavelength signal is input in the TE mode, the optical signal is output at the Output 2 port; 1 When a 1620nm wavelength signal is input in this mode, the optical signal is output at the Output 1 port.

[0013] The simulation results of the device are as follows Figure 5 (a)~ Figure 5 As shown in (d), insertion loss and crosstalk are two important indicators for measuring device performance. The calculation formula for insertion loss is: IL = -10 × lg (P out / Pin ), where P in is the efficiency at the input of the device, P out is the efficiency of the device's target output port, IL is the device's insertion loss; the crosstalk calculation formula is: CT = 10 × lg (P other / P out ), where P out is the efficiency of the device’s target output port, P other is the efficiency of the other output ports of the device, and CT is the crosstalk of the device.

[0014] When the device input TE 0 mode, 1550nm wavelength signal, the simulation results are as follows Figure 5 As shown in (a), the insertion loss of the wavelength-mode hybrid multiplexer is 0.45dB, and the maximum crosstalk value of the remaining ports is -20.55dB;

[0015] When the device input TE 0 mode, 1620nm wavelength signal, the simulation results are as follows Figure 5 As shown in (b), the insertion loss of the wavelength-mode hybrid multiplexer is 0.39 dB, and the maximum crosstalk value of the remaining ports is -22.18 dB;

[0016] When the device input TE 1 mode, 1550nm wavelength signal, the simulation results are as follows Figure 5 As shown in (c), the insertion loss of the wavelength-mode hybrid multiplexer is 0.46dB, and the maximum crosstalk value of the remaining ports is -20.84dB;

[0017] When the device input TE 1 mode, 1620nm wavelength signal, the simulation results are as follows Figure 5 As shown in (d), at this time, the insertion loss of the wavelength-mode hybrid multiplexer is 0.38dB, and the maximum crosstalk value of the remaining ports is -22.02dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of a cross-sectional structure of a wavelength-mode hybrid multiplexer;

[0019] Figure 2 is a schematic diagram of the top view structure of the core layer of the wavelength-mode hybrid multiplexer;

[0020] Figure 3 is a graph showing the effective refractive index of different modes of a germanium-doped silica core waveguide as a function of waveguide width;

[0021] Figure 4 For TE 0 TE 1Phase diagram of the two modes of optical signals at the end of 1×2 Y-branch waveguide I;

[0022] Figure 5 (a)~ Figure 5 (d) The simulated light field diagram of the device with four different signal inputs;

[0023] Figure 6 The present invention is a flow chart of the process for preparing the wavelength-mode hybrid multiplexer. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below through specific implementations in conjunction with the accompanying drawings.

[0025] Example 1

[0026] See attached Figure 1 The wavelength-mode hybrid multiplexer is composed of substrate, lower cladding, core layer, and upper cladding 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.

[0027] See attached Figure 2The core layer of the wavelength-mode hybrid multiplexer is along the transmission direction of light, and the core layer of the wavelength-mode hybrid multiplexer is composed of an input straight waveguide 1, a first curved waveguide 2 and a second curved waveguide 3 with the same structure and size, a first straight waveguide 4, a first tapered waveguide 5, a second tapered waveguide 6, a second straight waveguide 7, a third straight waveguide 8, a third tapered waveguide 9 and a fourth tapered waveguide 10 with the same structure and size, a 2×2 multimode interferometer II, a fifth tapered waveguide 11 and a sixth tapered waveguide 12 with the same structure and size, a first 1×2 multimode interferometer III and a second 1×2 multimode interferometer IV with the same structure and size, a seventh tapered waveguide 13 and a tenth tapered waveguide 16 with the same structure and size, an eighth tapered waveguide 17 with the same structure and size, and a The invention relates to a first 1×1 multimode interferometer V and a second 1×1 multimode interferometer VI having the same structure and size, a fourth straight waveguide 17 and a fifth straight waveguide 18 having the same structure and size, an eleventh tapered waveguide 19 and a twelfth tapered waveguide 20 having the same structure and size, a third curved waveguide 21 and a fourth curved waveguide 22 having the same structure and size, a thirteenth tapered waveguide 23, a fourteenth tapered waveguide 24, a fifteenth tapered waveguide 25 and a sixteenth tapered waveguide 26 having the same structure and size, a first output straight waveguide 27, a second output straight waveguide 28, a third output straight waveguide 29 and a fourth output straight waveguide 30 having the same structure and size; wherein the input straight waveguide 1, the first curved waveguide 2 The first straight waveguide 4, the first tapered waveguide 5, the second tapered waveguide 6 and the second straight waveguide 7 form an optical phase modulator. The first curved waveguide 2 and the first straight waveguide 4 are connected in sequence. The second curved waveguide 3, the third straight waveguide 8 and the fourth tapered waveguide 10 are connected in sequence. The third tapered waveguide 9 and the fourth tapered waveguide 10 are the two input ends of the 2×2 multimode interferometer II. The fifth tapered waveguide 11 and the sixth tapered waveguide 12 are the two output ends of the 2×2 multimode interferometer II. The fifth tapered waveguide 11 is also the input end of the first 1×2 multimode interferometer III. The seventh tapered waveguide 13 and the eighth tapered waveguide 14 are the two output ends of the first 1×2 multimode interferometer III. The eighth tapered waveguide 14, the fourth straight waveguide 17, the fourteenth tapered waveguide 24 and the second output straight waveguide 28 are connected in sequence; the sixth tapered waveguide 12 is also the input end of the second 1×2 multimode interferometer IV, the ninth tapered waveguide 15 and the tenth tapered waveguide 16 are the two output ends of the second 1×2 multimode interferometer IV, the ninth tapered waveguide 15, the fifth straight waveguide 18, the fifteenth tapered waveguide 25 and the third output straight waveguide 29 are connected in sequence; the seventh tapered waveguide 13 is the input end of the first 1×1 multimode interferometer V, the eleventh tapered waveguide 19 is the output end of the first 1×1 multimode interferometer V, the eleventh tapered waveguide 19, the third curved waveguide 21, the thirteenth tapered waveguide 23 and the first output straight waveguide 27 are connected in sequence;The tenth tapered waveguide 16 is the input end of the second 1×1 multimode interferometer VI, the twelfth tapered waveguide 20 is the output end of the second 1×1 multimode interferometer VI, and the twelfth tapered waveguide 20, the fourth curved waveguide 22, the sixteenth tapered waveguide 26 and the fourth output straight waveguide 30 are connected in sequence; the first curved waveguide 2 and the second curved waveguide 3, the third tapered waveguide 9 and the fourth tapered waveguide 10, the fifth tapered waveguide 11 and the sixth tapered waveguide 12, the first 1×2 multimode interferometer III and the second 1×2 multimode interferometer IV, the seventh tapered waveguide 13 and the fourth output straight waveguide 30 are connected in sequence; The ten-taper waveguide 16, the eighth tapered waveguide 14 and the ninth tapered waveguide 15, the first 1×1 multimode interferometer V and the second 1×1 multimode interferometer VI, the fourth straight waveguide 17 and the fifth straight waveguide 18, the third curved waveguide 21 and the fourth curved waveguide 22, the first output straight waveguide 23 and the fourth output straight waveguide 26, the second output straight waveguide 24 and the third output straight waveguide 25, the first output straight waveguide 27 and the fourth output straight waveguide 30, the second output straight waveguide 28 and the third output straight waveguide 29 are symmetrical structures about the extension line of the input straight waveguide 1. ;

[0028] Example 2

[0029] Determine the size parameters of each part of the core waveguide. The core waveguide height is fixed at 4μm. The input straight waveguide 1 can support TE 0 TE 1 Two modes, according to Figure 3 The effective refractive index of different modes of silica waveguide varies with the waveguide width. The width of the input straight waveguide 1 is set to W. 1 =8μm. The optical signal is transmitted in the first straight waveguide 4, the second straight waveguide 7, the third straight waveguide 8, the first output straight waveguide 27, the second output straight waveguide 28, the third output straight waveguide 29, and the fourth output straight waveguide 30 in the form of TE 0 The mode exists, the width of the first straight waveguide 4, the second straight waveguide 7, the third straight waveguide 8, the first output straight waveguide 27, the second output straight waveguide 28, the third output straight waveguide 29, and the fourth output straight waveguide 30 are equal to W 2 =4μm. The optical signal is transmitted in the fourth straight waveguide 17 and the fifth straight waveguide 18 at TE 0 The mode exists, and the widths of the fourth straight waveguide 17 and the fifth straight waveguide 18 are equal to W. 11 =2μm. The optical signal is transmitted in the first curved waveguide 2 and the second curved waveguide 3 at TE 0 The mode exists, and the widths of the first curved waveguide 2 and the second curved waveguide 3 are equal to W. 2 =4μm. The optical signal is transmitted in the third curved waveguide 21 and the fourth curved waveguide 22 at TE 0 The mode exists, and the widths of the third curved waveguide 21 and the fourth curved waveguide 22 are equal to W. 13 =2μm. The width of the first tapered waveguide 5 is from W2 =4μm linearly increases to W 3 =5μm, the width of the second tapered waveguide 6 is from W 3 =5μm linearly reduced to W 2 =4μm, length is L 1 =200 μm. The width of the third tapered waveguide 9 and the fourth tapered waveguide 10 is W 2 =4μm linearly increases to W 4 =6μm, the distance between the symmetry center of the third tapered waveguide 9, the fourth tapered waveguide 10 and the symmetry center of the 2×2 multimode interferometer II is X 1 =22 μm. The width of the fifth tapered waveguide 11 and the sixth tapered waveguide 12 is W 6 =23μm reduced to W 7 =20μm, length is L 3 =500μm, the outer sides of the fifth tapered waveguide 11 and the sixth tapered waveguide 12 are of right angle structure, and the outer sides of the fifth tapered waveguide 11 and the sixth tapered waveguide 12 are on the same straight line as the upper and lower sides of the 2×2 multimode interferometer II. The width of the seventh tapered waveguide 13 and the tenth tapered waveguide 16 is from W 9 =12μm reduced to W 10 =10μm, length is L 6 = 200 μm, the outer sides of the seventh tapered waveguide 13 and the tenth tapered waveguide 16 are right-angle structures, and are respectively on the same straight line with the upper side of the first 1×2 multimode interferometer III and the lower side of the second 1×2 multimode interferometer IV. The width of the eighth tapered waveguide 14 and the ninth tapered waveguide 15 is from W 8 =6μm linearly reduced to W 11 =2 μm. The width of the eleventh tapered waveguide 19 and the twelfth tapered waveguide 20 is W 12 =4μm linearly reduced to W 13 =2 μm. The widths of the thirteenth tapered waveguide 23, the fourteenth tapered waveguide 24, the fifteenth tapered waveguide 25, and the sixteenth tapered waveguide 26 are from W 13 =2μm linearly increases to W 14 =4μm.

[0030] The width of the 2×2 multimode interferometer II is determined to be W by the beam propagation method. 5 =50μm, length is L 2 =4945μm. The width of the first 1×2 multimode interferometer III and the second 1×2 multimode interferometer IV is W 7 =20μm, length is L 4 =1445μm. The width of the first 1×1 multimode interferometer V and the second 1×1 multimode interferometer VI is W 10 =10μm, length is L 5 =915μm.

[0031] Example 3

[0032] The following is combined with Figure 6 The specific preparation method of the device of the present invention is demonstrated, and the steps are as follows:

[0033] 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 water on the surface.

[0034] 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. By controlling the water vapor flow, substrate temperature and reaction time, a 10 μm thick silica lower cladding is grown on the cleaned silicon substrate in step 1.

[0035] 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, and the reaction gas SiH 4 The flow rate is 20 sccm, and 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;

[0036] 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;

[0037] 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 2The 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 germanium-doped silicon dioxide core layer to be prepared;

[0038] 6. Etching the germanium-doped 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;

[0039] 7. Removing the polysilicon mask layer: Use a 15% by mass KOH aqueous solution to remove the polysilicon mask layer remaining in step 6;

[0040] 8. Depositing a silica upper cladding layer: Using the same process as step 2, a silica upper cladding layer is deposited on the surface of the germanium-doped silica core layer and the silica lower cladding layer, and using chemical mechanical polishing, the thickness of the silica upper cladding layer is controlled to be 15 μm, and the refractive index of the silica upper cladding layer is controlled to be 1.4447; thereby, the wavelength-mode hybrid multiplexer described in the present invention is prepared.

Claims

1. A wavelength-mode hybrid multiplexer based on a cascaded multimode interferometer structure, 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, wherein the germanium-doped silicon dioxide core layer and the upper cladding are located on the lower cladding, and the germanium-doped silicon dioxide core layer is coated in the upper cladding; along the transmission direction of light, the germanium-doped silicon dioxide core layer is composed of an input straight waveguide (1), a first curved waveguide (2) and a second curved waveguide (3) with the same structure and size, a first straight waveguide (4), a first tapered waveguide (5), a second tapered waveguide (6), a second straight waveguide (7), a third straight waveguide (8), a third tapered waveguide (9) and a fourth tapered waveguide (10) with the same structure and size, a 2×2 multimode interferometer (II), a first curved waveguide (2) and a second curved waveguide (3) with the same structure and size, a first straight waveguide (4), a first tapered waveguide (5), a second tapered waveguide (6), a second straight waveguide (7), a third straight waveguide (8), a third tapered waveguide (9) and a fourth tapered waveguide (10) with the same structure and size, a 2×2 multimode interferometer (II), a first curved waveguide (2) and a second curved waveguide (3) with the same structure and size, a first tapered waveguide (5) and a second tapered waveguide (6) A fifth tapered waveguide (11) and a sixth tapered waveguide (12), a first 1×2 multimode interferometer (III) and a second 1×2 multimode interferometer (IV) having the same structure and size, a seventh tapered waveguide (13) and a tenth tapered waveguide (16) having the same structure and size, an eighth tapered waveguide (14) and a ninth tapered waveguide (15) having the same structure and size, a first 1×1 multimode interferometer (V) and a second 1×1 multimode interferometer (VI) having the same structure and size, a fourth straight waveguide (17) and a fifth straight waveguide (18) having the same structure and size, an eleventh tapered waveguide (19) and a twelfth tapered waveguide (20) having the same structure and size, a third curved waveguide (21) and a fourth curved waveguide (22) having the same structure and size. The invention relates to a waveguide (22), a thirteenth tapered waveguide (23), a fourteenth tapered waveguide (24), a fifteenth tapered waveguide (25) and a sixteenth tapered waveguide (26) having the same structure and size, and a first output straight waveguide (27), a second output straight waveguide (28), a third output straight waveguide (29) and a fourth output straight waveguide (30) having the same structure and size; wherein the input straight waveguide (1), the first curved waveguide (2) and the second curved waveguide (3) constitute a 1×2 Y-branch waveguide (I), the first straight waveguide (4), the first tapered waveguide (5), the second tapered waveguide (6) and the second straight waveguide (7) are sequentially connected to form an optical phase modulator, and the first curved waveguide (2) and the optical phase modulator are connected , the second curved waveguide (3), the third straight waveguide (8) and the fourth tapered waveguide (10) are connected in sequence; the third tapered waveguide (9) and the fourth tapered waveguide (10) are two input ends of the 2×2 multimode interferometer (II); the fifth tapered waveguide (11) and the sixth tapered waveguide (12) are two output ends of the 2×2 multimode interferometer (II); the fifth tapered waveguide (11) is also the input end of the first 1×2 multimode interferometer (III); the seventh tapered waveguide (13) and the eighth tapered waveguide (14) are two output ends of the first 1×2 multimode interferometer (III); the eighth tapered waveguide (14), the fourth straight waveguide (17), the fourteenth tapered waveguide (24) and the second output straight waveguide (28) are connected in sequence;The sixth tapered waveguide (12) is also the input end of the second 1×2 multimode interferometer (IV); the ninth tapered waveguide (15) and the tenth tapered waveguide (16) are the two output ends of the second 1×2 multimode interferometer (IV); the ninth tapered waveguide (15), the fifth straight waveguide (18), the fifteenth tapered waveguide (25) and the third output straight waveguide (29) are connected in sequence; the seventh tapered waveguide (13) is the input end of the first 1×1 multimode interferometer (V); the eleventh tapered waveguide (19) is the output end of the first 1×1 multimode interferometer (V); The output end of the interferometer (V), the eleventh tapered waveguide (19), the third curved waveguide (21), the thirteenth tapered waveguide (23) and the first output straight waveguide (27) are connected in sequence; the tenth tapered waveguide (16) is the input end of the second 1×1 multimode interferometer (VI), the twelfth tapered waveguide (20) is the output end of the second 1×1 multimode interferometer (VI), and the twelfth tapered waveguide (20), the fourth curved waveguide (22), the sixteenth tapered waveguide (26) and the fourth output straight waveguide (30) are connected in sequence. ; 2. A wavelength-mode hybrid multiplexer based on a cascaded multimode interferometer structure as claimed in claim 1, characterized in that: The width of the input straight waveguide (1) is W1=8μm, which can accommodate the transmission of TE0 and TE1 modes. After passing through the 1×2 Y-branch waveguide (I), the input straight waveguide (1) is divided into a first curved waveguide (2) and a second curved waveguide (3) with a width of W2=4μm. The widths of the first straight waveguide (4) and the second straight waveguide (7) are W2=4μm. The width of the first tapered waveguide (5) increases linearly from W2=4μm to W3=5μm. The width of the second tapered waveguide (6) decreases linearly from W3=5μm to W2=4μm. The lengths of the first tapered waveguide (5) and the second tapered waveguide (6) are both L1=200μm. The width of the third straight waveguide (8) is W2=4μm. The widths of the third tapered waveguide (9) and the fourth tapered waveguide (10) increase linearly from W2=4μm to W4=6μm. ) and the fourth tapered waveguide (10) are at a distance X1=22 μm from the symmetry center of the 2×2 multimode interferometer (II); the width of the 2×2 multimode interferometer (II) is W5=50 μm, and the length is L2=4945 μm; the fifth tapered waveguide (11) and the sixth tapered waveguide (12) are of right-angled trapezoidal structure, and the width of the fifth tapered waveguide (11) and the sixth tapered waveguide (12) is from W6=23 μm to The width of the first 1×2 multimode interferometer (III) and the second 1×2 multimode interferometer (IV) is W7=20μm and L4=1445μm. The seventh tapered waveguide (13) and the tenth tapered waveguide (16) are right-angled trapezoidal structures. The width of the seventh tapered waveguide (13) and the tenth tapered waveguide (16) is linearly reduced from W9=12μm to W7=20μm and the length is L3=500μm. The width of the first 1×2 multimode interferometer (III) and the second 1×2 multimode interferometer (IV) is W7=20μm and the length is L4=1445μm. The seventh tapered waveguide (13) and the tenth tapered waveguide (16) are right-angled trapezoidal structures. The width of the seventh tapered waveguide (13) and the tenth tapered waveguide (16) is 10 =10μm, length L6=200μm; The widths of the eighth tapered waveguide (14) and the ninth tapered waveguide (15) are linearly reduced from W8=6 μm to W 11 =2μm, the length is L6=200μm; the width of the first 1×1 multimode interferometer (V) and the second 1×1 multimode interferometer (VI) is W 10 =10 μm, the length is L5=915 μm; the width of the fourth straight waveguide (17) and the fifth straight waveguide (18) is W 11 =2 μm; the width of the eleventh tapered waveguide (19) and the twelfth tapered waveguide (20) is W 12 =4μm linearly reduced to W 13 =2 μm; the width W of the third curved waveguide (21) and the fourth curved waveguide (22) 13 = 2 μm; the widths of the thirteenth tapered waveguide (23), the fourteenth tapered waveguide (24), the fifteenth tapered waveguide (25) and the sixteenth tapered waveguide (26) are from W 13 =2μm linearly increases to W 14 =4 μm; the width of the first output straight waveguide (27), the second output straight waveguide (28), the third output straight waveguide (29) and the fourth output straight waveguide (30) is W 14 =4μm.

3. The wavelength-mode hybrid multiplexer based on the cascaded multimode interferometer structure as claimed in claim 1, characterized in that: A first curved waveguide (2) and a second curved waveguide (3), a third tapered waveguide (9) and a fourth tapered waveguide (10), a fifth tapered waveguide (11) and a sixth tapered waveguide (12), a first 1×2 multimode interferometer (III) and a second 1×2 multimode interferometer (IV), a seventh tapered waveguide (13) and a tenth tapered waveguide (16), an eighth tapered waveguide (14) and a ninth tapered waveguide (15), a first 1×1 multimode interferometer (V) and a second 1×1 multimode interferometer (VI) ), the fourth straight waveguide (17) and the fifth straight waveguide (18), the third curved waveguide (21) and the fourth curved waveguide (22), the first output straight waveguide (23) and the fourth output straight waveguide (26), the second output straight waveguide (24) and the third output straight waveguide (25), the first output straight waveguide (27) and the fourth output straight waveguide (30), the second output straight waveguide (28) and the third output straight waveguide (29) are symmetrical structures with respect to the input straight waveguide (1) and its extension line.

4. The wavelength-mode hybrid multiplexer based on the cascaded multimode interferometer structure according to claim 1, characterized in that: One side edge of the 2×2 multimode interferometer (II), the outer edge of the fifth tapered waveguide (11), the outer edge of the first 1×2 multimode interferometer (III), the outer edge of the seventh tapered waveguide (13), and the outer edge of the first 1×1 multimode interferometer (V) are on the same straight line; the other side edge of the 2×2 multimode interferometer (II), the outer edge of the sixth tapered waveguide (12), the outer edge of the second 1×2 multimode interferometer (IV), the outer edge of the tenth tapered waveguide (16), and the outer edge of the second 1×1 multimode interferometer (VI) are on the same straight line.

5. The wavelength-mode hybrid multiplexer based on the cascaded multimode interferometer structure according to claim 1, characterized in that: All straight waveguides or extensions of straight waveguides in the wavelength-mode hybrid multiplexer are arranged in a parallel relationship.

6. The wavelength-mode hybrid multiplexer based on the cascaded multimode interferometer structure according to claim 1, characterized in that: The input straight waveguide (1) serves as the input end of the wavelength-mode hybrid multiplexer, and the first output straight waveguide (27), the second output straight waveguide (28), the third output straight waveguide (29) and the fourth output straight waveguide (30) serve as the Output 1, Output 2, Output 3 and Output 4 ends of the wavelength-mode hybrid multiplexer respectively; when a 1550nm wavelength signal is input in TE0 mode, the optical signal is output at the Output 3 port; when a 1620nm wavelength signal is input in TE0 mode, the optical signal is output at the Output 4 port; when a 1550nm wavelength signal is input in TE1 mode, the optical signal is output at the Output 2 port; when a 1620nm wavelength signal is input in TE1 mode, the optical signal is output at the Output 1 port.

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