Multi-wavelength silicon photonics chip

Abstract

The present invention relates to the field of optical components, and in particular to a multi-wavelength silicon optical transmitter chip, whose input waveguide is used to input dual-band optical signals. A first multimode interference coupler is connected to the input waveguide and is used to distribute the dual-band optical signals from the input waveguide to two transmission paths. Each transmission path includes a silicon optical modulator and two second multimode interference couplers. The silicon optical modulator is connected between the two second multimode interference couplers via a waveguide. The silicon optical modulator includes a reverse bias electrode and two high-frequency electrodes, the two high-frequency electrodes being located on opposite sides of the waveguide and connected to the waveguide, and the reverse bias electrode being located in the middle of the waveguide. The high-frequency electrode includes multiple sub-electrodes arranged along a first direction, each of the multiple sub-electrodes including a main body, a connecting portion, and an end portion. The connecting portion and the end portion are connected to one side of the main body along a second direction, and the connecting portion and the end portion form a T-shaped structure. The end portion extends toward the waveguide and is connected to the waveguide. High-speed signal modulation is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of optical elements, and in particular relates to a multi-wavelength silicon light emitting chip. Background Art

[0002] In the communications field, to increase the capacity of optical signal transmission, optical components capable of single-fiber dual-wavelength transmission have become essential equipment at various control points. Because optical fiber near the 1310nm communication window has near-zero dispersion and the 1550nm communication window offers the lowest insertion loss, the 1310nm and 1550nm bands are commonly used. Furthermore, the modulation and long-distance transmission of high-speed electrical signals have become key research areas in today's communications industry. Consequently, achieving high-speed transmission of dual-band communication signals has become a key research direction, with the development of highly integrated silicon photonics chips capable of simultaneous dual-band modulation becoming a key focus.

[0003] However, the Mach-Zehnder silicon optical modulators used in common silicon photonics transmitter chips have a low electro-optical bandwidth, which results in a low transmission rate for high-frequency signals. Therefore, a silicon optical modulator with a significantly increased electro-optical bandwidth is needed. Summary of the Invention

[0004] In view of this, the present invention aims to provide a multi-wavelength silicon optical transmitter chip, which significantly increases the electro-optical bandwidth while keeping the microwave loss and modulation efficiency basically unchanged, thereby accelerating the transmission rate of high-frequency signals and realizing high-speed signal modulation.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0006] A multi-wavelength silicon light emitting chip, comprising:

[0007] An input waveguide, used for inputting a dual-band optical signal;

[0008] A first multimode interference coupler is connected to the input waveguide and is used to distribute the dual-band optical signal from the input waveguide to two transmission paths; each transmission path includes a silicon optical modulator and two second multimode interference couplers; the silicon optical modulator is connected between the two second multimode interference couplers via a waveguide;

[0009] The silicon optical modulator includes a reverse bias electrode and two high-frequency electrodes. The two high-frequency electrodes are located on opposite sides of the waveguide and are connected to the waveguide. The reverse bias electrode is located in the middle of the waveguide. The high-frequency electrode includes a plurality of sub-electrodes arranged along a first direction. The sub-electrodes include a main body, a connecting part and an end portion. The connecting part and the end portion are connected to one side of the main body along the second direction, and the connecting part and the end portion form a T-shaped structure. The end portion extends toward the direction of the waveguide and is connected to the waveguide. The first direction is perpendicular to the second direction.

[0010] Furthermore, the high-frequency electrode further includes a first metal plate for connecting to the high-frequency probe, and the first metal plate is connected to one side of the multi-segment sub-electrode along the first direction.

[0011] Furthermore, the reverse bias electrode includes a metal electrode and a second metal plate for connecting to a DC voltage source, the metal electrode is connected to the middle of the waveguide, the second metal plate is connected to the metal electrode, and a DC reverse bias signal is input to the metal electrode through the second metal plate.

[0012] Furthermore, the silicon light modulator further includes a terminal resistor, which is connected between the two high-frequency electrodes and located on one side of the output end of the silicon light modulator; the impedance value of the terminal resistor is 30Ω~70Ω.

[0013] Furthermore, it also includes a phase shifter set corresponding to the silicon light modulator. The phase shifter is located at a height of 2μm to 5μm above the waveguide. By changing the voltage applied to the phase shifter, the phase of the waveguide and the operating point of the silicon light modulator are changed.

[0014] Furthermore, the waveguide includes a P++-type doped region and two doped region groups arranged on both sides of the P++-type doped region along the second direction, each doped region group includes a P+-type doped region, a P-type doped region, an N-type doped region, an N+-type doped region and an N++-type doped region; the end portion is connected to the N++-type doped region, and the reverse bias electrode is connected to the P++-type doped region;

[0015] The doping concentration of the N-type doping region and the P-type doping region is 10 16 / cm 3 ~10 17 / cm 3 Magnitude; and / or

[0016] The doping concentration of the N+ doping region and the P+ doping region is 10 18 / cm 3 ~10 19 / cm 3 Magnitude; and / or

[0017] The doping concentration of the N++ type doping region and the P++ type doping region is 10 19 / cm 3~ 10 20 / cm 3 Magnitude; and / or

[0018] In the second direction, the lengths of the N-type doping region, the N+-type doping region, the P-type doping region, and the P+-type doping region are 0.4 μm to 2 μm; and / or

[0019] In the second direction, the lengths of the N++ type doping region and the P++ type doping region are greater than 5 μm.

[0020] Furthermore, in the first direction, the total size of the multi-segment sub-electrodes is 1.5 mm to 3 mm; and / or

[0021] In the first direction, the size of a single main body portion is 30 μm to 70 μm; and / or

[0022] In the first direction, the size of the single end portion is 0.7 to 0.9 times the size of the single main portion; and / or

[0023] In the second direction, the size of the main body is 20 μm to 80 μm; and / or

[0024] In the second direction, the size of the connecting portion is 20 μm to 80 μm; and / or

[0025] In the second direction, the distance between the ends of the two high-frequency electrodes is 15 μm to 70 μm.

[0026] Furthermore, the first multimode interference coupler includes a main structure and two sub-wavelength grating groups provided on the main structure, the two sub-wavelength grating groups are arranged opposite to each other, and the sub-wavelength grating groups include a plurality of sub-wavelength grating structures periodically arranged along the length direction of the main structure; the arrangement period of the sub-wavelength grating structures is 150nm to 200nm;

[0027] The distance between the two subwavelength grating groups is one-third of the width of the main structure;

[0028] The length of the main structure is 30 μm to 50 μm, the width of the main structure is 1 μm to 3 μm, and the length of the main structure is proportional to the square of the width of the main structure.

[0029] Furthermore, the sub-wavelength grating structure has a trapezoidal shape;

[0030] The length of the upper base of the trapezoid and the length of the lower base of the trapezoid are 0.3 to 0.7 times the arrangement period of the sub-wavelength grating structure; and / or

[0031] The height of the trapezoid is 30 nm to 100 nm.

[0032] Furthermore, the main structure includes a core layer portion and a cladding portion covering the outer surface of the core layer portion;

[0033] The material of the core layer is silicon, and the material of the cladding layer is silicon dioxide; and / or

[0034] In the thickness direction of the main structure, the size of the core layer is 220nm~400nm; and / or

[0035] The main structure is provided with a plurality of through slots, each of which corresponds to a sub-wavelength grating structure. The plurality of through slots are filled with silicon dioxide material to form two sub-wavelength grating groups.

[0036] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0037] Compared to traditional MZ (Mach-Zehnder) modulators, the silicon optical modulators of the present invention significantly increase the electro-optical bandwidth while maintaining essentially unchanged microwave loss and modulation efficiency, thereby accelerating the transmission rate of high-frequency signals. This allows for efficient high-speed transmission of 100 Gbps PAM4 signals and high-speed signal modulation. Furthermore, the first multimode interference coupler comprises a main structure and two subwavelength grating groups disposed on the main structure. The subwavelength grating groups comprise multiple subwavelength grating structures periodically arranged along the length of the main structure. This shortens the length of the first multimode interference coupler while achieving dual-band, low-crosstalk optical signal separation. Furthermore, the subwavelength grating structure is trapezoidal in shape. Changing the length of the upper and lower sides of the trapezoidal structure has a smaller impact on the change in the effective refractive index of the subwavelength grating structure than changing the length of the upper and lower sides of a rectangular structure. Furthermore, the size of the trapezoid is dynamically adjustable, effectively reducing the correlation between the effective refractive index and shape of the subwavelength grating structure, increasing process tolerances and minimizing the impact of process manufacturing on the first multimode interference coupler. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0039] Figure 1 This is a schematic diagram of the structure of the multi-wavelength silicon light emitting chip according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the structure of the silicon light modulator of the multi-wavelength silicon light emitting chip described in an embodiment of the present invention;

[0041] Figure 3 A longitudinal cross-sectional diagram of a silicon light modulator of a multi-wavelength silicon light emitting chip according to an embodiment of the present invention;

[0042] Figure 4 The simulation effect diagram and relationship curve diagram of the silicon light modulator of the multi-wavelength silicon light emitting chip described in the embodiment of the present invention;

[0043] Figure 5 A schematic diagram comparing the performance of the silicon optical modulator of the multi-wavelength silicon optical transmitter chip described in an embodiment of the present invention and two traditional MZ modulators;

[0044] Figure 6Schematic diagram of the structure of a traditional MZ modulator;

[0045] Figure 7 A schematic structural diagram of a first multimode interference coupler of a multi-wavelength silicon optical transmitter chip according to an embodiment of the present invention;

[0046] Figure 8 A schematic longitudinal cross-sectional view of a first multimode interference coupler of a multi-wavelength silicon optical transmitter chip according to an embodiment of the present invention;

[0047] Figure 9 A graph showing the relationship between the output power and wavelength of two channels of the first multimode interference coupler of the multi-wavelength silicon optical transmitter chip according to an embodiment of the present invention;

[0048] Figure 10 This is a light field simulation effect diagram of the first multi-mode interference coupler of the multi-wavelength silicon light emitting chip described in an embodiment of the present invention.

[0049] Description of reference numerals:

[0050] 10. Multi-wavelength silicon photonics transmitter chip; 11. Input waveguide; 12. First multimode interference coupler; 13, 14. Transmission path; 15. Silicon photonics modulator; 16, 17. Second multimode interference coupler; 18. Output waveguide; 19. Reverse bias electrode; 20, 21. High-frequency electrode; 22. Waveguide; 23. Sub-electrode; 24. Main body; 25. Connecting part; 26. End; 27. First metal plate; 28. Metal electrode; 29. Second metal plate; 30. Phase shifter; 31. Terminal resistor; 32. Main body structure; 33. Sub-wavelength grating group; 34. Sub-wavelength grating structure; 35. Core layer; 36. Cladding layer; 37, 38. Channel. DETAILED DESCRIPTION

[0051] Analysis revealed at least the following issues with existing technologies: Optical signals in the 1310nm and 1550nm bands often mix together. Because modulators have corresponding central operating wavelengths, and the voltage applied by the phase shifter is also wavelength-dependent, high-speed modulation and transmission of both bands cannot be achieved using a single silicon optical modulator. The mixed optical signals from these two bands can be separated using a multimode interference coupler, but existing multimode interference couplers are relatively large. The separated optical signals can then be modulated and transmitted at high speed using a silicon optical modulator. Common silicon optical modulators are Mach-Zehnder-type, which have a low electro-optical bandwidth.

[0052] To solve the above problems, the present invention provides a multi-wavelength silicon optical transmitter chip. The silicon optical modulator of the multi-wavelength silicon optical transmitter chip can significantly increase the electro-optical bandwidth while keeping the microwave loss and modulation efficiency basically unchanged, thereby accelerating the transmission efficiency of high-frequency signals and realizing high-speed signal modulation.

[0053] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention. Similar elements in different embodiments use associated similar element numbers. In the following embodiments, many detailed descriptions are intended to enable the present invention to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present invention are not shown or described in the specification. This is to avoid the core part of the present invention being overwhelmed by too much description. For those skilled in the art, it is not necessary to describe these related operations in detail. They can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0054] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various orders in the description and the drawings are only for the purpose of clearly describing a certain embodiment and are not intended to be a required order, unless otherwise specified that a certain order must be followed.

[0055] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0056] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0057] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0058] See also Figure 1 、 Figure 2 and Figure 3 As shown, an embodiment of the present invention provides a multi-wavelength silicon photonics transmitter chip 10 , which includes an input waveguide 11 , a first multi-mode interference coupler 12 , and two transmission paths 13 , 14 .

[0059] The input waveguide 11 is used to input a dual-band optical signal. The input waveguide 11 inputs a dual-band optical signal having a wavelength of 1.22 μm to 1.37 μm and a wavelength of 1.45 μm to 1.57 μm.

[0060] The first multimode interference coupler 12 can be a 2×2 multimode interference coupler. The first multimode interference coupler 12 is connected to the input waveguide 11 and is used to distribute the dual-band optical signal from the input waveguide 11 to two transmission paths 13 and 14. The first multimode interference coupler 12 can separate the dual-band optical signal input from the input waveguide 11 and distribute the dual-band optical signal to the two transmission paths 13 and 14 for transmission. In this embodiment, the 1310nm band optical signal output by the first multimode interference coupler 12 is distributed to one transmission path 13, and the 1550nm band optical signal output by the first multimode interference coupler 12 is distributed to the other transmission path 14.

[0061] Each transmission path includes a silicon optical modulator 15 and two second multimode interference couplers 16 and 17. The silicon optical modulator 15 is connected between the two second multimode interference couplers 16 and 17 through a waveguide. The two second multimode interference couplers 16 and 17 are both 1×2 multimode interference couplers, and the length of the second multimode interference coupler is 50μm~200μm. The width of the second multimode interference coupler is 5μm~10μm, and the length of the second multimode interference coupler is proportional to the square of the width. The length of the second multimode interference coupler is inversely proportional to the input wavelength, which refers to the wavelength of the input optical signal. The operating wavelength of the two second multimode interference couplers 16 and 17 of one transmission path 13 is 1.22μm~1.37μm, and the operating wavelength of the two second multimode interference couplers 16 and 17 of the other transmission path 14 is 1.45μm~1.57μm. Specifically, the output end of the first multimode interference coupler 12 is connected to the input end of a second multimode interference coupler 16 via a waveguide. The output end of the second multimode interference coupler 16 is connected to the input end of the silicon optical modulator 15 via a waveguide. The second multimode interference coupler 16 can achieve even distribution of optical signal power. The output end of the silicon optical modulator 15 is connected to the input end of another second multimode interference coupler 17 via a waveguide. The second multimode interference coupler 17 can achieve optical signal beam combining. The output end of the second multimode interference coupler 17 is connected to the output waveguide 18. In this embodiment, the operating wavelength of the silicon optical modulator 15 in the transmission path 13 is 1310 nm, the operating wavelength of the second multimode interference couplers 16 and 17 is 1310 nm, and the center wavelength of the output waveguide 18 is 1310 nm. The operating wavelength of the silicon optical modulator 15 in the transmission path 14 is 1550 nm, the operating wavelength of the second multimode interference couplers 16 and 17 is 1550 nm, and the center wavelength of the output waveguide 18 is 1550 nm. The output waveguides 18 of the two transmission paths 13 and 14 are used to output the high-frequency signal modulated by the silicon optical modulator 15. The modulated high-frequency signal can be used to test the eye diagram performance of the multi-wavelength silicon optical transmitter chip 10 and can be received by the optical receiver chip.

[0062] The silicon optical modulator 15 includes a reverse bias electrode 19 and two high-frequency electrodes 20 and 21. The reverse bias electrode 19 is used to receive a DC reverse bias signal. One high-frequency electrode 20 is used to receive a ground signal, and the other high-frequency electrode 21 is used to receive a high-frequency electrical signal. The two high-frequency electrodes 20 and 21 are located on opposite sides of a waveguide 22 and connected to the waveguide 22. The reverse bias electrode 19 is located in the middle of the waveguide 22. The silicon optical modulator 15 can adopt a segmented electrode structure. The high-frequency electrode includes multiple sub-electrodes 23 arranged along a first direction X. In one embodiment, the high-frequency electrode also includes a first metal plate 27 for connecting to a high-frequency probe. The first metal plate 27 is connected to one side of the multiple sub-electrodes 23 along the first direction X. The high-frequency probe inputs a high-frequency electrical signal. The high-frequency electrical signal includes a high-frequency signal and a ground signal. The first metal plate of the high-frequency electrode 20 and the first metal plate of the high-frequency electrode 21 are connected to the ground signal terminal and the high-frequency signal terminal of the high-frequency probe, respectively, to input the ground signal to the first metal plate of the high-frequency electrode 20 and the high-frequency signal to the first metal plate of the high-frequency electrode 21. Thus, a ground signal can be applied to the waveguide 22 through the high-frequency electrode 20, and a high-frequency signal can be applied to the waveguide 22 through the high-frequency electrode 21. In one embodiment, the reverse bias electrode 19 includes a metal electrode 28 and a second metal plate 29 for connecting to a DC voltage source. The metal electrode 28 is connected to the middle of the waveguide 22, and the second metal plate 29 is connected to the metal electrode 28. A DC reverse bias signal is input to the metal electrode 28 through the second metal plate 29, that is, a DC reverse bias voltage is input to the metal electrode 28 through the second metal plate 29. The DC reverse bias signal can be applied to the waveguide 22 through the metal electrode 28. The metal electrode 28 and the two high-frequency electrodes 20 and 21 can be made of metals such as aluminum, copper, and silver.

[0063] The sub-electrode 23 includes a main portion 24, a connecting portion 25, and an end portion 26. The connecting portion 25 and the end portion 26 are connected to one side of the main portion 24 along the second direction Y, forming a T-shaped structure. The end portion 26 is the top of the T-shaped structure, and the connecting portion 25 is the bottom of the T-shaped structure. The end portion 26 extends toward the waveguide 22 and is connected to the waveguide 22. The first direction X is perpendicular to the second direction Y.

[0064] In one embodiment, in the first direction X, the total size L of the multi-segment sub-electrode 23 is mod It is 1.5mm~3mm.

[0065] In one embodiment, in the first direction X, the dimension L of the single main body portion 24 is p1 The size of a single main body 24 is equal to the arrangement period of the multiple sub-electrodes 23 .

[0066] In one embodiment, in the first direction X, the dimension L of the single end portion 26 is p2 The size L of the single main body 24 p1 0.7 to 0.9 times.

[0067] In one embodiment, in the first direction X, the dimension L of a single connecting portion 25 is p3 Smaller than the dimension L of the single end 26 p2 .

[0068] In one embodiment, in the second direction Y, the dimension W of the main body 24 is m 20μm~80μm.

[0069] In one embodiment, in the second direction Y, the dimension G of the connecting portion 25 is t 20μm~80μm.

[0070] In one embodiment, in the second direction Y, the dimension G of the end portion 26 is p 5μm~30μm.

[0071] In one embodiment, in the second direction Y, the distance G between the ends of the two high-frequency electrodes 20 and 21 is mt 15μm~70μm.

[0072] In one embodiment, in the second direction Y, the distance G between the main bodies of the two high-frequency electrodes 20 and 21 is mm 60μm~150μm.

[0073] In one embodiment, the thicknesses of the main portion 24 , the connecting portion 25 and the end portion 26 are all 2 μm to 15 μm in the third direction Z. The third direction Z is perpendicular to the first direction X and the second direction Y.

[0074] In this embodiment, the total size L of the multi-segment electrode 23 is mod 2mm, the size L of the main body 24 p1 is 50 μm, and the dimension L of the end portion 26 is p2 is 45 μm, and the dimension L of the connection portion 25 is p3 The size W of the main body 24 is 10 μm. m is 50 μm, and the dimension G of the connection portion 25 is t The dimension G of the end portion 26 is 30 μm. p The distance G between the ends of the two high-frequency electrodes 20 and 21 is 10 μm. mt The distance G between the main bodies of the two high-frequency electrodes 20 and 21 is 30 μm. mm The thickness of the main body 24, the connecting portion 25 and the end portion 26 is 2 μm.

[0075] In one embodiment, the multi-wavelength silicon photonics transmitter chip 10 further includes a phase shifter 30 corresponding to the silicon photonic modulator 15. The phase shifter 30 is located at a height of 2 μm to 5 μm above the waveguide 22. By varying the voltage applied to the phase shifter 30, the phase of the waveguide 22 and the operating point of the silicon photonic modulator 15 are altered. The phase shifter 30 utilizes TiN (titanium nitride) material to implement its function. By varying the voltage applied to the TiN, the phase of the waveguide 22 and the operating point of the silicon photonic modulator 15 can be dynamically altered, enabling the silicon photonic modulator 15 to operate at a quadrature operating point. Specifically, by varying the voltage applied to the phase shifter 30, the output optical power is varied. When the optical power is half the maximum optical power, the silicon photonic modulator 15 is at a quadrature operating point.

[0076] In one embodiment, the silicon optical modulator 15 further includes a terminal resistor 31 , which may be made of TiN. The terminal resistor 31 is connected between the two high-frequency electrodes 20 and 21 and is located on one side of the output terminal of the silicon optical modulator 15 . The impedance of the terminal resistor 31 is 30Ω to 70Ω. In this embodiment, the impedance of the terminal resistor 31 is 40Ω.

[0077] In one embodiment, the waveguide 22 includes a P++-doped region and two doped region groups arranged on either side of the P++-doped region along a second direction Y. Each doped region group includes a P+-doped region, a P-doped region, an N-doped region, an N+-doped region, and an N++-doped region. An end 26 is connected to the N++-doped region. A reverse bias electrode 19 is connected to the P++-doped region, wherein a metal electrode 28 of the reverse bias electrode 19 is connected to the P++-doped region. Specifically, an end of the high-frequency electrode 20 is connected to the N++-doped region on one side of the P++-doped region, and an end of the high-frequency electrode 21 is connected to the N++-doped region on the other side of the P++-doped region. A DC reverse bias signal can be applied to the P++-doped region of the waveguide 22 via the metal electrode 28 of the reverse bias electrode 19. A ground signal can be applied to the N++-doped region on one side of the P++-doped region via the end of the high-frequency electrode 20. A high-frequency signal can be applied to the N++-doped region on the other side of the P++-doped region via the end of the high-frequency electrode 21. The silicon optical modulator 15 may adopt a series push-pull structure, that is, the reverse bias electrode 19 and the two high-frequency electrodes 20 and 21 may be arranged symmetrically with the central axis of the P++-type doped region as an axis.

[0078] In one embodiment, the doping concentration of the N-type doping region and the P-type doping region is 10 16 / cm 3 ~10 17 / cm 3 Magnitude.

[0079] In one embodiment, the doping concentration of the N+ type doping region and the P+ type doping region is 1018 / cm 3 ~10 19 / cm 3 Magnitude.

[0080] In one embodiment, the doping concentration of the N++ type doping region and the P++ type doping region is 10 19 / cm 3~ 10 20 / cm 3 Magnitude.

[0081] In one embodiment, in the second direction Y, the lengths of the N-type doping region, the N+-type doping region, the P-type doping region, and the P+-type doping region are 0.4 μm to 2 μm. The length of the N-type doping region is approximately the same as the length of the P-type doping region. The length of the N+-type doping region is approximately the same as the length of the P+-type doping region. The length of the N-type doping region and the length of the N+-type doping region may be the same or different.

[0082] In one embodiment, in the second direction Y, the lengths of the N++ type doping region and the P++ type doping region are greater than 5 μm. The lengths of the N++ type doping region and the P++ type doping region are different, and the length of the P++ type doping region may be 10 μm to 40 μm.

[0083] In one embodiment, the P-type doping region and the N-type doping region form a PN junction, a protrusion structure is formed at the PN junction, and the high-frequency electrodes 20 and 21 are arranged on the same side as the protrusion structure. In the second direction Y, the length W of the PN junction is wg A hot electrode is provided between the output end of the first multimode interference coupler 12 and a PN junction of the waveguide 22 of the silicon optical modulator 15 .

[0084] In one embodiment, in the third direction Z, the thickness H of the P++ type doping region, the P+ type doping region, the P type doping region, the N type doping region, the N+ type doping region and the N++ type doping region is rib The thicknesses of the P++-type doping region, the P+-type doping region, the P-type doping region, the N-type doping region, the N+-type doping region, and the N++-type doping region are all the same in the third direction Z.

[0085] In one embodiment, in the third direction Z, the thickness H of the PN junction is 220 nm.

[0086] In this embodiment, the doping concentration of the N-type doping region and the P-type doping region is 5×10 17 / cm 3 The doping concentration of N+ doping region and P+ doping region is 2×10 18 / cm 3The doping concentration of N++ type doping region and P++ type doping region is 1×10 20 / cm 3 In the second direction Y, the length of the N-type doping region and the P-type doping region is 350nm, and the length of the N+ type doping region and the P+ type doping region is 650nm. In the second direction Y, the length of the P++ type doping region is 13μm, and the length of the N++ doping region is 9μm. In the second direction Y, the length of the PN junction W wg is 450nm; in the third direction Z, the thickness H of the P++ type doped region, the P+ type doped region, the P type doped region, the N type doped region, the N+ type doped region and the N++ type doped region rib Both are 90nm; in the third direction Z, the thickness H of the PN junction is 220nm.

[0087] See also Figure 4 As shown, Figure 4 (a) is a simulation diagram of the N-type carrier concentration at different positions of the waveguide 22 when the DC reverse bias voltage applied to the waveguide 22 is -4V. Figure 4 (a) It can be seen that at different positions of the waveguide 22 , the concentration of N-type carriers in the waveguide 22 changes, which can generate junction capacitance and PN junction impedance, providing a basis for the realization of the silicon optical modulator 15 .

[0088] Figure 4 (b) is a graph showing the relationship between the junction capacitance of the PN junction and the DC reverse bias voltage applied to the waveguide 22. Figure 4 (b) As can be seen, as the DC reverse bias voltage increases from 0 to -6V, the junction capacitance of the PN junction gradually decreases, reducing the RC time constant and thereby increasing the bandwidth of the silicon optical modulator 15. As the absolute value of the DC reverse bias voltage increases, the reverse bias deepens, while the change in the PN junction capacitance decreases. Furthermore, an increase in the absolute value of the DC reverse bias voltage can lead to avalanche breakdown. Therefore, a DC reverse bias voltage of -4V is selected, at which point the junction capacitance of the PN junction is approximately 0.075fF / μm.

[0089] Figure 4 (c) is a graph showing the relationship between the phase shift of the silicon optical modulator 15 and the DC reverse bias voltage applied to the waveguide 22. mod When the waveguide 22 is 2 mm, the DC reverse bias voltage applied to the waveguide 22 is -4 V, and the phase shift of the silicon optical modulator 15 is 0.7556 rad. Therefore, the modulation efficiency of the silicon optical modulator 15 is .

[0090] Figure 4 (d) is a graph showing the relationship between the group refractive index of the optical signal and the DC reverse bias voltage applied to the waveguide 22. Figure 4(d) It can be seen that the group refractive index of the optical signal hardly changes with the change of the DC reverse bias voltage. The value of the group refractive index of the optical signal is approximately 3.9360. Therefore, when designing the electrodes of the silicon optical modulator 15, the effective refractive index of the microwave is close to the group refractive index of the optical signal, which can make the silicon optical modulator 15 have a higher electro-optical bandwidth.

[0091] See also Figure 5 and Figure 6 As shown, Figure 5 Design a is the silicon optical modulator 15 of this embodiment, and designs b and c are two traditional MZ (Mach-Zehnder) modulators. The width W of the electrode in design b is metal The distance between the two electrodes is 90 μm. space The total size of the electrode is 30 μm. mod 2 mm; Design c uses W metal 50μm, G space 110μm, L mod is 2 mm. Among them, the G of design a mt and design b in G space Same size, design a W m With design c in W metal Same size.

[0092] Figure 5 (a) is the relationship between the microwave effective refractive index and signal frequency of the three modulators. Figure 5 (a) It can be seen that the microwave effective refractive index of design a is between 3.4 and 3.6, which is closer to the group refractive index of the optical signal 3.9360 than designs b and c. Therefore, the silicon optical modulator 15 of this embodiment has a higher electro-optical bandwidth.

[0093] Figure 5 (b) is the relationship curve between the impedance of the three modulators and the frequency of the high-frequency signal, Figure 5 (b) It can be seen that when the terminal resistor 31 is set to 40 Ω, the impedance of design a is approximately 75 Ω. A low impedance value of the terminal resistor 31 will enable the silicon optical modulator 15 to have a higher electro-optical bandwidth. However, the impedance of the terminal resistor 31 cannot be too low, as this will result in significant microwave signal loss in the metal and microwave loss in the silicon optical modulator 15. Therefore, a terminal resistor 31 of 40 Ω is more suitable.

[0094] Figure 5 (c) is the relationship between microwave loss and high-frequency signal frequency of the three modulators. Figure 5(c) It can be seen that under a high-frequency signal of 50 GHz, the microwave loss of design a is about 3.5 dB / mm, which is between designs b and c. This shows that the microwave loss of the silicon optical modulator 15 of this embodiment is relatively small.

[0095] Figure 5 (d) is the relationship between the electro-optical response of the three modulators and the frequency of the high-frequency signal. Figure 5 (d) It can be seen that when the electro-optical response is -3dB, the signal frequency of design a is 55 GHz, indicating that the electro-optical bandwidth of the device can reach 55 GHz, while the electro-optical bandwidths of the other two designs are only about 43 GHz and 48 GHz. This shows that the electro-optical bandwidth of the silicon optical modulator 15 of the embodiment of the present invention is significantly improved. Figure 5 (a) can also be confirmed.

[0096] Compared with the traditional MZ modulator, the silicon optical modulator 15 of the embodiment of the present invention significantly increases the electro-optical bandwidth while keeping the microwave loss and modulation efficiency basically unchanged, thereby accelerating the transmission rate of high-frequency signals, and can effectively realize the high-speed transmission of 100 Gbps PAM4 signals, realizing high-speed signal modulation.

[0097] See also Figure 7 and Figure 8 As shown, in one embodiment, the first multimode interference coupler 12 includes a main structure 32 and two sub-wavelength grating groups 33 provided on the main structure 32. The two sub-wavelength grating groups 33 are arranged opposite each other. The sub-wavelength grating groups 33 include a plurality of sub-wavelength grating structures 34 periodically arranged along the length direction of the main structure 32. The arrangement period Period of the sub-wavelength grating structures 34 is 150 nm to 200 nm.

[0098] In one embodiment, the length of the main structure 32 is 30 μm-50 μm, the width of the main structure 32 is 1 μm-3 μm, and the length of the main structure 32 is proportional to the square of the width of the main structure 32 .

[0099] In one embodiment, the distance W between the two sub-wavelength grating groups 33 is sep It is one-third of the width of the main structure 32. In this case, the first multimode interference coupler 12 has a larger power separation ratio for optical signals in the dual-bands of 1.22 μm to 1.37 μm and 1.45 μm to 1.57 μm.

[0100] In one embodiment, the sub-wavelength grating structure 34 is in the shape of a trapezoid, and the length of the upper base side and the length of the lower base side of the trapezoid are 0.3 to 0.7 times the arrangement period of the sub-wavelength grating structure.

[0101] In one embodiment, the height of the trapezoid is 30 nm to 100 nm.

[0102] In one embodiment, the main structure 32 includes a core portion 35 and a cladding portion 36 covering the outer surface of the core portion 35. The core portion 35 is made of silicon, and the cladding portion 36 is made of silicon dioxide. In other words, the main structure 32 has an SOI (Silicon On Insulator) structure. The SOI structure significantly reduces the size of the main structure 32. Furthermore, the main structure 32 can be processed using integrated circuit technology.

[0103] In one embodiment, the dimension h of the core portion 35 is 220 nm to 400 nm in the thickness direction of the main structure 32. In this embodiment, the dimension h of the core portion 35 is 220 nm.

[0104] In one embodiment, the main structure 32 is provided with a plurality of through-grooves, each of which corresponds to the sub-wavelength grating structure 34 . The plurality of through-grooves are filled with silicon dioxide material to form two sub-wavelength grating groups 33 .

[0105] The input waveguide 11 inputs optical signals of dual wavelengths of 1.22-1.37 μm and 1.45-1.57 μm. The following description will be made by taking the input wavelengths of 1310 nm and 1550 nm as an example. In order to separate the two wavelengths, the length L of the conventional multimode interference coupler is MMI The expression needs to be satisfied:

[0106]

[0107] in, is the beat length of the multimode interference coupler, ;n eff0 (λ) is the effective refractive index of the TE0 mode of the optical signal in the multimode interference coupler at the input wavelength, n eff1 (λ) is the effective refractive index of the TE1 mode of the optical signal in the multimode interference coupler at the input wavelength; λ is the input wavelength, which is 1310nm and 1550nm respectively. Where p and q are prime numbers, L MMI The wavelength of 1310nm corresponds to Corresponding to a wavelength of 1550nm Since the wavelengths of 1310nm and 1550nm are relatively close, the least common multiple is large, so the length of the traditional multimode interference coupler is relatively long.

[0108] In this embodiment, the arrangement period of the sub-wavelength grating structure 34 is 180nm; the upper base length L2 of the trapezoid is 0.53×Period=95.4nm; the lower base length L1 of the trapezoid is 0.58×Period=104.4nm; the height dimension W of the trapezoid is swg is 50nm; when the wavelength is 1310nm, the calculated n eff0 (1310nm)=2.894,n eff1 (1310nm)=2.858, L π1 (1310nm)= ≈18.3μm; at a wavelength of 1550nm, the calculated n eff0 (1550nm)=2.721,n eff1 (1550nm)=2.657, L π2 (1550nm)= ≈12.2 μm. Thus, the length L of the main structure 32 MMI =2L π1 (1310nm)=3 L π2 (1550 nm) = 36.6 μm, the length L of the first multimode interference coupler 12 of this embodiment is MMI The separation of the two bands can be achieved with a wavelength of 36.6 μm, which effectively shortens the length of the first multimode interference coupler 12 .

[0109] See also Figure 9 As shown, Figure 9 The relationship between the output power and wavelength of the two channels of the first multimode interference coupler 12 of the multi-wavelength silicon light emitting chip 10 is shown. The two channels 37 and 38 of the first multimode interference coupler 12 are connected to the two transmission paths 13 and 14 respectively. Channel 37 is connected to the transmission path 13, and channel 38 is connected to the transmission path 14. Figure 9It can be seen that near a wavelength of 1310 nm, the output power value of channel 37 is the highest, approximately 29.3 dB greater than the output power value of channel 38, that is, the crosstalk value is approximately -29.3 dB. Near a wavelength of 1550 nm, the output power value of channel 38 is the highest, approximately 12.3 dB greater than the output power value of channel 37, that is, the crosstalk value is approximately -12.3 dB. This shows that there is low crosstalk between the two channels 37 and 38 of the first multimode interference coupler 12. Furthermore, near a wavelength of 1310 nm, the 1 dB bandwidth of the first multimode interference coupler 12 corresponds to a wavelength range of 1243 nm to 1350 nm. The 1 dB bandwidth refers to the wavelength value corresponding to a 1 dB drop in output power at the peak value. Near the wavelength of 1550nm, the wavelength range corresponding to the 1dB bandwidth of the first multimode interference coupler 12 is 1480nm~1557nm. This shows that the wavelength range corresponding to the 1dB bandwidth of the first multimode interference coupler 12 is at least greater than 70nm. The first multimode interference coupler 12 has the advantages of low crosstalk and large operating bandwidth, and can effectively separate the two wavelengths of 1310nm and 1550nm.

[0110] See also Figure 10 As shown, Figure 10 The horizontal axis in is the length direction of the first multimode interference coupler 12 , that is, the direction of light propagation, and the vertical axis is the width direction of the first multimode interference coupler 12 . Figure 10 (a) is the simulation effect diagram corresponding to the input wavelength of 1310nm. Figure 10 (b) is the corresponding simulation effect diagram when the input wavelength is 1550nm. Figure 10 (a) shows that the optical power signal is output along channel 37. Figure 10 (b) It can be seen that the optical power signal is mainly output along channel 38.

[0111] The first multimode interference coupler 12 of the present invention includes a main structure 32 and two subwavelength grating groups 33 disposed within the main structure 32. The subwavelength grating groups 33 include multiple subwavelength grating structures 34 periodically spaced along the length of the main structure 32. This reduces the length of the first multimode interference coupler 12 while achieving dual-band, low-crosstalk optical signal separation. Furthermore, the subwavelength grating structures 34 are trapezoidal in shape. Changing the lengths of the upper and lower bases of the trapezoidal structure has a smaller effect on the effective refractive index of the subwavelength grating structure 34 than changing the lengths of the upper and lower bases of a rectangular structure. Furthermore, the trapezoidal shape is dynamically adjustable, effectively reducing the correlation between the effective refractive index and shape of the subwavelength grating structure 34, increasing process tolerances and minimizing the impact of process manufacturing on the first multimode interference coupler 12.

[0112] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved. This is not limited herein.

[0113] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A multi-wavelength silicon light emitting chip, characterized in that: include: An input waveguide, used for inputting a dual-band optical signal; a first multimode interference coupler connected to the input waveguide and configured to distribute the dual-band optical signal from the input waveguide to two transmission paths; each transmission path comprising a silicon optical modulator and two second multimode interference couplers; the silicon optical modulator being connected between the two second multimode interference couplers via a waveguide; The silicon optical modulator includes a reverse bias electrode and two high-frequency electrodes, the two high-frequency electrodes are located on opposite sides of the waveguide and connected to the waveguide, and the reverse bias electrode is located in the middle of the waveguide; the high-frequency electrode includes a plurality of sub-electrodes arranged along a first direction, and the sub-electrodes include a main body, a connecting part and an end part; the connecting part and the end part are connected to one side of the main body along a second direction, and the connecting part and the end part form a T-shaped structure; the end part extends toward the direction of the waveguide and is connected to the waveguide; the first direction is perpendicular to the second direction.

2. The multi-wavelength silicon light emitting chip according to claim 1, characterized in that: The high-frequency electrode further includes a first metal plate for connecting to a high-frequency probe, wherein the first metal plate is connected to one side of the multi-segment sub-electrode along the first direction.

3. The multi-wavelength silicon light emitting chip according to claim 1, characterized in that: The reverse bias electrode includes a metal electrode and a second metal plate for connecting to a DC voltage source, the metal electrode is connected to the middle of the waveguide, the second metal plate is connected to the metal electrode, and a DC reverse bias signal is input to the metal electrode through the second metal plate.

4. The multi-wavelength silicon light emitting chip according to claim 1, characterized in that: The silicon light modulator further includes a terminal resistor, which is connected between the two high-frequency electrodes and located on one side of the output end of the silicon light modulator; the impedance value of the terminal resistor is 30Ω~70Ω.

5. The multi-wavelength silicon light emitting chip according to claim 1, characterized in that: It also includes a phase shifter set corresponding to the silicon light modulator, which is located at a height of 2μm to 5μm above the waveguide. By changing the voltage applied to the phase shifter, the phase of the waveguide and the operating point of the silicon light modulator are changed.

6. The multi-wavelength silicon light emitting chip according to claim 1, characterized in that: The waveguide includes a P++ type doped region and two doped region groups arranged on both sides of the P++ type doped region along the second direction, each of the doped region groups including a P+ type doped region, a P type doped region, an N type doped region, an N+ type doped region and an N++ type doped region; the end portion is connected to the N++ type doped region, and the reverse bias electrode is connected to the P++ type doped region; The doping concentration of the N-type doping region and the P-type doping region is 10 16 / cm 3 ~10 17 / cm 3 Magnitude; and / or The doping concentration of the N+ type doping region and the P+ type doping region is 10 18 / cm 3 ~10 19 / cm 3 Magnitude; and / or The doping concentration of the N++ type doping region and the P++ type doping region is 10 19 / cm 3~ 10 20 / cm 3 Magnitude; and / or In the second direction, the lengths of the N-type doping region, the N+-type doping region, the P-type doping region, and the P+-type doping region are 0.4 μm to 2 μm; and / or In the second direction, the lengths of the N++ type doping region and the P++ type doping region are greater than 5 μm.

7. The multi-wavelength silicon light emitting chip according to claim 1, characterized in that: In the first direction, the total size of the multi-segment sub-electrodes is 1.5 mm to 3 mm; and / or In the first direction, the size of a single main body portion is 30 μm to 70 μm; and / or In the first direction, the size of a single end portion is 0.7 to 0.9 times the size of a single main portion; and / or In the second direction, the size of the main body is 20 μm to 80 μm; and / or In the second direction, the size of the connecting portion is 20 μm to 80 μm; and / or In the second direction, the distance between the ends of the two high-frequency electrodes is 15 μm to 70 μm.

8. The multi-wavelength silicon light emitting chip according to claim 1, characterized in that: The first multimode interference coupler includes a main structure and two sub-wavelength grating groups provided on the main structure, the two sub-wavelength grating groups are arranged opposite to each other, and the sub-wavelength grating groups include a plurality of sub-wavelength grating structures periodically arranged along the length direction of the main structure; the arrangement period of the sub-wavelength grating structures is 150nm to 200nm; The distance between the two sub-wavelength grating groups is one-third of the width of the main structure; The length of the main structure is 30 μm to 50 μm, the width of the main structure is 1 μm to 3 μm, and the length of the main structure is proportional to the square of the width of the main structure.

9. The multi-wavelength silicon light emitting chip according to claim 8, characterized in that: The sub-wavelength grating structure has a trapezoidal shape; The length of the upper base of the trapezoid and the length of the lower base of the trapezoid are 0.3 to 0.7 times the arrangement period of the sub-wavelength grating structure; and / or The height of the trapezoid is 30 nm to 100 nm.

10. The multi-wavelength silicon light emitting chip according to claim 8, characterized in that: The main structure includes a core layer portion and a cladding portion covering the outer surface of the core layer portion; The material of the core layer is silicon, and the material of the cladding layer is silicon dioxide; and / or In the thickness direction of the main structure, the size of the core layer is 220nm~400nm; and / or The main structure is provided with a plurality of through slots, each of the through slots corresponds to the sub-wavelength grating structure, and the plurality of through slots are filled with silicon dioxide material to form the two sub-wavelength grating groups.

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