Multi-wavelength silicon light emitting chip

Abstract

The invention relates to the field of optical elements, in particular to a multi-wavelength silicon light emitting chip, and an input waveguide of the multi-wavelength silicon light emitting chip is used for inputting dual-band optical signals. The first multimode interference coupler is connected to the input waveguide and is used for distributing dual-band optical signals from the input waveguide to the two transmission paths. And each transmission path comprises a silicon optical modulator and two second multimode interference couplers. The silicon optical modulator is connected between the two second multimode interference couplers through a waveguide. The silicon light modulator comprises a reverse bias electrode and two high-frequency electrodes, the two high-frequency electrodes are located on the two opposite sides of the waveguide and connected with the waveguide, and the reverse bias electrode is located in the middle of the waveguide. The high-frequency electrode comprises multiple sections of sub-electrodes arranged in the first direction, and the multiple sections of sub-electrodes comprise main body parts, connecting parts and end parts. The connecting part and the end part are connected to one side, in the second direction, of the main body part, and the connecting part and the end part form a T-shaped structure. The end portion extends in the direction of the waveguide and is connected to the waveguide. And high-speed signal modulation is realized.

Description

Technical Field

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

[0002] In the communication field, in order to improve the capacity of optical signal transmission, optical components for single-fiber dual-wavelength transmission have become important devices at each control point. Since the dispersion of the optical fiber near the 1310 nm communication window is almost zero and the insertion loss of the optical fiber in the 1550 nm communication window is the lowest, the commonly used dual bands are selected as the 1310 nm and 1550 nm bands. In addition, the modulation of high-speed electrical signals and long-distance transmission have become the research focus in the current communication field. Therefore, simultaneously achieving high-speed transmission of dual-band communication signals has become an important research direction, and realizing a silicon optical emission chip that can simultaneously modulate dual bands and has a high integration degree has become the research focus.

[0003] However, in a common Mach-Zehnder type silicon optical modulator in a silicon optical emission chip, its electro-optic bandwidth is low, resulting in a low transmission rate of high-frequency signals. Therefore, a silicon optical modulator that can significantly increase the electro-optic bandwidth is needed. Summary of the Invention

[0004] In view of this, the present invention aims to provide a multi-wavelength silicon optical emission chip, which can significantly increase the electro-optic bandwidth while the microwave loss and modulation efficiency remain 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 of the present invention is realized as follows: A multi-wavelength silicon optical emission chip, which includes: An input waveguide for inputting dual-band optical signals; A first multimode interference coupler connected to the input waveguide for distributing 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 through a waveguide; The silicon optical modulator includes a reverse-biased 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, and the reverse-biased electrode is located in the middle of the waveguide; the high-frequency electrode includes multiple sub-electrodes arranged along a first direction. The sub-electrode includes a main body portion, a connecting portion, and an end portion; the connecting portion and the end portion are connected to one side of the main body portion along a second direction, and the connecting portion and the end portion form a T-shaped structure; the end portion extends towards the waveguide and is connected to the waveguide; the first direction is perpendicular to the second direction.

[0006] Further, the high-frequency electrode further includes a first metal plate for connecting to a high-frequency probe, and the first metal plate is connected to one side of the multiple sub-electrodes along the first direction.

[0007] Further, 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, and the second metal plate is connected to the metal electrode. A DC reverse bias signal is input to the metal electrode through the second metal plate.

[0008] Further, the silicon optical modulator further includes a termination resistor connected between two high-frequency electrodes and located on one side of the output end of the silicon optical modulator; the impedance value of the termination resistor is 30Ω - 70Ω.

[0009] Further, a phase shifter corresponding to the silicon optical modulator is further included. The phase shifter is located at a height of 2μm - 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 optical modulator are changed.

[0010] Further, 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 is connected to the N++ type doped region, and the reverse bias electrode is connected to the P++ type doped region; The doping concentrations of the N type doped region and the P type doped region are in the order of 10 16 / cm 3 ~10 17 / cm 3 order of magnitude; and / or The doping concentrations of the N+ type doped region and the P+ type doped region are in the order of 10 18 / cm 3 ~10 19 / cm 3 order of magnitude; and / or The doping concentrations of the N++ type doped region and the P++ type doped region are in the order of 10 19 / cm 3~ 10 20 / cm 3 order of magnitude; and / or In the second direction, the lengths of the N type doped region, the N+ type doped region, the P type doped region, and the P+ type doped region are 0.4μm - 2μm; and / or In the second direction, the lengths of the N++ type doped region and the P++ type doped region are greater than 5μm.

[0011] Further, in the first direction, the total size of the multi-segment sub-electrodes is 1.5mm - 3mm; and / or In the first direction, the size of a single main body is 30μm - 70μm; and / or In the first direction, the size of a single end is 0.7 to 0.9 times the size of the single main body part; and / or In the second direction, the size of the main body part is 20 μm to 80 μm; and / or In the second direction, the size of the connecting part 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.

[0012] Furthermore, the first multimode interference coupler includes a main body structure and two sub-wavelength grating groups arranged on the main body structure. The two sub-wavelength grating groups are arranged oppositely, and the sub-wavelength grating group includes a plurality of sub-wavelength grating structures arranged at periodic intervals along the length direction of the main body structure; the arrangement period of the sub-wavelength grating structures is 150 nm to 200 nm; The distance between the two sub-wavelength grating groups is one-third of the width of the main body structure; The length of the main body structure is 30 μm to 50 μm, the width of the main body structure is 1 μm to 3 μm, and the length of the main body structure is proportional to the square of the width of the main body structure.

[0013] Furthermore, the shape of the sub-wavelength grating structure is trapezoidal; The length of the upper base 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 size of the height of the trapezoid is 30 nm to 100 nm.

[0014] Furthermore, the main body structure includes a core layer part and a cladding part covering the outer surface of the core layer part; The material of the core layer part is silicon, and the material of the cladding part is silicon dioxide; and / or In the thickness direction of the main body structure, the size of the core layer part is 220 nm to 400 nm; and / or The main body structure is provided with a plurality of through grooves, each through groove corresponding to a sub-wavelength grating structure, and silicon dioxide material is filled in the plurality of through grooves to form two sub-wavelength grating groups.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: Compared with the traditional MZ (Mach-Zehnder) modulator, the silicon optical modulator of the embodiment of the present invention significantly increases the electro-optic bandwidth while the microwave loss and modulation efficiency remain basically unchanged, thereby accelerating the transmission rate of high-frequency signals, effectively realizing the high-speed transmission of 100 Gbps PAM4 signals, and achieving high-speed signal modulation. The first multimode interference coupler includes a main structure and two sub-wavelength grating groups provided on the main structure. The sub-wavelength grating group includes a plurality of sub-wavelength grating structures arranged at intervals along the length direction of the main structure. In this way, while shortening the length of the first multimode interference coupler, dual-band and low-crosstalk optical signal separation can be achieved. At the same time, the shape of the sub-wavelength grating structure is trapezoidal. When the upper side length and the lower side length of the trapezoidal structure change, the influence on the change of the effective refractive index of the sub-wavelength grating structure is smaller than that when the upper side length and the lower side length of the rectangular structure change, and the size of the trapezoid is dynamically adjustable. In this way, the correlation between the effective refractive index and the shape of the sub-wavelength grating structure can be effectively reduced, the process tolerance is increased, and the influence of the process preparation on the first multimode interference coupler is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is a schematic structural diagram of a multi-wavelength silicon optical emission chip according to an embodiment of the present invention; Figure 2 is a schematic structural diagram of a silicon optical modulator of a multi-wavelength silicon optical emission chip according to an embodiment of the present invention; Figure 3 is a schematic longitudinal sectional view of a silicon optical modulator of a multi-wavelength silicon optical emission chip according to an embodiment of the present invention; Figure 4 is a simulation effect diagram and a relationship curve diagram of a silicon optical modulator of a multi-wavelength silicon optical emission chip according to an embodiment of the present invention; Figure 5 is a schematic diagram of performance comparison between a silicon optical modulator of a multi-wavelength silicon optical emission chip according to an embodiment of the present invention and two traditional MZ modulators; Figure 6 is a schematic structural diagram of a traditional MZ modulator; Figure 7 is a schematic structural diagram of a first multimode interference coupler of a multi-wavelength silicon optical emission chip according to an embodiment of the present invention; Figure 8 is a schematic longitudinal sectional view of a first multimode interference coupler of a multi-wavelength silicon optical emission chip according to an embodiment of the present invention; Figure 9 Relationship diagram of output power and wavelength of two channels of the first multimode interference coupler of the multi-wavelength silicon optical emission chip described in the embodiment of the present invention Figure 10 Optical field simulation effect diagram of the first multimode interference coupler of the multi-wavelength silicon optical emission chip described in the embodiment of the present invention

[0017] Description of reference numerals: 10. Multi-wavelength silicon optical emission chip; 11. Input waveguide; 12. First multimode interference coupler; 13, 14. Transmission paths; 15. Silicon optical modulator; 16, 17. Second multimode interference coupler; 18. Output waveguide; 19. Reverse bias electrode; 20, 21. High-frequency electrodes; 22. Waveguide; 23. Sub-electrode; 24. Main body part; 25. Connection part; 26. End part; 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 part; 36. Cladding part; 37, 38. Channels. Detailed implementation manners

[0018] Through analysis, it is found that there are at least the following problems in the prior art: The optical signals in the two bands of 1310 nm and 1550 nm are often mixed together. Since the modulator has its corresponding central operating wavelength, and the voltage value applied by the phase shifter is also related to the operating wavelength, it is impossible to achieve high-speed modulation and signal emission of the optical signals in the two bands only through one silicon optical modulator. The mixed optical signals in these two bands can be separated by a multimode interference coupler, but the existing multimode interference coupler has a large size. The separated optical signals can be subjected to high-speed modulation and signal emission through a silicon optical modulator. A common silicon optical modulator is of the Mach-Zehnder type, and its electro-optic bandwidth is low.

[0019] To solve the above problems, the present invention provides a multi-wavelength silicon optical emission chip. The silicon optical modulator of the multi-wavelength silicon optical emission chip can significantly increase the electro-optic bandwidth under the condition that the microwave loss and modulation efficiency are basically unchanged, thereby accelerating the transmission efficiency of high-frequency signals and realizing high-speed signal modulation.

[0020] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be 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, rather than constituting a limitation to the present invention. Similar elements in different embodiments are labeled with related similar reference numerals. In the following embodiments, many detailed descriptions are provided to enable a better understanding of the present invention. 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 to avoid overshadowing the core part of the present invention by excessive description. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the description in the specification and the general technical knowledge in the field.

[0021] It should be noted that, without conflict, the embodiments and the features in the embodiments of the present invention can be combined with each other to form various embodiments. At the same time, the steps or actions in the method description can also be adjusted in the order that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for clearly describing a certain embodiment, and do not mean that they are the necessary sequences, unless it is stated that a certain sequence must be followed.

[0022] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is 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 should not be construed as a limitation to 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. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0023] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0024] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments.

[0025] See Figure 1 、 Figure 2 and Figure 3 As shown in

[0026] The input waveguide 11 is used to input a dual-band optical signal. The input waveguide 11 inputs a dual-band optical signal with a wavelength range of 1.22 μm to 1.37 μm and 1.45 μm to 1.57 μm.

[0027] 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 the two transmission paths 13 and 14. The first multimode interference coupler 12 can separate the dual-band optical signal input by 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 1310 nm band optical signal output by the first multimode interference coupler 12 is distributed to one transmission path 13, and the 1550 nm band optical signal output by the first multimode interference coupler 12 is distributed to the other transmission path 14.

[0028] 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. Both of the two second multimode interference couplers 16 and 17 are 1×2 multimode interference couplers, and the length of the second multimode interference coupler is 50 μm to 200 μm. The width of the second multimode interference coupler is 5 μm to 10 μm, 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, where the input wavelength refers to the wavelength of the input optical signal. The operating wavelengths of the two second multimode interference couplers 16 and 17 in one transmission path 13 are 1.22 μm to 1.37 μm, and the operating wavelengths of the two second multimode interference couplers 16 and 17 in the other transmission path 14 are 1.45 μm to 1.57 μm. Specifically, the output end of the first multimode interference coupler 12 is connected to the input end of a second multimode interference coupler 16 through a waveguide, the output end of a second multimode interference coupler 16 is connected to the input end of the silicon optical modulator 15 through a waveguide, and the second multimode interference coupler 16 can achieve the average distribution of the 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 through a waveguide, and the second multimode interference coupler 17 can achieve the beam combination of the optical signal. 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 wavelengths of the second multimode interference couplers 16 and 17 are 1310 nm, and the central 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 wavelengths of the second multimode interference couplers 16 and 17 are 1550 nm, and the central 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, and this modulated high-frequency signal can be used to test the eye diagram performance of the multi-wavelength silicon optical emission chip 10 and can be received by the optical receiving chip.

[0029] The silicon optical modulator 15 includes a reverse-biased electrode 19 and two high-frequency electrodes 20 and 21. Among them, the reverse-biased electrode 19 is used to access a DC reverse-biased signal. One high-frequency electrode 20 is used to access a ground signal, and the other high-frequency electrode 21 is used to access a high-frequency electrical signal. The two high-frequency electrodes 20 and 21 are located on opposite sides of the waveguide 22 and are connected to the waveguide 22, and the reverse-biased electrode 19 is located in the middle of the waveguide 22. The silicon optical modulator 15 can adopt a segmented electrode structure. Its high-frequency electrode includes multiple sub-electrodes 23 arranged along the first direction X. In one embodiment, the high-frequency electrode further includes a first metal plate 27 for connecting to a high-frequency probe, and 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. Among them, the first metal plate of the high-frequency electrode 20 and the first metal plate of the high-frequency electrode 21 are respectively connected to the ground signal terminal and the high-frequency signal terminal of the high-frequency probe, so as to input a ground signal to the first metal plate of the high-frequency electrode 20 and input a high-frequency signal to the first metal plate of the high-frequency electrode 21. Thus, the ground signal can be applied to the waveguide 22 through the high-frequency electrode 20, and the high-frequency signal can be applied to the waveguide 22 through the high-frequency electrode 21. In one embodiment, the reverse-biased 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, and a DC reverse-biased signal is input to the metal electrode 28 through the second metal plate 29, that is, a DC reverse-biased voltage is input to the metal electrode 28 through the second metal plate 29. The DC reverse-biased signal can be applied to the waveguide 22 through the metal electrode 28. Among them, the materials of the metal electrode 28 and the two high-frequency electrodes 20 and 21 can be metals such as aluminum, copper, and silver.

[0030] The sub-electrode 23 includes a main body 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 body portion 24 along the second direction Y, and the connecting portion 25 and the end portion 26 form a T-shaped structure. Among them, 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 towards the waveguide 22 and is connected to the waveguide 22. The first direction X is perpendicular to the second direction Y.

[0031] In one embodiment, in the first direction X, the total size L of the multiple sub-electrodes 23 mod is 1.5 mm to 3 mm.

[0032] In one embodiment, in the first direction X, the size L of a single main body portion 24 p1 is 30 μm to 70 μm. Among them, the size of a single main body portion 24 is equal to the arrangement period of the multiple sub-electrodes 23.

[0033] In one embodiment, in the first direction X, the size L of a single end portion 26p2 is 0.7 to 0.9 times the dimension L of the single main body portion 24 p1 .

[0034] In one embodiment, in the first direction X, the dimension L of the single connecting portion 25 p3 is less than the dimension L of the single end portion 26 p2 .

[0035] In one embodiment, in the second direction Y, the dimension W of the main body portion 24 m is 20 μm to 80 μm

[0036] In one embodiment, in the second direction Y, the dimension G of the connecting portion 25 t is 20 μm to 80 μm

[0037] In one embodiment, in the second direction Y, the dimension G of the end portion 26 p is 5 μm to 30 μm

[0038] In one embodiment, in the second direction Y, the distance G between the ends of the two high-frequency electrodes 20, 21 mt is 15 μm to 70 μm

[0039] In one embodiment, in the second direction Y, the distance G between the main body portions of the two high-frequency electrodes 20, 21 mm is 60 μm to 150 μm

[0040] In one embodiment, in the third direction Z, the thicknesses of the main body portion 24, the connecting portion 25, and the end portion 26 are all 2 μm to 15 μm. The third direction Z is perpendicular to the first direction X and the second direction Y

[0041] In this embodiment, the total dimension L of the multi-segment sub-electrode 23 mod is 2 mm, the dimension L of the main body portion 24 p1 is 50 μm, the dimension L of the end portion 26 p2 is 45 μm, the dimension L of the connecting portion 25 p3 is 10 μm, the dimension W of the main body portion 24 m is 50 μm, the dimension G of the connecting portion 25 t is 30 μm, the dimension G of the end portion 26 p is 10 μm, the distance G between the ends of the two high-frequency electrodes 20, 21 mt is 30 μm, the distance G between the main body portions of the two high-frequency electrodes 20, 21 mm is 110 μm. The thicknesses of the main body portion 24, the connecting portion 25, and the end portion 26 are 2 μm

[0042] In one embodiment, the multi-wavelength silicon optical emission chip 10 further includes a phase shifter 30 provided corresponding to the silicon optical modulator 15. The phase shifter 30 is located at a height of 2 μm to 5 μm above the waveguide 22. By changing the voltage applied to the phase shifter 30, the phase of the waveguide 22 and the operating point of the silicon optical modulator 15 are changed. The phase shifter 30 utilizes a TiN (titanium nitride) material to achieve its function. By changing the voltage applied to the TiN, the phase of the waveguide 22 and the operating point of the silicon optical modulator 15 can be dynamically changed, and the silicon optical modulator 15 can be made to be in an orthogonal operating point. That is, by changing the voltage applied to the phase shifter 30, the output optical power is changed. When the value of the optical power is half of the maximum optical power value, the silicon optical modulator 15 is in an orthogonal operating point.

[0043] In one embodiment, the silicon optical modulator 15 further includes a termination resistor 31. The material of the termination resistor 31 can be TiN. The termination resistor 31 is connected between two high-frequency electrodes 20 and 21 and is located on one side of the output end of the silicon optical modulator 15. The impedance value of the termination resistor 31 is 30 Ω to 70 Ω. In this embodiment, the impedance value of the termination resistor 31 is 40 Ω.

[0044] In one embodiment, the waveguide 22 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 Y. 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 26 is connected to the N++-type doped region. The reverse bias electrode 19 is connected to the P++-type doped region, where the metal electrode 28 of the reverse bias electrode 19 is connected to the P++-type doped region. Specifically, the end of the high-frequency electrode 20 is connected to the N++-type doped region on one side of the P++-type doped region, and the end of the high-frequency electrode 21 is connected to the N++-type doped region on the other side of the P++-type doped region. A DC reverse bias signal can be applied to the P++-type doped region of the waveguide 22 through the metal electrode 28 of the reverse bias electrode 19, a ground signal can be applied to the N++-type doped region on one side of the P++-type doped region through the end of the high-frequency electrode 20, and a high-frequency signal can be applied to the N++-type doped region on the other side of the P++-type doped region through the end of the high-frequency electrode 21. The silicon optical modulator 15 can adopt a series push-pull structure, that is, the reverse bias electrode 19 and the two high-frequency electrodes 20 and 21 can be symmetrically arranged with the central axis of the P++-type doped region as the axis of symmetry.

[0045] In one embodiment, the doping concentrations of the N-type doped region and the P-type doped region are in the order of 10 16 / cm 3 ~10 17 / cm 3 order of magnitude.

[0046] In one embodiment, the doping concentrations of the N+-type doped region and the P+-type doped region are in the order of 10 18 / cm3 ~10 19 / cm 3 order of magnitude

[0047] In one embodiment, the doping concentrations of the N++-type doped region and the P++-type doped region are in the range of 10 19 / cm 3~ 10 20 / cm 3 order of magnitude

[0048] In one embodiment, in the second direction Y, the lengths of the N-type doped region, the N+-type doped region, the P-type doped region, and the P+-type doped region are 0.4 μm to 2 μm. Among them, the lengths of the N-type doped region and the P-type doped region are approximately the same. The lengths of the N+-type doped region and the P+-type doped region are approximately the same. The lengths of the N-type doped region and the N+-type doped region may be the same or different.

[0049] In one embodiment, in the second direction Y, the lengths of the N++-type doped region and the P++-type doped region are greater than 5 μm. The lengths of the N++-type doped region and the P++-type doped region are different, and the length of the P++-type doped region may be 10 μm to 40 μm.

[0050] In one embodiment, a PN junction is formed between the P-type doped region and the N-type doped region, and a convex structure is formed at the PN junction. The high-frequency electrodes 20 and 21 are arranged on the same side as the convex structure. In the second direction Y, the length W of the PN junction wg is 380 nm to 550 nm. Among them, a thermal 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.

[0051] In one embodiment, in the third direction Z, the thicknesses 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 are all 60 nm to 120 nm. Among them, in the third direction Z, the thicknesses 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 are the same.

[0052] In one embodiment, in the third direction Z, the thickness H of the PN junction is 220 nm.

[0053] In this embodiment, the doping concentrations of the N-type doped region and the P-type doped region are in the range of 5×10 17 / cm 3 order of magnitude; the doping concentrations of the N+-type doped region and the P+-type doped region are in the range of 2×10 18 / cm 3Magnitude; the doping concentrations of the N++-type doping region and the P++-type doping region are on the order of 1×10 20 / cm 3 Magnitude; in the second direction Y, the lengths of the N-type doping region and the P-type doping region are 350 nm, and the lengths of the N+-type doping region and the P+-type doping region are 650 nm. In the second direction Y, the length of the P++-type doping region is 13 μm, and the length of the N++ doping region is 9 μm; in the second direction Y, the length W of the PN junction wg is 450 nm; in the third direction Z, the thicknesses 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 rib are all 90 nm; in the third direction Z, the thickness H of the PN junction is 220 nm.

[0054] See Figure 4 as shown Figure 4 (a) is a simulation effect 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. From Figure 4 (a), it can be seen that at different positions of the waveguide 22, the N-type carrier concentration in the waveguide 22 changes, so that a junction capacitance and a PN junction impedance can be generated, providing a basis for the realization of the silicon optical modulator 15.

[0055] Figure 4 (b) is a relationship curve diagram of the junction capacitance value of the PN junction and the DC reverse bias voltage applied to the waveguide 22. From Figure 4 (b), it can be seen that in the direction of the DC reverse bias voltage from 0 to -6V, the junction capacitance value of the PN junction also gradually becomes smaller, making the RC time constant smaller, so that the bandwidth of the silicon optical modulator 15 can be increased. As the absolute value of the DC reverse bias voltage increases, the reverse bias degree deepens, but the change degree of the junction capacitance value of the PN junction becomes smaller and smaller. At the same time, the increase in the absolute value of the DC reverse bias voltage may cause avalanche breakdown. Therefore, the DC reverse bias voltage is selected to be -4V. At this time, the junction capacitance value of the PN junction is about 0.075 fF / μm.

[0056] Figure 4 (c) is a relationship curve diagram of the phase shift of the silicon optical modulator 15 and the DC reverse bias voltage applied to the waveguide 22. When the total size L mod of the multi-segment sub-electrode 23 is 2 mm and the DC reverse bias voltage applied to the waveguide 22 is -4V, the phase shift of the silicon optical modulator 15 is 0.7556 rad. Thus, it can be known that the modulation efficiency of the silicon optical modulator 15 is .

[0057] Figure 4 (d) is a relationship curve diagram of the group refractive index of the optical signal and the DC reverse bias voltage applied to the waveguide 22. From Figure 4As can be seen from (d), the group refractive index of the optical signal hardly changes with the variation of the DC reverse bias voltage, and the value of the group refractive index of the optical signal is approximately 3.9360. Thus, when designing the electrodes of the silicon optical modulator 15, if the effective refractive index of the microwave is close to the group refractive index of the optical signal, the silicon optical modulator 15 can have a higher electro-optical bandwidth.

[0058] See Figure 5 and Figure 6 as shown in Figure 5 In the design, Design a is the silicon optical modulator 15 of this embodiment, and Design b and Design c are two traditional MZ (Mach-Zehnder) modulators. In Design b, the width W of the electrode metal is 90 μm, the distance G between the two electrodes space is 30 μm, and the total size L of the electrode mod is 2 mm; in Design c, W metal is 50 μm, G space is 110 μm, and L mod is 2 mm. Among them, the G of Design a mt is the same as the G in Design b space , and the W of Design a m is the same as the W in Design c metal .

[0059] Figure 5 Figure (a) is a curve graph showing the relationship between the effective refractive index of the microwave and the signal frequency of the three modulators. As can be seen from Figure 5 Figure (a), the effective refractive index of Design a is between 3.4 and 3.6, and is closer to the group refractive index of the optical signal, which is 3.9360, compared with Design b and Design c. Therefore, the silicon optical modulator 15 of this embodiment has a higher electro-optical bandwidth.

[0060] Figure 5 Figure (b) is a curve graph showing the relationship between the impedance of the three modulators and the high-frequency signal frequency. As can be seen from Figure 5 Figure (b), when the terminal resistance 31 is selected as 40 Ω, the impedance of Design a is approximately 75 Ω. If the impedance value of the terminal resistance 31 is low, the silicon optical modulator 15 will have a higher electro-optical bandwidth. However, the impedance value of the terminal resistance 31 cannot be too low, otherwise, the electrical signal loss of the microwave in the metal will be large, resulting in a large microwave loss of the silicon optical modulator 15. Therefore, it is more appropriate to select the terminal resistance 31 as 40 Ω.

[0061] Figure 5 Figure (c) is a curve graph showing the relationship between the microwave loss of the three modulators and the high-frequency signal frequency. As can be seen from Figure 5As can be seen from (c), at a high-frequency signal of 50 GHz, the microwave loss of Design a is approximately 3.5 dB / mm, which is between that of Design b and Design c. This indicates that the silicon optical modulator 15 in this embodiment has a relatively small microwave loss.

[0062] Figure 5 (d) is a graph showing the relationship between the electro-optic response of the three modulators and the high-frequency signal frequency. As can be seen from Figure 5 (d), when the electro-optic response is -3 dB, the signal frequency of Design a is 55 GHz at this time, indicating that the electro-optic bandwidth of the device can reach 55 GHz, while the electro-optic bandwidths of the other two designs are only approximately 43 GHz and 48 GHz. This shows that the electro-optic bandwidth of the silicon optical modulator 15 in the embodiment of the present invention is significantly improved, which can also be verified from Figure 5 (a).

[0063] Compared with the traditional MZ modulator, the silicon optical modulator 15 in the embodiment of the present invention significantly increases the electro-optic bandwidth while keeping the microwave loss and modulation efficiency basically unchanged, thereby accelerating the transmission rate of high-frequency signals, effectively realizing the high-speed transmission of 100 Gbps PAM4 signals, and achieving high-speed signal modulation.

[0064] See 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 oppositely, and the sub-wavelength grating group 33 includes a plurality of sub-wavelength grating structures 34 arranged at intervals in the length direction of the main structure 32. The arrangement period Period of the sub-wavelength grating structure 34 is 150 nm to 200 nm.

[0065] In one embodiment, the length of the main structure 32 is 30 μm to 50 μm, the width of the main structure 32 is 1 μm to 3 μm, and the length of the main structure 32 is proportional to the square of the width of the main structure 32.

[0066] In one embodiment, the distance W sep between the two sub-wavelength grating groups 33 is one-third of the width of the main structure 32. In this case, the first multimode interference coupler 12 has a relatively large power splitting ratio for optical signals in the dual bands of 1.22 μm to 1.37 μm and 1.45 μm to 1.57 μm.

[0067] In one embodiment, the shape of the sub-wavelength grating structure 34 is trapezoidal. The upper base length and the lower base length of the trapezoid are 0.3 times to 0.7 times the arrangement period of the sub-wavelength grating structure.

[0068] In one embodiment, the height of the trapezoid is sized from 30 nm to 100 nm.

[0069] In one embodiment, the main structure 32 includes a core layer portion 35 and a cladding layer portion 36 coated on the outer surface of the core layer portion 35. The material of the core layer portion 35 is silicon, and the material of the cladding layer portion 36 is silicon dioxide. That is, the structure of the main structure 32 is SOI (Silicon On Insulator), and adopting the SOI structure can significantly reduce the size of the main structure 32. Among them, the processing of the main structure 32 can be realized through integrated circuit processes.

[0070] In one embodiment, in the thickness direction of the main structure 32, the size h of the core layer portion 35 is from 220 nm to 400 nm. In this embodiment, the size h of the core layer portion 35 is 220 nm.

[0071] In one embodiment, the main structure 32 is provided with a plurality of through grooves, each through groove corresponding to a sub-wavelength grating structure 34, and silicon dioxide materials are filled in the plurality of through grooves to form two sub-wavelength grating groups 33.

[0072] The input waveguide 11 inputs optical signals in a dual-band of 1.22 - 1.37 μm and 1.45 - 1.57 μm. Hereinafter, the input wavelengths of 1310 nm and 1550 nm are taken as examples for illustration. To separate the two bands, the length L of the traditional multimode interference coupler MMI needs to satisfy the expression:

[0073] where is the beat length of the multimode interference coupler, ; n eff0 (λ) is the effective refractive index of the optical signal TE0 mode at the input wavelength in the multimode interference coupler, and n eff1 (λ) is the effective refractive index of the optical signal TE1 mode at the input wavelength in the multimode interference coupler; λ is the input wavelength, which are 1310 nm and 1550 nm respectively here. Among them, p and q are relatively prime, and L MMI is the corresponding to the wavelength of 1310 nm and the corresponding to the wavelength of 1550 nm. Since the wavelengths of 1310 nm and 1550 nm are relatively close and the least common multiple is large, the length of the traditional multimode interference coupler is long.

[0074] In this embodiment, the arrangement period of the sub-wavelength grating structure 34 is 180 nm; the upper base length L2 of the trapezoid is 0.53 × Period = 95.4 nm; the lower base length L1 of the trapezoid is 0.58 × Period = 104.4 nm; the height size W of the trapezoidswg is 50 nm; when the wavelength is 1310 nm, n eff0 (1310 nm) = 2.894, n eff1 (1310 nm) = 2.858, L π1 (1310 nm) = ≈18.3 μm; when the wavelength is 1550 nm, n eff0 (1550 nm) = 2.721, n eff1 (1550 nm) = 2.657, L π2 (1550 nm) = ≈12.2 μm. Thus, the length L MMI of the main body structure 32 = 2L π1 (1310 nm) = 3L π2 (1550 nm) = 36.6 μm, the length L MMI of the first multimode interference coupler 12 in this embodiment is 36.6 μm, which can achieve the separation of two wavelength bands and effectively shorten the length of the first multimode interference coupler 12.

[0075] See Figure 9 as shown Figure 9 shows the relationship diagram between the output power of two channels of the first multimode interference coupler 12 of the multi-wavelength silicon optical emission chip 10 and the wavelength. The two channels 37, 38 of the first multimode interference coupler 12 are respectively connected to two transmission paths 13, 14. Channel 37 is connected to transmission path 13, and channel 38 is connected to transmission path 14. As Figure 9 can be seen, near the wavelength of 1310 nm, the output power value of channel 37 is the largest, which is about 29.3 dB larger than the output power value of channel 38, that is, the crosstalk value is about -29.3 dB. Near the wavelength of 1550 nm, the output power value of channel 38 is the largest, which is about 12.3 dB larger than the output power value of channel 37, that is, the crosstalk value is about -12.3 dB. This shows that there is a low crosstalk between the two channels 37, 38 of the first multimode interference coupler 12. And near the wavelength of 1310 nm, the wavelength range corresponding to the 1 dB bandwidth of the first multimode interference coupler 12 is 1243 nm ~ 1350 nm. Among them, the 1 dB bandwidth refers to the wavelength value corresponding to the output power dropping by 1 dB at the peak. Near the wavelength of 1550 nm, the wavelength range corresponding to the 1 dB bandwidth of the first multimode interference coupler 12 is 1480 nm ~ 1557 nm. This shows that the wavelength range corresponding to the 1 dB bandwidth of the first multimode interference coupler 12 is at least greater than 70 nm. The first multimode interference coupler 12 has the advantages of low crosstalk and large working bandwidth, and can effectively separate the two wavelengths of 1310 nm and 1550 nm.

[0076] See Figure 10 as shown Figure 10 In Figure 10 , the abscissa is the length direction of the first multimode interference coupler 12, i.e., the light propagation direction. The ordinate is the width direction of the first multimode interference coupler 12. Figure 10 Figure (a) is the corresponding simulation result diagram when the input wavelength is 1310 nm Figure 10 Figure (b) is the corresponding simulation result diagram when the input wavelength is 1550 nm. From Figure 10 Figure (a), it can be seen that the optical power signal is output along channel 37. From Figure 10 Figure (b), it can be seen that the optical power signal is mainly output along channel 38.

[0077] The first multimode interference coupler 12 of the embodiment of the present invention includes a main structure 32 and two sub-wavelength grating groups 33 provided on the main structure 32. The sub-wavelength grating group 33 includes a plurality of sub-wavelength grating structures 34 arranged at intervals in the length direction of the main structure 32. In this way, while shortening the length of the first multimode interference coupler 12, dual-band and low-crosstalk optical signal separation can be achieved. At the same time, the shape of the sub-wavelength grating structure 34 is trapezoidal. When the upper base length and the lower base length of the trapezoidal structure change, compared with the change of the upper side length and the lower side length of the rectangular structure, the influence on the change of the effective refractive index of the sub-wavelength grating structure 34 is smaller, and the size of the trapezoid is dynamically adjustable. In this way, the correlation between the effective refractive index and the shape of the sub-wavelength grating structure 34 can be effectively reduced, the process tolerance is increased, and the influence of the process preparation on the first multimode interference coupler 12 is reduced.

[0078] It should be understood that the various forms of the processes shown above can be used, steps can be reordered, added or deleted. For example, the steps recorded in the present invention disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is made herein.

[0079] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A multi-wavelength silicon optical emission chip, characterized in that Comprising: An input waveguide for inputting optical signals of two bands; A first multimode interference coupler connected to the input waveguide for distributing the optical signals of two bands from the input waveguide to two transmission paths; each of the two transmission paths includes a silicon optical modulator and two second multimode interference couplers; the silicon optical modulator is connected between the two second multimode interference couplers through 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 multiple sub-electrodes arranged along a first direction. The sub-electrode includes a main body portion, a connecting portion, and an end portion; the connecting portion and the end portion are connected to one side of the main body portion along a second direction, and the connecting portion and the end portion form a T-shaped structure; the end portion extends towards the waveguide and is connected to the waveguide; the first direction is perpendicular to the second direction.

2. The multi-wavelength silicon optical emission chip according to claim 1, wherein The high-frequency electrode further includes a first metal plate for connecting to a high-frequency probe, and the first metal plate is connected to one side of the multiple sub-electrodes along the first direction.

3. The multi-wavelength silicon optical emission chip according to claim 1, wherein, 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, and the second metal plate is connected to the metal electrode to input a DC reverse bias signal to the metal electrode through the second metal plate.

4. The multi-wavelength silicon optical emission chip according to claim 1, wherein The silicon optical modulator further includes a termination resistor, which is connected between the two high-frequency electrodes and is located on one side of the output end of the silicon optical modulator; the impedance value of the termination resistor is 30Ω - 70Ω.

5. The multi-wavelength silicon optical emission chip according to claim 1, wherein It further includes a phase shifter provided corresponding to the silicon optical modulator. The phase shifter is located at a height of 2μm - 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 optical modulator are changed.

6. The multi-wavelength silicon optical emission 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 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; The doping concentrations of the N-type doping region and the P-type doping region are in the range of 10 16 / cm 3 ~10 17 / cm 3 order of magnitude; and / or The doping concentrations of the N+-type doping region and the P+-type doping region are in the range of 10 18 / cm 3 ~10 19 / cm 3 order of magnitude; and / or The doping concentrations of the N++-type doped region and the P++-type doped region are in the order of 10 19 / cm 3~ 10 20 / cm 3 magnitude; and / or In the second direction, the lengths of the N-type doped region, the N+-type doped region, the P-type doped region, and the P+-type doped region are 0.4μm - 2μm; And / or In the second direction, the lengths of the N++-type doped region and the P++-type doped region are greater than 5μm.

7. The multi-wavelength silicon optical emission chip according to claim 1, wherein In the first direction, the total size of the multiple sub-electrodes is 1.5mm - 3mm; and / or In the first direction, the size of a single main body portion is 30μm - 70μm; and / or In the first direction, the size of a single end portion is 0.7 times - 0.9 times the size of a single main body portion; and / or In the second direction, the size of the main body portion is 20μm - 80μm; 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 optical emission 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 oppositely. The sub-wavelength grating group includes a plurality of sub-wavelength grating structures arranged at intervals in the length direction of the main structure; the arrangement period of the sub-wavelength grating structures is 150 nm to 200 nm; 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 optical emission chip according to claim 8, wherein The shape of the sub-wavelength grating structure is trapezoidal; The length of the upper base of the trapezoid and the length of the lower base of the trapezoid are 0.3 times to 0.7 times the arrangement period of the sub-wavelength grating structure; and / or The size of the height of the trapezoid is 30 nm to 100 nm.

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

Images