Graphene all-optical modulator and its applications

Abstract

The present invention relates to the technical field of devices for light modulation, and discloses a graphene all-optical modulator and its application. The graphene all-optical modulator comprises a thin silicon slot waveguide, a mode converter unit and a silicon dioxide substrate, wherein the thin silicon slot waveguide and the mode converter unit are located on the silicon dioxide substrate; a group of mode converter units are respectively connected to both sides of the thin silicon slot waveguide, and the two groups of mode converter units are symmetrically distributed on both sides of the thin silicon slot waveguide; the thin silicon slot waveguide is covered with a graphene-hexagonal boron nitride heterojunction. It can effectively enhance the interaction between light and matter, realize efficient all-optical modulation, and has ultrafast response time and broadband modulation capability, providing new possibilities for the development of optical communication and optical information processing technology, and is of great significance to the development of ultrafast and low-energy silicon-based optoelectronic chips.

Description

Technical Field

[0001] The present invention relates to the technical field of devices for light modulation, and in particular to a graphene all-optical modulator and applications thereof. Background Art

[0002] With the rapid development of communication technology, the performance requirements of optical modulators are increasing, especially in terms of compactness, response speed, switching energy and modulation efficiency. Traditional electro-optic modulators face many limitations in high-frequency applications, such as RC time constant limitations and the bulky size, high cost and difficulty of integration of lithium niobate modulators. These limitations have prompted researchers to seek new materials and technologies to meet the needs of modern optical communications. Summary of the invention

[0003] The present invention provides a graphene all-optical modulator and application thereof, so as to solve the technical problems of existing optical modulators, such as bulky volume, high cost and great integration difficulty.

[0004] According to one aspect of the present invention, a graphene all-optical modulator is provided, comprising a thin silicon slot waveguide, a mode converter unit and a silicon dioxide substrate, wherein the thin silicon slot waveguide and the mode converter unit are located on the silicon dioxide substrate; a group of mode converter units are respectively connected to both sides of the thin silicon slot waveguide, and the two groups of mode converter units are symmetrically distributed on both sides of the thin silicon slot waveguide; and the thin silicon slot waveguide is covered with a graphene-hexagonal boron nitride heterojunction.

[0005] Furthermore, the mode converter unit includes a thin silicon grating coupler, a thin silicon straight waveguide and a thin silicon mode converter, the thin silicon grating coupler is connected to the thin silicon straight waveguide, the thin silicon straight waveguide is connected to the thin silicon mode converter, and the thin silicon mode converter is connected to the thin silicon slot waveguide.

[0006] Further, the height h1 of the thin silicon grating coupler is consistent with the height h3 of the thin silicon slot waveguide.

[0007] Furthermore, the etching of the thin silicon grating coupler is full etching, and the etching depth is h1.

[0008] Further, the height h2 of the thin silicon straight waveguide is consistent with the height h3 of the thin silicon slot waveguide.

[0009] Furthermore, the coverage area of ​​the graphene-hexagonal boron nitride heterojunction is the same as that of the thin silicon slot waveguide.

[0010] Furthermore, the width w1 of the thin silicon slot waveguide is 10nm-30nm, the width w2 of the silicon column of the thin silicon slot waveguide is 300nm-400nm; and / or the height h1 of the thin silicon grating coupler, the height h2 of the thin silicon straight waveguide, the height h4 of the thin silicon mode converter and the height h3 of the thin silicon slot waveguide are equal, all of which are 50nm-150nm; and / or the conversion length L1 of the thin silicon mode converter is 500mm-700nm.

[0011] According to another aspect of the present invention, there is also provided an application of using the above-mentioned graphene all-optical modulator to couple the mode in the optical fiber into a thin silicon slot waveguide, input the signal light and the pump light into the optical fiber, couple the signal light and the pump light into the thin silicon straight waveguide through a thin silicon grating coupler, and couple them into the thin silicon slot waveguide through a thin silicon mode converter.

[0012] According to another aspect of the present invention, there is also provided an application of all-optical modulation using the above-mentioned graphene all-optical modulator, comprising the following steps: S100, inputting signal light and pump light into optical fiber; S200, inputting the optical signal into a mode converter unit for coupling and mode conversion of the optical signal, and inputting it into a thin silicon slot waveguide; S300, in the thin silicon slot waveguide, due to the Pauli exclusion principle of the graphene material, the signal light with low energy is modulated by the pump light with high energy; S400, in the same manner as the method of inputting the optical signal into the mode converter unit in steps S100 to S300, the modulated optical signal is output from the other end of the thin silicon slot waveguide through a symmetrical mode converter unit and coupled to the optical fiber.

[0013] Further, in step S200, the optical signal is input into the mode converter unit for mode conversion and input into the thin silicon slot waveguide, specifically including: S201, coupling the optical signal into the thin silicon grating coupler; S202, the optical signal enters the thin silicon mode converter through the thin silicon straight waveguide; S203, the optical signal is converted into an optical signal in the thin silicon slot waveguide in the thin silicon mode converter, thereby completing the mode conversion; S204, the optical signal after mode conversion is input into the thin silicon slot waveguide.

[0014] The present invention has the following beneficial effects:

[0015] The graphene all-optical modulator of the present invention, the thin silicon slot waveguide can concentrate the light field mainly in the slot with low refractive index. Compared with the silicon strip waveguide, the light field intensity in the slot is enhanced, and the effective mode area of ​​the light field is reduced, which is beneficial to improve the efficiency of the interaction between light and matter; the mode converter unit uses the thermo-optical effect and nonlinear effect of graphene to achieve efficient optical signal modulation; two groups of mode converter units are symmetrically distributed on both sides of the thin silicon slot waveguide, which can achieve efficient conversion between different modes, and the final signal is transmitted through the mode converter unit at the other end (such as: thin silicon mode converter and thin silicon grating coupling The graphene-hexagonal boron nitride heterojunction is covered on the thin silicon slot waveguide, and the nonlinear absorption characteristics of graphene can be utilized. For example, due to the Pauli exclusion principle of graphene, when graphene absorbs high-energy pump light, it will no longer absorb low-energy signal light, allowing the signal light to pass through, and vice versa, thereby realizing the use of pump light to control the signal light and achieving efficient all-optical modulation. The modulator of this structure shows significant advantages in response time, loss, driving energy, extinction ratio and modulation depth; graphene has an ultra-wide working frequency band (300-6000 nm), and has been realized in broadband supercontinuum all-optical fiber modulators and ultra-wideband absorbers, which enables graphene-based all-optical modulators to cover a wide wavelength range and be suitable for a variety of communication windows; the time for photogenerated carrier generation-recombination in graphene is only a few picoseconds, with an ultrafast relaxation process, which makes it possible to realize ultrafast all-optical modulators; combining the accelerated cooling of graphene electrons by hexagonal boron nitride with the enhancement of the interaction between light and graphene after waveguide optimization parameters, it has high modulation efficiency and fast cooling time, which is of great significance for the development of ultrafast and low-energy silicon-based optoelectronic chips. In summary, the structural design of graphene all-optical modulators can effectively enhance the interaction between light and matter, realize efficient all-optical modulation, and have ultrafast response time and broadband modulation capabilities, which provides new possibilities for the development of optical communication and optical information processing technology, and is of great significance for the development of ultrafast and low-energy silicon-based optoelectronic chips.

[0016] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 This is a schematic diagram of the structure of a graphene all-optical modulator provided in Example 1 of the present invention;

[0019] Figure 2This is a partial enlarged view of a thin silicon slot waveguide in a graphene all-optical modulator provided in Example 1 of the present invention;

[0020] Figure 3 A graph showing the relationship between the modulation efficiency and the cross-sectional parameters of a graphene all-optical modulator provided in Example 1 of the present invention;

[0021] Figure 4 It is the optical mode of the 1550nm wavelength of the thin silicon straight waveguide in Example 1 of the present invention. This mode is the TE mode in the 100×1000nm² thin silicon waveguide. This mode can exist stably in the waveguide, and the height of 100nm is the same as the height of the modulator body, which is convenient for mass processing and transfer of heterojunctions.

[0022] Figure 5 It is the optical mode of the thin silicon slot waveguide with a wavelength of 1550nm in Example 1 of the present invention. This mode is the TE mode in the thin slot silicon waveguide of 100×20nm². This mode can exist stably in the waveguide with low loss and can enhance the interaction between light and heterojunction, thereby increasing the modulation efficiency.

[0023] Legend:

[0024] 100. Thin silicon slot waveguide; 200. Mode converter unit; 201. Thin silicon grating coupler; 202. Thin silicon straight waveguide; 203. Thin silicon mode converter; 300. Silicon dioxide substrate; 400. Graphene-hexagonal boron nitride heterojunction. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0026] Figure 1 This is a schematic diagram of the structure of a graphene all-optical modulator provided in Example 1 of the present invention; Figure 2 This is a partial enlarged view of a thin silicon slot waveguide in a graphene all-optical modulator provided in Example 1 of the present invention; Figure 3 A graph showing the relationship between the modulation efficiency and the cross-sectional parameters of a graphene all-optical modulator provided in Example 1 of the present invention; Figure 4 It is the TE mode of the thin silicon straight waveguide with a wavelength of 1550nm in Example 1 of the present invention. This mode has stable transmission, and the cross-sectional height of the silicon waveguide is consistent with the overall structure of the device, which is convenient for processing and manufacturing; Figure 5 This is the TE mode of the thin silicon slot waveguide with a wavelength of 1550nm in Example 1 of the present invention. This mode has stable transmission, and under this cross-sectional parameter, there is a stronger interaction between light and matter to improve the modulation efficiency of the device.

[0027] like Figure 1As shown, the graphene all-optical modulator of this embodiment includes a thin silicon slot waveguide 100, a mode converter unit 200 and a silicon dioxide substrate 300. The thin silicon slot waveguide 100 and the mode converter unit 200 are located on the silicon dioxide substrate 300; a group of mode converter units 200 are connected to both sides of the thin silicon slot waveguide 100, respectively, and the two groups of mode converter units 200 are symmetrically distributed on both sides of the thin silicon slot waveguide 100; the thin silicon slot waveguide 100 is covered with a graphene-hexagonal boron nitride heterojunction 400. In the graphene all-optical modulator of the present invention, the thin silicon slot waveguide 100 can concentrate the light field mainly in the slot with a low refractive index. Compared with the silicon strip waveguide, the light field intensity in the slot is enhanced, and the effective mode area of ​​the light field is reduced, which is beneficial to improving the efficiency of the interaction between light and matter; the mode converter unit 200 utilizes the thermo-optical effect and nonlinear effect of graphene to achieve efficient optical signal modulation; two groups of mode converter units 200 are symmetrically distributed on both sides of the thin silicon slot waveguide 100, which can achieve efficient conversion between different modes, and finally the signal is transmitted through the mode converter unit 200 at the other end (such as: thin silicon mode converter 203 and thin Silicon grating coupler 201) outputs to the optical fiber; graphene-hexagonal boron nitride heterojunction 400 is covered on the thin silicon slot waveguide 100, and the nonlinear absorption characteristics of graphene can be utilized. For example, due to the Pauli exclusion principle of graphene, when graphene absorbs high-energy pump light, it will no longer absorb low-energy signal light, allowing the signal light to pass through, and vice versa, thereby realizing the use of pump light to control the signal light and realize efficient all-optical modulation. The modulator of this structure shows significant advantages in response time, loss, driving energy, extinction ratio and modulation depth; graphene has an ultra-wide operating frequency band (300-6000 nm), and has been realized in broadband supercontinuum all-optical fiber modulators and ultra-wideband absorbers, which enables graphene-based all-optical modulators to cover a wide wavelength range and be suitable for a variety of communication windows; the time for photogenerated carrier generation-recombination in graphene is only a few picoseconds, with an ultrafast relaxation process, which makes it possible to realize ultrafast all-optical modulators; combining the accelerated cooling of graphene electrons by hexagonal boron nitride with the enhancement of the interaction between light and graphene after waveguide optimization parameters, it has high modulation efficiency and fast cooling time, which is of great significance for the development of ultrafast and low-energy silicon-based optoelectronic chips. In summary, the structural design of graphene all-optical modulators can effectively enhance the interaction between light and matter, realize efficient all-optical modulation, and have ultrafast response time and broadband modulation capabilities, which provides new possibilities for the development of optical communication and optical information processing technology, and is of great significance for the development of ultrafast and low-energy silicon-based optoelectronic chips.

[0028] As a two-dimensional material with excellent physical and chemical properties, graphene has a unique zero-bandgap structure, high electrical conductivity and high thermal conductivity, which makes it perform well in light-matter interaction and nonlinear optical effects, and can theoretically achieve extremely high modulation speed. Graphene modulators not only have advantages in speed, but also can adjust their optical properties through electric field regulation, chemical doping and other methods, providing new possibilities for improving the performance of all-optical modulators. Compared with traditional modulators, graphene-based all-optical modulators show significant advantages in response time, loss, driving energy, extinction ratio and modulation depth. With the continuous maturity of graphene production technology and the continuous discovery of new two-dimensional materials, graphene-based all-optical modulators are expected to play a key role in optical communication systems and promote the development of all-optical signal processing technology. Graphene all-optical modulators can not only meet the growing communication needs, but also find wide applications in artificial intelligence, ultra-sensitive sensors and high-density data storage. Therefore, the research on graphene all-optical modulators is not only of great theoretical significance, but also provides broad prospects for practical applications.

[0029] like Figure 1As shown, in this embodiment, the mode converter unit 200 includes a thin silicon grating coupler 201, a thin silicon straight waveguide 202 and a thin silicon mode converter 203, the thin silicon grating coupler 201 is connected to the thin silicon straight waveguide 202, the thin silicon straight waveguide 202 is connected to the thin silicon mode converter 203, and the thin silicon mode converter 203 is connected to the thin silicon slot waveguide 100. The thin silicon grating coupler 201 is responsible for efficiently coupling light from the optical fiber or free space into the thin silicon straight waveguide 202. This coupling method can reduce the loss of light when entering the waveguide structure and improve the transmission efficiency of light. The thin silicon straight waveguide 202 serves as a channel for the transmission of optical signals, and transmits the optical signal coupled from the thin silicon grating coupler 201 to the thin silicon mode converter 203. The design of the straight waveguide helps to maintain the intensity and phase of the optical signal and reduce the loss during the transmission process. The function of the thin silicon mode converter 203 is to convert the optical mode in the thin silicon straight waveguide 202 into a mode suitable for transmission in the thin silicon slot waveguide 100. This mode conversion is crucial to achieving effective docking between different waveguide structures and efficient transmission of optical signals. The thin silicon slot waveguide 100 can transmit light due to its unique structure. The field is confined to a very small area, thereby enhancing the interaction between light and the graphene-hexagonal boron nitride heterojunction 400 covering it, and this enhanced interaction is conducive to achieving efficient all-optical modulation; through the combination of the above structures, the entire process from light input, transmission to mode conversion can be realized, and finally all-optical modulation is achieved on the thin silicon slot waveguide 100, and the nonlinear absorption characteristics of graphene, such as the saturation absorption effect, can be used to achieve intensity or phase modulation of the optical signal; the design of the entire mode converter unit 200 is compact and easy to integrate into larger-scale photonic integrated circuits, which helps to achieve high-performance, low-cost optical communication systems; due to the high carrier mobility and ultrafast relaxation time of graphene, this graphene-based all-optical modulator can achieve fast response and high modulation efficiency.

[0030] like Figure 1As shown, in this embodiment, the height h1 of the thin silicon grating coupler 201 is consistent with the height h3 of the thin silicon slot waveguide 100. The consistency of the height of the thin silicon grating coupler 201 and the thin silicon slot waveguide 100 helps to achieve better mode matching, thereby improving the coupling efficiency of light from the grating coupler to the waveguide, because the design of the thin silicon grating coupler 201 needs to be exactly the same as the waveguide device to reduce the distortion during synthesis, and the height consistency is one of the key factors to achieve this goal; there is usually a certain distance between the thin silicon grating coupler 201 and the thin silicon slot waveguide 100 to reduce the mode mismatch. When the height of the thin silicon grating coupler 201 and the thin silicon slot waveguide 100 is the same, this mismatch can be further reduced, thereby reducing the additional loss and improving the coupling efficiency. Optionally, the arc grating coupler utilizes the optical focusing characteristics of the circular or elliptical structure. All the arc lines have a common focus, and the waveguide is placed at this focus, which greatly reduces the spacing between the grating area and the waveguide. When the height of the thin silicon grating coupler 201 is consistent with that of the thin silicon slot waveguide 100, the spacing between them can be further reduced, the integration density can be increased, and the additional loss between the waveguide and the waveguide can be reduced. In the all-optical modulator, the height of the thin silicon grating coupler 201 is consistent with that of the thin silicon slot waveguide 100, which helps to improve the modulation efficiency. The thin silicon grating coupler 201 is responsible for effectively transmitting the optical signal to the thin silicon slot waveguide 100, while the thin silicon slot waveguide 100 is responsible for transmitting the optical signal to the modulation area. The high consistency helps to maintain the intensity and phase of the optical signal, thereby improving the modulation efficiency.

[0031] like Figure 1 As shown, in this embodiment, the etching of the thin silicon grating coupler 201 is full etching, and the etching depth is h1. Full etching processing (for example, reactive ion etching (RIE) method) can combine the advantages of physical and chemical etching, significantly improve the etching rate, increase the ability of anisotropic downward etching, and facilitate the formation of a thin silicon grating coupler 201 with a high aspect ratio and a vertical sidewall structure; the etching depth h1 has a great influence on the coupling efficiency. When the etching depth reaches a certain optimal value, which is the same as the height h1 of the thin silicon grating coupler 201, the coupling efficiency is the maximum. Accurately controlling the etching depth h1 helps to achieve the best coupling efficiency, which can reduce unnecessary reflections and improve the transmission efficiency of light; the thin silicon grating coupler 201 with a full etching structure can be manufactured by one-step overlay and can be integrated with other devices, which improves the integration and is compatible with CMOS technology; full etching can reduce the microscopic load effect, make the etching depth of different regions more uniform, and help improve the performance of the grating coupler.

[0032] like Figure 1As shown, in this embodiment, the height h2 of the thin silicon straight waveguide 202 is consistent with the height h3 of the thin silicon slot waveguide 100. The high consistency helps to achieve better mode matching, thereby improving the coupling efficiency of light from the straight waveguide to the slot waveguide. This is because in the conversion between waveguides, the continuity and consistency of the mode are crucial to reducing mode mismatch and improving transmission efficiency; in the waveguide, the transmission loss of light is related to the height of the waveguide. When the height h2 of the thin silicon straight waveguide 202 is the same as the height h3 of the thin silicon slot waveguide 100, the transmission loss caused by mode discontinuity can be reduced, thereby improving the overall transmission efficiency; the high consistency simplifies the device design, and the same manufacturing process can be used to process the two waveguides, which helps The invention is useful for reducing the complexity and cost of the manufacturing process; in integrated photonics, highly consistent waveguides can be more easily integrated on the same chip, which is very important for realizing high-density integration and multifunctional integrated photonic circuits; the dispersion characteristics of the waveguide include material dispersion, waveguide dispersion and inter-mode dispersion. When the height h2 of the thin silicon straight waveguide 202 is consistent with the height h3 of the thin silicon slot waveguide 100, these dispersion characteristics can be better controlled and utilized, especially in applications in the 2μm band; highly consistent waveguides help control the polarization characteristics of the waveguide, which is very important for realizing polarization-independent devices or polarization-sensitive applications.

[0033] like Figure 1As shown, in this embodiment, the coverage area of ​​the graphene-hexagonal boron nitride heterojunction 400 is the same as the area of ​​the thin silicon slot waveguide 100. The graphene-hexagonal boron nitride heterojunction 400 covers the entire surface of the thin silicon slot waveguide 100, which can maximize the interaction between light and graphene, which is very important for improving the efficiency and speed of the modulator; because graphene has high electron mobility and thermal conductivity, the heterojunction formed with hexagonal boron nitride can exhibit excellent nonlinear optical properties, and this structure helps to achieve efficient all-optical modulation; the ultra-wide operating frequency band of graphene (300-6000 nm) enables graphene-based all-optical modulators to cover a wide wavelength range and be suitable for a variety of communication windows; the time for photogenerated carrier generation and recombination in graphene is very short, only a few picoseconds, which makes it possible to achieve ultrafast all-optical modulation; the graphene-hexagonal boron nitride heterojunction 400 can enhance the nonlinear effect, which is beneficial to the realization of wavelength conversion, optical frequency comb, optical logic and other applications; hexagonal boron nitride as a graphene substrate can maintain the high mobility and other characteristics of graphene, which is beneficial to improve the performance of electronic components; hexagonal boron nitride as a graphene substrate can destroy the spatial inversion symmetry of graphene, thereby opening the band gap of graphene, which is beneficial to the manufacture of semiconductor components; the atomic-level seamless connection between graphene and hexagonal boron nitride greatly reduces the electron scattering at the edge of the graphene domain, ensuring a higher carrier mobility. The complete coverage of the graphene-hexagonal boron nitride heterojunction 400 and the thin silicon slot waveguide 100 can significantly improve the performance of the optical modulator, including modulation efficiency, speed and nonlinear effects, which is of great significance to the development of optical communication and optical information processing technology.

[0034] like Figure 1 and Figure 2As shown, in this embodiment, the width w1 of the thin silicon slot waveguide 100 is 10nm-30nm, and the width w2 of the silicon column of the thin silicon slot waveguide 100 is 300nm-400nm; and / or the height h1 of the thin silicon grating coupler 201, the height h2 of the thin silicon straight waveguide 202, the height h4 of the thin silicon mode converter 203 and the height h3 of the thin silicon slot waveguide 100 are equal, all of which are 50nm-150nm; and / or the conversion length L1 of the thin silicon mode converter 203 is 500mm-700nm. The width w1 of the thin silicon slot waveguide 100 is 10nm-30nm, which helps to limit the propagation of the light mode in the waveguide, increase the intensity of the light field, and thus improve the efficiency of the interaction between light and matter. The width w2 of the silicon column is 300nm-400nm, which affects the power limiting factor of the waveguide, that is, the distribution of the optical power in the waveguide. By adjusting the width of the silicon column, the nonlinear effect and light limiting ability of the waveguide can be optimized. The heights h1, h2, h4, and h3 of the thin silicon grating coupler 201, the thin silicon straight waveguide 202, the thin silicon mode converter 203, and the thin silicon slot waveguide 100 are equal, which helps to achieve efficient mode matching and coupling between different waveguide structures and reduce mode mismatch and transmission loss. The conversion length L1 of the thin silicon mode converter 203 is 500mm-700nm. The conversion length L1 within this range helps to optimize the performance of the mode converter and achieve efficient mode conversion while maintaining low insertion loss and high extinction ratio. The width and height of the waveguide play an important role in the support and propagation of the mode. Narrow waveguides often support single-mode operation and are preferred in many applications due to their simplicity and lower dispersion. As the waveguide width increases, multiple modes can be supported, resulting in mode dispersion and may complicate device design and performance. Therefore, careful control of the waveguide size is very important to ensure optimal performance.

[0035] In this embodiment, the mode in the optical fiber is coupled into the application of the thin silicon slot waveguide, the signal light and the pump light are input into the optical fiber, the signal light and the pump light are coupled into the thin silicon straight waveguide 202 through the thin silicon grating coupler 201, and are coupled into the thin silicon slot waveguide 100 through the thin silicon mode converter 203. Through the thin silicon grating coupler 201, the signal light and pump light from the optical fiber can be effectively coupled into the thin silicon straight waveguide 202. This coupling method can reduce the loss of light when entering the waveguide structure and improve the transmission efficiency of light. The thin silicon mode converter 203 is responsible for converting the light mode in the thin silicon straight waveguide 202 into a mode suitable for transmission in the thin silicon slot waveguide 100, which is conducive to the effective docking between different waveguide structures and the efficient transmission of optical signals. Due to its unique structure, the thin silicon slot waveguide 100 can confine the light field to a very small area, thereby enhancing the interaction between the light and the graphene-hexagonal boron nitride heterojunction 400 covered thereon, thereby realizing efficient nonlinear optical effects and all-optical modulation. Through the combination of the above structures, the whole process from light input, transmission to mode conversion can be realized, and finally all-optical modulation is realized on the thin silicon slot waveguide 100. This modulation can utilize the nonlinear absorption characteristics of graphene, such as the saturation absorption effect, to achieve intensity or phase modulation of the optical signal; the entire mode converter unit 200 is compactly designed and easy to integrate into a larger-scale photonic integrated circuit. This integrated design helps to achieve high-performance, low-cost optical communication systems; due to the high carrier mobility and ultrafast relaxation time of graphene, this graphene-based all-optical modulator can achieve fast response and high modulation efficiency; this structural design can effectively realize efficient coupling, transmission, mode conversion and all-optical modulation of optical signals, which is of great significance for promoting the development of optical communication and optical information processing technologies.

[0036] In this embodiment, the application of all-optical modulation includes the following steps: S100, inputting signal light and pump light into optical fiber; S200, inputting the optical signal into the mode converter unit 200 for coupling and mode conversion of the optical signal, and inputting it into the thin silicon slot waveguide 100; S300, in the thin silicon slot waveguide 100, due to the Pauli exclusion principle of the graphene material, the signal light with low energy is modulated by the pump light with high energy: S400, the method of inputting the optical signal into the mode converter unit 200 is the same as that of steps S100 to S300, and the modulated optical signal is output from the other end of the thin silicon slot waveguide 100 through the symmetrical mode converter unit 200 and coupled to the optical fiber. In step S100, the signal light and the pump light are input into the optical fiber, which ensures the input and transmission efficiency of the optical signal. The optical signal transmitted through the optical fiber has the characteristics of high fidelity and low loss, laying the foundation for the subsequent all-optical modulation; in step S200, the optical signal is input into the mode converter unit 200 for coupling and mode conversion of the optical signal, and is input into the thin silicon slot waveguide 100, which ensures the efficient conversion of the optical signal from the optical fiber to the waveguide, and at the same time achieves the matching between different modes, reducing the loss caused by mode mismatch; in step S300, the Pauli exclusion principle of graphene material is used to modulate the signal light with low energy by the pump light with high energy. The high nonlinear characteristics and fast response time of graphene make this modulation process efficient and rapid, and can realize ultra-fast optical signal processing; in step S400, the modulated optical signal is transmitted from the thin silicon slot waveguide 100 to the other side of the thin silicon slot waveguide 100, and the optical signal is transmitted to ... One end is output through a symmetrical mode converter unit 200 and coupled to the optical fiber. The design of this symmetrical structure helps to maintain the integrity and stability of the optical signal, while improving the output efficiency and quality of the modulated signal; the coverage of the graphene-hexagonal boron nitride heterojunction 400 enhances the interaction between light and matter, especially in the thin silicon slot waveguide 100. This enhanced interaction is critical for achieving efficient nonlinear optical effects and all-optical modulation; the high carrier mobility and ultrafast relaxation time of graphene enable the all-optical modulator to achieve fast response and high modulation efficiency; the ultra-wide operating frequency band of graphene enables the graphene-based all-optical modulator to cover a wide range of wavelengths and is suitable for a variety of communication windows; the entire all-optical modulation process is integrated on a compact chip, which helps to achieve high-performance, low-cost optical communication systems and provides the possibility for large-scale integration. This all-optical modulation application achieves efficient, fast, and broadband optical signal modulation through precise optical signal coupling, mode conversion, modulation using the properties of graphene materials, and efficient output coupling, which is of great significance for promoting the development of optical communication and optical information processing technologies.

[0037] In this embodiment, in step S200, the optical signal is input into the mode converter unit 200 for mode conversion and is input into the thin silicon slot waveguide 100, which specifically includes: S201, coupling the optical signal into the thin silicon grating coupler 201; S202, the optical signal enters the thin silicon mode converter 203 through the thin silicon straight waveguide 202; S203, the optical signal is converted into an optical signal in the thin silicon slot waveguide 100 in the thin silicon mode converter 203, thereby completing the mode conversion; S204, the optical signal after mode conversion is input into the thin silicon slot waveguide 100. In step S201, the optical signal is coupled into the thin silicon grating coupler 201. This step is the starting point of the entire optical signal transmission and modulation process. The design of the thin silicon grating coupler 201 helps to achieve efficient optical coupling from the optical fiber to the waveguide structure and reduce the loss of light when entering the waveguide structure. In step S202, the optical signal enters the thin silicon mode converter 203 through the thin silicon straight waveguide 202. The thin silicon straight waveguide 202 serves as a channel for optical signal transmission and transmits the optical signal coupled from the thin silicon grating coupler 201 to the thin silicon mode converter 203, maintaining the intensity and phase of the optical signal and reducing the loss during transmission. consumption; in step S203, the optical signal is converted into an optical signal in the thin silicon slot waveguide 100 in the thin silicon mode converter 203, thereby completing the mode conversion, realizing effective docking between different waveguide structures and efficient transmission of optical signals, and the thin silicon mode converter 203 uses its special design to convert the optical signal from one mode to another mode to adapt to the transmission characteristics of the thin silicon slot waveguide 100; in step S204, the optical signal after mode conversion is input into the thin silicon slot waveguide 100, ensuring that the optical signal can smoothly enter the thin silicon slot waveguide 100 and be effectively transmitted therein, providing a basis for subsequent all-optical modulation. Through this series of steps, the optical signal is effectively confined in the thin silicon slot waveguide 100, which helps to enhance the interaction between the light and the graphene-hexagonal boron nitride heterojunction 400 covering the waveguide, which is critical for achieving efficient all-optical modulation; due to the high carrier mobility and ultrafast relaxation time of graphene, this graphene-based all-optical modulator can achieve fast response and high modulation efficiency; the design of the entire mode converter unit 200 is compact and easy to integrate into a larger-scale photonic integrated circuit. This integrated design helps to achieve high-performance, low-cost optical communication systems. The specific steps S201 to S204 in step S200 ensure the efficient coupling, transmission, mode conversion and input of the optical signal, which is of great significance for achieving high-performance all-optical modulators.

[0038] During implementation, a graphene all-optical modulator with high modulation efficiency is provided for silicon-based optoelectronic chips, including a thin silicon grating coupler 201, a thin silicon straight waveguide 202, a thin silicon mode converter 203, a thin silicon slot waveguide 100, and a graphene-hexagonal boron nitride heterojunction 400; the signal light and the pump light are coupled into the thin silicon slot waveguide 100 through the thin silicon grating coupler 201. In the modulation, due to the optimization of the waveguide size and the nonlinear medium, the modulator can achieve a higher modulation efficiency. The present invention combines the accelerated cooling of graphene electrons by hexagonal boron nitride with the enhancement of the interaction between light and graphene after the waveguide parameters are optimized, and has high modulation efficiency and fast cooling time, which is of great significance for the development of ultrafast and low-energy silicon-based optoelectronic chips.

[0039] It has the following advantages:

[0040] As an all-optical modulator with high modulation efficiency and ultrafast cooling time, the height h1 of the thin silicon grating coupler 201 is consistent with the height h3 of the thin silicon slot waveguide 100, and the etching of the thin silicon grating coupler 201 is full etching with an etching depth of h1; the height h2 of the thin silicon straight waveguide 202 is consistent with the height h3 of the thin silicon slot waveguide 100; the coverage area of ​​the graphene-hexagonal boron nitride heterojunction 400 is the same as that of the thin silicon slot waveguide 100, and the same height and etching depth are conducive to large-scale processing and graphene transfer and etching; the modulator is symmetrically distributed on both sides, with the same parameters and opposite directions. The signal light and the pump light input optical fiber are coupled into the thin silicon straight waveguide 202 through the thin silicon grating coupler 201, and the fundamental mode signal light is coupled into the thin silicon slot waveguide 100 through the thin silicon mode converter 203 to modulate the optical signal. The optical signal passes through the thin silicon slot waveguide 100 and the graphene-hexagonal boron nitride heterojunction 400. Due to the Pauli exclusion principle of graphene, when graphene absorbs high-energy pump light, it will no longer absorb low-energy signal light, allowing the signal light to pass through, and vice versa, thereby realizing the control of signal light by pump light, that is, all-optical modulation; finally, the signal is output to the optical fiber via the thin silicon mode converter 203 and the thin silicon grating coupler 201 at the other end.

[0041] The present invention uses the thin silicon slot waveguide 100 to achieve a higher light-matter interaction with graphene, thereby obtaining a higher modulation efficiency. The phonon-electron interaction between hexagonal boron nitride and graphene is then used to assist in heat dissipation, thereby obtaining a faster electron relaxation time. The advantages of the silicon-based graphene all-optical modulator in modulation efficiency and cooling speed make it have a wide range of application prospects on silicon-based optoelectronic chips.

[0042] The significance of achieving higher light-matter interaction with graphene by means of thin silicon slot waveguides 100 is mainly reflected in the following aspects:

[0043] Enhance the interaction strength between light and graphene: By integrating graphene into the thin silicon slot waveguide 100, the interaction strength between light and graphene can be effectively improved. This is because the thin silicon slot waveguide 100 can confine the light field to the low refractive index region, thereby forming a more concentrated light field in the region where the graphene is located, and enhancing the interaction between light and graphene.

[0044] Suppressing the two-photon absorption effect: In the thin silicon slot waveguide 100, since most of the light field of the waveguide mode is located in the air, this can effectively reduce the two-photon absorption effect caused by the waveguide itself, providing a basis for realizing a high-efficiency all-optical modulation device.

[0045] Achieving efficient all-optical modulation: By integrating the thin silicon slot waveguide 100 with graphene, the nonlinear absorption characteristics of graphene, such as the saturation absorption effect, can be utilized to achieve efficient on-chip all-optical modulation. Experiments show that a modulation depth of more than 2 dB can be achieved in a 50 μm long silicon waveguide, and the modulation efficiency is as high as 52 dB / mm.

[0046] Improve modulation speed and reduce power consumption: The integration of thin silicon slot waveguide 100 and graphene helps to realize all-optical modulation devices with faster response and lower power consumption. Due to its excellent optoelectronic properties and friendly integration compatibility with various nanostructures, graphene shows great potential in ultrafast and energy-saving all-optical modulation.

[0047] CMOS compatible and easy to fabricate: This all-optical modulator based on ultrathin silicon / graphene hybrid waveguide is compatible with complementary metal oxide semiconductor (CMOS) and easy to fabricate, which enables large-scale integration.

[0048] Broaden the scope of application: The integration of thin silicon slot waveguide 100 and graphene is not only used in all-optical modulation, but can also be used in optical communication, optical sensing and other fields, showing great development potential.

[0049] By using thin silicon slot waveguides 100 to achieve higher light-matter interaction on graphene, the performance of graphene optoelectronic devices can be significantly improved, bringing new technological breakthroughs and application prospects to the field of optoelectronics.

[0050] Example 1

[0051] See also Figure 1 and Figure 2 , Embodiment 1 of the present invention provides an ultrafast graphene all-optical modulator structure with high modulation efficiency, comprising a thin silicon grating coupler 201, a thin silicon straight waveguide 202, a thin silicon mode converter 203, a thin silicon slot waveguide 100 and a graphene-hexagonal boron nitride heterojunction 400;

[0052] The thin silicon grating coupler 201, the thin silicon straight waveguide 202 and the thin silicon mode converter 203 form a coupling and mode conversion structure of the optical signal;

[0053] The thin silicon slot waveguide 100 and the graphene-hexagonal boron nitride heterojunction 400 form a modulation structure;

[0054] The thin silicon grating coupler 201 , the thin silicon straight waveguide 202 , the thin silicon mode converter 203 and the thin silicon slot waveguide 100 are all located on a silicon dioxide substrate 300 .

[0055] In this embodiment, a high modulation efficiency ultrafast graphene all-optical modulator structure is composed of a thin silicon grating coupler 201, a thin silicon straight waveguide 202, a thin silicon mode converter 203 and a thin silicon slot waveguide 100 in sequence; the slot waveguide of the thin silicon slot waveguide 100 is located in the middle of the structure and is symmetrically distributed on both sides; the upper part of the thin silicon slot waveguide 100 is covered with a graphene-hexagonal boron nitride heterojunction 400 to form the main structure of the modulator.

[0056] In this embodiment, the width w1 of the thin silicon slot waveguide 100 and the width w2 of the silicon pillar are determined by simulation calculation;

[0057] The height h1 of the thin silicon grating coupler 201, the height h2 of the thin silicon straight waveguide 202, the height h4 of the thin silicon mode converter 203 and the height h3 of the thin silicon slot waveguide 100 are equal;

[0058] The etching depth of the thin silicon grating coupler 201 is equal to its own height;

[0059] The width w1 of the thin silicon slot waveguide 100 is 20 nm; the width w2 of the silicon column of the thin silicon slot waveguide 100 is 360 nm; the height h1 of the thin silicon grating coupler 201, the height h2 of the thin silicon straight waveguide 202, the height h4 of the thin silicon mode converter 203 and the height h3 of the thin silicon slot waveguide 100 are all equal, which are 100 nm. The above parameters are based on Figure 3 The area of ​​the graphene-hexagonal boron nitride heterojunction 400 is the same as that of the thin silicon slot waveguide 100 ; the conversion length L1 of the thin silicon mode converter 203 is 600 mm.

[0060] The present invention comprises a thin silicon grating coupler 201, a thin silicon straight waveguide 202, a thin silicon mode converter 203, a thin silicon slot waveguide 100 and a graphene-hexagonal boron nitride heterojunction 400; the thin silicon grating coupler 201 is connected to the thin silicon mode converter 203 through the thin silicon straight waveguide 202; the thin silicon slot waveguide 100 is located in the middle of the structure, connected to the thin silicon mode converter 203 on both sides, and the upper part is covered with the graphene-hexagonal boron nitride heterojunction 400 to form the core part of the modulator; the thin silicon grating coupler 201, the thin silicon straight waveguide 202, the thin silicon mode converter 203 and the thin silicon slot waveguide 100 are all located on a silicon dioxide substrate 300. The present invention makes use of the higher light-matter interaction of the slot waveguide combined with graphene, so that the modulator has a higher modulation efficiency; and because the heterojunction formed by graphene and hexagonal boron nitride has a faster electron relaxation time, the modulator has a faster modulation speed. The advantages of the silicon-based graphene all-optical modulator in modulation efficiency and cooling speed make it have broad application prospects in silicon-based optoelectronic chips.

[0061] A method for using an ultrafast graphene all-optical modulator with high modulation efficiency comprises the following steps:

[0062] Step 1: Input signal light and pump light into the optical fiber;

[0063] Step 2: coupling the above optical signal into the thin silicon grating coupler 201;

[0064] Step 3: The optical signal enters the thin silicon mode converter 203 through the thin silicon straight waveguide 202;

[0065] Step 4: The optical signal is converted into an optical signal in the thin silicon slot waveguide 100 in the thin silicon mode converter 203, thereby completing the mode conversion;

[0066] Step 5: In the thin silicon slot waveguide 100, due to the Pauli exclusion principle of graphene materials, the signal light with low energy is modulated by the pump light with high energy and output from the other end:

[0067] Step 6: Similar to the method of optical signal input, the modulated optical signal is output and coupled to the optical fiber through a symmetrical structure from the other end.

[0068] Matters not covered by the present invention are known technologies.

[0069] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A graphene all-optical modulator, characterized in that: It comprises a thin silicon slot waveguide (100), a mode converter unit (200) and a silicon dioxide substrate (300), wherein the thin silicon slot waveguide (100) and the mode converter unit (200) are located on the silicon dioxide substrate (300); A group of mode converter units (200) are respectively connected to both sides of the thin silicon slot waveguide (100), and the two groups of mode converter units (200) are symmetrically distributed on both sides of the thin silicon slot waveguide (100); The mode converter unit (200) comprises a thin silicon grating coupler (201), a thin silicon straight waveguide (202) and a thin silicon mode converter (203); the thin silicon grating coupler (201) is connected to the thin silicon straight waveguide (202), the thin silicon straight waveguide (202) is connected to the thin silicon mode converter (203), and the thin silicon mode converter (203) is connected to the thin silicon slot waveguide (100); The thin silicon slot waveguide (100) is covered with a graphene-hexagonal boron nitride heterojunction (400); The width w1 of the thin silicon slot waveguide (100) is 10nm-30nm, and the width w2 of the silicon column of the thin silicon slot waveguide (100) is 300nm-400nm.

2. The graphene all-optical modulator according to claim 1, characterized in that: The height h1 of the thin silicon grating coupler (201) is consistent with the height h3 of the thin silicon slot waveguide (100).

3. The graphene all-optical modulator according to claim 2, characterized in that: The etching of the thin silicon grating coupler (201) is full etching, and the etching depth is h1.

4. The graphene all-optical modulator according to claim 3, characterized in that: The height h2 of the thin silicon straight waveguide (202) is consistent with the height h3 of the thin silicon groove waveguide (100).

5. The graphene all-optical modulator according to claim 4, characterized in that: The coverage area of ​​the graphene-hexagonal boron nitride heterojunction (400) is the same as that of the thin silicon slot waveguide (100).

6. The graphene all-optical modulator according to any one of claims 1 to 5, characterized in that: The height h1 of the thin silicon grating coupler (201), the height h2 of the thin silicon straight waveguide (202), the height h4 of the thin silicon mode converter (203) and the height h3 of the thin silicon slot waveguide (100) are equal, and are all 50nm-150nm; and / or The switching length L1 of the thin silicon mode converter (203) is 500 mm-700 nm.

7. Application of the graphene all-optical modulator according to any one of claims 1 to 6, to couple a mode in an optical fiber into a thin silicon slot waveguide, It is characterized in that Signal light and pump light are input into an optical fiber, coupled into a thin silicon straight waveguide (202) through a thin silicon grating coupler (201), and coupled into a thin silicon slot waveguide (100) through a thin silicon mode converter (203).

8. Application of the graphene all-optical modulator according to any one of claims 1 to 6, for all-optical modulation, It is characterized in that The following steps are involved: S100, inputting signal light and pump light into an optical fiber; S200, the optical signal input mode converter unit (200) performs coupling and mode conversion on the optical signal, and inputs the optical signal into the thin silicon slot waveguide (100); S300. In the thin silicon slot waveguide (100), due to the Pauli exclusion principle of graphene materials, the signal light with low energy is modulated by the pump light with high energy: S400, the method of inputting the optical signal into the mode converter unit (200) is the same as that in steps S100 to S300, the modulated optical signal is output from the other end of the thin silicon slot waveguide (100) through the symmetrical mode converter unit (200) and coupled to the optical fiber.

9. The application of the graphene all-optical modulator according to claim 8, characterized in that: In step S200, the optical signal is input into the mode converter unit (200) for mode conversion and input into the thin silicon slot waveguide (100), which specifically includes: S201, coupling the optical signal into the thin silicon grating coupler (201); S202, the optical signal enters the thin silicon mode converter (203) through the thin silicon straight waveguide (202); S203, the optical signal is converted in the thin silicon mode converter (203) into an optical signal in the thin silicon slot waveguide (100), thereby completing the mode conversion; S204, the optical signal after mode conversion is input into the thin silicon slot waveguide (100).

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