Silicon waveguide integrated graphene-mos2 heterojunction all-optical modulator

Abstract

The application provides a silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator, and belongs to the field of integrated optoelectronic devices, which comprises a silicon dioxide substrate, an ultrathin slit silicon waveguide integrated on the silicon dioxide substrate, and a graphene-MoS2 heterojunction film covering the surface of the ultrathin slit silicon waveguide; a multimode interference mode converter symmetrically arranged at both ends of the ultrathin slit silicon waveguide, wherein the multimode interference mode converter comprises an ultrathin silicon grating coupler, a multimode interferometer and a tapered waveguide mode converter connected in sequence. The graphene-MoS2 heterojunction film is prepared by a chemical vapor deposition method and is transferred to the surface of the ultrathin slit silicon waveguide, and the synergistic effect of the two is used to enhance the nonlinear absorption effect. The nonlinear property of graphene is greatly enhanced due to the formation of the graphene-MoS2 heterojunction film by compounding with MoS2, and the response speed and other performances of the modulator are further improved.

Description

Technical Field

[0001] This invention relates to the field of integrated optoelectronic device technology, and in particular to a silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator. Background Technology

[0002] With the rapid development of information technology, higher demands are being placed on the speed and energy efficiency of optical communication and optical interconnects. All-optical modulators, as core devices that avoid the bottleneck of photoelectric-to-electro-optical conversion, are crucial for achieving ultra-high-speed, ultra-low-power optical information processing. Traditional silicon-based all-optical modulators are limited by the relatively weak nonlinear optical effects of silicon material (such as the Kerr effect), making it difficult to simultaneously achieve ultra-fast response at the picosecond (ps) level and ultra-low energy consumption at the femtojoule (fJ) per bit level.

[0003] Two-dimensional materials, especially graphene, offer a novel material platform for high-performance all-optical modulators due to their ultra-high carrier mobility, ultra-wideband optical response, and excellent nonlinear properties. However, the limited intensity of the light-interaction between monolayer graphene and light (approximately 2.3% absorption rate) restricts further improvements in its modulation efficiency. Simultaneously, its carrier relaxation time limits the modulation speed to some extent.

[0004] On the other hand, the optical waveguide structure of the device determines the intensity of the interaction between the optical field and the two-dimensional material. Conventional silicon waveguides (such as 220nm thick strip waveguides) have limited localization capabilities for the optical field.

[0005] Therefore, there is an urgent need for a novel all-optical modulator design that combines advanced waveguide structures with high-performance two-dimensional material heterojunctions to simultaneously achieve ultrafast response, ultra-low power consumption, and high modulation efficiency. Summary of the Invention

[0006] The present invention aims to provide a silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator to solve the technical problem that existing all-optical modulators are difficult to balance in terms of modulation rate, energy consumption and modulation depth.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] According to one aspect of the present invention, a silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator is provided for realizing all-optical modulation, comprising: Silica substrate; An ultrathin slit silicon waveguide integrated on the silicon dioxide substrate and a graphene-MoS2 heterojunction film covering the surface of the ultrathin slit silicon waveguide. A multimode interference mode converter symmetrically arranged at both ends of the ultrathin slit silicon waveguide includes an ultrathin silicon grating coupler, a multimode interferometer, and a tapered waveguide mode converter connected in sequence.

[0009] Furthermore, the ultrathin slit silicon waveguide includes two parallel silicon pillars and an air slit between them, with the graphene-MoS2 heterojunction film covering the top surface of the two silicon pillars and the area above the air slit.

[0010] Furthermore, the graphene-MoS2 heterojunction film is formed by vertically stacking a graphene layer and at least one MoS2 layer. By setting different numbers of MoS2 layers, the interlayer coupling strength and nonlinear absorption coefficient of the graphene-MoS2 heterojunction are changed, thereby optimizing the nonlinear saturated absorption characteristics and carrier relaxation time under all-optical modulation.

[0011] The aforementioned silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator is used to achieve all-optical modulation, including the following steps: The signal light and pump light are coupled into the multimode interferometer via the ultrathin silicon grating coupler at one end of the ultrathin slit silicon waveguide, and then coupled into the ultrathin slit silicon waveguide via the tapered waveguide mode converter. The pump light has a shorter wavelength than the signal light and a higher energy than the signal light. In the ultrathin slit silicon waveguide, the high-energy pump light preferentially interacts with the graphene-MoS2 heterojunction film. The pump light energy is absorbed by the graphene, and the charge carriers in the graphene undergo interband transitions, causing the graphene-MoS2 heterojunction to reach an absorption saturation state, forming a Pauli blockade effect during the duration of the pump light pulse. During the duration of the Pauli blockade effect, low-energy signal light passes through the graphene-MoS2 heterojunction film in an absorption saturation state, thereby achieving all-optical modulation of the signal light. The modulated signal light is output from the other end of the ultrathin slit silicon waveguide, and after mode conversion by the corresponding tapered waveguide mode converter, it is output through the ultrathin silicon grating coupler at the other end.

[0012] The present invention has the following beneficial effects: This invention provides a silicon waveguide-integrated graphene-MoS2 heterojunction all-optical modulator, comprising an ultrathin slit silicon waveguide integrated on a silicon dioxide substrate and a graphene-MoS2 heterojunction film coated on the surface of the ultrathin slit silicon waveguide. The nonlinearity of graphene is greatly enhanced by its combination with MoS2 to form the graphene-MoS2 heterojunction film, further improving the modulator's response speed and other performance characteristics. The ultrathin slit waveguide can highly localize the optical field within its low-refractive-index slit region, greatly enhancing the optical field intensity and thus significantly improving the effective nonlinear response of the two-dimensional material integrated on its surface. The graphene-MoS2 heterojunction film is prepared by chemical vapor deposition and transferred to the entire upper surface of the ultrathin slit silicon waveguide, utilizing the synergistic effect of the two to enhance the nonlinear absorption effect.

[0013] This invention innovatively combines an ultrathin slit silicon waveguide with a graphene-MoS2 heterojunction film. The ultrathin slit silicon waveguide strongly localizes the light field in a low-refractive-index region, greatly enhancing the interaction strength between light and the graphene heterojunction. The graphene-MoS2 heterojunction, in turn, significantly enhances the nonlinearity of graphene and increases the saturable absorption intensity. The synergistic effect of these two technologies enables the all-optical modulator to theoretically achieve sub-picosecond response times and femtojoule-level switching power consumption per bit, while simultaneously obtaining high modulation depth.

[0014] The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator provided by this invention has high integration compatibility. The entire device is fabricated based on a silicon dioxide substrate and CMOS-compatible micro-nano fabrication processes (such as electron beam lithography and reactive ion etching). The ultrathin silicon layer (e.g., 100 nm) and uniform structural height reduce the risk of breakage during the transfer of two-dimensional material heterojunctions, improving process feasibility and yield.

[0015] The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator provided by this invention uses a multimode interference mode converter instead of a traditional tapered coupler. It is insensitive to process errors, has no sharp structures, and is easy to fabricate. Through simulation optimization of its dimensional parameters, a coupling efficiency exceeding 95% can be achieved, significantly reducing the device's insertion loss.

[0016] The multimode interferometer has a compact structure and superior performance, making it suitable for next-generation high-speed optical communication systems, optical interconnects, photonic neural networks, and ultrafast optical signal processing. It has significant scientific value and engineering application potential. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of a silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator provided in one embodiment; Figure 2 A cross-sectional view of the ultrathin slit silicon waveguide of a silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator provided in one embodiment. Figure 3 This is a schematic diagram of the structure of an ultrathin silicon grating coupler 1 in one embodiment; Figure 4A top view and a diagram defining the key structural parameters of a silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator provided in one embodiment; Figure 5 A schematic diagram illustrating the principle of improving the nonlinearity of graphene-MoS2 composite films. Figure 6 The graph shows the relationship between the modulation efficiency obtained from the simulation and the optimized parameters of the ultrathin slit waveguide structure. Figure 7 The cross-sectional optical field distribution of an ultrathin slit silicon waveguide at a wavelength of 1550 nm is shown in the simulation. Explanation of the labels in the diagram: 1. Ultrathin silicon grating coupler; 101. First ultrathin silicon grating coupler; 102. Second ultrathin silicon grating coupler; 103. Lateral grating; 104. Longitudinal grating; 2. Multimode interferometers: 201. First multimode interferometer; 202. Second multimode interferometer; 3. Tapered waveguide mode converter, 301, First tapered waveguide mode converter, 302, Second tapered waveguide mode converter; 4. Ultrathin slit silicon waveguide; 401, silicon pillar; 402, air slit; 5. Silicon dioxide substrate; 6. Graphene-MoS2 heterojunction film; 601, graphene layer; 602, MoS2 layer. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described through specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] Reference Figure 1 and Figure 2 A silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator is provided for realizing all-optical modulation, comprising: 5. Silica substrate; An ultrathin slit silicon waveguide 4 integrated on the silicon dioxide substrate 5 and a graphene-MoS2 heterojunction film 6 covering the surface of the ultrathin slit silicon waveguide 4. A multimode interference mode converter is symmetrically arranged at both ends of the ultrathin slit silicon waveguide 4. The multimode interference mode converter includes an ultrathin silicon grating coupler 1, a multimode interference 2, and a tapered waveguide mode converter 3 connected in sequence.

[0021] In the above embodiments, the ultrathin slit silicon waveguide 4 is formed by etching the top silicon layer and is integrated on a silicon dioxide substrate 5 together with the multimode interference mode converter (MMC) consisting of the ultrathin silicon grating coupler 1, the multimode interferometer 2, and the tapered waveguide mode converter 3. The MMC is symmetrically positioned at both ends of the ultrathin slit silicon waveguide 4 to achieve low-loss coupling of optical signals. Two ultrathin silicon grating couplers 1 are symmetrically distributed; one coupler couples spatial optical signals into the corresponding MMC, while the other couples output the modulated optical signal. Specifically, the MMC located at the first end of the ultrathin slit silicon waveguide 4 performs mode conversion on the input optical signal and couples it into the ultrathin slit silicon waveguide 4 with low loss, while the MMC located at the second end of the ultrathin slit silicon waveguide 4 performs mode conversion on the modulated optical signal and outputs it. The multimode interference mode converter at the first end of the ultrathin slit silicon waveguide 4 includes a first ultrathin silicon grating coupler 101, a first multimode interferometer 201, and a first tapered waveguide mode converter 301. The multimode interference mode converter at the second end of the ultrathin slit silicon waveguide 4 includes a second ultrathin silicon grating coupler 102, a second multimode interferometer 202, and a second tapered waveguide mode converter 302.

[0022] The ultrathin slit silicon waveguide 4 and the graphene-MoS2 heterojunction film 6 coated on the surface of the ultrathin slit silicon waveguide 4, wherein the MoS2 in the graphene-MoS2 heterojunction film 6 can participate in and enhance the nonlinear absorption of graphene. The ultrathin slit waveguide can highly localize the optical field in its low-refractive-index slit region, greatly enhancing the optical field intensity, thereby significantly improving the effective nonlinear response of the two-dimensional material integrated on its surface. In addition, mode conversion is performed by using the multimode interference (MMI) effect combined with a tapered waveguide, and the self-image principle of MMI is used to achieve more flexible mode control and low-loss coupling.

[0023] Reference Figure 2 The ultrathin slit silicon waveguide 4 includes two parallel silicon pillars 401 and an air slit 402 located between the two silicon pillars 401. The graphene-MoS2 heterojunction film 6 is coated on the top surface of the two silicon pillars 401 and the area above the air slit 402. That is, the graphene-MoS2 heterojunction film 6 is coated on the entire upper surface of the ultrathin slit silicon waveguide 4, and its coating area is equal to the upper surface area of ​​the ultrathin slit silicon waveguide 4.

[0024] The graphene-MoS2 heterojunction film 6 is composed of a graphene layer 601 and at least one MoS2 layer 602. Under high excitation intensity, for a single layered graphene or MoS2, the population of photon-generated carriers leads to the filling of states at the band gap edge, thereby hindering further absorption. However, for the graphene-MoS2 heterojunction film 6 proposed in this invention, composed of a graphene layer 601 and at least one MoS2 layer 602, the donor-forming... With its acceptor structure, MoS2 can act as an electron donor through its interaction with graphene, enabling electrons to be effectively transferred from the valence band to the conduction band of both MoS2 and graphene, and allowing interband transitions between MoS2 and graphene. This effectively enhances the nonlinear absorption coefficient of the graphene-MoS2 heterojunction, optimizing the nonlinear saturated absorption characteristics and carrier relaxation time under all-optical modulation.

[0025] Reference Figure 2 The graphene-MoS2 heterojunction film 6 is composed of a graphene layer 601 and a MoS2 layer 602. By combining it with MoS2, the nonlinearity of graphene can be improved, and the nonlinear saturated absorption characteristics and carrier relaxation time during all-optical modulation can be optimized.

[0026] The structural parameter design of each component in the silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator plays a crucial role in its performance. In the ultrathin slit silicon waveguide 4, the silicon pillars 401 have equal height h, ranging from 50 nm to 150 nm. The air slit 402 has a slit width of 20 nm to 100 nm, and each silicon pillar in the ultrathin slit silicon waveguide 4 has the same width d, ranging from 250 nm to 600 nm.

[0027] Furthermore, the heights of the ultrathin silicon grating coupler 1, the multimode interferometer 2, and the tapered waveguide mode converter 3 can be equal to the height h of the silicon pillar 401 in the ultrathin slit silicon waveguide 4, with a height range of 50 nm to 150 nm. This uniformity design is beneficial for wafer fabrication and subsequent large-area, low-damage transfer of two-dimensional materials.

[0028] The etching of the ultrathin silicon grating coupler 1 is a full etching, and the etching depth is equal to the height of the ultrathin silicon grating coupler (1).

[0029] The conversion length Lc of the tapered waveguide mode converter 3 is 500nm-1500nm.

[0030] The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator provided by this invention has the advantages of ultra-fast response speed (sub-picosecond level), ultra-low switching power consumption (femtojoule per bit level) and CMOS process compatibility. It is suitable for high-speed optical communication, optical interconnect and optical computing systems, and is of great significance for the development of ultra-fast low-power silicon-based optoelectronic chips that are easy to implement in engineering.

[0031] The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator described in any of the above embodiments is used to achieve all-optical modulation, including the following steps: The signal light and pump light undergo mode conversion via a multimode interference mode converter at the first end of the ultrathin slit silicon waveguide 4 and are coupled into the ultrathin slit silicon waveguide 4 with low loss. Specifically, the signal light and pump light illuminate the first ultrathin silicon grating coupler 101, are coupled into the first multimode interferometer 201 via the first ultrathin silicon grating coupler 101, and are coupled into the ultrathin slit silicon waveguide 4 via the first tapered waveguide mode converter 301. The pump light has a shorter wavelength than the signal light, higher energy than the signal light, and is pulsed. Preferably, the pump light wavelength is around 1550 nm to minimize loss in the optical fiber. In the ultrathin slit silicon waveguide 4, the high-energy pump light preferentially interacts with the graphene-MoS2 heterojunction film 6. The pump light energy is absorbed by the graphene, and the charge carriers in the graphene undergo interband transitions, causing the graphene-MoS2 heterojunction to reach the absorption saturation state and forming a Pauli blockade effect during the duration of the pump light pulse. During the duration of the Pauli blockade effect, low-energy signal light passes through the graphene-MoS2 heterojunction film 6, which is in an absorption saturation state, thereby achieving all-optical modulation of the signal light. The modulated signal light is output from the second end of the ultrathin slit silicon waveguide 4, and after mode conversion by the second tapered waveguide mode converter 302, it is coupled into the second ultrathin silicon grating coupler 102 via the second multimode interferometer 202, and output through the second ultrathin silicon grating coupler 102 (which can be further coupled to an optical fiber).

[0032] After the pump light pulse ends, the excited carriers in the graphene-MoS2 heterojunction film 6 rapidly relax and recombine, regaining their ability to absorb signal light and waiting for the next pump light pulse.

[0033] The graphene-MoS2 heterojunction film 6 achieves ultrafast all-optical modulation based on the Pauli blockade effect. A strong pump light saturates the carrier distribution in the heterojunction, altering its absorption state and thus regulating the transmittance of weak signal light. Weak signal light is modulated by a strong pump light. The response speed of the silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator is closely related to the nonlinearity of graphene. In this invention, the nonlinearity of graphene is greatly enhanced due to its combination with MoS2 to form the graphene-MoS2 heterojunction film 6, further improving the modulator's response speed and other performance characteristics.

[0034] like Figure 2 and Figure 5 As shown, the ultrathin slit silicon waveguide 4 consists of two parallel silicon pillars 401 and an air slit 402 in between. Its key structural parameters include: silicon pillar height h, air slit width w, and the width of a single silicon pillar d. Through simulation optimization (using the finite-time difference simulation software FDTD), these parameters were set to optimal ranges: h = 50-150 nm (preferably 100 nm), w = 10-50 nm (preferably 20 nm-50 nm), and d = 250 nm-600 nm (preferably 300 nm-400 nm). Under these parameters, the optical field energy at the operating wavelength (e.g., 1550 nm) can be effectively confined and enhanced in the slit and its surrounding surface region, such as... Figure 7 As shown.

[0035] The graphene-MoS2 heterojunction film 6 is prepared and transferred onto the surface of the ultrathin slit silicon waveguide 4 using chemical vapor deposition (CVD) combined with wet transfer or direct growth. The area of ​​the covered region is equal to the area of ​​the top of the silicon pillar 401 and the air slit 402. The number of MoS2 layers 602 in the graphene-MoS2 heterojunction film 6 can be adjusted as needed to optimize the charge transfer and recombination dynamics between MoS2 and graphene, thereby obtaining the best nonlinear saturated absorption characteristics and carrier relaxation time.

[0036] The ultrathin silicon grating coupler 1 is used to couple the incident light to the multimode interferometer 2, and then to the ultrathin slit silicon waveguide 4 via the tapered waveguide mode converter 3. Figure 3This is a schematic diagram of the structure of an ultrathin silicon grating coupler 1 in one embodiment. The ultrathin silicon grating coupler 1 is an ultrathin silicon subwavelength grating coupler. The overall outline of the ultrathin silicon subwavelength grating coupler is trumpet-shaped or fan-shaped. The first end of the ultrathin silicon subwavelength grating coupler is a free end, and the second end of the ultrathin silicon subwavelength grating coupler is coupled to a multimode interferometer 2. The width of the first end of the ultrathin silicon subwavelength grating coupler is greater than the width of its second end. The ultrathin silicon subwavelength grating coupler integrates a transverse grating 103 and a longitudinal grating 104. The transverse grating 103 is periodically arranged along a direction perpendicular to the light propagation direction, and the longitudinal grating 104 is periodically arranged along the light propagation direction. The extension length of the transverse grating 103 gradually shortens as it approaches the second end, and the grating unit density of the longitudinal grating 104 gradually increases as it approaches the second end. Compared with uniform one-dimensional grating couplers, ultrathin silicon subwavelength grating couplers can improve mode matching between the subwavelength grating coupler and the waveguide, and the subwavelength grating coupler has lower back reflection, which helps to reduce light loss in the coupler and better couple light into the slit waveguide.

[0037] Figure 4 This is a top view of a silicon waveguide-integrated graphene-MoS2 heterojunction all-optical modulator. The length L_mmi and width W_mmi of the multimode interferometer 2 are optimized to ensure efficient and low-loss conversion from straight waveguide mode to slit waveguide mode, with a coupling efficiency exceeding 90%. The conversion length Lc of the tapered waveguide mode converter 3 (marked in the figure, referring to the length of the tapered waveguide mode converter 3) is also one of the optimized parameters, typically on the order of several micrometers to tens of micrometers.

[0038] After optimizing the structural parameters of the ultrathin slit waveguide structure using electromagnetic simulation software (Lumerical FDTD), the modulation efficiency (here expressed as the absorption coefficient α per unit length) is obtained. s The relationship between the characteristics (directly related to the modulation depth) and the parameters of the ultrathin slit waveguide structure, such as... Figure 6 As shown in the figure. The results show that the modulation efficiency reaches an optimal value (>0.27 dB / μm) when h=100 nm, w≈50 nm, and d≈350 nm, proving the effectiveness of the structure design.

[0039] The working principle of the all-optical modulator described in this invention is as follows: Pump light (shorter wavelength, higher power) and signal light (longer wavelength, lower power) are output as spatial light through optical fiber and illuminate the first ultrathin silicon grating coupler 101. The light is then coupled into the all-optical modulator via the first ultrathin silicon grating coupler 101. After passing through the first multimode interferometer 201 and the first tapered waveguide mode converter 301, the two beams are efficiently coupled into the ultrathin slit silicon waveguide 4 via mode conversion. Due to the presence of the strong pump light, its photons first interact with and are absorbed by the graphene-MoS2 heterojunction film 6, causing interband transitions of the charge carriers. According to the Pauli blockade principle, during the duration of the pump light pulse, the heterojunction is in an absorption saturation state, and the absorption of the subsequently arriving signal light is weakened, exhibiting an "on" state. When the pump light disappears, the charge carriers of the heterojunction recover to their initial state through ultrafast relaxation (thanks to the heterojunction structure), reabsorbing the signal light, exhibiting a "off" state. By controlling the on / off state of the pump light, the intensity modulation of the signal light can be achieved. The modulated signal light is reverse-coupled and output through the multimode interference mode converter at the second end of the ultrathin slit silicon waveguide 4, and then enters the receiving optical fiber.

[0040] In summary, this invention, through the synergistic innovative design of an ultrathin slit silicon waveguide 4 and a graphene-MoS2 heterojunction thin film 6, and by optimizing the mode conversion interface, successfully proposes an all-optical modulator solution that combines ultra-fast speed, ultra-low power consumption, high modulation efficiency, and compatibility with CMOS processes, providing a new technical path for the development of next-generation high-performance silicon-based photonic integrated chips.

[0041] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator, characterized in that, include: Silica substrate (5); An ultrathin slit silicon waveguide (4) integrated on the silicon dioxide substrate (5) and a graphene-MoS2 heterojunction film (6) covering the surface of the ultrathin slit silicon waveguide (4). A multimode interference mode converter symmetrically arranged at both ends of the ultrathin slit silicon waveguide (4) includes an ultrathin silicon grating coupler (1), a multimode interferometer (2), and a tapered waveguide mode converter (3) connected in sequence.

2. The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator according to claim 1, characterized in that, The ultrathin slit silicon waveguide (4) includes two parallel silicon pillars and an air slit between them, and the graphene-MoS2 heterojunction film (6) is coated on the top surface of the two silicon pillars and the area above the air slit.

3. The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator according to claim 1 or 2, characterized in that, The graphene-MoS2 heterojunction film (6) is composed of a graphene layer and at least one MoS2 layer.

4. The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator according to claim 2, characterized in that, The width of the air slit is 20nm-100nm, and the width d of each silicon pillar in the ultrathin slit silicon waveguide (4) is the same, which is 250nm-600nm.

5. The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator according to claim 2, characterized in that, The heights of the ultrathin silicon grating coupler (1), the multimode interferometer (2), the tapered waveguide mode converter (3), and the ultrathin slit silicon waveguide (4) are all equal, ranging from 50 nm to 150 nm.

6. The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator according to claim 5, characterized in that, The etching of the ultrathin silicon grating coupler (1) is a full etching, and the etching depth is equal to the height of the ultrathin silicon grating coupler (1).

7. The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator according to claim 1, 2, 4, 5, or 6, characterized in that, The conversion length of the tapered waveguide mode converter (3) is 500nm-1500nm.

8. The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator according to claim 7, characterized in that, The multimode interference mode converter located at the first end of the ultrathin slit silicon waveguide (4) is used to perform mode conversion on the input optical signal and couple it into the ultrathin slit silicon waveguide (4) with low loss. The multimode interference mode converter located at the second end of the ultrathin slit silicon waveguide (4) is used to perform mode conversion on the modulated optical signal and output it.

9. The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator according to claim 1, 2, 4, 5, 6, or 8, characterized in that, The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator can achieve all-optical modulation, including the following steps: The signal light and the pump light are coupled into the multimode interferometer (2) through the ultrathin silicon grating coupler (1) at one end of the ultrathin slit silicon waveguide (4), and coupled into the ultrathin slit silicon waveguide (4) through the tapered waveguide mode converter (3). The pump light has a shorter wavelength than the signal light, and the pump light energy is higher than the signal light energy. The pump light is a pulsed light. In the ultrathin slit silicon waveguide (4), the high-energy pump light preferentially interacts with the graphene-MoS2 heterojunction film (6). The pump light energy is absorbed by the graphene, and the charge carriers in the graphene undergo interband transitions, causing the graphene-MoS2 heterojunction to reach the absorption saturation state and forming a Pauli blockage effect during the duration of the pump light pulse. During the duration of the Pauli blockade effect, the low-energy signal light passes through the graphene-MoS2 heterojunction film (6) which is in an absorption saturation state, thereby achieving full optical modulation of the signal light. The modulated signal light is output from the other end of the ultrathin slit silicon waveguide (4), and after mode conversion via the corresponding tapered waveguide mode converter (3), it is output through the ultrathin silicon grating coupler (1) at the other end.

10. The silicon waveguide integrated graphene-MoS2 heterojunction all-optical modulator according to claim 9, characterized in that, After the pump light pulse ends, the excited carriers in the graphene-MoS2 heterojunction film (6) rapidly relax and recombine, regaining their ability to absorb signal light and waiting for the next pump light pulse.

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