Calibration-free non-volatile integrated silicon-based optical switch, and method

Abstract

Disclosed in the present invention is a calibration-free non-volatile integrated silicon-based optical switch. A mode (de)multiplexer is connected to two ends of a multi-mode waveguide grating by means of adiabatic tapered waveguides, a phase-change material is arranged on and covers the multi-mode waveguide grating, and external excitation is applied to the phase change material; by means of changing the pulse power and pulse width of the external excitation, the crystalline state of the phase change material is changed in a non-volatile manner, such that the wavelength range of the multi-mode waveguide grating that meets the Bragg condition is changed, thereby changing the transmission and reflection characteristics of a signal with a specific wavelength in a multi-mode waveguide grating region; furthermore, the mode (de)multiplexer is used to realize switching between different output ports, thereby realizing the function of a non-volatile optical switch. The present invention can work in a relatively wide wavelength range, and does not need to be calibrated since the pulse power and pulse width of the external excitation required for changing the crystalline state of the phase change material float within a large range, and therefore the problem of existing silicon-based optical switches having a high power consumption and all requiring calibration before use is solved, and the present invention has broad application prospects.

Description

A calibration-free, non-volatile integrated silicon-based optical switch and method Technical Field

[0001] This invention relates to the field of integrated optics technology, and more specifically to a calibration-free, non-volatile integrated silicon-based optical switch and method. Background Technology

[0002] In recent years, with the rapid development of cloud computing and artificial intelligence, the requirements for signal transmission bandwidth and chip computing power have been increasing, making "computing power" a major bottleneck restricting the development of related technologies. Faced with ever-increasing business demands, the contradiction between existing microelectronics technology and the demands for high-speed, low-power, high-bandwidth, and high-computing power has become irreconcilable. Replacing electrical signals with optical signals for signal transmission and processing on a larger scale is an inevitable trend, and "fiber optics replacing copper" has become an industry consensus. Against this backdrop, optical interconnects and optical computing, as effective paths to further improve transmission bandwidth and computing power, have received widespread attention. Photonic integration is the only way to realize optical interconnects and optical computing.

[0003] The concept of photonic integration can be traced back to the 1960s and 70s. By integrating various traditional discrete optical devices with different functions onto the same chip, photonic integration can achieve higher density and higher performance integration of complex functions on a single chip. Over the past few decades, the field of photonic integration has seen rapid development in material selection, fabrication processes, and device design. In terms of materials, various material platforms have been developed, among which silicon-based materials have received the most attention due to their excellent photothermal and electrical properties and perfect compatibility with existing CMOS processes. In terms of devices, on-chip devices with various functions have been developed, and research has progressed from single-device studies to complex on-chip integration containing thousands of different functional devices, such as optical transceiver modules, lidar, and multi-channel optical switch arrays.

[0004] Despite significant achievements, existing photonic integration technologies still face numerous challenges: firstly, excessive power consumption; and secondly, the performance of individual devices still falls short of full requirements. Specifically, existing photonic integration schemes, in addition to the power consumption of the light source, detector, modulator, and optical switch themselves, require additional power to drive the thermal management module, maintain on-chip temperature stability, and ensure normal device operation. Taking optical switches as an example, existing optical switches are primarily based on thermal tuning, using electrodes to directionally heat the waveguide, leveraging the high thermo-optical coefficient of silicon to achieve the switching function of the optical path. While this approach maintains low optical path loss, the switching state is "volatile," requiring continuous heating to maintain the waveguide temperature and thus the switching state, with power consumption typically ranging from several mW to tens of mW. As the integration density of on-chip photonic devices increases, the number of "volatile" devices such as thermo-optical switches also increases significantly, directly leading to the emergence of an on-chip "power wall"—the rate of power consumption increase far exceeds the rate of increase in signal processing capabilities. Power consumption has become one of the main factors limiting the development of photonic integration. Furthermore, existing optical switches are mainly based on Mach-Zehnder interferometers (MZI) or microring resonators (MRR) structures, utilizing light interference as their working principle. Their optical field output is highly dependent on the geometric dimensions of the structure. Taking MZI as an example, its working principle is highly dependent on the phase difference between the two interferometer waveguides, and the phase within the interferometer waveguides is determined by both the waveguide temperature and waveguide dimensions. In actual fabrication, unavoidable process errors cause random variations in the geometric dimensions of the interferometer arms within a certain range, leading to random perturbations in the heating power required for the on / off states of the MZI optical switches. In practical applications, to ensure optimal chip operation, the heating power required for each MZI optical switch's specific switching state needs to be calibrated. With increasing integration density, silicon-based photonic chips typically contain dozens or even hundreds of MZI thermo-optical switches. Calibrating each MZI thermo-optical switch before use significantly increases the workload of the packaging and testing process and adds complexity to the on-chip system, hindering further development of photonic integration.

[0005] In summary, how to solve the above two problems—namely, developing "non-volatile" devices that do not require external power to maintain the switching state, thereby reducing on-chip power consumption requirements, and developing calibration-free integrated silicon-based optical switches to reduce packaging and testing requirements—has become a key issue for further promoting the development of on-chip photonic integration. Summary of the Invention

[0006] To address the issues of high power consumption (requiring additional power to maintain the switching state, thus exhibiting "volatility") and the need for calibration before use in existing on-chip silicon-based optical switches, this invention proposes a 2×2 calibration-free, non-volatile integrated silicon-based optical switch design and switching method.

[0007] This invention solves the problems of high power consumption and the need for individual calibration before use in existing silicon-based optical switches, and has broad application prospects. The invention incorporates low-loss phase change materials and multimode waveguide grating structures, utilizing the Bragg reflection principle to solve the problems of existing silicon-based thermo-optical switches (MZI, MRR) requiring external power to maintain the switching state and requiring calibration before use.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] I. A calibration-free, non-volatile integrated silicon-based optical switch:

[0010] The optical switch includes a mode demultiplexer, an adiabatic tapered waveguide, a multimode waveguide grating, a mode multiplexer, and a phase change material. The mode demultiplexer and the mode multiplexer are both connected to the two ends of the multimode waveguide grating through the adiabatic tapered waveguide. The multimode waveguide grating is covered with a phase change material. The phase change material is subjected to an external excitation to change its crystal state, thereby affecting the multimode waveguide grating and adjusting the state and switching of the optical switch.

[0011] Both the mode demultiplexer and the mode multiplexer include a trunk waveguide and an access waveguide. The trunk waveguide is used for end connection through an adiabatic tapered waveguide and a multimode waveguide grating, and the access waveguide is arranged parallel to and spaced apart from the trunk waveguide.

[0012] The main waveguide has a wider width to support the transmission of the higher-order mode TE1; the access waveguide has a narrower width and only supports the transmission of the fundamental mode TE0; and the TE1 mode in the main waveguide and the TE0 mode in the access waveguide satisfy the mode matching condition.

[0013] The multimode waveguide grating is used to reflect light of a specific wavelength (satisfying the Bragg reflection condition) in the input light field, while light of other wavelengths is transmitted normally; wherein the transmitted light is output from one port, and the reflected light is converted into another mode by a mode multiplexer and then output from another port.

[0014] The multimode waveguide grating includes a multimode waveguide grating tapered waveguide and a multimode waveguide; each end of the multimode waveguide is connected to a multimode waveguide grating tapered waveguide, the width of the multimode waveguide grating tapered waveguide gradually increases from the end connected to the multimode waveguide outward, grating teeth are provided on both sides of the multimode waveguide grating tapered waveguide and the multimode waveguide, and the grating teeth on both sides of the multimode waveguide grating tapered waveguide and the multimode waveguide are arranged in anti-symmetrical manner.

[0015] The phase change material can change its crystal state by applying an external excitation pulse power and pulse width non-volatilely, thereby changing its refractive index and altering the Bragg reflection conditions of the multimode waveguide grating, i.e., changing the reflection wavelength.

[0016] The phase change material is arranged on the multimode waveguide grating tapered waveguide and the multimode waveguide, and both ends of the phase change material are set as pointed.

[0017] The width of the adiabatic conical waveguide gradually decreases from the end connected to the multimode waveguide grating outwards.

[0018] The external excitation is either electrical heating excitation or optical excitation.

[0019] When the phase change material is subjected to an external excitation and its crystal state is changed to a "non-volatile" crystalline state, the multimode waveguide grating at the operating wavelength satisfies the Bragg condition; the signal light is reflected at the multimode waveguide grating; the signal light input from the input side port of the mode demultiplexer trunk waveguide will be output from the input side port of the access waveguide; the signal light input from the output side port of the mode multiplexer access waveguide will be output from the output side port of the trunk waveguide.

[0020] When the phase change material is subjected to an external excitation that changes its crystal state to a "non-volatile" amorphous state, the multimode waveguide grating at the operating wavelength no longer satisfies the Bragg condition. The signal light then transmits through the multimode waveguide grating without loss. Signal light input from the input port of the mode demultiplexer's trunk waveguide will be output from the output port of the mode demultiplexer's access waveguide; conversely, signal light input from the output port of the mode demultiplexer's access waveguide will be output from the input port of the mode demultiplexer's access waveguide.

[0021] After the phase change material is subjected to an external excitation and changes its crystallization state to a crystalline or amorphous state, it can still maintain its crystallization state as a crystalline or amorphous state without the external excitation.

[0022] II. A non-volatile optical switch switching method:

[0023] S1. When the phase change material is in a crystalline state, the multimode waveguide grating at the operating wavelength satisfies the Bragg condition and operates as follows:

[0024] The signal light of operating wavelength λ1 and TE0 mode, input from the input port of the trunk waveguide of the mode demultiplexer, passes through the mode demultiplexer without loss, and then enters the multimode waveguide grating through the adiabatic tapered waveguide, where it undergoes Bragg reflection and is reflected into TE1 mode. The reflected TE1 mode signal light returns to the mode demultiplexer after passing through the adiabatic tapered waveguide again. Due to the mode matching condition of the mode demultiplexer, the reflected TE1 mode signal light is fully coupled from the trunk waveguide of the mode demultiplexer into the access waveguide and converted into TE0 mode, and is output from the input port of the access waveguide of the mode demultiplexer.

[0025] Similarly, the signal light with operating wavelength λ1 and TE0 mode input from the output port of the access waveguide of the mode multiplexer enters the trunk waveguide of the mode multiplexer, is coupled into the access waveguide, and is converted into TE0 mode. The TE1 mode signal light further enters the multimode waveguide grating through the adiabatic tapered waveguide and undergoes Bragg reflection, and is reflected into TE0 mode. The reflected TE0 mode signal light returns to the mode multiplexer after passing through the adiabatic tapered waveguide again, and is transmitted through the trunk waveguide of the mode multiplexer and output from the output port of the trunk waveguide of the mode multiplexer.

[0026] S2. Then, an external excitation with a certain pulse power and a pulse width of a few microseconds is applied to the phase change material to change the crystalline state of the phase change material to the amorphous state, so that the multimode waveguide grating at the working wavelength does not satisfy the Bragg condition, and it works in the following manner:

[0027] The signal light of the working wavelength λ1 and TE0 mode input from the input side port of the trunk waveguide of the mode demultiplexer passes through the mode demultiplexer without loss, then enters the multimode waveguide grating through the first adiabatic tapered waveguide without loss transmission, then enters the mode multiplexer after the second adiabatic tapered waveguide, and finally outputs from the trunk waveguide of the mode demultiplexer.

[0028] Similarly, the signal light with operating wavelength λ1 and TE0 mode input from the input side port of the access waveguide of the mode multiplexer enters the access waveguide of the mode multiplexer, is coupled into the trunk waveguide and converted into TE1 mode, passes through the mode demultiplexer without loss, then enters the multimode waveguide grating through the second adiabatic tapered waveguide without loss transmission, and then enters the access waveguide of the mode demultiplexer after the first adiabatic tapered waveguide, is coupled into the trunk waveguide and converted into TE0 mode, and is output from the trunk waveguide of the mode demultiplexer.

[0029] S3. When a phase change material is stimulated by an external excitation, it will instantly heat up and become amorphous, and remain in the amorphous state. Then it will cool down to room temperature. Next, a pulse excitation with low power (the specific power depends on the material geometry) but long duration (tens of microseconds) is applied to the phase change material to make its temperature higher than its crystallization temperature and maintain it for a period of time. After natural cooling, it will change from the amorphous state to the crystalline state, so that the multimode waveguide grating at the working wavelength satisfies the Bragg condition and works again according to the S1 method.

[0030] In S2, if the crystalline state of the phase change material is to be changed to the amorphous state, a pulse with high power (the specific power depends on the geometric size of the material, generally tens of microjoules but with a short duration (hundreds of nanoseconds to microseconds)) is applied to the phase change material to make the temperature of the phase change material exceed the melting point of the material (above the crystallization temperature) and maintain it for a short time, and then it is naturally cooled.

[0031] In step S3, if the amorphous state of the phase change material is to be changed to the crystalline state, a pulse excitation with low power (the specific power depends on the geometric size of the material, generally in the range of 100 nanojoules) but long duration (tens of microseconds) is applied to the phase change material to make the temperature of the phase change material exceed the material's crystallization temperature (below the material's melting point) and maintain it for a long period of time, after which it is allowed to cool naturally.

[0032] This process of switching the optical switch on and off is repeated, thus achieving the non-volatile switching function of the optical signal.

[0033] After each state switch of the optical switch, there is no need to maintain the external excitation. Each time an external excitation is applied for a very short time, the temperature will rise instantaneously and change the state. After the state changes, the temperature will drop to room temperature and remain in the amorphous state. In this way, the optical switch will maintain the current state under normal conditions, which makes the optical switch non-volatile.

[0034] A wide-spectrum signal operating bandwidth can be achieved by adjusting the geometric parameters of the multimode waveguide grating and the mode multiplexer / demultiplexer. The operating state of the switch is determined only by the crystallization state (crystalline or amorphous) of the phase change material, requiring no precise control. Therefore, switching can be performed over a wide range of applied excitation pulse power and pulse width without the need for precise calibration.

[0035] This invention alters the crystallization state of a phase change material by changing the power and pulse width of the applied excitation pulse, thereby changing the wavelength range that satisfies the Bragg condition of a multimode waveguide grating. This alters the transmission and reflection characteristics of a specific wavelength signal in the multimode waveguide grating region, and then utilizes a mode (de)multiplexer to achieve switching between different output ports, realizing a non-volatile optical switch function.

[0036] Meanwhile, all the structures included in the optical switch of the present invention can operate in a wide wavelength range, and the external excitation pulse power and pulse width required to switch the crystallization state of the phase change material can fluctuate within a certain range. Therefore, the optical switch of the present invention does not need to be calibrated before use.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] This invention innovatively provides a new optical switch implementation mechanism, which adjusts the operating wavelength of the optical switch over a wide range by changing the Bragg reflection conditions, thereby realizing the switching of the optical path.

[0039] The technical solution of this invention does not require precise control of the applied power and can realize the switching of the phase change material state within a wide range of selectable power, thereby realizing the function of an optical switch and avoiding the problem of precise calibration required by traditional MZI and MRR optical switches.

[0040] Meanwhile, the introduction of non-volatile phase-change materials eliminates the need for external power to maintain the state of the optical switch; only a brief application of external power is required during state transitions. The non-volatile switching state ensures the low-power characteristics of this invention. This invention provides a low-power, calibration-free optical switch implementation scheme, significantly reducing the power consumption and packaging requirements of on-chip optical switches, and promoting the further development of photonic integration technology. Attached Figure Description

[0041] 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.

[0042] Figure 1 is a schematic diagram of the structure of the calibration-free non-volatile integrated silicon-based optical switch provided in the embodiment.

[0043] Figure 2 is a schematic diagram of the pattern (de-) multiplexer provided in the embodiment.

[0044] Figure 3 is a schematic diagram of the structure of the multimode waveguide grating provided in the embodiment.

[0045] Figure 4 shows the simulation results of the transmission and reflection spectra of the phase change material in the crystalline state provided in the embodiment from the multimode waveguide grating.

[0046] Figure 5 shows the simulation results of the transmission and reflection spectra of the phase change material provided in the embodiment in the amorphous state from the multimode waveguide grating.

[0047] Figure 6 is a simulation calculation result of the output spectrum of the other end of the trunk waveguide and the access waveguide when the TE1 mode is input into the trunk waveguide of the mode multiplexer provided in the embodiment.

[0048] In the figure: 1-Mode demultiplexer, 2-Adiabatic tapered waveguide, 3-Multimode waveguide grating, 4-Mode multiplexer, 5-Phase change material, 6-First input port, 7-Second input port, 8-First output port, 9-Second output port, 11-Trunk waveguide, 12-Access waveguide, 31-Multimode waveguide grating tapered waveguide, 32-Grate teeth, 33-Multimode waveguide. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0050] As shown in Figure 1, the embodiment provides a calibration-free, non-volatile 2×2 integrated silicon-based optical switch, whose waveguide part is made of silicon, and the cladding and substrate materials are silicon dioxide. It includes a mode demultiplexer 1, an adiabatic tapered waveguide 2, a multimode waveguide grating 3, a mode multiplexer 4, and a phase change material 5.

[0051] Mode demultiplexer 1 and mode multiplexer 4 are both connected to the two ends of multimode waveguide grating 3 through their respective adiabatic tapered waveguides 2. Phase change material 5 is arranged on the multimode waveguide grating 3, and the phase change material 5 covers the top surface of the multimode waveguide grating 3 in the middle. This makes mode demultiplexer 1 and mode multiplexer 4, the first adiabatic tapered waveguide 2, the multimode waveguide grating 3, the second adiabatic tapered waveguide 2, and mode multiplexer 4 connected in sequence.

[0052] The phase change material 5 is subjected to an external excitation to change its crystal state, thereby affecting the Bragg matching state of the multimode waveguide grating 3 and thus adjusting the state and switching of the optical switch.

[0053] The optical switch changes the crystallization state of the phase change material 5 by applying pulse power and pulse width to the external excitation of the phase change material 5, thereby realizing the switching function of the optical path.

[0054] As shown in Figure 2, mode demultiplexer 1 and mode multiplexer 4 have the same structure. They adopt an asymmetric directional coupler structure that includes trunk waveguides and access waveguides of different widths. They are arranged in a mirror symmetric manner at both ends of the multimode waveguide grating 3 to realize the coupling conversion and separation between TE0 and TE1 modes in the waveguide.

[0055] Mode demultiplexer 1 and mode multiplexer 4 have the same structure, both including trunk waveguide 11 and access waveguide 12. Trunk waveguide 11 is used for end connection through adiabatic tapered waveguide 2 and multimode waveguide grating 3. Access waveguide 12 is arranged parallel to trunk waveguide 11 and is located on the side of trunk waveguide 11.

[0056] Among them, the trunk waveguide 11 has a wider width to meet the stable transmission of the higher-order mode TE1; the access waveguide 12 has a narrower width and only supports the transmission of the fundamental mode TE0. By setting the widths of the two, the TE1 mode in the trunk waveguide 11 and the TE0 mode in the access waveguide 12 always meet the mode matching condition, so that the TE1 mode in the trunk waveguide 11 and the TE0 mode in the access waveguide 12 can be coupled to each other.

[0057] The multimode waveguide grating 3 includes a multimode waveguide grating tapered waveguide 31 located on both sides and a multimode waveguide 33 located in the middle. The two ends of the multimode waveguide 33 are respectively connected to a multimode waveguide grating tapered waveguide 31. The inner end of the multimode waveguide grating tapered waveguide 31 is connected to the multimode waveguide 33, and the outer end is used to connect to the mode demultiplexer 1 / mode multiplexer 4 via the adiabatic tapered waveguide 2. The width of the multimode waveguide grating tapered waveguide 31 gradually increases from the end connected to the multimode waveguide 33 outwards, while the width of the adiabatic tapered waveguide 2 is the opposite. The sides of the multimode waveguide grating tapered waveguide 31 and the multimode waveguide 33 are provided with periodically arranged grating teeth 32. The grating teeth 32 on both sides of the multimode waveguide grating tapered waveguide 31 and the multimode waveguide 33 are arranged in an anti-symmetrical manner.

[0058] As shown in Figure 3, in the multimode waveguide grating section, the tapered waveguides 31 of the multimode waveguide grating have identical structures and are arranged symmetrically on both sides of the multimode waveguide 33. Grating teeth 32 are arranged on both sides of the tapered waveguides 31 and 33. The tapered waveguides 31 have a gradually changing width to connect the adiabatic tapered waveguide 2 and the multimode waveguide 33, reducing losses in the transition region. The width of the multimode waveguide 33 should simultaneously satisfy lossless transmission in both TE0 and TE1 modes.

[0059] The grating teeth 32 are periodic structures. By adjusting the geometric parameters of the grating teeth 32 and the multimode waveguide 33, light of a specific wavelength can satisfy the Bragg condition. This wavelength can be used as the working wavelength, and the TE0 / TE1 mode input at the working wavelength can be reflected and converted into TE1 / TE0 mode.

[0060] In practice, the width of the two ends of the multimode waveguide 33 can also be gradually changed.

[0061] The phase change material 5 is arranged on the top surface of the multimode waveguide grating tapered waveguide 31 and the multimode waveguide 33 located in the middle. It can be arranged along the waveguide length direction / extension direction. Both ends of the phase change material 5 are set as pointed to reduce scattering loss.

[0062] More specifically, the phase change material 5 is in the form of a thin film and is arranged at least on top of the multimode waveguide 33 portion of the multimode waveguide grating 3.

[0063] The adiabatic tapered waveguide is used to connect the trunk waveguide and multimode waveguide grating of the mode multiplexer / demultiplexer. The width of the adiabatic tapered waveguide 2 gradually decreases from the end connected to the multimode waveguide grating 3 outwards, and the widths of the two ends of the adiabatic tapered waveguide 2 are equal when connected to the trunk waveguide / multimode waveguide grating of the mode multiplexer and mode demultiplexer, respectively.

[0064] The phase change material 5 includes, but is not limited to, germanium-antimony-tellurium alloy (Ge2Sb2Te5, GST), germanium-antimony-selenium-tellurium alloy (Ge2Sb2Se4Te1, GSST), antimony selenide (Sb2Se3), antimony sulfide (Sb2S3), InSe3, VO2, etc.

[0065] The external excitation is either electric heating excitation or high-power optical excitation.

[0066] The range of external excitation pulse power depends on the geometric parameters of the phase change material 5. Its purpose is to bring the temperature of the phase change material 5 to a specific range. The pulse width is on the order of microseconds, usually from hundreds of nanoseconds to tens of microseconds.

[0067] When the phase change material 5 is subjected to an external excitation and changes its crystal state to a "non-volatile" crystalline state, the multimode waveguide grating 3 at the working wavelength satisfies the Bragg condition.

[0068] When the phase change material 5 is subjected to an external excitation and its crystal state is changed to a "non-volatile" amorphous state, the multimode waveguide grating 3 at the working wavelength does not satisfy the Bragg condition.

[0069] After the phase change material 5 is subjected to an external excitation and changes its crystallization state to a crystalline or amorphous state, it can still maintain its current crystallization state as a crystalline or amorphous state without maintaining the external excitation.

[0070] As shown in Figure 4, through simulation testing, when the phase change material 5 is in a crystalline state, in the wavelength range of 1540-1560nm, the TE0 mode of the input multimode waveguide grating 3 is mainly reflected, while the transmitted light field intensity is only about -20dB.

[0071] As shown in Figure 5, when the phase change material 5 is in the amorphous state, the wavelength range that satisfies the Bragg condition of the multimode waveguide grating 3 becomes the range of 1505-1525nm. In the band of 1540-1560nm, the TEO mode of the input multimode waveguide grating 3 is mainly transmitted, while the intensity of the reflected light field is below -30dB.

[0072] As shown in Figure 6, when the optical field is input from the trunk waveguide 11 in TE1 mode, the mode (de)multiplexer can achieve ultra-low loss TE1-TE0 mode conversion and output from the access waveguide within a broadband range of 1510-1600nm. At the same time, the residual optical field in the trunk waveguide is below -20dB.

[0073] The following provides a specific example of an optical switch.

[0074] In a specific implementation, the input ports of the trunk waveguide 11 and the access waveguide 12 of the mode demultiplexer 1 are respectively used as the first input port 6 and the first output port 8. The output port of the trunk waveguide 11 of the mode demultiplexer 1 is connected to one end of the first adiabatic tapered waveguide 2 and the multimode waveguide grating 3. The output port of the access waveguide 12 of the mode demultiplexer 1 is left unused.

[0075] The output ports of the main waveguide 11 and the access waveguide 12 of the mode multiplexer 4 are respectively used as the second output port 9 and the second input port 7. The input port of the main waveguide 11 of the mode multiplexer 4 is connected to the other end of the first adiabatic tapered waveguide 2 and the multimode waveguide grating 3. The input port of the access waveguide 12 of the mode multiplexer 4 is left unused.

[0076] S1. When phase change material 5 is in a crystalline state:

[0077] The signal light of a specific wavelength (λ1) (TE0 mode) input from the first input port 6 passes losslessly through the mode demultiplexer 1, then through the adiabatic tapered waveguide 2 on the left and into the multimode waveguide grating 3. At this point, the wavelength satisfies the Bragg condition of the multimode waveguide grating 3, and is reflected into TE1 mode at the multimode waveguide grating 3. The reflected TE1 mode signal light then passes through the adiabatic tapered waveguide 2 on the left again and enters the mode demultiplexer 1. Due to the satisfaction of the mode matching condition, the reflected TE1 mode signal light is further fully coupled from the trunk waveguide 11 of the mode demultiplexer 1 into the access waveguide 12 and converted into TE0 mode, then output from the first output port 8.

[0078] Simultaneously, the same wavelength (λ1) signal light (TE0 mode) input from the second input port 7 is coupled into the trunk waveguide 11 via the mode multiplexer 4 and converted to TE1 mode. This TE1 mode signal light further enters the multimode waveguide grating 3 via the right-side adiabatic tapered waveguide 2. Since the wavelength λ1 satisfies the Bragg condition of the multimode waveguide grating 3, the TE1 mode signal light undergoes Bragg reflection at the multimode waveguide grating 3, and the reflected TE0 mode signal light returns to the mode multiplexer 4 via the right-side adiabatic tapered waveguide 2. Because the reflected TE0 mode signal light is located in the trunk waveguide 11 of the mode demultiplexer 1 at this time, it no longer satisfies the mode matching condition of the mode demultiplexer 1 and will not couple to the access waveguide 12 of the mode demultiplexer 1, so it is directly output from the second output port 9.

[0079] In summary, when the phase change material 5 is in a crystalline state, the signal light input from the first input port 6 is output from the first output port 8; the signal light input from the second input port 7 is output from the second output port 9.

[0080] S2. By applying external excitation pulse power and pulse width, such as through electrical modulation or optical modulation, the phase change material 5 is changed from a non-volatile state to an amorphous state. This alters its refractive index, thereby changing the Bragg condition of the multimode waveguide grating 3. At this point, the phase change material 5 is in an amorphous state.

[0081] At this point, the signal light (TE0 mode) of a specific wavelength (λ1) input from the first input port 6 passes through the mode demultiplexer 1 without loss, and enters the multimode waveguide grating 3 via the adiabatic tapered waveguide 2 on the left. The signal light of this wavelength (λ1) no longer satisfies the Bragg condition of the multimode waveguide grating 3 and cannot be emitted at the multimode waveguide grating 3. Therefore, the signal light (λ1) directly and without loss maintains the TE0 mode and transmits through the multimode waveguide grating 3 and the adiabatic tapered waveguide 2 on the right into the mode multiplexer 4. Similarly, because the TE0 mode signal light (λ1) is located in the main waveguide 11 of the mode multiplexer 4, it does not satisfy the mode matching condition, thus further maintaining its TE0 mode output from the second output port 9.

[0082] At this time, the signal light of a specific wavelength (λ1) (TE0 mode) input from the second input port 7 is coupled into TE1 mode via mode multiplexer 4 and enters the trunk waveguide 11, and then enters the multimode waveguide grating 3 via the right-side adiabatic tapered waveguide 2. Similarly, because wavelength λ1 does not satisfy the Bragg condition of the multimode waveguide grating 3, the TE1 mode signal light passes through the multimode waveguide grating 3 without loss and enters the mode demultiplexer 1 via the left-side adiabatic tapered waveguide 2. Since the TE1 mode signal light satisfies the mode matching condition in the trunk waveguide 11 of the mode demultiplexer 1, it is further coupled into the TE0 mode in the access waveguide 12 and output from the first output port 8.

[0083] In summary, when the phase change material 5 is in an amorphous state, the signal light input from the first input port 6 is output from the second output port 9; the signal light input from the second input port 7 is output from the first output port 8.

[0084] As can be seen from the above process, the crystallization state of phase change material 5 can be adjusted non-volatilely between crystalline and amorphous states by applying different excitation pulse power and pulse width. Furthermore, the power for the interconversion between crystalline and amorphous states can be adjusted within a wide range by adjusting the excitation pulse power, pulse width, and duration.

[0085] Furthermore, considering that the device structures used in this design can all operate over a wide wavelength range, this invention realizes a 2×2 calibration-free, non-volatile integrated silicon-based optical switch.

[0086] The embodiments of the present invention are as follows:

[0087] The designed multimode waveguide grating has a total waveguide width of 1 μm, a grating period of 285 nm, a grating duty cycle of 0.5, a grating tooth depth of 180 nm, and a phase change material thickness of 50 nm. The widths at both ends of the main waveguide 11 of the designed mode (demultiplexer) are 0.5 μm and 0.86 μm, respectively, and the widths at both ends of the access waveguide 12 are 0.15 μm and 0.3 μm, respectively. The spacing between the two waveguides is 200 nm, and the coupling region length is 13.3 μm.

[0088] Figure 4 shows the simulation results of the reflection spectrum and transmission spectrum of the multimode waveguide grating tapered waveguide 31 on the left and right sides of the multimode waveguide grating tapered waveguide 31 when the phase change material 5 is in a crystalline state (refractive index 4.05) and the TE0 mode is input from the first input port 6 and enters the tapered waveguide 31 on the left side of the multimode waveguide grating 3. It can be seen that optical signals within a specific wavelength range (1540-1560nm) are reflected back to the input port in TE1 mode by the multimode waveguide grating 3, while optical signals in other wavelength bands are transmitted normally in TE0 mode and are finally output from the second output port 9 of the mode multiplexer 4. At this time, the reflected TE1 mode signal light is converted into TE0 mode by the mode demultiplexer 1 on the left and output from the first output port 8.

[0089] When the phase change material 5 is in an amorphous state (refractive index 3.285), optical signals within a specific wavelength range (1540-1560nm) input to the first input port 6 are no longer reflected by the multimode waveguide grating 3, but are normally transmitted from the right side in TE0 mode and output through the second output port 9. Thus, the switching function for optical signals in the 1540-1560nm range is realized. In summary, the switching state of this invention can be determined by the crystalline state of the phase change material 5.

[0090] When the phase change material 5 is initially fabricated, it is in an amorphous state. Subsequently, its state can be non-volatilely switched between amorphous and crystalline states by applying high-power, short-duration pulse excitation or low-power, long-duration pulse excitation. Moreover, the pulse excitation required for switching states does not require overly precise control. The required excitation power and pulse width are only related to the geometric parameters of the phase change material 5 and can be achieved within a wide range (see reference 10.1002 / adfm.202304601, supporting material Figure S3).

[0091] Furthermore, this invention can achieve optical switching functionality over a relatively wide wavelength range (~20nm). The state of the phase change material 5 is transformed between a crystalline state (100% crystallinity) and an amorphous state (0% crystallinity) through external pulse excitation, corresponding to different operating wavelength ranges of the multimode waveguide grating 3 (different reflection bands in Figures 3 and 4). Slight inaccuracies in the applied pulse excitation power and pulse width, resulting in imperfect crystalline or amorphous states of the phase change material 5 (such as 98% or 2% crystallinity), will only cause a minor drift in the operating wavelength range of the multimode waveguide grating 3 and will not significantly affect the overall performance of the optical switch.

[0092] In summary, through the innovative structural design that combines non-volatile phase change materials and multimode waveguide grating Bragg reflection, this invention can achieve non-volatile, calibration-free optical switching functionality.

[0093] Comparative Example 1

[0094] Using a patent application with application number 201810449137.3, a polarization-insensitive thermo-optical switch is proposed, employing a traditional MZI-type structure. All MZI-based optical switch designs rely on thermal tuning for their switching function, requiring continuous external power to maintain the temperature of the heating arm and thus control the phase difference between the two interferometer arms. Therefore, their function is "volatile," significantly increasing power consumption. Simultaneously, the phase difference between the two interferometer arms is highly dependent on the waveguide's size and temperature, inevitably affected by ambient temperature and manufacturing errors. Consequently, its initial state is difficult to control, and the power required for each switch's two states needs separate calibration (see reference 10.1364 / OL.413724).

[0095] Comparative Example 2

[0096] Using a patent with application number CN202310710345.5, an optical switch based on a microring resonator is proposed. Due to the limited architecture design of the microring resonator, its operating bandwidth is extremely narrow, and it can only realize the optical switching function in the sub-nm wavelength range. Its operating wavelength is also significantly affected by the manufacturing error, requiring precise calibration to achieve wavelength alignment.

[0097] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A calibration-free, non-volatile integrated silicon-based optical switch, characterized in that, The device includes a mode demultiplexer (1), an adiabatic tapered waveguide (2), a multimode waveguide grating (3), a mode multiplexer (4), and a phase change material (5). The mode demultiplexer (1) and the mode multiplexer (4) are connected to both ends of the multimode waveguide grating (3) through the adiabatic tapered waveguide (2). The multimode waveguide grating (3) is covered with the phase change material (5). The phase change material (5) is subjected to an external excitation to change its crystal state, thereby affecting the multimode waveguide grating (3) and adjusting the state and switching of the optical switch.

2. The calibration-free, non-volatile integrated silicon-based optical switch according to claim 1, characterized in that: Both the mode demultiplexer (1) and the mode multiplexer (4) include a trunk waveguide (11) and an access waveguide (12). The trunk waveguide (11) is used for end connection via an adiabatic tapered waveguide (2) and a multimode waveguide grating (3). The access waveguide (12) is arranged parallel to the trunk waveguide (11). The trunk waveguide (11) is wider to meet the transmission of the higher-order mode TE1. The access waveguide (12) is narrower and only supports the transmission of the fundamental mode TE0. The TE1 mode in the trunk waveguide (11) and the TE0 mode in the access waveguide (12) meet the mode matching condition.

3. The calibration-free, non-volatile integrated silicon-based optical switch according to claim 1, characterized in that: The multimode waveguide grating (3) includes a multimode waveguide grating tapered waveguide (31) and a multimode waveguide (33); both ends of the multimode waveguide (33) are connected to a multimode waveguide grating tapered waveguide (31), and the width of the multimode waveguide grating tapered waveguide (31) gradually increases from the end connected to the multimode waveguide (33) outward. Grating teeth (32) are provided on both sides of the multimode waveguide grating tapered waveguide (31) and the multimode waveguide (33), and the grating teeth (32) on both sides of the multimode waveguide grating tapered waveguide (31) and the multimode waveguide (33) are arranged in anti-symmetrical manner.

4. The calibration-free, non-volatile integrated silicon-based optical switch according to claim 3, characterized in that: The phase change material (5) is arranged on the multimode waveguide grating tapered waveguide (31) and the multimode waveguide (33), and both ends of the phase change material (5) are set as pointed.

5. The calibration-free, non-volatile integrated silicon-based optical switch according to claim 1, characterized in that: The width of the adiabatic conical waveguide (2) gradually decreases from the end connected to the multimode waveguide grating (3) outwards.

6. The calibration-free, non-volatile integrated silicon-based optical switch according to claim 1, characterized in that: The external excitation is either electrical heating excitation or optical excitation.

7. The calibration-free, non-volatile integrated silicon-based optical switch according to claim 1, characterized in that: When the phase change material (5) is subjected to an external excitation and changes its crystal state to a crystalline state, the multimode waveguide grating (3) at the working wavelength satisfies the Bragg condition. When the phase change material (5) is subjected to an external excitation and its crystal state is changed to an amorphous state, the multimode waveguide grating (3) at the working wavelength does not satisfy the Bragg condition.

8. A calibration-free, non-volatile integrated silicon-based optical switch according to claim 7, characterized in that: After the phase change material (5) is subjected to an external excitation and changes its crystal state to a crystalline or amorphous state, it can still maintain its crystal state as a crystalline or amorphous state without the external excitation.

9. A non-volatile optical switch switching method applied to any one of the non-volatile integrated silicon-based optical switches described in claims 1-8, characterized in that: S1. When the phase change material (5) is in a crystalline state, the multimode waveguide grating (3) at the working wavelength satisfies the Bragg condition and operates in the following manner: The signal light of working wavelength λ1 and TE0 mode input from the input side port of the main waveguide (11) of the mode demultiplexer (1) passes through the mode demultiplexer (1), and then enters the multimode waveguide grating (3) through the adiabatic tapered waveguide (2) where it undergoes Bragg reflection and is reflected into TE1 mode. The reflected TE1 mode signal light passes through the adiabatic tapered waveguide (2) again and returns to the mode demultiplexer (1). The reflected TE1 mode signal light is fully coupled from the main waveguide (11) of the mode demultiplexer (1) into the access waveguide (12) and converted into TE0 mode, and is output from the input side port of the access waveguide (12) of the mode demultiplexer (1). The signal light of working wavelength λ1 and TE0 mode input from the output port of the access waveguide (12) of the mode multiplexer (4) enters the trunk waveguide (11) of the mode multiplexer (4), is coupled into the access waveguide (12) and converted into TE0 mode. The signal light of TE1 mode further enters the multimode waveguide grating (3) through the adiabatic tapered waveguide (2) and is reflected into TE0 mode. The reflected TE0 mode signal light returns to the mode multiplexer (4) after passing through the adiabatic tapered waveguide (2) again. It is then transmitted through the trunk waveguide (11) of the mode multiplexer (4) and output from the output port of the trunk waveguide (11) of the mode multiplexer (4). S2. Then, an external excitation is applied to the phase change material (5) to change its crystalline state to an amorphous state, so that the multimode waveguide grating (3) at the working wavelength does not satisfy the Bragg condition and operates in the following manner: The signal light of working wavelength λ1 and TE0 mode input from the input side port of the trunk waveguide (11) of the mode demultiplexer (1) passes through the mode demultiplexer (1), then enters the multimode waveguide grating (3) through the first adiabatic tapered waveguide (2) for lossless transmission, then enters the mode multiplexer (4) through the second adiabatic tapered waveguide (2), and finally outputs from the trunk waveguide (11) of the mode demultiplexer (1); The signal light with working wavelength λ1 and TE0 mode input from the input side port of the access waveguide (12) of the mode multiplexer (4) enters the access waveguide (12) of the mode multiplexer (4), is coupled into the trunk waveguide (11) and converted into TE1 mode. After passing through the mode demultiplexer (1), it enters the multimode waveguide grating (3) through the second adiabatic tapered waveguide (2) for lossless transmission. Then, after passing through the first adiabatic tapered waveguide (2), it enters the access waveguide (12) of the mode demultiplexer (1), is coupled into the trunk waveguide (11) and converted into TE0 mode, and is output from the trunk waveguide (11) of the mode demultiplexer (1). S3. Next, an external excitation is applied to the phase change material (5) to make the temperature of the phase change material (5) higher than the crystallization temperature and maintain it. Then, it is naturally cooled, and then it changes from an amorphous state to a crystalline state, so that the multimode waveguide grating (3) at the working wavelength satisfies the Bragg condition and works again according to the S1 method.

10. A non-volatile optical switch switching method for a non-volatile integrated silicon-based optical switch according to claim 9, characterized in that: In S2, if the crystalline state of the phase change material (5) is to be changed to the amorphous state, a pulse excitation with high power but short duration is applied to the phase change material (5) to make the temperature of the phase change material (5) exceed the melting point of the material and maintain it, and then it is naturally cooled. In S3, if the amorphous state of the phase change material (5) is to be changed to the crystalline state, a pulse excitation with low power but long duration is applied to the phase change material (5) to make the temperature of the phase change material (5) exceed the material crystallization temperature and maintain it, and then it is naturally cooled.

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