MZI optical switch device and method based on cooperation of electric heating and phase change materials

Abstract

The invention relates to the technical field of silicon-based photonic integrated chips, and discloses an MZI optical switch device based on cooperation of electric heating and a phase change material, the MZI optical switch device comprises a coarse adjustment unit and a fine adjustment unit, the phase change material of the coarse adjustment unit is utilized to realize non-volatile large-range phase coarse adjustment, and the electric heating effect of the fine adjustment unit is utilized to carry out rapid and continuous phase fine adjustment. Therefore, drift is compensated and accurate dynamic control is realized. Through the hierarchical regulation and control mechanism, wide-range, high-precision and repeatable phase dynamic management is finally realized. And the length of the interference arm required for realizing the same function is greatly shortened, so that the chip integration density is improved, the transmission loss is reduced, and the response speed is improved. And meanwhile, the overall operation energy consumption and thermal crosstalk of the device can be remarkably reduced, and the device is particularly suitable for large-scale integrated photon circuits. The invention further discloses a phase regulation and control method based on the MZI optical switch device.

Description

Technical Field

[0001] This invention relates to the field of silicon-based photonic integrated chip technology, and in particular to an MZI optical switch device and method based on the synergy of electrothermal and phase change materials. Background Technology

[0002] In integrated photonics, the Mach-Zehnder interferometer (MZI) is one of the core structures for realizing optical signal modulation, switching, filtering, and phase control. Achieving controllable modulation of the phase difference between the two interferometer arms of an MZI is crucial for constructing functional modules of photonic integrated chips such as reconfigurable optical networks, phased arrays, and quantum interference devices.

[0003] Currently, the mainstream on-chip phase modulation technologies mainly include the following categories: 1. Thermo-optic Phase Shifter (TOPS): This technology leverages the high thermo-optical coefficient of silicon (dn / dT≈1.86×10⁻⁴ / K). By integrating metal heating electrodes above or near the waveguide, the effective refractive index is modulated by locally altering the waveguide temperature through the Joule heating effect. Electrothermal control offers advantages such as mature technology, good compatibility with CMOS processes, high stability, and good linearity. However, its drawbacks are also significant, including slow response speed due to limitations in heat diffusion and dissipation; and high power consumption, especially when maintaining a fixed phase requires continuous power supply, resulting in high static power consumption.

[0004] 2. Carrier-based Phase Shifter: This technology utilizes the free carrier dispersion effect of silicon to alter the effective refractive index of a waveguide by constructing PN or PIN structures and injecting or depleting carriers. Its greatest advantage lies in its fast response speed (down to the nanosecond level), making it suitable for high-speed optical communication. However, its drawbacks also limit its application in certain scenarios: relatively low phase modulation efficiency, small phase change per unit length (typically requiring a phase shift region of hundreds of micrometers to achieve a π phase shift); high insertion loss, mainly due to free carrier absorption; significant nonlinear effects; and difficulty in maintaining a fixed carrier concentration over long periods, making it unsuitable for applications requiring stable phase maintenance.

[0005] 3. Mechanical micro-actuator control (MEMS-based Phase Shifter): This technology achieves phase modulation by directly changing the optical path length through moving waveguides or mirrors using micro / nano mechanical structures. Its advantages include extremely low power consumption, with energy only consumed during state switching. However, its complex structure makes manufacturing difficult and costly; reliability and lifespan are affected by factors such as mechanical fatigue and adhesion; response speed is limited by mechanical inertia, making high-speed modulation difficult; and its low integration density makes it difficult to compactly integrate with large-scale photonic circuits.

[0006] However, existing phase modulation techniques have the following drawbacks: 1. Disadvantages of electrothermal regulation (TOPS): slow response speed, high power consumption, and significant thermal crosstalk.

[0007] Reason: Due to the thermo-optical coefficient of silicon material itself and the physical process of heat conduction, heat generation and dissipation take time; maintaining the change in refractive index requires continuous heating.

[0008] 2. Disadvantages of carrier modulation: low phase modulation efficiency and high insertion loss.

[0009] Reason: The refractive index change caused by the free carrier plasma dispersion effect of silicon is limited; free carriers will cause unavoidable light absorption.

[0010] 3. Disadvantages of mechanical micro-drive control (MEMS): complex structure, poor reliability, limited response speed, and low integration.

[0011] Reasons: It relies on complex movable mechanical structures and has a demanding manufacturing process; the mechanical motion has inertia and friction, and is easily affected by environmental interference.

[0012] Therefore, current phase modulation technology for MZI optical switches has many bottlenecks and trade-offs in terms of power consumption, accuracy, integration, and dynamic controllability. Summary of the Invention

[0013] The purpose of this invention is to provide an MZI optical switch device and method based on the synergy of electrothermal and phase change materials, which has high modulation efficiency, low power consumption, high control accuracy and high integration.

[0014] To achieve the above objectives, the present invention provides an MZI optical switch device based on the synergy of electrothermal and phase change materials, comprising an input waveguide, a first beam splitter, a first connecting waveguide, an interferometer arm, a second connecting waveguide, a second beam splitter, an output waveguide, a coarse adjustment unit, and a fine adjustment unit. The output end of the input waveguide is connected to the input end of the first beam splitter. The output end of the first beam splitter is connected to the input ends of the two interferometer arms respectively through two first connecting waveguides. The output ends of the two interferometer arms are connected to the input end of the second beam splitter respectively through second connecting waveguides. The output end of the second beam splitter is connected to the input end of the output waveguide. At least one of the interferometer arms integrates the coarse adjustment unit, and at least one of the interferometer arms integrates the fine adjustment unit. The coarse adjustment unit and the fine adjustment unit are used to modulate the phase of the optical signal in the corresponding interferometer arm, and the phase adjustment range of the coarse adjustment unit is greater than the phase adjustment range of the fine adjustment unit. The coarse adjustment unit achieves phase modulation based on phase change materials, and the fine adjustment unit achieves phase modulation based on electrothermal control.

[0015] As a preferred embodiment, the coarse adjustment unit includes a phase change material layer, and the top and / or side surfaces of the interference arm are covered with the phase change material layer.

[0016] As a preferred embodiment, the fine-tuning unit includes a pair of microheaters symmetrically arranged on both sides of the interferometer arm, the microheaters being thermally coupled to the interferometer arm and extending along the direction of light propagation.

[0017] As a preferred embodiment, the fine-tuning unit includes a pair of microheaters symmetrically arranged on both sides of the interferometer arm, the microheaters being thermally coupled to the interferometer arm and extending along the light propagation direction, and the coarse-tuning unit including a phase change material layer, the top surface and / or side surface of the interferometer arm being covered by the phase change material layer; The effective heating length of the microheater is 2 to 5 times the length of the phase change material layer.

[0018] As a preferred embodiment, the coarse adjustment unit includes a phase change material layer disposed on the top or side surface of the interferometer arm, and the fine adjustment unit includes a pair of micro heaters symmetrically arranged on both sides of the interferometer arm. The micro heaters include heavily doped P-type and N-type regions. The interferometer arm is a silicon waveguide. The P-type and N-type regions are located on both sides of the interferometer arm. Electrodes are provided on both the P-type and N-type regions. A dielectric isolation layer is provided between the electrodes and the phase change material layer, and between the electrodes and the interferometer arm.

[0019] As a preferred embodiment, the phase change material of the fine-tuning unit is Sb2Se3.

[0020] As a preferred embodiment, both the first beam splitter and the second beam splitter are multimode interferometers, and the first beam splitter and the second beam splitter are configured to operate in the 1500-1600 nm communication band.

[0021] As a preferred embodiment, the two interference arms are symmetrically arranged, and each interference arm integrates the coarse adjustment unit and the fine adjustment unit.

[0022] This invention also provides a method for phase modulation of MZI optical switches based on the synergy of electrothermal and phase change materials, comprising: A first excitation signal is applied to the coarse adjustment unit integrated on the MZI optical switch, causing the input light to be distributed to the two output ports according to the first beam splitting ratio; A second excitation signal is applied to the fine-tuning unit integrated on the MZI optical switch, causing the input light to be distributed to two output ports according to a second beam splitting ratio, wherein the difference between the second beam splitting ratio and the first beam splitting ratio is greater than the first beam splitting ratio.

[0023] As a preferred option, it also includes: Before applying the first excitation signal to the coarse adjustment unit integrated on the MZI optical switch to distribute the input light to the two output ports according to the first beam splitting ratio, the optical power switching target value of the two output ports of the MZI optical switch and the current optical power of the two output ports of the MZI optical switch are obtained, and the phase adjustment amount and direction of the interference arm of the MZI optical switch are determined according to the optical power switching target value and the current optical power. When a first excitation signal is applied to the coarse adjustment unit integrated on the MZI optical switch, the input light is distributed to the two output ports according to the first beam splitting ratio. By applying the first excitation signal to the coarse adjustment unit, the phase difference between the two interference arms is made to approach the preset neighborhood range of the phase adjustment amount. Before applying the second excitation signal to the fine-tuning unit integrated on the MZI optical switch to distribute the input light to the two output ports according to the second beam splitting ratio, the adjusted optical power of the two output ports of the MZI optical switch after the first excitation signal is applied is obtained. Based on the optical power switching target value and the adjusted optical power, it is determined whether the optical power switching is completed. If yes, the control ends; if no, the second excitation signal is applied to the fine-tuning unit integrated on the MZI optical switch. When a second excitation signal is applied to the fine-tuning unit integrated on the MZI optical switch, the input light is distributed to the two output ports according to the second beam splitting ratio. Based on the difference between the optical power switching target value and the adjusted optical power, the second excitation signal is applied to the fine-tuning unit integrated on the MZI optical switch within the preset neighborhood range.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention integrates a coarse-tuning unit based on phase-change materials and a fine-tuning unit based on electrothermal control onto the interferometer arm of an MZI optical switch. The phase-change material in the coarse-tuning unit enables non-volatile, wide-range phase coarse-tuning; simultaneously, the electrothermal effect of the fine-tuning unit allows for rapid, continuous phase fine-tuning to compensate for drift and achieve precise dynamic control. This hierarchical control mechanism ultimately achieves wide-range, high-precision, and repeatable phase dynamic management. Furthermore, the phase-change material can achieve the same phase difference within a significantly shorter optical path. This allows for a substantial reduction in the length of the interferometer arm required to achieve the same function, thereby increasing chip integration density and reducing transmission loss and improving response speed. Simultaneously, utilizing the non-volatile nature of the phase-change material, zero static power consumption can be maintained after coarse-tuning. The electrothermal-controlled fine-tuning unit only operates briefly during fine-tuning, significantly reducing overall device power consumption and thermal crosstalk, making it particularly suitable for large-scale integrated photonic circuits. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the MZI optical switch device according to an embodiment of the present invention.

[0026] Figure 2 yes Figure 1 Cross-sectional view at point A.

[0027] Figure 3 This is the refractive index diagram of Sb₂Se₃.

[0028] Figure 4 This is a diagram showing the electric field distribution results from MMI (Multimode Interference) simulation.

[0029] Figure 5 It is an MMI (multimode interference) transmission spectrum.

[0030] Figure 6 This is a diagram showing the effect of phase modulation of the interferometer arm of the MZI optical switch on the output power.

[0031] Figure 7 This is a schematic diagram of the dynamic precision control of the MZI optical switch.

[0032] Figure 8 This is a flowchart of the MZI optical switch phase modulation method.

[0033] In the figure, 1-input waveguide; 2-first beam splitter; 3-first connecting waveguide; 4-interference arm; 5-second connecting waveguide; 6-second beam splitter; 7-output waveguide; 8-coarse adjustment unit; 801-phase change material layer; 9-fine adjustment unit; 901-P-type region; 902-N-type region; 903-electrode; 10-silicon substrate; 11-silicon dioxide layer. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0035] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] Example 1 like Figures 1 to 7As shown, a preferred embodiment of the present invention provides an MZI optical switch device based on the synergy of electrothermal and phase change materials, comprising an input waveguide 1, a first beam splitter 2, a first connecting waveguide 3, an interferometer arm 4, a second connecting waveguide 5, a second beam splitter 6, an output waveguide 7, a coarse adjustment unit 8, and a fine adjustment unit 9. The output end of the input waveguide 1 is connected to the input end of the first beam splitter 2. The output end of the first beam splitter 2 is connected to the input ends of two interferometer arms 4 respectively through two first connecting waveguides 3. The output ends of the two interferometer arms 4 are connected to the input ends of the second beam splitter 6 respectively through second connecting waveguides 5. The output end of the second beam splitter 6 is connected to the input end of the output waveguide 7. At least one interferometer arm 4 integrates a coarse adjustment unit 8, and at least one interferometer arm 4 integrates a fine adjustment unit 9. The coarse adjustment unit 8 and the fine adjustment unit 9 are used to modulate the phase of the optical signal in the corresponding interferometer arm 4, and the phase adjustment range of the coarse adjustment unit 8 is greater than the phase adjustment range of the fine adjustment unit 9. The coarse adjustment unit 8 achieves phase modulation based on the phase change material, and the fine adjustment unit 9 achieves phase modulation based on electrothermal control. This embodiment integrates a coarse adjustment unit 8 based on phase change material and a fine adjustment unit 9 based on electrothermal control on the interferometer arm 4 of the MZI optical switch. The phase change material in the coarse adjustment unit 8 enables non-volatile, wide-range phase coarse adjustment; simultaneously, the electrothermal effect of the fine adjustment unit 9 allows for rapid, continuous phase fine adjustment to compensate for drift and achieve precise dynamic control. This hierarchical control mechanism ultimately achieves wide-range, high-precision, and repeatable phase dynamic management. Furthermore, the phase change material can achieve the same phase difference within a significantly shorter optical path. This allows for a substantial reduction in the length of the interferometer arm required to achieve the same function, thereby increasing chip integration density and reducing transmission loss and improving response speed. Simultaneously, utilizing the non-volatile characteristics of the phase change material, zero static power consumption can be maintained after coarse phase adjustment. The electrothermal control-based fine adjustment unit 9 only operates briefly during fine adjustment, significantly reducing the overall operating power consumption and thermal crosstalk of the device, making it particularly suitable for large-scale integrated photonic circuits.

[0039] In the MZI optical switch, the input optical signal enters the first beam splitter 2 via the input waveguide 1, where it is split into two beams of equal intensity and coupled to the upper and lower interferometer arms 4, respectively. After propagating in the interferometer arms 4, the two beams enter the second beam splitter 6 for beam combining interference. Finally, based on the phase difference between the two interferometer arms 4, the interference result is output from the output waveguide 7. The upper and lower interferometer arms 4 adopt a silicon-based optical waveguide structure, and the interferometer arms 4 integrate a coarse adjustment unit 8 and / or a fine adjustment unit 9 to achieve phase modulation.

[0040] Optionally, at least one interferometer arm 4 integrates a coarse adjustment unit 8 and at least one interferometer arm 4 integrates a fine adjustment unit 9, including: providing a coarse adjustment unit 8 on one interferometer arm 4 and a fine adjustment unit 9 on the other interferometer arm 4; or providing both a coarse adjustment unit 8 and a fine adjustment unit 9 on one interferometer arm 4 and a fine adjustment unit 9 on the other interferometer arm 4; providing both a coarse adjustment unit 8 and a fine adjustment unit 9 on one interferometer arm 4 and a coarse adjustment unit 8 on the other interferometer arm 4; or providing both a coarse adjustment unit 8 and a fine adjustment unit 9 on one interferometer arm 4 and also providing both a coarse adjustment unit 8 and a fine adjustment unit 9 on the other interferometer arm 4. In this embodiment, the two interferometer arms 4 are symmetrically arranged, and both interferometer arms 4 integrate a coarse adjustment unit 8 and a fine adjustment unit 9.

[0041] Specifically, the coarse adjustment unit 8 includes a phase change material layer 801, which covers the top surface and / or sides of the interferometer arm 4. The phase change material layer 801 can be provided on both the top surface and both sides of the interferometer arm 4, or only on the top surface or sides of the interferometer arm 4. In this embodiment, the phase change material layer 801 is provided on the top surfaces of both interferometer arms 4 and is symmetrically arranged. Additionally, the phase change material layer 801 can be symmetrically covered on both sides of one interferometer arm 4. The symmetrical arrangement of the phase change material layer 801 ensures the symmetry of the light field distribution, thereby achieving uniform phase modulation. The symmetrical covering design of the phase change material layer 801 on the interferometer arm 4 helps maintain the stability and uniformity of the light field mode.

[0042] The refractive index change of phase change materials between crystalline and amorphous states (Δn≈0.7–0.9) is much greater than the thermo-optical effect of pure silicon (Δn≈10). -4 The modulation amplitude that can be achieved by the free carrier effect.

[0043] Therefore, to achieve the same phase modulation, the interference arm length of the MZI in this invention can be significantly shortened to 1 / 5–1 / 10 of that of conventional electrothermal devices. This not only greatly increases the chip's integration density but also reduces transmission loss due to the shortened optical path and reduces phase errors caused by temperature drift, thereby improving the device's stability and repeatability.

[0044] Furthermore, once the phase change material of the phase change material layer 801 is heated to a specific crystalline or amorphous state, its optical properties can be stably maintained without the need for external point elements, which enables the device to achieve near-zero static power consumption while maintaining a specific phase.

[0045] Compared to traditional thermo-optical devices that must be continuously powered to maintain phase, this invention consumes only a small amount of power during the brief electrothermal fine-tuning phase, resulting in extremely low average energy consumption. This characteristic gives it a significant advantage in large-scale array applications such as photonic neural networks and reconfigurable optical computing cores.

[0046] The fine-tuning unit 9 includes a pair of microheaters symmetrically arranged on both sides of the interferometer arm 4. The microheaters are thermally coupled to the interferometer arm 4 and extend along the light propagation direction. The effective heating length of the microheaters is 2 to 5 times the length of the phase change material layer 801. This ensures that after the phase change material has completed coarse-tuning and set an approximate operating point, the electrothermal unit has a sufficiently long operating area to provide a sufficient and flexible phase fine-tuning range. This allows for high-precision phase compensation to the target value and dynamic tracking and correction of phase drift caused by environmental fluctuations. The effective heating length of the microheaters in the fine-tuning unit 9 is designed to be 2 to 5 times the length of the phase change material layer 801 in the coarse-tuning unit 8. This design ensures that, based on the phase change coarse-tuning, the electrothermal unit has a sufficient operating range to achieve precise and flexible phase fine-tuning capabilities.

[0047] In this embodiment, as Figure 1 and Figure 2 As shown, the coarse adjustment unit 8 includes a phase change material layer 801, which is disposed on the top or side surface of the interference arm 4. The fine adjustment unit 9 includes a pair of micro heaters symmetrically arranged on both sides of the interference arm 4. The micro heaters include heavily doped P-type regions 901 and N-type regions 902. The interference arm 4 is a silicon waveguide. The P-type regions 901 and N-type regions 902 are located on both sides of the interference arm 4. Electrodes 903 are provided on both the P-type regions 901 and N-type regions 902. Dielectric isolation layers are provided between the electrodes 903 and the phase change material layer 801, and between the electrodes 903 and the interference arm 4.

[0048] The coarse adjustment unit 8 heats the electrode 903, which is integrated with a doped PIN near the phase change material layer 801, by applying electrical pulses of specific amplitude and width. The resulting Joule heating induces a reversible phase change between the crystalline and amorphous states of the phase change material. This process enables a wide range of non-volatile phase "coarse adjustment" at the π phase difference level. Once the phase change is complete, the crystalline or amorphous state of the material will be maintained for a long time without the need for additional energy input to maintain this phase state. The phase state of the phase change material layer 801 is changed using the fine adjustment unit 9. Applying a large excitation signal to the fine adjustment unit 9 changes the phase state of the phase change material layer 801 in the coarse adjustment unit 8, and then applying a small excitation signal performs fine adjustment.

[0049] The fine-tuning unit 9 also uses doped PIN for heating. By controlling the current flowing through the heating unit, the heat generated can be precisely adjusted, thereby utilizing the thermo-optical effect of silicon (dn / dT≈1.86×10⁻⁶). -4 / K) The effective refractive index of the waveguide is continuously and precisely changed to achieve "fine-tuning" of the phase. With the phase change material layer 801 of the coarse-tuning unit 8 fixed, the micro-heater of the fine-tuning unit 9 can perform high-precision, dynamic compensation and fine-tuning of the phase.

[0050] Therefore, the phase change material layer 801 of the coarse adjustment unit 8 is responsible for achieving a wide range of non-volatile "phase coarse adjustment" to set the basic operating point of optical interference. The microheater of the fine adjustment unit 9 is responsible for achieving high-precision "phase fine adjustment" to dynamically compensate for ambient temperature drift or achieve programmable precise phase control. This collaborative mechanism allows the device to consume no static power after phase coarse adjustment, generating extremely low power consumption only when dynamic fine adjustment is needed, thus achieving a high extinction ratio, low power consumption, and dynamically switchable optical switching function.

[0051] In this embodiment, the phase change material layer 801 is responsible for achieving a wide-range, non-volatile "coarse phase adjustment" to set the basic operating point for optical interference. The microheater is responsible for achieving high-precision "fine phase adjustment" to dynamically compensate for ambient temperature drift or to achieve programmable, precise phase control. This collaborative mechanism allows the device to consume no static power after coarse phase adjustment, generating extremely low power consumption only when dynamic fine adjustment is needed, thereby achieving a high extinction ratio, low power consumption, and dynamically switchable optical switching function.

[0052] In this embodiment, the MZI optical switch also includes a silicon substrate 10, on which a silicon dioxide layer 11 is disposed. An input waveguide 1, a first beam splitter 2, a first connecting waveguide 3, an interference arm 4, a second connecting waveguide 5, a second beam splitter 6, an output waveguide 7, a coarse adjustment unit 8, and a fine adjustment unit 9 are disposed on the silicon dioxide layer 11. The electrode 903 is a gold electrode 903, and a dielectric isolation layer is provided between the electrode 903 and the phase change material layer 801, and between the interference arms 4. This allows the micro-heater to be thermally coupled but electrically insulated from the interference arms 4 and the phase change material layer 801. This ensures effective heat transfer to excite phase change or generate thermo-optical effects, while avoiding absorption loss of the optical field caused by the metal electrode 903. It minimizes insertion loss caused by light absorption and scattering, thereby achieving high-performance, low-loss phase modulation. The electrode 903 may also be made of an oxidation-resistant, high-thermal-stability metal material (such as TiN or a Cr / Au composite layer), ensuring the stability of the device during long-term thermal cycling.

[0053] In this embodiment, the phase change material of the fine-tuning unit 9 is Sb₂Se₃. Sb₂Se₃ is a typical low-loss phase change material, such as... Figure 3The figure shows the refractive index characteristics of the phase change material Sb₂Se₃ in the 0-2500 nm range. In the near-infrared band, this material exhibits high refractive indices in both crystalline and amorphous states, along with extremely high refractive index contrast. More importantly, its amorphous state exhibits extremely low absorption coefficient (k ≈ 10⁻⁵) in the communication window, approaching zero absorption. This allows for efficient, low-loss phase modulation of optical signals passing through phase-shifting arms based on this material, laying the material foundation for subsequent high extinction ratio interference effects. The refractive index change between the crystalline and amorphous states can reach Δn ≈ 0.7–0.9, compared to only Δn ≈ 10⁻⁵ for silicon-based electrothermal modulation. -4 The change in phase can achieve the same phase difference within a significantly shorter optical path. This allows for a substantial reduction in the length of the interference arm required to achieve the same function, thereby increasing chip integration density and helping to reduce transmission loss and improve response speed. Furthermore, the phase change material of the fine-tuning unit 9 can also be Sb₂S₃.

[0054] In this embodiment, both the first beam splitter 2 and the second beam splitter 6 are multimode interferometers, configured to operate in the 1500-1600 nm communication band. Compared to traditional directional couplers (DC), multimode interferometers offer advantages such as stable beam splitting ratio, wide wavelength bandwidth, low insertion loss, and insensitivity to process errors and temperature drift, providing a highly stable interference platform for subsequent precise phase modulation. In this embodiment, both the first beam splitter 2 and the second beam splitter 6 employ rectangular multimode waveguide structures, with the input and output waveguides connected by a tapered transition section to reduce mode mismatch loss. The length and width of the multimode interferometer are designed based on the self-imaging principle, configured to operate in the 1500-1600 nm communication band, such as the 1550 nm communication band, achieving a stable and near 50:50 beam splitting ratio. The beam splitting ratio is the ratio of the optical power at the two output ports of the second beam splitter 6.

[0055] Figure 1 This is a schematic diagram of the overall structure of the MZI optical switch device in this embodiment. The optical signal enters from the input waveguide 1, is split into two paths by the first beam splitter 2, and enters the two interferometer arms 4 respectively. The core of phase modulation lies in the composite functional units integrated on the two interferometer arms 4: the coarse adjustment unit 8 and the fine adjustment unit 9.

[0056] The coarse adjustment unit 8 achieves phase modulation based on a phase change material: the phase change material layer 801 located on the top surface of the interferometer arm 4 is crucial. By applying a short, high-energy electrical pulse to the coarse adjustment unit 8, the generated Joule heating induces a reversible phase transition between the crystalline and amorphous states. Due to the extremely large refractive index contrast between the two states, this process can achieve a large-range, non-volatile phase coarse adjustment at the π-phase difference level within an extremely short length.

[0057] Fine-tuning unit 9 achieves phase modulation based on electrothermal control: electrode 903 located above the heavily doped PIN (e.g. Figure 2 The Au shown constitutes the electrothermal unit. By applying a continuous, low-power current, the thermo-optical effect of silicon is used to locally heat the wave interferometer arm 4, thereby producing a continuous, linear refractive index change and achieving precise phase fine-tuning. By independently controlling the phase of the optical signals in the two interferometer arms 4, interference will occur when they are recombined in the second beam splitter 6, ultimately determining whether the optical power is mainly output from the Cross port or the Bar port.

[0058] Figure 2 for Figure 1 Cross-sectional view at point A. (See diagram below.) Figure 2 As shown, a phase change material layer 801 is integrated on the top surface of the interferometer arm 4. The interferometer arm 4 is a silicon waveguide, and the phase change material layer 801 can be electrothermally excited through the metal electrode 903. In addition, the P++ doped region (P-type region 901) and N++ doped region (N-type region 902) integrated in the interferometer arm 4 can be used to form a carrier injection structure to assist in efficient local heating and accurately induce a phase change in the phase change material layer 801.

[0059] The working principle of this MZI optical switch device is determined by the interference effect. The output ports of the MZI optical switch device are the two output ports of the second beam splitter 6, namely the Cross port and the Bar port. The power transmittance of the output ports follows the following relationship: The transmittance of the cross port is:

[0060] The transmittance of the Bar port is:

[0061] in, This represents the cumulative phase difference between the two interference arms 4. The phase difference is significantly altered by switching the states of the phase change material. This allows for the switching of optical signals between the Cross port and the Bar port. For example, when... At 0, light is mainly output from the Bar port; when At this time, light is mainly output from the Cross port, thereby realizing the "on" and "off" state switching of the optical switch.

[0062] To achieve precise phase control, the length of the phase change material on the interferometer arm needs to be determined. When the phase change material in interferometer arm 4 completely transforms from an amorphous state to a crystalline state, and generates a π phase difference in the output, the length of the phase change material layer 801 is derived using the formula:

[0063] The above formula is given when light passes through a segment of length . The waveguide's effective refractive index changes. The phase change introduced at that time.

[0064] The phase change material length of phase change material layer 801 can be obtained from this formula. for:

[0065] in, It is the effective refractive index difference between the amorphous and fully crystalline states of a phase change material. λ is the wavelength of light in a vacuum.

[0066] In this embodiment, the two interferometer arms 4 of the MZI employ a symmetrical design, possessing the same phase change material layer 801 length and the same waveguide length. The phase change material portion is used for coarse phase modulation, while the waveguide portion is used for fine modulation, thereby achieving high-precision, low-power phase control. In the coordinated modulation scheme, the total phase difference... The coarse tuning of the phase change material and the fine tuning of the silicon waveguide's thermo-optical properties contribute to the result. The specific calculations are divided into two cases: When the phase difference of one of the interferometer arms 4 is slightly less than π after coarse adjustment, positive compensation using the electrothermal effect is required, which means fine electrothermal adjustment of the interferometer arm 4 is needed. At this time, the phase difference between the two arms is:

[0067] When the phase difference of one of the interferometer arms 4 is slightly greater than π after coarse adjustment, an electrothermal effect is needed for reverse correction, which means that the other interferometer arm 4 needs to be finely adjusted using electrothermal means. At this time, the phase difference between the two arms is:

[0068] In the formula, and These are the effective lengths of the phase change material and the silicon waveguide thermal conductivity unit, respectively. and These represent the changes in effective refractive index caused by the two factors, respectively. This composite calculation model accurately describes the collaborative working mechanism of "coarse adjustment of phase transition as the benchmark and fine adjustment of electrothermal parameters for precise compensation."

[0069] To verify and ensure the performance of the beam splitting / combining unit in the device, optical simulations were performed on the MZI optical switch. Figure 4The simulated electric field distribution of the MMI (second beam splitter 6) at the operating wavelength is shown. The figure clearly demonstrates that the input optical field, after undergoing multimode interference within the MMI, is effectively decomposed into two output optical fields with equal energy. This simulation result intuitively confirms that the designed MMI structure can achieve a stable 1:1 splitting ratio at both output ports, providing balanced input optical power for the two interference arms 4 of the MZI, which is fundamental to achieving high extinction ratio interference.

[0070] Figure 5 The transmission spectrum of this MMI structure is further presented. Simulation results show that the transmittance of the two output ports remains highly consistent and exhibits minimal fluctuation within a wide wavelength range of 1500 nm to 1600 nm. This demonstrates that the MMI possesses characteristics of wide bandwidth, low loss, and insensitivity to wavelength changes. Its stable 50:50 beam splitting ratio provides a reliable guarantee for subsequent precise phase interference, effectively improving the process tolerance and operational stability of the entire optical switching device.

[0071] Figure 6 Simulation results of the optical mode distribution of the cross-section of MZI interferometer arm 4 are presented, specifically showing the distribution of the electric field component Re(Ey) on the waveguide cross-section (yz plane). From the grayscale distribution, it can be clearly observed that in the composite structure composed of the silicon waveguide of interferometer arm 4 and the phase change material integrated on the top surface, the optical field is effectively confined to the propagation in the core region of the waveguide.

[0072] Figure 7 The complete relationship curve of the MZI output port transmittance as a function of the phase difference between the two interferometer arms 4 is shown. As shown in the figure, the transmittance of the Bar port and the Cross port exhibits typical complementary characteristics, consistent with the basic principle of interferometers. When there is no phase difference between the two interferometer arms 4, the Cross port transmittance reaches its maximum value, while the Bar port is in its minimum transmittance state; when the phase difference reaches π radians, the situation is completely reversed, and the transmittance states of the two ports are interchanged. The key to achieving a high-performance optical switch lies in precisely controlling the operating point near these two extreme states. Therefore, this invention can quickly set the phase difference near the target value through the coarse adjustment mechanism of the phase change material, and then perform precise compensation by combining the fine adjustment function of the electrothermal effect, ensuring that a high extinction ratio of over 30 dB is always maintained in actual operation, while effectively overcoming the performance instability problems caused by temperature drift or manufacturing errors in traditional solutions.

[0073] The MZI optical switch device in this embodiment achieves dynamic optical phase control through the coarse adjustment unit 8 and the fine adjustment unit 9. The phase change material layer 801 of the coarse adjustment unit 8 and the silicon-based electrothermal microheater of the fine adjustment unit 9 work together to achieve excellent balance of multi-dimensional performance. Compared with existing technologies that often require trade-offs between response speed, power consumption, size and accuracy, this invention achieves comprehensive superior performance of high extinction ratio, low power consumption, fast fine adjustment and high phase accuracy (nanoradian level) on a single device through a collaborative mechanism. It also has enhanced system-level scalability, volatile characteristics and low thermal crosstalk design, which enables this device to effectively avoid the "thermal crosstalk barrier" and power accumulation problems caused by continuous heating and thermal coupling in traditional thermo-optical devices when performing large-scale array integration. This provides a feasible technical path for building high-density, large-scale programmable photonic integrated circuits. At the same time, it has excellent dynamic network adaptability and unique "state preservation and fast fine adjustment" capabilities, making it particularly suitable for dynamic reconstruction scenarios that require frequent but small changes (such as dynamic routing in optical communication and weight fine adjustment in photonic neural networks). Compared to technologies requiring a complete reset of the state, this invention significantly reduces control complexity and energy consumption. It also offers improved long-term reliability and stability. Compared to the mechanical fatigue problems of MEMS technology and the carrier migration effects in carrier regulation, the solid-state regulation mechanism (phase transition and thermo-optic effects) of this invention has no moving parts and operates at lower current densities, resulting in higher long-term operational stability and reliability. Furthermore, it simplifies control system requirements: its non-volatile characteristics reduce reliance on real-time monitoring and dynamic feedback control, simplifying drive circuit design. Simultaneously, the hierarchical regulation approach couples a wide range of settings with precise micro-tuning, reducing the requirements for the dynamic range of a single actuator and simplifying control system complexity.

[0074] Example 2 like Figure 8 As shown, this embodiment of the invention provides a phase modulation method for MZI optical switches based on the synergy of electrothermal and phase change materials, and is based on the MZI optical switch device of Embodiment 1. The method includes: A first excitation signal is applied to the coarse adjustment unit integrated on the MZI optical switch, causing the input light to be distributed to the two output ports according to the first beam splitting ratio; A second excitation signal is applied to the fine-tuning unit integrated on the MZI optical switch, causing the input light to be distributed to the two output ports according to a second beam splitting ratio, wherein the difference between the second beam splitting ratio and the first beam splitting ratio is greater than the first beam splitting ratio.

[0075] The method in this embodiment also includes: Before applying the first excitation signal to the coarse adjustment unit integrated on the MZI optical switch to distribute the input light to the two output ports according to the first beam splitting ratio, the target value of optical power switching of the two output ports of the MZI optical switch and the current optical power of the two output ports of the MZI optical switch are obtained. Based on the target value of optical power switching and the current optical power, the phase adjustment amount and direction of the interference arm of the MZI optical switch are determined. By applying a first excitation signal to the coarse adjustment unit integrated on the MZI optical switch, the input light is distributed to the two output ports according to the first beam splitting ratio. By applying the first excitation signal to the coarse adjustment unit, the phase difference between the two interferometer arms is made to approach the preset neighborhood range of the phase adjustment amount. Before applying a second excitation signal to the fine-tuning unit integrated on the MZI optical switch to distribute the input light to the two output ports according to the second beam splitting ratio, the adjusted optical power of the two output ports of the MZI optical switch after the first excitation signal is applied is obtained. Based on the optical power switching target value and the adjusted optical power, it is determined whether the optical power switching is completed. If yes, the control ends; if no, the second excitation signal is applied to the fine-tuning unit integrated on the MZI optical switch. A second excitation signal is applied to the fine-tuning unit integrated on the MZI optical switch to distribute the input light to the two output ports according to the second beam splitting ratio. Based on the difference between the optical power switching target value and the adjusted optical power, the second excitation signal is applied to the fine-tuning unit integrated on the MZI optical switch within a preset neighborhood range.

[0076] In this embodiment, both the first excitation signal and the second excitation signal are electrical pulses. The control method of this embodiment first induces a phase transition by applying an electrical pulse to the phase change material unit, thereby achieving non-volatile, wide-range coarse phase adjustment and setting the basic operating point of the interferometer; then, based on the fixed state of the phase change material, the power of the electrothermal unit is controlled to perform continuous and dynamic fine phase adjustment using the thermo-optic effect, so as to achieve precise phase locking, compensation, or rapid switching.

[0077] This embodiment begins by receiving an optical power switching command and determines the required phase adjustment strategy by accurately measuring the current optical power state of the output port. First, it utilizes the non-volatile characteristics of the phase change material in the coarse adjustment unit for coarse phase adjustment, rapidly establishing a basic operating point by applying specific electrical pulses to control its crystallization degree. Subsequently, the system automatically verifies the switch switching state and, based on real-time measured extinction ratio data, activates the electrothermal control of the fine adjustment unit for precise phase fine-tuning compensation. This hierarchical control mechanism ensures both a wide range of rapid phase setting capabilities and high-precision phase stability control, ultimately achieving a high extinction ratio state switch and entering a non-volatile state maintenance phase. This fully embodies the core concept and technical advantages of coordinated control between phase change coarse adjustment and electrothermal fine adjustment.

[0078] Specifically, such as Figure 8 As shown, the method steps in this embodiment are as follows: S1. Receive Switching Command: The system receives a control request to switch the optical power status of the two output ports (Cross and Bar) of the MZI device. The MZI device is the MZI optical switch, and the two output ports, Cross and Bar, are the output ports of the second optical splitter. The switching control request specifically specifies the target value for switching the optical power of the two output ports.

[0079] S2. Initial State Judgment and Target Setting: Measure the optical power of the current output port of the device, determine the phase difference between the two interferometer arms based on the target value of the optical power switching between the two output ports and the difference between the current optical power of the two output ports, and determine the phase adjustment amount and direction required to achieve the target switching. S3. Perform phase transition coarse adjustment: According to the required phase adjustment amount, a first excitation signal is applied to the coarse adjustment unit integrated on the MZI optical switch. Specifically, by applying a specific electrical pulse to the phase transition material layer unit of the target interferometer arm, its crystallization degree is precisely controlled to achieve a wide-range, non-volatile phase coarse adjustment, setting the phase difference to near the target value (such as π). In this embodiment, the phase difference between the two interferometer arms needs to be π. Therefore, coarse adjustment is used to make the phase difference between the two interferometer arms approach a preset neighborhood of π.

[0080] S4. Verify switch status: Measure the optical power at the device output port again to determine whether the core optical power switching has been completed. Based on the optical power switching target value and the adjusted optical power, determine whether the optical power switching is complete. If yes, end the adjustment; if not, apply a second excitation signal to the fine-tuning unit integrated on the MZI optical switch, i.e., step S5.

[0081] S5. Perform electrothermal fine-tuning: Based on the measured output optical power, calculate the current extinction ratio. If it is not optimal, activate the electrothermal control unit to precisely fine-tune the phase difference using the thermo-optical effect to maximize the extinction ratio. The electrothermal control unit, also known as the fine-tuning unit, applies a second excitation signal to the fine-tuning unit integrated on the MZI optical switch, causing the input light to be distributed to the two output ports according to the second beam splitting ratio. The second excitation signal is an electrical pulse, and its magnitude is obtained based on the difference between the optical power switching target value and the adjusted optical power.

[0082] S6. Complete the switching and maintain: Finally, a high extinction ratio optical switch state is achieved. At this time, the phase change material maintains its state, and the device operates stably with zero static power consumption until the next switching command is received.

[0083] The working process of this invention is as follows: The optical signal first enters the first beam splitter via the input waveguide, where it is split into two beams of equal intensity with a fixed phase relationship, and then coupled into the upper and lower interference arms respectively. The phase of the optical signal transmitted in the two interference arms is independently controlled: by applying an electrical pulse to excite the phase change material layer, it can undergo a transition between a crystalline and amorphous state, and the large refractive index change can be used to achieve a wide-range, non-volatile phase coarse adjustment, thereby setting a basic phase operating point; based on this, by controlling the power of the micro-heater, the phase can be finely adjusted in a small range, continuously, and dynamically using the thermo-optical effect of silicon to accurately compensate for deviations. When the two separately controlled optical signals re-converge in the second beam splitter, the final phase difference Δφ between them will determine their interference result, thereby controlling the energy distribution at the output port and realizing the switching of the optical switch between "on" (light transmission) and "off" (light blocking) states or dynamic optical power distribution. Throughout the process, the phase change material layer is responsible for maintaining and significantly adjusting the state over a long period, while the electrothermal microheater ensures the precision of control and dynamic response capability. The two work together to achieve a dynamic optical switch function with high extinction ratio and low power consumption.

[0084] In summary, this invention provides an MZI optical switch device based on the synergy of electrothermal and phase change materials. It integrates a coarse adjustment unit based on phase change materials and a fine adjustment unit based on electrothermal control onto the interferometer arm of the MZI optical switch. This invention clearly divides phase control into two levels: non-volatile phase change coarse adjustment and dynamic continuous electrothermal fine adjustment. The synergistic mechanism of phase change materials and electrothermal microheaters is deeply integrated into the MZI interferometer arm: the coarse adjustment unit is responsible for achieving non-volatile "phase coarse adjustment," utilizing its large refractive index change to quickly set the phase operating point by π or even multiples of π, for rapid and wide-range setting of the optical operating point; the fine adjustment unit, based on the thermo-optical effect of silicon, is responsible for achieving continuous and rapid "phase fine adjustment," performing precise dynamic compensation and perturbation, specifically for offsetting environmental drift or performing fine phase adjustment. After phase change control is completed, its state (crystalline / amorphous) and the corresponding phase reference can be maintained for a long time without continuous energy consumption; while electrothermal control only intervenes when fine adjustment is needed, reducing overall energy consumption by more than an order of magnitude compared to traditional continuous heating schemes. This hierarchical strategy greatly expands the effective dynamic range of the device, enabling it to achieve both large-scale phase settings and high-precision stable control at the nanoradian level. Its comprehensive control capability is significantly better than that of a single-mechanism controller. This "coarse setting, fine setting and fine adjustment" mode provides a precise and low-power phase control basis for achieving high extinction ratio optical switching operation. Specifically, (1) a phase change material with high refractive index contrast is introduced into the coarse setting unit. Its huge effective refractive index change (Δn≈0.9) allows the length of the interference arm required to achieve π phase difference to be significantly shortened to 1 / 5 to 1 / 10 of that of traditional electrothermal devices. This not only reduces the device size but also reduces optical transmission loss, and ultimately achieves high extinction ratio optical switching operation at the output end. (2) The first and second beam splitters use multimode interference couplers instead of traditional directional couplers, and their splitting ratio is insensitive to manufacturing process errors and external temperature fluctuations. This characteristic gives the device a wider operating wavelength bandwidth, lower insertion loss, and higher interference stability, laying a solid foundation for precise phase control. (3) It creatively combines the non-volatile "coarse adjustment" of phase change materials with the continuous "fine adjustment" of electrothermal effects. This clearly defined collaborative mechanism enables the device to simultaneously possess a wide range of phase setting capabilities and high-precision dynamic phase fine adjustment capabilities, achieving integrated control with a wide range and high precision. (4) Thanks to the non-volatility of phase change materials, after completing the coarse phase adjustment, the core phase state of the device does not need to be continuously powered to maintain its state. Only when dynamic fine adjustment is required will the electrothermal unit operate at milliwatt-level or even lower power, thereby significantly reducing the overall energy consumption, which is particularly suitable for large-scale array integration. (5) By adopting a low-optical-loss phase change material system and optimizing the dielectric isolation layer design, light absorption and scattering are effectively suppressed. At the same time, the adoption of the MMI structure enhances the tolerance to process deviations.These measures together ensure that the device achieves high performance while also having low insertion loss and high operational reliability.

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A MZI optical switch device based on the synergy of electrothermal and phase change materials, characterized in that, It includes an input waveguide (1), a first beam splitter (2), a first connecting waveguide (3), an interferometer (4), a second connecting waveguide (5), a second beam splitter (6), an output waveguide (7), a coarse adjustment unit (8), and a fine adjustment unit (9). The output end of the input waveguide (1) is connected to the input end of the first beam splitter (2). The output end of the first beam splitter (2) is connected to the input ends of the two interferometer arms (4) through the two first connecting waveguides (3). The output ends of the two interferometer arms (4) are connected to the input ends of the second beam splitter (6) through the second connecting waveguides (5). The output end of the second beam splitter (6) is connected to the input end of the output waveguide (7). At least one of the interferometer arms (4) integrates the coarse adjustment unit (8), and at least one of the interferometer arms (4) integrates the fine adjustment unit (9). The coarse adjustment unit (8) and the fine adjustment unit (9) are used to modulate the phase of the optical signal in the corresponding interferometer arm (4), and the phase adjustment range of the coarse adjustment unit (8) is greater than the phase adjustment range of the fine adjustment unit (9). The coarse adjustment unit (8) achieves phase modulation based on phase change material, and the fine adjustment unit (9) achieves phase modulation based on electrothermal control.

2. The MZI optical switch device according to claim 1, characterized in that, The coarse adjustment unit (8) includes a phase change material layer (801), and the top and / or side surfaces of the interference arm (4) are covered with the phase change material layer (801).

3. The MZI optical switch device according to claim 1, characterized in that, The fine-tuning unit (9) includes a pair of micro heaters symmetrically arranged on both sides of the interference arm (4), the micro heaters being thermally coupled to the interference arm (4), and the micro heaters extending along the light propagation direction.

4. The MZI optical switch device according to claim 1, characterized in that, The fine adjustment unit (9) includes a pair of micro heaters symmetrically arranged on both sides of the interference arm (4). The micro heaters are thermally coupled to the interference arm (4) and extend along the light propagation direction. The coarse adjustment unit (8) includes a phase change material layer (801). The top surface and / or side surface of the interference arm (4) are covered with the phase change material layer (801). The effective heating length of the microheater is 2 to 5 times the length of the phase change material layer (801).

5. The MZI optical switch device according to claim 1, characterized in that, The coarse adjustment unit (8) includes a phase change material layer (801), which is disposed on the top or side surface of the interference arm (4). The fine adjustment unit (9) includes a pair of micro heaters symmetrically arranged on both sides of the interference arm (4). The micro heaters include heavily doped P-type regions (901) and N-type regions (902). The interference arm (4) is a silicon waveguide. The P-type regions (901) and N-type regions (902) are located on both sides of the interference arm (4). Electrodes (903) are provided on both the P-type regions (901) and N-type regions (902). Dielectric isolation layers are provided between the electrodes (903) and the phase change material layer (801) and between the electrodes (903) and the interference arm (4).

6. The MZI optical switch device according to claim 1, characterized in that, The phase change material of the fine-tuning unit (9) is Sb2Se3.

7. The MZI optical switch device according to claim 6, characterized in that, Both the first beam splitter (2) and the second beam splitter (6) are multimode interferometers, and the first beam splitter (2) and the second beam splitter (6) are configured to operate in the 1500-1600nm communication band.

8. The MZI optical switch device according to claim 1, characterized in that, The two interference arms (4) are symmetrically arranged, and each interference arm (4) integrates the coarse adjustment unit (8) and the fine adjustment unit (9).

9. A phase modulation method for MZI optical switches based on the synergy of electrothermal and phase change materials, characterized in that, include: A first excitation signal is applied to the coarse adjustment unit (8) integrated on the MZI optical switch, so that the input light is distributed to the two output ports according to the first beam splitting ratio; A second excitation signal is applied to the fine-tuning unit (9) integrated on the MZI optical switch, so that the input light is distributed to the two output ports according to the second beam splitting ratio, wherein the difference between the second beam splitting ratio and the first beam splitting ratio is greater than the first beam splitting ratio.

10. The method according to claim 9, characterized in that, Also includes: Before applying the first excitation signal to the coarse adjustment unit (8) integrated on the MZI optical switch to distribute the input light to the two output ports according to the first beam splitting ratio, the optical power switching target value of the two output ports of the MZI optical switch and the current optical power of the two output ports of the MZI optical switch are obtained, and the phase adjustment amount and direction of the interference arm (4) of the MZI optical switch are determined according to the optical power switching target value and the current optical power. When a first excitation signal is applied to the coarse adjustment unit (8) integrated on the MZI optical switch, the input light is distributed to the two output ports according to the first beam splitting ratio. By applying the first excitation signal to the coarse adjustment unit (8), the phase difference between the two interference arms (4) is made to approach the preset neighborhood range of the phase adjustment amount. Before applying the second excitation signal to the fine-tuning unit (9) integrated on the MZI optical switch to distribute the input light to the two output ports according to the second beam splitting ratio, the adjusted optical power of the two output ports of the MZI optical switch after the first excitation signal is applied is obtained. Based on the optical power switching target value and the adjusted optical power, it is determined whether the optical power switching is completed. If yes, the control ends; if no, the second excitation signal is applied to the fine-tuning unit (9) integrated on the MZI optical switch. When a second excitation signal is applied to the fine-tuning unit (9) integrated on the MZI optical switch, the input light is distributed to the two output ports according to the second beam splitting ratio. Based on the difference between the optical power switching target value and the adjusted optical power, the second excitation signal is applied to the fine-tuning unit (9) integrated on the MZI optical switch within the preset neighborhood range.

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