Spatial light modulator, wavelength selective switch, optical communication device, and system

Abstract

The embodiments of the present application relate to the technical field of optical communications. Disclosed are a spatial light modulator, a wavelength selective switch, an optical communication device, and a system. The spatial light modulator comprises a first modulation assembly and a second modulation assembly, which are sequentially disposed in a specific direction. The first modulation assembly comprises a first common electrode, a first pixel electrode array, and a first liquid crystal layer located between the first common electrode and the first pixel electrode array, wherein liquid crystal molecules in the first liquid crystal layer are arranged in a periodic fan-shaped columnar shape in a plane perpendicular to the direction of incidence of optical signals. The second modulation assembly comprises a second common electrode, a second pixel electrode array, and a second liquid crystal layer located between the second common electrode and the second pixel electrode array, and further comprises a metasurface layer, a reflecting layer and a CMOS silicon-based backplane, which are sequentially disposed in the specific direction, wherein pixel electrodes in the second pixel electrode array are electrically connected to the CMOS silicon-based backplane. The spatial light modulator has polarization-independent phase response characteristics, and enables fast and crosstalk-free switching of an output port for optical signals when applied to a wavelength selective switch.

Description

Spatial light modulators, wavelength selective switches, optical communication equipment and systems

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on December 15, 2023, with application number 202311735376.2 and application name “Spatial light modulator, wavelength selective switch, optical communication equipment and system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of optical communication technology, and in particular to a spatial light modulator, a wavelength selective switch, an optical communication device and a system. Background Art

[0003] Optical communication networks utilize reconfigurable optical add-drop multiplexers (ROADMs) and optical cross-connects (OXCs) to flexibly configure and freely schedule the add / drop and pass-through wavelengths of optical signals at each optical network node. A wavelength selective switch (WSS), also known as a wavelength selective switch, serves as a core component of ROADM or OXC devices. It outputs any one or more wavelengths of an input wavelength division multiplexing (WDM) signal (e.g., a multi-wavelength optical signal) to any output port, thereby enabling dynamic port switching and energy balancing (e.g., signal attenuation control) for each wavelength of the optical signal in the fiber link.

[0004] Typically, WSS achieves the above functions based on technologies such as microelectromechanical mirrors (MEMS), liquid crystal on silicon (LCoS), liquid crystal (LC), and digital micro-mirror devices (DMD). Among them, WSS based on LCoS has many advantages, such as flexible grid, small size, no mechanical vibration, and high reliability, making it the mainstream technology for WSS. However, when LCoS devices are used as beam deflection elements (or optical switching engines) in WSS, due to the fringe field effect of LCoS, stray light is generated during beam deflection. Furthermore, during port switching, stray light can easily enter other ports as crosstalk signals, generating transient crosstalk.

[0005] Therefore, for LCoS-based WSS, how to avoid transient crosstalk associated with port switching has become a technical problem that needs to be solved urgently.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a spatial light modulator, a wavelength selective switch, an optical communication device, and a system. The main purpose is to provide a spatial light modulator that is polarization-independent and can quickly switch the transmission direction of an optical signal, as well as a wavelength selective switch based on the spatial light modulator. On the one hand, the wavelength selective switch can quickly complete port switching and avoid transient crosstalk generated during the port switching process. On the other hand, the wavelength selective switch can also have polarization-independent characteristics and has the advantages of a simple and easy-to-implement optical path and low polarization-dependent loss. On the other hand, the wavelength selective switch can achieve attenuation processing of optical signals without the need for complex algorithms.

[0008] In a first aspect, embodiments of the present application provide a spatial light modulator having polarization-independent characteristics. The spatial light modulator may include a first modulation component and a second modulation component sequentially arranged along a specific direction, such that an incident light signal may sequentially pass through the first modulation component and the second modulation component. The specific direction may be, for example, the incident direction of the light signal. The first modulation component includes a first liquid crystal layer, a first common electrode, and a first pixel electrode array; the first common electrode and the first pixel electrode array are respectively arranged on either side of the first liquid crystal layer; the liquid crystal molecules in the first liquid crystal layer are arranged in a periodic fan-shaped pattern in a plane perpendicular to the incident direction of the light signal. Specifically, the liquid crystal molecules in the first liquid crystal layer are periodically arranged in a preset direction, with the azimuth angle of the liquid crystal molecules within a period continuously and linearly varying by 180°; the preset direction is perpendicular to the incident direction of the light signal. The second modulation component includes a second common electrode, a second pixel electrode array, and a second liquid crystal layer located therebetween. Furthermore, the second modulation component may include a metasurface layer, a reflective layer, and a CMOS silicon-based backplane, sequentially arranged along a specific direction on a side of the second liquid crystal layer away from the first liquid crystal layer. The pixel electrodes in the second pixel electrode array are electrically connected to the CMOS silicon-based backplane.

[0009] In the above-mentioned spatial light modulator, the first common electrode and the first pixel electrode apply a first voltage to the first liquid crystal layer to change the state of the liquid crystal molecules in the first liquid crystal layer. The first liquid crystal layer is used to modulate the transmission direction of the light signal passing through the first liquid crystal layer based on the first voltage. The second common electrode and the second pixel electrode are used to apply a second voltage to the second liquid crystal layer to change the state of the liquid crystal molecules in the second liquid crystal layer. The second liquid crystal layer is used to modulate the transmission direction of the light signal passing through the second liquid crystal layer based on the second voltage. The metasurface layer is used to change the polarization direction of the light signal passing through the metasurface layer. The reflective layer is used to reflect the light signal emitted by the metasurface layer. The CMOS silicon-based backplane is used to configure the second voltage.

[0010] Because both the first and second modulators can deflect the direction of optical signal transmission by adjusting the state of their internal liquid crystals, when this spatial light modulator is used in a wavelength selective switch, the first and second modulators work together to rapidly switch ports. During port switching, the second modulator undergoes only a single configuration change, achieving a "single-step" switching, resulting in a relatively fast switching speed.

[0011] In addition, because the liquid crystal molecules in the first liquid crystal layer are periodically arranged in a preset direction within a plane perpendicular to the incident direction of the light signal (such as the XY plane), the azimuth angle of the liquid crystal molecules within one period continuously and linearly changes by 180°. Therefore, when looking down at the XY plane, the first liquid crystal layer forms a strip grating, and the light beam has a geometric phase when passing through the first liquid crystal layer. Based on this, when no voltage is applied to the first liquid crystal layer (the first voltage is zero), the first liquid crystal layer can deflect the propagation direction of the light beam based on the diffraction effect on the light beam. Moreover, when the first liquid crystal layer is used for light beam deflection, it has polarization-independent characteristics. That is, for an incident light beam of any polarization state, the light beam propagation direction can be deflected. In addition, when a voltage is applied to the first liquid crystal layer (the first voltage is greater than zero), the liquid crystal molecules in the first liquid crystal layer can assume different states depending on the magnitude of the voltage. When a first voltage (greater than zero, with a driving electric field) is applied to the first liquid crystal layer, ideally, the long axes of all liquid crystal molecules, except those near the alignment layer, are perpendicular to the XY plane. In other words, their long axes are tilted at an angle of 90° or nearly 90° relative to the XY plane. At this point, incident light can pass through the first liquid crystal layer without changing its direction. Of course, when a second voltage (greater than zero and less than the first voltage, with a driving electric field) is applied to the first liquid crystal layer, ideally, the long axes of all liquid crystal molecules, except those near the alignment layer, are tilted at an angle of less than 90° relative to the XY plane. At this point, the intensity of the incident light is attenuated by the first liquid crystal layer.

[0012] As a possible implementation, assume that the liquid crystal molecules are periodically arranged along a preset direction in the XY plane, the azimuth angle of the liquid crystal molecules continuously changes by 180° within one period, and the director n(x) of the liquid crystal is a function of the coordinate variable x, and satisfies n(x) = [sin(πx / Λ), cos(πx / Λ), 0]

[0013] Here, the range of x is 0-Λ. Looking down at the XY plane, the first liquid crystal layer forms a stripe grating, Λ is the grating period, and the x-axis direction is the direction of the grating period.

[0014] In the above-mentioned spatial light modulator, the metasurface layer is used to convert the polarization direction of the optical signal passing through the metasurface layer from the optical signal of the first direction to the optical signal of the second direction, and convert the polarization direction of the optical signal passing through the metasurface layer from the optical signal of the second direction to the first direction; the first direction is orthogonal to the second direction. Furthermore, the second modulation component has a polarization-independent phase response characteristic. Regardless of the optical signal polarized in the first direction or the second direction, the same phase modulation can be obtained once in the entire process from the incident to the second modulation component to the final emission. Since the optical signal with any other polarization state in the incident optical signal can always be decomposed into a combination of an optical component with the first polarization state and an optical component with the first polarization state, and each polarization state optical component also obtains only one phase modulation, the second modulation component has a polarization-independent phase response characteristic.

[0015] Since both the first modulation component and the second modulation component have polarization-independent phase response characteristics, when such a spatial light modulator is applied to a wavelength selective switch, there is no need to set a polarization conversion structure in the wavelength selective switch. This can simplify the structure of the wavelength selective switch and reduce the device volume, optical path complexity, and polarization-dependent loss.

[0016] In one possible implementation of the first aspect, in the spatial light modulator, the second pixel electrode array is formed in the reflective layer. For example, the second pixel electrode array can be specifically implemented as a pixelated metal layer that reflects light, or in other words, the second pixel electrode array has a light-reflecting function. In this implementation, the second pixel electrode array is formed in the reflective layer, or is formed integrally with the metal material for light reflection.

[0017] In another possible implementation of the first aspect, in the spatial light modulator, the second pixel electrode array is disposed between the reflective layer and the CMOS silicon-based backplane. In this implementation, the second pixel electrode array is independent of the reflective layer and can, for example, be disposed on a surface of the reflective layer that is close to the CMOS silicon-based backplane.

[0018] In one possible implementation of the first aspect, the spatial light modulator further includes N signal interfaces, where N is an integer greater than or equal to 1; the first common electrode, the first pixel electrode array, the second common electrode, and the CMOS silicon-based backplane are electrically connected to the same or different signal interfaces. For example, the first modulation component may include a first signal interface, to which the first common electrode and the first pixel electrode array are electrically connected. The first signal interface is configured to electrically connect to a drive circuit, which is configured to output a voltage signal to the first pixel circuit. The first pixel circuit outputs a voltage to the first pixel electrode and the first common electrode based on the voltage signal input by the drive circuit. The second modulation component may include a second signal interface, to which the CMOS silicon-based backplane is connected via a data line. The second signal interface is configured to electrically connect to the drive circuit. The drive circuit is further configured to output a data signal to the data line. Furthermore, the second common electrode may be electrically connected to the drive circuit via the second signal interface to obtain a voltage. The drive circuit may be a circuit structure external to the spatial light modulator.

[0019] In another possible implementation manner of the first aspect, the driving circuit is integrated into the spatial light modulator, and the N signal interfaces are electrically connected to the driving circuit.

[0020] In another possible implementation of the first aspect, the spatial light modulator also includes a first opposing substrate and a second opposing substrate; the first opposing substrate is arranged on a side of the first liquid crystal layer away from the second liquid crystal layer; the first common electrode is arranged on a surface of the first opposing substrate close to the first liquid crystal layer; the second opposing substrate is arranged on a side of the second liquid crystal layer away from the CMOS silicon-based backplane; and the second common electrode is arranged on a surface of the second opposing substrate close to the second liquid crystal layer.

[0021] In another possible implementation of the first aspect, the spatial light modulator further includes a first alignment layer and a second alignment layer; the first alignment layer and the second alignment layer are respectively disposed on either side of the first liquid crystal layer. The first alignment layer is used to anchor adjacent liquid crystal molecules in the first liquid crystal layer, causing the adjacent liquid crystal molecules to be pre-oriented. The second alignment layer is used to anchor adjacent liquid crystal molecules in the first liquid crystal layer, causing the adjacent liquid crystal molecules to be pre-oriented. Under the action of the first alignment layer and the second alignment layer, the pre-orientation produced by the liquid crystal molecules in the first liquid crystal layer closest to the first alignment layer is the same as the pre-orientation produced by the liquid crystal molecules in the first liquid crystal layer closest to the second alignment layer. In other words, the first alignment layer and the second alignment layer have the same orientation direction.

[0022] In another possible implementation of the first aspect, the spatial light modulator further includes a third alignment layer and a fourth alignment layer; the third alignment layer and the fourth alignment layer are respectively disposed on either side of the second liquid crystal layer. The third alignment layer is used to anchor the liquid crystal molecules adjacent to it in the second liquid crystal layer, causing the adjacent liquid crystal molecules to be pre-aligned. The fourth alignment layer is used to anchor the liquid crystal molecules adjacent to it in the second liquid crystal layer, causing the adjacent liquid crystal molecules to be pre-aligned. Under the action of the third and fourth alignment layers, the pre-alignment produced by the liquid crystal molecules in the second liquid crystal layer closest to the third alignment layer is the same as the pre-alignment produced by the liquid crystal molecules in the second liquid crystal layer closest to the fourth alignment layer. In other words, the third and fourth alignment layers have the same orientation direction.

[0023] In another possible implementation of the first aspect, the spatial light modulator further includes a light-enhancing layer; the light-enhancing layer is disposed on a side of the first opposing substrate away from the first liquid crystal layer, and is configured to increase the transmittance of an incident light signal.

[0024] In a second aspect, embodiments of the present application provide a method for phase modulation of an optical signal, applied to a spatial light modulator, the spatial light modulator comprising a first modulation component and a second modulation component, such as any of the spatial light modulators mentioned in the first aspect. The method comprises:

[0025] The first modulation component receives an incident first optical signal of any polarization state, and emits a second optical signal to the second modulation component by diffracting or transmitting the first optical signal; the transmission direction of the second optical signal is a first preset direction;

[0026] The second modulation component receives the second optical signal from the first modulation component, performs phase modulation on the second optical signal, and reflects a third optical signal to the first modulation component; the transmission direction of the third optical signal is the second preset direction;

[0027] The first modulation component receives the third optical signal from the second modulation component, and emits a fourth optical signal in a target direction by diffracting or transmitting the third optical signal.

[0028] Any two of the first optical signal, the second optical signal, the third optical signal, and the fourth optical signal carry the same service information, but may have different transmission directions and polarization states.

[0029] In a possible implementation of the second aspect, the target direction is opposite to the transmission direction of the first optical signal; or, the target direction is parallel to one of the first preset plane and the second preset plane, and is deflected by a preset angle relative to the transmission direction of the first optical signal; the first preset plane, the second preset plane, and the light receiving surface provided by the first modulation component are perpendicular to each other.

[0030] In a possible implementation of the second aspect, the first modulation component includes a first common electrode, a first pixel electrode array, and a first liquid crystal layer located between the first common electrode and the first pixel electrode array; the first modulation component receives an incident first light signal of any polarization state, and emits a second light signal to the second modulation component by diffracting or transmitting the first light signal, including:

[0031] A first voltage is generated between the first common electrode and the first pixel electrode array; the first liquid crystal layer receives an incident light signal and, based on the first voltage, diffracts or transmits the first light signal to emit a second light signal to the second modulation component.

[0032] In a possible implementation of the second aspect, the second modulation component includes a metasurface layer, a second common electrode, a second pixel electrode array, and a second liquid crystal layer located between the second common electrode and the second pixel electrode array; the second pixel electrode array is formed on the reflective layer, or the second modulation component further includes a reflective layer; the second modulation component receives the second optical signal from the first modulation component, phase modulates the second optical signal, and reflects a third optical signal to the first modulation component, including:

[0033] A second voltage is generated between the second common electrode and the second pixel electrode array; the second liquid crystal layer receives the second optical signal from the first modulation component; if the polarization direction of the second optical signal is the first direction, the second optical signal is phase modulated based on the second voltage; the metasurface layer converts the polarization direction of the second optical signal from the first direction to the second direction, or converts the polarization direction of the second optical signal from the second direction to the first direction, and the first direction is orthogonal to the second direction; the reflective layer receives the optical signal emitted from the metasurface layer and reflects the optical signal; the second liquid crystal layer receives the reflected optical signal emitted by the reflective layer, and if the polarization direction of the reflected optical signal is the first direction, the reflected optical signal is phase modulated based on the second voltage, and a third optical signal is emitted to the first modulation component in a second preset direction.

[0034] In a possible implementation manner of the second aspect, the second optical signal and / or the fourth optical signal undergoes a preset degree of energy attenuation relative to the first optical signal.

[0035] In a third aspect, an embodiment of the present application provides a wavelength selective switch, comprising an input and output fiber array, a grating dispersive element, a lens assembly, and any one of the spatial light modulators provided in the first aspect above; wherein the input and output fiber array comprises a plurality of input and output ports; the grating dispersive element is located on the transmission path of the incident light signal S input from the input and output ports, and is used to disperse the incident light signal S into at least one light signal Si, and different light signals Si correspond to different wavelengths; the lens assembly is located on the transmission path of at least one light signal Si, and is used to project at least one light signal Si to different wavelength channels of the spatial light modulator; the spatial light modulator is used to receive at least one light signal Si, and output light signals Si of different wavelengths to different input and output ports based on different wavelength channels.

[0036] In a fourth aspect, an embodiment of the present application provides a port switching method, which is applied to the spatial light modulator in the wavelength selective switch provided in the third aspect. The method includes:

[0037] receiving a light signal projected by the lens assembly;

[0038] During a first time period, based on a first preset voltage between the first common electrode and the first pixel electrode, the optical signal is output to a location outside the preset port; at a first moment, the voltage between the second common electrode and the second pixel electrode is a second preset voltage, and at a second moment, the voltage between the second common electrode and the second pixel electrode is a third preset voltage; the second moment is a moment later than the first moment during the first time period; the preset port includes one or more input and output ports in the input and output optical fiber array;

[0039] In a second time period, based on a fourth preset voltage between the first common electrode and the first pixel electrode, and a third preset voltage between the second common electrode and the second pixel electrode, an optical signal is output to the first port; the second time period is later than the first time period; the first port is an input / output port in the input / output optical fiber array.

[0040] As can be seen from the above embodiment, by adjusting the voltage configuration of the first modulation component and the second modulation component, the first modulation component and the second modulation component cooperate to achieve rapid port switching. The configuration change of the second modulation component is a necessary condition for switching the optical signal output from the first port to the second port, while the configuration change of the first modulation component is intended to deflect the optical signal from a preset port to a location outside the preset port, or deflect the optical signal from a location outside the preset port back to a preset port, thereby ensuring that no stray light is transmitted to the preset port during the process of changing the configuration of the second modulation component. The preset port here can be a pre-recorded valid port for service signal transmission.

[0041] For the second modulation component, only one configuration change occurs during the port switching process, so it can be understood that the embodiment of the present application realizes port switching through "single-step switching". Compared with the "multi-step switching" scheme in which multiple phase diagrams are interspersed in the middle, the embodiment of the present application completes the adjustment of the phase plane of the liquid crystal layer in the second modulation component at one time, which can ensure a faster switching speed. In addition, since the liquid crystal layer in the second modulation component is loaded with the final phase plane during the process (that is, in the intermediate state), the optical signal will be deflected to a position outside the preset port based on the first modulation component, so it will not become a crosstalk signal and be transmitted to the effective port.

[0042] In a possible implementation of the fourth aspect, the port switching method further includes:

[0043] In a third time period, based on a fifth preset voltage between the first common electrode and the first pixel electrode, and a second preset voltage between the second common electrode and the second pixel electrode, an optical signal is output to the second port; the third time period is earlier than the first time period; the second port is an input and output port in the input and output optical fiber array, and the first port is different from the second port.

[0044] In a fifth aspect, embodiments of the present application further provide a signal attenuation method, which is applied to the spatial light modulator in the wavelength selective switch provided in the third aspect; the method comprises:

[0045] The first modulation component receives the optical signal projected by the lens component;

[0046] The first modulation component emits the optical signal to the second modulation component based on a first target voltage between the first common electrode and the first pixel electrode;

[0047] the second modulation component reflects the optical signal from the first modulation component to the first modulation component based on a second target voltage between the second common electrode and the second pixel electrode;

[0048] The first modulation component emits the optical signal from the second modulation component to a target port based on a first target voltage between the first common electrode and the first pixel electrode; the target port is an input / output port in the input / output optical fiber array;

[0049] The optical signal emitted by the first modulation component to the second modulation component, and / or the optical signal emitted by the first modulation component to the target port, undergoes a preset degree of energy attenuation relative to the optical signal projected by the lens component.

[0050] It can be seen that in the embodiment of the present application, the first modulation component is used to realize the attenuation control of the optical signal. In the related art, taking the LCoS-based spatial light modulator as an example, in the face of some application scenarios that require signal attenuation control, extremely complex algorithms are required to control the voltage applied to the electrodes in the LCoS device, so that the target phase plane formed by the liquid crystal layer in the LCoS device can achieve both phase modulation and attenuation of signal intensity. Compared with the related art, the spatial light modulator provided in the embodiment of the present application decouples signal attenuation control from phase modulation. For example, signal attenuation is realized by the first modulation component, and phase modulation is realized by the second modulation component. Therefore, the attenuation processing of the optical signal can be realized without complex algorithms, while not affecting the phase modulation effect.

[0051] In a sixth aspect, embodiments of the present application further provide a method for controlling a spatial light modulator, wherein the spatial light modulator is the spatial light modulator in the wavelength selective switch described in the third aspect; the method comprising:

[0052] receiving a port switching instruction, wherein the port switching instruction includes a target port;

[0053] In response to the port switching instruction, at a first moment, the voltage between the first common electrode and the first pixel electrode is adjusted to a first preset voltage; at the first moment, the voltage between the second common electrode and the second pixel electrode is a second preset voltage; the first preset voltage is used to cause the spatial light modulator to output the light signal projected by the lens assembly to a position outside the preset port;

[0054] At a second moment, controlling the generation of a third preset voltage between the second common electrode and the second pixel electrode;

[0055] At the third moment, a fourth preset voltage is controlled to be generated between the first common electrode and the first pixel electrode; the fourth preset voltage and the third preset voltage are used to enable the spatial light modulator to output the light signal projected by the lens assembly to the target port.

[0056] The technical effects of the method for controlling the spatial light modulator provided in the sixth aspect can be found in the content of the fourth aspect and will not be elaborated here.

[0057] In a seventh aspect, an embodiment of the present application further provides a method for controlling a spatial light modulator, wherein the spatial light modulator is the spatial light modulator in the wavelength selective switch described in the third embodiment; the method comprises:

[0058] receiving a signal attenuation instruction, the signal attenuation instruction including an attenuation parameter, the attenuation parameter representing a preset attenuation degree of the optical signal;

[0059] In response to the signal attenuation instruction, controlling the generation of a first target voltage between the first common electrode and the first pixel electrode; and controlling the generation of a second target voltage between the second common electrode and the second pixel electrode;

[0060] The first target voltage and the second target voltage are used to enable the spatial light modulator to output the incident optical signal to the target port; the first target voltage is used to cause the optical signal output to the target port to attenuate energy by a preset degree relative to the incident optical signal.

[0061] The technical effects of the method for controlling the spatial light modulator provided in the seventh aspect can be found in the content of the fifth aspect and will not be elaborated here.

[0062] In an eighth aspect, an embodiment of the present application further provides an optical communication device, comprising the spatial light modulator described in any one of the first aspects, or the wavelength selective switch described in the third aspect.

[0063] In a ninth aspect, an embodiment of the present application further provides an optical communication system, comprising the optical communication device described in the eighth aspect.

[0064] In the contents of the first to ninth aspects above, the technical effects brought about by any possible implementation method of the second and third aspects can also refer to the technical effects brought about by the implementation method of the first aspect above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] FIG1 is a schematic structural diagram of an optical communication system;

[0066] FIG2 is a schematic structural diagram of an optical add / drop multiplexer;

[0067] FIG3 is a schematic structural diagram of a wavelength selective switch;

[0068] FIG4 is a schematic structural diagram of an LCoS-based spatial light modulator 40;

[0069] FIG5 is a schematic diagram of a liquid crystal layer;

[0070] FIG6 is a schematic diagram of an ideal phase plane and a non-ideal phase plane formed by a liquid crystal layer;

[0071] FIG7 is a schematic structural diagram of a wavelength selective switch provided in an embodiment of the present application;

[0072] FIG8 is a schematic structural diagram of a spatial light modulator provided in an embodiment of the present application;

[0073] FIG9 is another schematic structural diagram of a spatial light modulator provided in an embodiment of the present application;

[0074] FIG10 is a schematic diagram of the distribution of liquid crystal molecules in the first liquid crystal layer of the spatial light modulator provided in an embodiment of the present application;

[0075] FIG11 is a schematic diagram of another distribution of liquid crystal molecules in the first liquid crystal layer of the spatial light modulator provided in an embodiment of the present application;

[0076] FIG12 is a schematic diagram of several light beam transmission direction deflection effects of a spatial light modulator provided in an embodiment of the present application;

[0077] FIG13 is a flow chart of a method for controlling a spatial light modulator according to an embodiment of the present application. DETAILED DESCRIPTION

[0078] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0079] Unless otherwise defined, all scientific and technological terms used herein have the same meaning as those known to those of ordinary skill in the art. In the embodiments of the present application, "at least one" refers to one or more, and "a plurality" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, wherein A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following items" or its similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can represent: a, b, c, a and b, a and c, b and c or a, b and c, wherein a, b and c can be single or multiple. In addition, in the embodiments of the present application, words such as "first" and "second" do not limit quantity and order.

[0080] In addition, in the embodiments of the present application, directional terms such as "upper" and "lower" are defined relative to the orientation of the components in the drawings. It should be understood that these directional terms are relative concepts. They are used for relative description and clarification, and they can change accordingly according to changes in the orientation of the components in the drawings.

[0081] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being more preferred or advantageous than other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0082] Before introducing the technical solutions in the embodiments of the present application, the technical terms involved in the embodiments of the present application are first introduced.

[0083] The nominal central wavelength refers to the central wavelength corresponding to each channel in an optical fiber communication system based on optical wavelength division multiplexing technology. It reflects the channel spacing, spectrum position, etc. of the optical signal (optical carrier) in the optical fiber communication system. Frequency and wavelength can be calculated by the formula of the speed of light, specifically c / n=λf, where c represents the speed of light, n represents the core refractive index of the optical fiber, λ is the wavelength of the optical signal, and f represents the frequency of the optical signal. Therefore, the frequency calculated according to the above formula for a nominal central wavelength is also called the nominal center frequency. In the embodiments of the present application, unless otherwise specified, the wavelength of the optical signal mentioned below refers to the nominal central wavelength of the optical signal.

[0084] A multi-wavelength optical signal is an optical signal formed by combining multiple optical signals with different nominal center wavelengths. Its spectrum contains multiple spectral segments, and generally, each spectral segment corresponds to an optical signal with a specific nominal center wavelength. In contrast to a multi-wavelength optical signal, a single-wavelength optical signal is an optical signal with a specific nominal center wavelength.

[0085] Colorless means that each signal receiving end can receive optical signals of any wavelength in the communication band used by the optical communication system, and each signal transmitting end can send optical signals of any wavelength in the communication band to the optical fiber.

[0086] Directionlessness means that each signal receiving end can receive optical signals in any direction / dimension in the optical communication system, and each signal transmitting end can send optical signals to the optical fiber in any direction / dimension in the optical communication system.

[0087] Contentionless means that in any n directions / dimensions (1≤n) in the optical communication system, optical signals of the same wavelength can be sent to n signal receiving ends (each signal receiving end only receives one optical signal); any n signal transmitting ends can send optical signals of the same wavelength to any optical fiber in any n directions / dimensions in the optical fiber communication system.

[0088] Geometric phase: In the spatial domain, the specific information of light can be expressed by amplitude, phase, and polarization state. Light field control refers to the control of the amplitude, phase, and polarization state information of light to meet the requirements of the light field in different application scenarios. The phase of light is mainly related to the path it passes through during propagation, that is, the optical path. The optical path is determined by the average refractive index and geometric path of the propagation medium, and is usually called the dynamic phase. There is also another optical phase that depends on the evolution of the polarization state of the light beam. When light passes through an anisotropic medium, the process of polarization state evolution will also accumulate another phase at the same time. This phase is only related to the geometric path of the evolution of the polarization state of the light beam in the anisotropic space. This special phase is called the geometric phase.

[0089] The technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings.

[0090] Figure 1 is a schematic diagram of the structure of an optical communication system 10. As shown in Figure 1, the optical communication system 10 includes an access room 11 and an optical add-drop multiplexing system (as shown in Figure 1, the optical add-drop multiplexing system 12a, the optical add-drop multiplexing system 12b, and the optical add-drop multiplexing system 12c). The line-side optical signal transmitted in the optical communication system 10 is output from the access room 11 and passes through one or more optical add-drop multiplexing systems in sequence according to a predetermined direction. The line-side optical signal can be generated by the access room 11, or an optical signal transmitted by another optical communication system and received by the access room 11. In addition, the line-side optical signal transmitted in the optical communication system 10 is usually a multi-wavelength optical signal formed by combining wavelength division multiplexing technology to improve the communication capacity and communication rate of the optical communication system 10.

[0091] In the optical communication system shown in Figure 1, each optical add-drop multiplexing system can serve as a "relay node" to transmit the optical signal transmitted from the previous node (such as the previous optical add-drop multiplexing system) to the next node (such as the next optical add-drop multiplexing system). As a result, the optical add-drop multiplexing system can support optical signal transmission in two directions. For example, taking the optical add-drop multiplexing system 12b in Figure 1 as an example, it supports signal transmission from optical add-drop multiplexing system 12a to optical add-drop multiplexing system 12b in one direction (hereinafter assumed to be "from east to west"), and also supports signal transmission from optical add-drop multiplexing system 12c to optical add-drop multiplexing system 12b in the other direction (hereinafter assumed to be "from west to east").

[0092] In addition, each optical add / drop multiplexing system can also serve as a "signal originating node" to transmit the optical signal input by the local communication equipment on the node side, such as the optical transponder unit (OTU), to other optical add / drop multiplexing systems. Each optical add / drop multiplexing system can also serve as a "signal terminating node" to transfer the line-side optical signal to the local communication equipment on the node side. In a specific implementation, the optical add / drop multiplexing system includes an optical add / drop multiplexer (OADM), which includes multiple signal input and output ports, some of which serve as add-wave ports, and some of which serve as drop-wave ports. The add-wave port and / or the drop-wave port are connected to the local communication equipment. In some cases, the local communication device generates an uplink optical signal of a predetermined wavelength, transmits the uplink optical signal of the predetermined wavelength to the add-in port of the optical add-drop multiplexer, and the optical add-drop multiplexing system multiplexes the uplink optical signal into the line-side optical signal, and / or the local communication device receives one or more optical signals of different wavelengths from the line-side optical signal transmitted from the drop-in port of the optical add-drop multiplexer.

[0093] For example, referring to the enlarged schematic diagram of the site optical layer of optical add-drop multiplexing system 12b shown in the dashed box in FIG1 , assuming that the line-side optical signal S1 transmitted in the optical communication system 10 passes through the optical add-drop multiplexing system 12b in the "east-to-west" direction, then in the optical add-drop multiplexing system 12b, the optical add-drop multiplexer can drop the signal component S2 with a wavelength λa in the line-side optical signal S1 to the local communication device. The local communication device can generate an uplink optical signal S3 with a wavelength λb and uplink the uplink optical signal S3 to the optical add-drop multiplexer. The optical add-drop multiplexer combines the uplink optical signal S3 with the optical signals of other wavelengths in the line-side optical signal S1, excluding S2, to generate a new line-side optical signal S4.

[0094] As can be seen, in the optical communication system 10, each optical add-drop multiplexing system needs to add wavelengths and drop wavelengths of single-wavelength optical signals and / or multi-wavelength optical signals, while also ensuring unblocked pass-through of optical signals of any wavelength. As described above, this is generally achieved by providing an optical add-drop multiplexer in the optical add-drop multiplexing system.

[0095] Currently, the optical add-drop multiplexer (OADM) used in OADM systems is typically a reconfigurable optical add-drop multiplexer (ROADM). A ROADM can dynamically adjust the wavelengths of added and dropped optical signals, thereby increasing the flexibility of the OADM system.

[0096] Figure 2 is a schematic diagram of the structure of an optical add-drop multiplexer 20. As shown in Figure 2, a typical colorless (C), directionless (D), and contentionless (C) optical add-drop multiplexer 20 includes a line-side component 21 and a client-side component 22. The line-side component 21 can receive optical signals of any wavelength and any dimension (direction) within the communication band used by the optical communication system and transmit them to other optical add-drop multiplexing systems 12 or client-side components 22. The client-side component 22 can drop optical signals of any wavelength from the line-side component 21 to any local communication device, and can also drop optical signals of any wavelength generated by any local communication device to any dimension (direction) through the line-side component 21.

[0097] In a specific implementation, the line-side component 21 typically includes multiple wavelength selective switches (WSSs), which are cross-connected to achieve "wavelength-independent" and "direction-independent" signal transmission of the line-side optical signal. For example, the line-side component shown in Figure 2 specifically includes three WSSs: WSS1, WSS2, and WSS3. WSS1, WSS2, and WSS3 are cross-connected, for example, one port of WSS1 is connected to one port of WSS2, one port of WSS1 is connected to one port of WSS3, and one port of WSS2 is connected to one port of WSS3.

[0098] It should be noted that the optical add-drop multiplexer 20 shown in FIG2 also includes more functional components. For example, the optical add-drop multiplexer 20 also includes an optical amplifier. The optical amplifier is coupled to the wavelength selective switch and can amplify the optical signal transmitted to the wavelength selective switch or amplify the optical signal output by the wavelength selective switch. This application does not elaborate on this.

[0099] Typically, WSS implements the above functions based on MEMS, LCoS, LC, DMD and other technologies. Among them, LCoS-based WSS has many advantages, such as flexible grid, small size, no mechanical vibration, and high reliability, making it the mainstream WSS technology.

[0100] To facilitate the following description, some of the drawings in the embodiments of the present application show a three-dimensional spatial coordinate system, namely an XYZ coordinate system. Below, in conjunction with Figure 3, the meaning of the various coordinate axis representations of the three-dimensional spatial coordinate system in the embodiments of the present application are defined. Figure 3 is a structural schematic diagram of a wavelength selection switch 30 in the related art, and the wavelength selection switch 30 is implemented based on an LCoS device. As shown in Figure 3, the wavelength selection switch 30 includes an input and output port array (P1, P2, ..., Pi, Pi+1..., Pn-1, Pn), a collimating lens array, a grating dispersion element, a lens assembly (including one or more lenses), and an LCoS-based spatial light modulator.

[0101] The wavelength selective switch 30 is located in a three-dimensional space coordinate system XYZ coordinate system.

[0102] The Z-axis direction is the incident direction of the optical signal. In other words, the transmission direction of the optical signal when input into the wavelength selective switch 30 is parallel to or approximately parallel to the Z-axis direction within the manufacturing tolerance range.

[0103] The Y-axis direction is the arrangement direction of the input and output port arrays in the wavelength selective switch 30, and therefore can also be referred to as the port direction. Unless otherwise specified, the schematic diagram of the port direction mentioned below refers to a schematic diagram in the YZ plane. In the schematic diagram of the YZ plane, the transmission path of the optical signal can show through which port the optical signal modulated by the spatial light modulator is output. In some examples of the embodiments of the present application, the deflection direction of the optical signal is described by the Y-axis direction, the port direction or the YZ plane. For example, when describing the deflection of the optical signal in the Y-axis direction or the port direction, it can also be understood that the optical signal is deflected in the YZ plane, or that the transmission direction after deflection is parallel to the YZ plane.

[0104] The X-axis direction is a direction perpendicular to the Z-axis direction and perpendicular to the Y-axis direction. In the schematic diagram of the XZ plane, the transmission path of the optical signal can show the dispersion of the optical signal, so the X-axis direction can also be called the dispersion direction. Unless otherwise specified, the schematic diagram of the dispersion direction mentioned below refers to the schematic diagram in the XZ plane. In some examples of the embodiments of the present application, the deflection direction of the optical signal is described by the X-axis direction, the dispersion direction or the XZ plane. For example, when describing the deflection of the optical signal in the X-axis direction or the dispersion direction, it can also be understood that the optical signal is deflected in the XZ plane, or that the transmission direction after deflection is parallel to the XZ plane.

[0105] In the wavelength selective switch 30 shown in FIG3 , some ports in the input / output port array can serve as signal input ports for receiving incident optical signals. For example, an optical signal S is input to port Pi+1, and the transmission direction of the incident optical signal S is indicated by the solid line with an arrow in FIG3 . Some ports in the input / output port array can serve as signal output ports, such as P1, P2, Pi, Pn-1, and Pn. Referring to the schematic diagram in the dispersion direction in FIG3 , it can be seen that after the incident optical signal S enters port Pi+1, the collimating lens collimates the incident optical signal, and the grating dispersion element disperses the collimated incident optical signal into multiple optical signals with different wavelengths. The lens projects these multiple optical signals to the signal receiving areas (liquid crystal areas) corresponding to different wavelength channels of the spatial light modulator, and the spatial light modulator outputs each optical signal to the corresponding signal output port. Referring to the schematic diagram in the port direction in FIG3 , it can be seen that the LCoS-based spatial light modulator can output the optical signal in each wavelength channel to any signal output port. For example, an optical signal of any wavelength can be output from the current port Pi. In fact, the optical signal of this wavelength can also be deflected by the spatial light modulator to be output to ports P1, P2, Pi, Pn-1, or Pn. The corresponding optical signals and their transmission directions are shown by the dotted lines with arrows in Figure 3.

[0106] As shown in Figure 4, an LCoS-based spatial light modulator 40 includes a liquid crystal layer 41, with a plurality of pixel electrodes 42 and a common electrode 43 arranged in a two-dimensional array on either side of the liquid crystal layer 41. The liquid crystal layer 41 includes a plurality of liquid crystal molecules 410. The liquid crystal molecules can phase modulate light signals of a certain polarization state. For example, if the liquid crystal molecules in the liquid crystal layer 41 are all rod-shaped, the liquid crystal molecules can phase modulate light signals with the same polarization direction as their long axis orientation. When a voltage is applied to the pixel electrodes 42 and the common electrode 43 on either side of the liquid crystal layer, a driving electric field is formed between the pixel electrodes 42 and the common electrode 43. Under the action of the driving electric field, the liquid crystal molecules in the liquid crystal layer 41 change state, such as deflection, with varying degrees of deflection depending on the strength of the electric field. The degree of deflection of the liquid crystal molecules can generally be characterized by their orientation, which refers to the angle between the long axis orientation of the liquid crystal molecules and the plane in which the liquid crystal layer is located (or the plane in which the arrangement direction is located). Different orientations of the liquid crystal molecules may result in different phase modulation effects (light beam deflection effects) on the light signal.

[0107] Furthermore, as shown in Figure 5, multiple pixel electrodes distributed in two dimensions can be grouped into multiple groups based on factors such as bandwidth, the spot width corresponding to the optical signal, and pixel electrode size. Each group of pixel electrodes corresponds to a liquid crystal region and is used to drive the deflection of the liquid crystal molecules within that region. Each liquid crystal region corresponds to a wavelength channel and is used to phase modulate an optical signal of a wavelength by providing the phase plane required for phase modulation under the action of a driving electric field.

[0108] Figures A and B in Figure 6 show the phase planes formed by the liquid crystal molecules within the two liquid crystal regions in Figure 5, respectively. For LCoS-based spatial modulators, for example, two consecutive liquid crystal regions are susceptible to fringe field effects, making it difficult to form an ideal phase plane, as shown in Figure 6A. Instead, a non-ideal phase plane, as shown in Figure 6B, is often formed. Figure 6B shows that the phase plane corresponding to a single phase cycle exhibits phase distortion, with severe phase distortion occurring in the return path between two phase cycles. Consequently, when the light beam is deflected, some light energy (stray light) can enter other ports as crosstalk.

[0109] Port switching refers to the wavelength selective switch 30 switching the optical signal within a wavelength channel from one port to another. Typically, this is accomplished by adjusting the phase plane provided by the liquid crystal layer in the LCoS to adjust the deflection angle of the LCoS's output light, thereby directing it to the target port. The phase plane can be represented by a phase pattern. However, port switching by the wavelength selective switch 30 can be accompanied by issues such as excessive transient crosstalk or prolonged switching times.

[0110] Specifically, in the process of controlling the LCoS to switch from the initial phase diagram (a phase diagram that enables the outgoing light to be output to the current port) to the final phase diagram (a phase diagram that enables the outgoing light to be output to the target port), since the phase surface formed during the switching process is not ideal, a part of the outgoing light is easily output to the non-target port as a crosstalk signal, thereby causing transient crosstalk to the non-target port.

[0111] To mitigate transient crosstalk, multiple additional phase maps are typically loaded between the initial and final phase maps loaded on the LCoS, ultimately directing the output light to the target port. This process can be understood as achieving port switching through "multi-step switching." This increases the time it takes to load the phase maps on the LCoS, resulting in prolonged port switching times for the wavelength selective switch 30, which is detrimental to its switching performance.

[0112] In addition, for wavelength selective switches based on LCoS, since the liquid crystal layer in LCoS can only perform phase modulation on optical signals with a polarization direction in the first direction, most wavelength selective switches based on LCoS are set to a polarization-dependent architecture. For example, a polarization conversion unit is also provided between the collimating lens array and the grating dispersion element shown in FIG3 , which can be specifically composed of a Wollaston prism and a half-wave plate. The polarization conversion unit needs to generate two beams of orthogonally polarized optical signals based on the received optical signal, wherein the light in one polarization state is the same as the orientation direction of the LCoS, and the light in the other polarization state is perpendicular to the orientation direction of the LCoS. The two beams of orthogonally polarized optical signals are transmitted to the LCoS through different optical paths, which increases the optical path complexity of the wavelength selective switch and the polarization dependent loss (PDL) will be relatively large.

[0113] In addition, LCoS-based wavelength selective switches, in response to some necessary signal attenuation requirements, require extremely complex algorithms to configure the voltages of each pixel electrode in the LCoS so that the target phase plane formed by the liquid crystal layer can achieve both phase modulation and attenuation of signal strength.

[0114] In view of this, embodiments of the present application provide a spatial light modulator and a wavelength selective switch incorporating the same. On one hand, the wavelength selective switch can rapidly complete port switching and avoid transient crosstalk generated during port switching. On the other hand, the wavelength selective switch can also exhibit polarization-independence, combining the advantages of a simple and easy-to-implement optical path with low polarization-dependent loss. Still another aspect is that the wavelength selective switch can implement attenuation processing for optical signals without the need for complex algorithms.

[0115] Various implementations of the spatial light modulator and wavelength selective switch provided in the embodiments of the present application are introduced below.

[0116] FIG7 is a schematic structural diagram of a wavelength selective switch 70 provided in an embodiment of the present application, wherein the wavelength selective switch 70 includes a spatial light modulator 80 provided in any one of the following embodiments. As shown in FIG7 , the wavelength selective switch 70 may include an input and output fiber array 71, a collimating lens array 72, a grating dispersion element 73, a lens assembly (including one or more lenses 74) and a spatial light modulator 80. In the wavelength selective switch 70, the input and output fiber array 71 includes a plurality of input and output ports, such as P1, P2, ..., Pi, Pi+1..., Pn-1, Pn shown in FIG7 . A portion of the input and output ports can be used for signal input, namely, signal input ports. For example, port Pi+1 has an optical signal S input, and the transmission direction of the incident optical signal S is indicated by the solid line with an arrow in FIG7 . A portion of the input and output ports can be used for signal output, namely, signal output ports, such as P1, P2, Pi, Pn-1, Pn shown in FIG7 . Referring to the schematic diagram of the wavelength selective switch 70 in the dispersion direction shown in FIG7 , after the incident light signal S is incident from the signal input port, the collimating lens (one of the collimating lens arrays 72) collimates the incident light signal S, and the grating dispersion element 73 disperses the collimated light signal S into multiple light signals Si with different wavelengths (i is used to identify different light signals in at least one light signal and the corresponding wavelength channels), such as S1, S2, and S3 shown in FIG7 , where different light signals Si correspond to different wavelengths. The light signal Si can be a single-wavelength light signal of a certain wavelength, or a multi-wavelength light signal including multiple wavelengths. The lens 74 is located on the propagation path of the light signal Si and is used to project light signals Si of different wavelengths to different wavelength channels of the spatial light modulator 80. The spatial light modulator 80 is used to receive the light signal Si and, based on different wavelength channels, output the light signals Si of different wavelengths to different input and output ports, respectively. Referring to the schematic diagram of the wavelength selective switch 70 in the port direction shown in FIG7 , it can be seen that the spatial light modulator 80 can deflect the optical signal Si in the i-th wavelength channel to output port Pi. In practice, the spatial light modulator 80 can deflect the optical signal in any wavelength channel to any signal output port. For example, the spatial light modulator 80 can also deflect the optical signal Si in the i-th wavelength channel to output port P1, P2, Pi, Pn-1, or Pn. The optical signal Si and its transmission direction are shown by the dashed arrow in FIG7 .

[0117] FIG8 is a schematic diagram of the structure of a spatial light modulator 80 and a corresponding optical path diagram provided in an embodiment of the present application. As shown in FIG8 , the spatial light modulator 80 may include a first modulation component 81 and a second modulation component 82. Referring to FIG8 , the plane in which the spatial light modulator 80 is located is the XY plane, which may also be referred to as the light receiving surface of the spatial light modulator 80. Taking the first modulation component 81 and the second modulation component 82 shown in FIG8 as rectangular parallelepipeds as an example, the X-axis direction (the dispersion direction in the wavelength selective switch 70) may be the length direction of the first modulation component 81 and the second modulation component 82, the Y-axis direction (the port direction in the wavelength selective switch 70) may be the width direction of the first modulation component 81 and the second modulation component 82, and the Z-axis direction is perpendicular to, or approximately perpendicular to, the first modulation component 81 and the second modulation component 82 within the manufacturing tolerance range. In the embodiment of the present application, the Z-axis direction is the incident direction of the optical signal.

[0118] When the spatial light modulator 80 shown in FIG8 is in operation, the first modulation component 81 first receives the first optical signal S1 of any polarization state projected by the lens 74 and then emits a second optical signal S2 to the second modulation component 82. The transmission direction of the second optical signal S2 is the first predetermined direction. For example, the first modulation component 81 can transmit or diffract the first optical signal S1. When the first modulation component 81 diffracts the first optical signal S1, the emitted second optical signal S2 can be a single beam or split into two beams with different directions. Subsequently, the second modulation component 82 receives the second optical signal S2 from the first modulation component 81 and reflects a third optical signal S3 to the first modulation component 81. The transmission direction of the third optical signal S3 is the second predetermined direction. Finally, the first modulation component 81 receives the third optical signal S3 from the second modulation component 82 and emits a fourth optical signal S4 to the target port. The transmission direction of the fourth optical signal S4 is the target direction. The target port is an input / output port of the wavelength selective switch 70 in FIG7 . Any two of the first optical signal S1 , the second optical signal S2 , the third optical signal S3 and the fourth optical signal S4 carry the same service information, but may have different transmission directions and deflection states.

[0119] As can be seen from the above embodiment, the optical signal carrying the same service information passes through the first modulation component and the second modulation component in sequence, and after being reflected by the first modulation component, passes through the first modulation component again. The target direction mentioned above is opposite to the incident direction of the first optical signal S1 (parallel to the Z-axis direction); or, it is parallel to one of the first preset plane (such as the XZ plane) and the second preset plane (such as the YZ plane), and is deflected by a first preset angle relative to the incident direction (Z-axis direction). The first preset plane, the second preset plane, and the light receiving surface (XY plane) provided by the first modulation component 81 are perpendicular to each other.

[0120] In the embodiment of the present application, both the first modulation component 82 and the second modulation component 82 can utilize the spatial phase modulation effect of liquid crystal on the optical signal to achieve the directional deflection effect of the optical signal, but are not limited thereto.

[0121] Thus, it can be seen that in the embodiment of the present application, the first modulation component 81 and the second modulation component 82 cooperate to complete the deflection of the transmission direction of the optical signal. In the case where the first modulation component and the second modulation component achieve the directional deflection of the optical signal based on the spatial phase modulation effect of the liquid crystal on the optical signal, by adjusting the state of the liquid crystal in the first modulation component and the second modulation component, the phase plane of the liquid crystal layer is adjusted, thereby achieving different directional deflection effects. Specifically, the phase plane of the liquid crystal layer can be adjusted by adjusting the intensity of the electric field in which the liquid crystal layer in the component is located (i.e., the electrode voltage on both sides of the liquid crystal layer).

[0122] For ease of explanation, this article refers to the state of the spatial light modulator when the optical signal is deflected to the first port as the initial state, the state of the spatial light modulator when the optical signal is deflected to the second port as the final state, and the states between the initial and final states as intermediate states. The process of port switching performed by the spatial light modulator can be described as follows:

[0123] In the initial state, based on the deflection effect of the first modulation component 81 and the second modulation component 82 on the transmission direction of the optical signal, the optical signal is deflected to the first port.

[0124] In the intermediate state, the optical signal is deflected to a location outside the preset port by adjusting the configuration of the first modulation component 81. During this process, since there are no fringe field effects within the first modulation component 81, this optical signal deflection process does not cause transient crosstalk to any port. After the optical signal is deflected outside the preset port, the configuration of the second modulation component 82 is adjusted to prepare for the optical signal to be deflected to the second port. During the configuration adjustment of the second modulation component 82, since the optical signal is deflected outside the preset port, it does not cause transient crosstalk to any port.

[0125] In the final state, by adjusting the configuration of the first modulation component 81 , the first modulation component 81 and the second modulation component 82 can cooperate to deflect the optical signal to the second port.

[0126] Thus, port switching is achieved through the coordination of the first modulation component 81 and the second modulation component 82. Changing the configuration of the second modulation component 82 is necessary to switch the optical signal from the first port output to the second port output. Changing the configuration of the first modulation component 81 is intended to deflect the optical signal from a predetermined port to a location outside the predetermined port, or vice versa. This ensures that no stray light reaches the predetermined port during the configuration change of the second modulation component 82. The predetermined port can be a pre-recorded valid port for service signal transmission.

[0127] For the second modulation component 82, only one configuration change occurs during the port switching process, so it can be understood that the embodiment of the present application realizes port switching through "single-step switching". Compared with the "multi-step switching" scheme in which multiple phase diagrams are interspersed in the middle, the embodiment of the present application completes the adjustment of the phase plane of the liquid crystal layer in the second modulation component 82 at one time, which can ensure a faster switching speed. In addition, since the liquid crystal layer in the second modulation component 82 is loaded with the final phase plane during the process (that is, in the intermediate state), the optical signal will be deflected to a position outside the preset port based on the first modulation component 81, so it will not become a crosstalk signal and be transmitted to the effective port.

[0128] In the embodiment of the present application, since both the first modulation component 81 and the second modulation component 82 can deflect the transmission direction of the optical signal by adjusting the state of the internal liquid crystal, the configuration change process of the first modulation component 81 and the second modulation component 82 and the corresponding change process of the optical signal transmission direction during the above-mentioned port switching process can be briefly described as follows:

[0129] ① In the initial state, the light signal is deflected to the first port → ② The state of the liquid crystal inside the first modulation component 81 changes → ③ The light signal is deflected outside the preset port → ④ The state of the liquid crystal inside the second modulation component 82 changes → ⑤ The light signal is still deflected outside the preset port → ⑥ The state of the liquid crystal inside the first modulation component 81 changes → ⑦ The light signal is deflected to the second port.

[0130] In some scenarios of the embodiments of the present application, ②, ④, and ⑥ can be executed serially. In other scenarios of the embodiments of the present application, the time corresponding to ② and ④ can overlap, and the time corresponding to ④ and ⑥ can overlap, thereby achieving a faster port switching speed. Specifically: in the initial state, the first modulation component 81 and the second modulation component 82 cooperate to deflect the optical signal to the first port for output (①), and will not cause crosstalk to other ports. After entering the intermediate state, the state of the liquid crystal inside the first modulation component 81 begins to change (i.e., execution ② begins). During this change, the energy of the optical signal is gradually deflected outside the preset port, and the intensity of the optical signal (including stray light) that can be received by the first port and other effective ports gradually decreases. When the intensity of the optical signal is small enough, even if the liquid crystal inside the first modulation component 81 has not reached the target state, if the intensity of the stray light that may be generated at this time can be ignored, then the state of the liquid crystal inside the second modulation component 82 is allowed to start changing, that is, execution ④ is executed in advance. Similarly, during the state change process of the liquid crystal inside the second modulation component 82, even if the liquid crystal inside the second modulation component 82 has not yet reached the target state, if the stray light that may be generated at this time can be ignored, then the state of the liquid crystal inside the first modulation component 81 is allowed to start changing, that is, execute ⑥ in advance.

[0131] FIG9 is a schematic diagram of the structure of a spatial light modulator 80 provided in an embodiment of the present application. As shown in FIG9 , the first modulation component 81 includes a first liquid crystal layer 811, a transparent first common electrode 812, and a transparent first pixel electrode array 813. The first common electrode 812 and the first pixel electrode array 813 are respectively disposed on either side of the first liquid crystal layer 811. The second modulation component 82 includes a complementary metal oxide semiconductor (CMOS) silicon-based backplane 821 (hereinafter referred to as the CMOS silicon-based backplane), a second liquid crystal layer 822, a transparent second common electrode 823, a second pixel electrode array 824, a metasurface layer 827, and a reflective layer. The second common electrode 823 and the second pixel electrode array 824 are respectively disposed on either side of the second liquid crystal layer 822. The CMOS silicon-based backplane 821 is disposed on the side of the second liquid crystal layer 822 away from the first liquid crystal layer 821. The metasurface layer 827 is disposed between the CMOS silicon-based backplane 821 and the second liquid crystal layer 822. The pixel electrodes in the second pixel electrode array 824 are electrically connected to the CMOS silicon-based backplane 821. For the convenience of the following description, the pixel electrodes in the first pixel electrode array 813 are referred to as first pixel electrodes, and the pixel electrodes in the second pixel electrode array 824 are referred to as second pixel electrodes. For the convenience of the following description, the pixel electrodes in the first pixel electrode array 813 are referred to as first pixel electrodes, and the pixel electrodes in the second pixel electrode array 824 are referred to as second pixel electrodes. As shown in Figure 9, along the incident direction of the light signal (such as the Z-axis direction), the first common electrode 812, the first liquid crystal layer 811, the first pixel electrode array 813, the second common electrode 823, the second liquid crystal layer 822, the super surface layer 827, the second pixel electrode array 824 and the CMOS silicon-based backplane 821 are stacked in sequence.

[0132] In the spatial light modulator shown in Figure 9, the first common electrode 812 is used to generate a first voltage between itself and the first pixel electrode. The first voltage can be zero or greater than zero. When the first voltage is greater than zero, a first driving electric field is generated, causing the first liquid crystal layer 811 to deflect under the influence of the first driving electric field. The deflection angle can be represented by a first orientation. For example, the first orientation can be the angle between the long axis of the liquid crystal molecules in the first liquid crystal layer 811 and the XY plane. The second common electrode 823 is used to generate a second voltage between itself and the second pixel electrode. When the second voltage is greater than zero, a second driving electric field is generated. Caused by the second driving electric field, the second liquid crystal layer 822 can deflect under the influence of the second driving electric field. The deflection angle can be represented by a second orientation. For example, the second orientation can be the angle between the long axis of the liquid crystal molecules in the second liquid crystal layer 822 and the XY plane. It should be understood that when the first voltage generated between the first common electrode 812 and the first pixel electrode changes, the first orientation formed by the first liquid crystal layer 811 changes accordingly, thereby changing the transmission direction of light emitted from the first liquid crystal layer 811. Similarly, when the second voltage generated between the second common electrode 823 and the second pixel electrode changes, the second orientation formed by the second liquid crystal layer 822 changes accordingly, and thus the transmission direction of the light emitted from the second liquid crystal layer 822 changes accordingly. Thus, by adjusting the first voltage configured for the first modulation component 81 and / or the second voltage configured for the second modulation component 82, different directional deflection effects of the light signal are achieved.

[0133] In one possible implementation, the first pixel electrode array 813 includes a plurality of pixel electrodes distributed in a two-dimensional array, or a plurality of strip electrodes arranged in a one-dimensional direction. That is, the first pixel electrode can be a point-shaped pixel electrode or a strip electrode. The first pixel electrode can be an N-type oxide semiconductor-indium tin oxide (ITO) transparent electrode or a thin film field effect transistor (TFT) electrode. The second pixel electrode array 824 includes a plurality of pixel electrodes distributed in a two-dimensional array.

[0134] In the above embodiment, each second pixel electrode is electrically connected to the CMOS silicon backplane 821, thereby being controlled by the pixel circuitry on the CMOS silicon backplane 821. Therefore, the second modulation component 82 can be specifically implemented as an LCoS-based spatial light modulation component. Therefore, the spatial light modulator 80 combines the advantages of LCoS, including its flexible grid, compact size, lack of mechanical vibration, and high reliability.

[0135] Continuing with FIG. 9 , as a possible implementation, the spatial light modulator 80 further includes a transparent first opposing substrate 814 and a transparent second opposing substrate 815. The first opposing substrate 814 is disposed on a side of the first liquid crystal layer 811 away from the second liquid crystal layer 822. The first common electrode 812 is disposed on a surface of the first opposing substrate 814 that is closer to the first liquid crystal layer 811. The second opposing substrate 815 is disposed on a side of the second liquid crystal layer 822 away from the CMOS silicon-based backplane 821. The second common electrode 823 is disposed on a surface of the second opposing substrate 815 that is closer to the second liquid crystal layer 822. For example, the first opposing substrate 814 and the second opposing substrate 815 form a first liquid crystal cell, in which the first liquid crystal layer 811 is encapsulated. The second opposing substrate 815 and the CMOS silicon-based backplane 821 form a second liquid crystal cell, in which the second liquid crystal layer 822 is encapsulated. More specifically, the first opposing substrate 814 and the second opposing substrate 815 may be glass plates.

[0136] Continuing with FIG. 9 , as a possible implementation, the spatial light modulator 80 may further include a first alignment layer 816 and a second alignment layer 817 ; the first alignment layer 816 and the second alignment layer 817 are respectively disposed on either side of the first liquid crystal layer 811 . The first alignment layer 816 is configured to anchor the liquid crystal molecules adjacent thereto in the first liquid crystal layer 811 , causing the adjacent liquid crystal molecules to be pre-aligned. For example, the liquid crystal molecules adjacent to the first alignment layer 816 in the first liquid crystal layer 811 may be the liquid crystal molecules closest to the first alignment layer 816 in the first liquid crystal layer 811 . The second alignment layer 817 is configured to anchor the liquid crystal molecules adjacent thereto in the first liquid crystal layer 811 , causing the adjacent liquid crystal molecules to be pre-aligned. For example, the liquid crystal molecules adjacent to the second alignment layer 817 in the first liquid crystal layer 811 may be the liquid crystal molecules closest to the second alignment layer 817 in the first liquid crystal layer 811 . Under the action of the first alignment layer 816 and the second alignment layer 817, the pre-alignment of the liquid crystal molecules in the first liquid crystal layer 811 closest to the first alignment layer 816 is the same as the pre-alignment of the liquid crystal molecules in the first liquid crystal layer 811 closest to the second alignment layer 817. In other words, the alignment directions corresponding to the first alignment layer 816 and the second alignment layer 817 are the same.

[0137] Continuing with FIG. 9 , as a possible implementation, the spatial light modulator 80 may further include a third alignment layer 825 and a fourth alignment layer 826 ; the third alignment layer 825 and the fourth alignment layer 826 are disposed on either side of the second liquid crystal layer 822 . The third alignment layer 825 is configured to anchor adjacent liquid crystal molecules in the second liquid crystal layer 822 , causing these adjacent liquid crystal molecules to be pre-aligned. For example, the liquid crystal molecules in the second liquid crystal layer 822 adjacent to the third alignment layer 825 may be the liquid crystal molecules closest to the third alignment layer 825 in the second liquid crystal layer 822 . The fourth alignment layer 826 is configured to anchor adjacent liquid crystal molecules in the second liquid crystal layer 822 , causing these adjacent liquid crystal molecules to be pre-aligned. For example, the liquid crystal molecules in the second liquid crystal layer 822 adjacent to the fourth alignment layer 826 may be the liquid crystal molecules closest to the fourth alignment layer 826 in the second liquid crystal layer 822 . Under the action of the third alignment layer 825 and the fourth alignment layer 826, the pre-alignment of the liquid crystal molecules in the second liquid crystal layer 822 closest to the third alignment layer 825 is the same as the pre-alignment of the liquid crystal molecules in the second liquid crystal layer 822 closest to the fourth alignment layer 826. In other words, the alignment directions corresponding to the third alignment layer 825 and the fourth alignment layer 826 are the same.

[0138] In the above embodiment, the first liquid crystal layer can be specifically implemented as a liquid crystal polarization grating array (LCPGA), which can cause incident light to undergo first-order diffraction and deflection. When the light wavelength is fixed, the smaller the grating period, the greater the beam deflection angle. As a possible implementation, the thickness d of the first liquid crystal layer satisfies Δnd = λ / 2, thereby achieving optimal diffraction efficiency. Furthermore, the liquid crystal layer thickness d, which is constrained by the diffraction efficiency, is much greater than the critical thickness dc of the liquid crystal layer that can induce alignment.

[0139] In an embodiment of the present application, the arrangement of liquid crystal molecules in the first liquid crystal layer may be as shown in FIG10 . The first liquid crystal layer is sandwiched between two opposing substrates, and the grating vector is parallel to the opposing substrates, i.e., the XY plane. The liquid crystal molecules lie flat in the XY plane and are arranged in a periodic fan-shaped pattern. Specifically, the azimuth angles of the liquid crystal molecules in the first liquid crystal layer vary continuously and linearly in space. Assuming that the liquid crystal molecules are periodically arranged along a preset direction in the XY plane, the azimuth angles of the liquid crystal molecules vary continuously by 180° within one period. The director n(x) of the liquid crystal is a function of the coordinate variable x, and satisfies n(x) = [sin(πx / Λ), cos(πx / Λ), 0]

[0140] Here, x ranges from 0 to Λ. Looking down on the XY plane, the first liquid crystal layer forms a stripe grating, with Λ being the grating period and the x-axis being the direction of the grating period. When a light beam passes through the first liquid crystal layer, it acquires a geometric phase.

[0141] Based on this, when no voltage is applied to the first liquid crystal layer (the first voltage is zero), the first liquid crystal layer can realize the deflection of the transmission direction of the light beam based on the diffraction effect on the light beam. Moreover, when the first liquid crystal layer is used for light beam deflection, it has the characteristic of being polarization-independent. That is, for an incident light beam of any polarization state, the deflection effect of the light beam transmission direction can be realized. Specifically, when the incident light is left-handed circularly polarized light, the outgoing light beam is right-handed circularly polarized light, and the transmission direction of the outgoing light is deflected in the grating direction; when the incident light is right-handed circularly polarized light, the outgoing light beam is left-handed circularly polarized light, and the transmission direction of the outgoing light is deflected in the grating direction; when the incident light is linearly polarized light, the linearly polarized light can be decomposed into left-handed circularly polarized light and right-handed circularly polarized light, so two outgoing lights with deflection directions will be emitted in the grating direction; for an elliptically polarized incident light beam, there will also be two outgoing lights with deflection directions in the grating direction.

[0142] Furthermore, when a voltage is applied to the first liquid crystal layer (the first voltage is greater than zero), the liquid crystal molecules in the first liquid crystal layer can assume different states depending on the voltage value. Figure 11 is a schematic diagram of the states of the liquid crystal molecules in the first liquid crystal layer when a certain voltage is applied to the first liquid crystal layer. As shown in Figure 11, when a first voltage (greater than zero, with a driving electric field) is applied to the first liquid crystal layer, ideally, the long axes of all liquid crystal molecules, except those near the alignment layer, are perpendicular to the XY plane. In other words, their long axes are aligned at or near 90° relative to the XY plane. In this case, incident light can pass through the first liquid crystal layer without changing its direction. Of course, when a second voltage (greater than zero and less than the first voltage, with a driving electric field) is applied to the first liquid crystal layer, ideally, the long axes of all liquid crystal molecules, except those near the alignment layer, are aligned at less than 90° relative to the XY plane. In this case, the intensity of the incident light is attenuated by the first liquid crystal layer.

[0143] As previously described, the second modulation component 82 reflects the light signal from the first modulation component 81, causing the light signal to be retransmitted to the first modulation component 81 and ultimately output by the first modulation component 81. In one possible implementation, as shown in FIG9 , the second modulation component 82 includes a reflective layer, which includes the aforementioned second pixel electrode array 824. For example, the second pixel electrode array 824 can be specifically implemented as a pixelated metal layer that reflects light, or in other words, the second pixel electrode array 824 has a light-reflecting function. In this implementation, the second pixel electrode array 824 is formed in the reflective layer, or is integrally formed with the light-reflecting metal material. In another possible implementation, the second modulation component 82 also includes a reflective layer, which is disposed on a side of the second liquid crystal layer 822 away from the first liquid crystal layer 811, thereby reflecting the light signal transmitted by the second liquid crystal layer 822. In this implementation, the second pixel electrode array 824 is independent of the reflective layer and, for example, can be disposed on a surface of the reflective layer that is proximal to the CMOS silicon backplane 821.

[0144] Taking the spatial light modulator shown in Figure 9 as an example, after the second modulation component 82 receives the optical signal from the first modulation component 81, the optical signal is transmitted through the second opposing substrate 815 and the second common electrode 823 to the second liquid crystal layer 822. Under the first phase modulation of the second liquid crystal layer 822, its transmission direction may be deflected. The optical signal then passes through the second liquid crystal layer 822 and reaches the reflective layer. The reflective layer reflects the optical signal, causing it to be emitted again through the second liquid crystal layer 822. Under the second phase modulation of the second liquid crystal layer 822, its transmission direction may be deflected again, reaching the first modulation component 81. It can be seen that the optical signal undergoes deflection, reflection, and deflection in the second modulation component 82.

[0145] In the spatial light modulator 80 shown in FIG9 , the second common electrode 823 is disposed near the first liquid crystal layer 811 relative to the second pixel electrode array 824, and the second pixel electrode array 824 is formed in the reflective layer. It should be understood that in other embodiments of the present application, the second pixel electrode array 824 can be disposed near the first liquid crystal layer 811 relative to the second common electrode 823, and the second common electrode 823 can be formed in the reflective layer. Alternatively, the second pixel electrode array 824 can be disposed near the first liquid crystal layer 811 relative to the second common electrode 823, and the second common electrode 823 can be independent of the reflective layer and disposed between the reflective layer and the CMOS silicon-based backplane 821.

[0146] Continuing with reference to Figure 9, as a possible implementation, the second modulation component 82 also includes a supersurface layer 827, which is arranged between the reflective layer and the second liquid crystal layer 822; the supersurface layer 827 is used to convert the incident optical signal with a polarization direction of the first direction into a second direction, and convert the incident optical signal with a polarization direction of the second direction into the first direction; the first direction is orthogonal to the second direction.

[0147] For the aforementioned second modulation component 82, it is assumed that the liquid crystal molecules in the second liquid crystal layer 822 are rod-shaped, with their long axes aligned parallel to the first direction. In one example, a light signal polarized in the first direction enters the second liquid crystal layer 822 for the first time after passing through the second common electrode 823. The liquid crystal molecules in the second liquid crystal layer 822 undergo an orientation change under the influence of the driving electric field generated by the second common electrode 823 and the second pixel electrode. Because the first direction is parallel to the long axes of the liquid crystal molecules in the second liquid crystal layer 822, the liquid crystal molecules with this orientation change can modulate the phase of the light signal polarized in the first direction. Subsequently, the light signal enters the metasurface layer 827, which converts the polarization of the light signal from the first direction to the second direction. The light signal then reflects from the reflective layer and enters the second liquid crystal layer 822 again. Because the second direction is perpendicular to the orientation of the liquid crystal molecules in the second liquid crystal layer 822, the liquid crystal molecules with this orientation change do not phase-modulate the light signal polarized in the second direction. In another example, a light signal polarized in the second direction enters the second liquid crystal layer 822 for the first time after passing through the second common electrode 823. The liquid crystal molecules in the second liquid crystal layer 822 undergo an orientation change under the action of the driving electric field generated by the second common electrode 823 and the second pixel electrode. Since the second direction is perpendicular to the long axis orientation of the liquid crystal molecules in the second liquid crystal layer 822, the liquid crystal molecules after the orientation change will not phase modulate the light signal polarized in the second direction. Subsequently, the light signal enters the metasurface layer 827, which converts the second direction of the polarization direction of the light signal into the first direction. Then, after being reflected by the reflective layer, the light signal enters the second liquid crystal layer 822 again. Since the first direction is parallel to the orientation of the liquid crystal molecules in the second liquid crystal layer 822, the liquid crystal molecules after the orientation change can phase modulate the light signal polarized in the second direction.

[0148] In summary, regardless of whether the optical signal is polarized in the first or second direction, the same phase modulation is achieved throughout the entire process from the time it enters the second modulation component 82 until it is finally emitted. Since an optical signal with any other polarization state in the incident optical signal can always be decomposed into a combination of an optical component with the first polarization state and an optical component with the first polarization state, and each optical component with the first polarization state also only experiences a single phase modulation, the second modulation component exhibits a polarization-independent phase response characteristic. When such a spatial light modulator is applied to a wavelength selective switch, the structure of the wavelength selective switch is simplified, reducing device size, optical path complexity, and polarization-dependent loss.

[0149] Based on the spatial light modulator 80 described in the above embodiment, it can be seen that by adjusting the first voltage configured for the first modulation component 81 and / or the second voltage configured for the second modulation component 82, different directional deflection effects of the optical signal can be achieved. The following describes several control modes of the spatial light modulator and the corresponding beam deflection effects.

[0150] In the example shown in Figure 12A, the grating direction of the first liquid crystal layer is in the X-axis direction (dispersion direction) or the Y-axis direction (port direction). As shown in Figure 12A, in the first control mode, the voltage configured for the first modulation component 81 is V1, and the voltage configured for the second modulation component 82 is V2. When the light signal is incident on the spatial light modulator along the Z-axis direction, the outgoing light is not deflected in any direction. Specifically: First, the first modulation component 81 receives the light signal and transmits it to the second modulation component 82. At this time, the transmission direction of the light signal is parallel to the Z-axis direction. Then, the second modulation component 82 receives the light signal and reflects it to the first modulation component 81. At this time, the transmission direction of the light signal is parallel to the Z-axis direction. Finally, the first modulation component 81 receives the light signal and transmits it to the outside of the spatial light modulator. At this time, the transmission direction of the light signal is parallel to the Z-axis direction.

[0151] In the example shown in B of FIG12 , the grating direction of the first liquid crystal layer is the X-axis direction (dispersion direction). As shown in B of FIG12 , in the second control mode, the voltage configured for the first modulation component 81 is V3, and the voltage configured for the second modulation component 82 is V4. When the light signal is incident on the spatial light modulator along the Z-axis direction, the outgoing light is deflected in the X-axis direction (or deflected in the XZ plane, or the direction after deflection is parallel to the XZ plane). And, under the action of the first modulation component 81, it is divided into two beams. Specifically: First, the first modulation component 81 receives the light signal, diffracts the light signal, and emits two light signals to the second modulation component 82. The transmission direction of the two light signals is deflected in the X-direction relative to the Z-axis direction. The second modulation component 82 then receives the two optical signals and sequentially deflects, reflects, and deflects each optical signal before transmitting the two optical signals to the first modulation component 81. The transmission direction of each optical signal may or may not be deflected along the X-axis. After receiving the two optical signals, the first modulation component 81 transmits the two optical signals, with the transmission direction being either deflected or not deflected along the X-axis.

[0152] In the example shown in Figure 12C, the grating direction of the first liquid crystal layer is along the Y-axis (port direction). As shown in Figure 12C, in the third control mode, the voltage assigned to the first modulation component 81 is V5, and the voltage assigned to the second modulation component 82 is V6. When an optical signal is incident on the spatial light modulator along the Z-axis, the outgoing light is deflected in the Y-axis direction (or deflected within the YZ plane, or in a direction parallel to the YZ plane after deflection), but not in the X-axis direction. Specifically, first, the first modulation component 81 receives the optical signal and transmits it to the second modulation component 82, with the transmission direction parallel to the Z-axis. Then, the second modulation component 82 receives the optical signal and deflects, reflects, and deflects it, before transmitting the optical signal to the first modulation component 81, where the transmission direction of the optical signal is deflected in the Y-axis direction relative to the Z-axis. After receiving the optical signal, the first modulation component 81 transmits the optical signal, with the transmission direction either deflected or not deflected in the Y-axis direction.

[0153] In the example shown in Figure 12D, the angle between the grating direction of the first liquid crystal layer and the Y-axis direction (port direction) is greater than zero, and the angle between the grating direction and the X-axis direction (dispersion direction) is also greater than zero. As shown in Figure 12D, in the fourth control mode, the voltage configured for the first modulation component 81 is V7, and the voltage configured for the second modulation component 82 is V8. When the optical signal is incident on the spatial light modulator along the Z-axis, the outgoing light is deflected in the Y-axis direction (or deflected within the YZ plane, or the deflection direction has a component parallel to the YZ plane) and also deflected in the X-axis direction (or deflected within the XZ plane, or the deflection direction has a component parallel to the XZ plane). Furthermore, the light is split into two beams by the action of the first modulation component 81. Specifically, the first modulation component 81 receives the optical signal, diffracts it, and emits two optical signals to the second modulation component 82. The transmission directions of the two optical signals are deflected in the X-axis direction relative to the Z-axis direction. The second modulation component 82 then receives the two optical signals and sequentially deflects, reflects, and deflects each optical signal before transmitting the two optical signals to the first modulation component 81. Each optical signal is deflected along the Y-axis. After receiving the two optical signals, the first modulation component 81 transmits the two optical signals, with or without deflection along the X-axis.

[0154] The four control modes and corresponding beam deflection effects described above serve as examples of the control modes and beam deflection effects of a spatial light modulator and do not limit the functionality of the spatial light modulator. It should be understood that different beam deflection effects can be achieved by configuring the voltages of the first and second modulation components differently. Any two of the voltages V1, V2, V3, V4, V5, V6, V7, and V8 may be the same or different, and their specific values ​​can be designed based on actual port switching requirements.

[0155] Continuing with the above embodiment, for ease of explanation, the time period in which the spatial light modulator is in the initial state (the state of the spatial light modulator when the optical signal is deflected to the first port) is referred to as time period one, the time period in which the spatial light modulator is in the intermediate state (the state between the initial state and the final state) is referred to as time period two, and the time period in which the spatial light modulator is in the final state (the state of the spatial light modulator when the optical signal is deflected to the second port) is referred to as time period three. The control process of the spatial light modulator and the port switching process performed by the spatial light modulator can be described as follows (as shown in FIG13 ):

[0156] First, the spatial light modulator receives the light signal projected by the lens assembly. Then:

[0157] S101 , controlling a first voltage to be generated between a first common electrode and a first pixel electrode of a spatial light modulator, and controlling a second voltage to be generated between a second common electrode and a second pixel electrode.

[0158] Accordingly, in time period one, the spatial light modulator outputs the optical signal to the first port based on the first voltage between the first common electrode and the first pixel electrode, and the second voltage between the second common electrode and the second pixel electrode.

[0159] S102, at a first moment, receiving a port switching instruction, and in response to the port switching instruction, adjusting the voltage between the first common electrode and the first pixel electrode array to a third voltage, and maintaining the voltage between the second common electrode and the second pixel electrode at the second voltage.

[0160] S103 , at the second moment, adjusting the voltage between the second common electrode and the second pixel electrode to the fourth voltage, and maintaining the voltage between the first common electrode and the first pixel electrode to the third voltage.

[0161] The first moment and the second moment are moments in time period 2, and the first moment is earlier than the second moment. Accordingly, in time period 2, the spatial light modulator outputs the optical signal to a location other than the preset input and output port based on the fourth voltage between the first common electrode and the first pixel electrode, and the second voltage or the third voltage between the second common electrode and the second pixel electrode.

[0162] S104 , at a third moment, controlling the generation of a fifth voltage between the first transparent common electrode and the first pixel electrode, and maintaining the voltage between the second common electrode and the second pixel electrode at the third voltage.

[0163] The third moment is within time period 3, which is later than time period 2. Accordingly, within time period 3, based on the fifth voltage between the first common electrode and the first pixel electrode, and the third voltage between the second common electrode and the second pixel electrode, the optical signal is output to the second port indicated by the port switching instruction.

[0164] In summary, in the initial state (corresponding to time period one), based on the deflection effect of the first modulation component 81 and the second modulation component 82 on the transmission direction of the optical signal, the optical signal is deflected to the first port. In the intermediate state (corresponding to time period two), by adjusting the configuration of the first modulation component 81, the optical signal is deflected to a position outside the preset port. During this deflection process, no transient crosstalk is caused to any port. At the same time, after the optical signal is deflected outside the preset port, the configuration of the second modulation component 82 is adjusted to prepare for the optical signal to be deflected to the second port. During this process, no transient crosstalk is caused to any port. In the final state (corresponding to time period three), by adjusting the configuration of the first modulation component 81, the first modulation component 81 and the second modulation component 82 can cooperate to deflect the optical signal to the second port. It can be seen that since the optical signal is deflected to a position outside the preset port in the intermediate state, transient crosstalk is avoided on other ports.

[0165] In one possible implementation, a first pixel circuit is provided on a surface of the first opposing substrate close to the first liquid crystal layer, and a first pixel circuit can be electrically connected to at least one first pixel electrode in the first pixel electrode array to output a voltage to the at least one first pixel electrode.

[0166] In one possible implementation, the first modulation component may further include a first signal interface, and the first pixel circuit may be connected to a drive circuit via the first signal interface. The drive circuit is configured to output a voltage signal to the first pixel circuit, and the first pixel circuit outputs a voltage to the first pixel electrode based on the voltage signal input by the drive circuit. In addition, the first common electrode may be electrically connected to the drive circuit via the first signal interface to obtain a voltage.

[0167] In one possible implementation, a CMOS silicon-based backplane may include a data line (DL) and a second pixel circuit electrically connected to the data line, wherein the data line is configured to transmit a data signal. A first pixel circuit is electrically connected to at least one second pixel electrode in a second pixel electrode array, and the second pixel circuit is configured to output a voltage to the at least one second pixel electrode according to the data signal transmitted by the data line.

[0168] In one possible implementation, the spatial light modulator may be disposed on or include a flexible circuit board. The flexible circuit board includes a driving circuit. The CMOS silicon-based backplane is connected to the driving circuit on the flexible circuit board via its data lines to obtain data signals.

[0169] In one possible implementation, the second modulation component may further include a second signal interface, through which the data line is connected to the drive circuit. The drive circuit is further configured to output a data signal to the data line. Furthermore, the second common electrode may be electrically connected to the drive circuit via the second signal interface to obtain a voltage.

[0170] In some embodiments, the voltage applied to each first pixel electrode in the first pixel electrode array is the same. This prevents fringe field effects between different first pixel electrodes, allowing each group of liquid crystal molecules in the first liquid crystal layer to form an ideal phase plane. Consequently, crosstalk is not generated when the light beam is deflected. This ensures that, in the intermediate state, when switching the optical signal from the first port to a port other than the preset port, transient crosstalk is not generated at any port.

[0171] Continuing to refer to FIG9 , in some embodiments, the spatial light modulator provided in the embodiments of the present application may further include a light-enhancing layer 818 ; the light-enhancing layer 818 is disposed on a side of the first opposing substrate 814 away from the first liquid crystal layer 811 to increase the transmittance of the incident light signal.

[0172] In some embodiments, the optical signal emitted by the first modulation component 81 to the second modulation component 82, and / or the optical signal emitted by the first modulation component 81 to the input and output ports, undergoes a preset degree of energy attenuation relative to the incident optical signal. In other words, the first modulation component 81 can also be used to implement attenuation control of the optical signal. In the related art, taking the LCoS-based spatial light modulator as an example, in the face of some application scenarios that require signal attenuation control, extremely complex algorithms are required to control the voltage applied to the electrodes in the LCoS device so that the target phase plane formed by the liquid crystal layer in the LCoS device can achieve both phase modulation and attenuation of signal intensity. Compared with the related art, the spatial light modulator provided in the embodiment of the present application decouples signal attenuation control from phase modulation, for example, signal attenuation is achieved by the first modulation component 81, and phase modulation is achieved by the second modulation component 82. Therefore, the attenuation processing of the optical signal can be achieved without complex algorithms, while not affecting the phase modulation effect.

[0173] In a specific application, upon receiving a signal attenuation instruction, the device controls the generation of a first target voltage between the first common electrode and the first pixel electrode, and controls the generation of a second target voltage between the second common electrode and the second pixel electrode, in response to the signal attenuation instruction. The signal attenuation instruction includes an attenuation parameter, which represents a predetermined degree of attenuation of the optical signal. The first target voltage and the second target voltage are used to cause the spatial light modulator to output the incident optical signal to the target port. The first target voltage is used to cause the optical signal output to the target port to experience a predetermined degree of attenuation relative to the incident optical signal.

[0174] The present application also provides an optical communication device, comprising any one of the wavelength selective switches described in the above embodiments. The optical communication device may be a colorless (C), directionless (D), and contentionless (C) ROADM device or OXC device.

[0175] An embodiment of the present application further provides an optical communication system, which includes any one or more of the above-mentioned optical communication devices.

[0176] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0177] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A spatial light modulator, characterized in that: It includes a first modulation component and a second modulation component which are sequentially arranged along the incident direction of the optical signal; The first modulation component includes a first common electrode, a first liquid crystal layer and a first pixel electrode array; the first common electrode and the first pixel electrode array are respectively arranged on both sides of the first liquid crystal layer, and are used to apply a first voltage to the first liquid crystal layer; the first liquid crystal layer is used to modulate the transmission direction of the optical signal passing through the first liquid crystal layer based on the first voltage; the liquid crystal molecules in the first liquid crystal layer are periodically arranged in a preset direction, and the azimuth angles of the liquid crystal molecules in one period continuously and linearly change by 180°; the preset direction is parallel to the plane where the first liquid crystal layer is located; The second modulation component includes a second common electrode, a second liquid crystal layer, a super-surface layer, a reflective layer, a second pixel electrode array and a complementary metal oxide semiconductor (CMOS) silicon-based backplane; the second common electrode and the second pixel electrode array are respectively arranged on both sides of the second liquid crystal layer, for applying a second voltage to the second liquid crystal layer; the second liquid crystal layer is used to modulate the transmission direction of the optical signal passing through the second liquid crystal layer based on the second voltage; the super-surface layer is arranged on the side of the second liquid crystal layer away from the first liquid crystal layer, for changing the polarization direction of the optical signal passing through the super-surface layer; the reflective layer is located on the side of the super-surface layer away from the second liquid crystal layer, for reflecting the optical signal emitted by the super-surface layer; the CMOS silicon-based backplane is located on the side of the reflective layer away from the super-surface layer, and is electrically connected to the pixel electrodes in the second pixel electrode array, for configuring the second voltage.

2. The spatial light modulator according to claim 1, characterized in that The metasurface layer is used to convert the polarization direction of the optical signal passing through the metasurface layer from a first direction to a second direction, and to convert the polarization direction of the optical signal passing through the metasurface layer from the second direction to the first direction; the first direction is orthogonal to the second direction.

3. The spatial light modulator according to claim 1 or 2, characterized in that: The second pixel electrode array is formed in the reflective layer.

4. The spatial light modulator according to claim 1 or 2, characterized in that: The second pixel electrode array is arranged between the reflective layer and the CMOS silicon-based backplane.

5. The spatial light modulator according to any one of claims 1 to 4, characterized in that: It also includes N signal interfaces, where N is an integer greater than or equal to 1; the first common electrode, the first pixel electrode array, the second common electrode and the CMOS silicon-based backplane are electrically connected to the same or different signal interfaces.

6. The spatial light modulator according to claim 5, characterized in that It also includes a driving circuit; the N signal interfaces are electrically connected to the driving circuit.

7. The spatial light modulator according to any one of claims 1 to 6, characterized in that: Also included is a first opposing substrate and a second opposing substrate; The first opposing substrate is disposed on a side of the first liquid crystal layer away from the second liquid crystal layer; the first common electrode is disposed on a surface of the first opposing substrate on a side close to the first liquid crystal layer; The second opposing substrate is arranged on a side of the second liquid crystal layer away from the CMOS silicon-based backplane; the second common electrode is arranged on a surface of a side of the second opposing substrate close to the second liquid crystal layer.

8. The spatial light modulator according to any one of claims 1 to 7, characterized in that: It also includes a first alignment layer and a second alignment layer; the first alignment layer and the second alignment layer are respectively arranged on both sides of the first liquid crystal layer; the first alignment layer is used to anchor the alignment of liquid crystal molecules in the first liquid crystal layer that are close to the first alignment layer; The second alignment layer is used to anchor the alignment of liquid crystal molecules in the first liquid crystal layer that are close to the second alignment layer.

9. The spatial light modulator according to any one of claims 1 to 8, characterized in that: It also includes a third alignment layer and a fourth alignment layer; the third alignment layer and the fourth alignment layer are respectively arranged on both sides of the second liquid crystal layer; the third alignment layer is used to anchor the alignment of liquid crystal molecules in the second liquid crystal layer that are close to the third alignment layer; The fourth alignment layer is used to anchor the alignment of liquid crystal molecules in the second liquid crystal layer that are close to the fourth alignment layer.

10. The spatial light modulator according to claim 8, characterized in that The device also includes a light-enhancing layer; the light-enhancing layer is arranged on a side of the first opposing substrate away from the first liquid crystal layer; the light-enhancing layer is used to increase the transmittance of the light signal when it enters the first modulation component.

11. A phase modulation method for an optical signal, characterized in that: Applied to a spatial light modulator, the spatial light modulator includes a first modulation component and a second modulation component; the method includes: The first modulation component receives an incident first optical signal of any polarization state, and emits a second optical signal to the second modulation component by diffracting or transmitting the first optical signal; the transmission direction of the second optical signal is a first preset direction; The second modulation component receives the second optical signal, performs phase modulation on the second optical signal, and reflects a third optical signal to the first modulation component; the transmission direction of the third optical signal is a second preset direction; The first modulation component receives the third optical signal, and emits a fourth optical signal in a target direction by diffracting or transmitting the third optical signal.

12. The phase modulation method of an optical signal according to claim 11, characterized in that: The target direction is opposite to the incident direction of the first optical signal; or, the target direction is parallel to one of the first preset plane and the second preset plane, and is deflected by a preset angle relative to the transmission direction of the first optical signal; the first preset plane, the second preset plane and the light receiving surface provided by the first modulation component are perpendicular to each other.

13. The phase modulation method of an optical signal according to claim 11 or 12, characterized in that: The first modulation component includes a first common electrode, a first pixel electrode array, and a first liquid crystal layer located between the first common electrode and the first pixel electrode array; the first modulation component receives an incident first light signal of any polarization state, and emits a second light signal to the second modulation component by diffracting or transmitting the first light signal, including: A first voltage is generated between the first common electrode and the first pixel electrode array; The first liquid crystal layer receives an incident light signal, and based on the first voltage, diffracts or transmits the first light signal to emit the second light signal to the second modulation component.

14. The phase modulation method of an optical signal according to claim 13, characterized in that: The second modulation component includes a super surface layer, a second common electrode, a second pixel electrode array, and a second liquid crystal layer between the second common electrode and the second pixel electrode array; the second pixel electrode array is formed on a reflective layer, or the second modulation component further includes a reflective layer; the second modulation component receives the second optical signal, performs phase modulation on the second optical signal, and reflects a third optical signal to the first modulation component, including: A second voltage is generated between the second common electrode and the second pixel electrode array; The second liquid crystal layer receives a second optical signal from the first modulation component; if the polarization direction of the second optical signal is the first direction, phase modulates the second optical signal based on the second voltage; The metasurface layer converts the polarization direction of the second optical signal from the first direction to the second direction, or converts the polarization direction of the second optical signal from the second direction to the first direction, and the first direction is orthogonal to the second direction; The reflective layer receives the optical signal emitted from the metasurface layer and reflects the optical signal; The second liquid crystal layer receives the reflected light signal emitted by the reflective layer. If the polarization direction of the reflected light signal is the first direction, the reflected light signal is phase modulated based on the second voltage, and the third light signal is emitted to the first modulation component in the second preset direction.

15. The phase modulation method of an optical signal according to any one of claims 11 to 14, characterized in that: The second optical signal and / or the fourth optical signal undergoes a preset degree of energy attenuation relative to the first optical signal.

16. A wavelength selective switch, characterized in that: The method comprises an input and output optical fiber array, a grating dispersion element, a lens assembly and a spatial light modulator as claimed in any one of claims 1 to 10; The input and output optical fiber array includes a plurality of input and output ports; The grating dispersion element is located on the transmission path of the incident light signal S input from the input and output ports, and is used to disperse the incident light signal S into at least one light signal Si, and different light signals Si correspond to different wavelengths; The lens assembly is located on the transmission path of the at least one optical signal Si and is used to project the at least one optical signal Si to different wavelength channels of the spatial light modulator; The spatial light modulator is used to receive the at least one optical signal Si, and output the optical signals Si of different wavelengths to different input and output ports respectively based on the different wavelength channels.

17. A port switching method, characterized in that: A spatial light modulator used in a wavelength selective switch as claimed in claim 16; the method comprising: receiving a light signal projected by the lens assembly; In a first time period, based on a first preset voltage between the first common electrode and the first pixel electrode, the optical signal is output to a position outside the preset port; at a first moment, the voltage between the second common electrode and the second pixel electrode is a first preset voltage between the first common electrode and the first pixel electrode. second preset voltage, at a second moment, the voltage between the second common electrode and the second pixel electrode is a third preset voltage; the second moment is a moment later than the first moment in the first time period; the preset port includes one or more input and output ports in the input and output optical fiber array; In a second time period, based on a fourth preset voltage between the first common electrode and the first pixel electrode, and a third preset voltage between the second common electrode and the second pixel electrode, the optical signal is output to a first port; the second time period is later than the first time period; the first port is an input / output port in the input / output optical fiber array.

18. The port switching method according to claim 17, characterized in that: The method further comprises: In a third time period, based on a fifth preset voltage between the first common electrode and the first pixel electrode, and the second preset voltage between the second common electrode and the second pixel electrode, the optical signal is output to a second port; the third time period is earlier than the first time period; the second port is an input / output port in the input / output optical fiber array, and the first port is different from the second port.

19. A method for attenuating an optical signal, characterized in that: A spatial light modulator used in a wavelength selective switch as claimed in claim 16; the method comprising: The first modulation component receives the optical signal projected by the lens component; The first modulation component emits the optical signal to the second modulation component based on a first target voltage between the first common electrode and the first pixel electrode; The second modulation component reflects the optical signal from the first modulation component to the first modulation component based on a second target voltage between the second common electrode and the second pixel electrode; The first modulation component emits the optical signal from the second modulation component to a target port based on the first target voltage between the first common electrode and the first pixel electrode; the target port is an input / output port in the input / output optical fiber array; The optical signal emitted by the first modulation component to the second modulation component, and / or the optical signal emitted by the first modulation component to the target port, undergoes a preset degree of energy attenuation relative to the optical signal projected by the lens component.

20. A method for controlling a spatial light modulator, characterized in that: The spatial light modulator is a spatial light modulator in a wavelength selective switch as claimed in claim 16; the method comprises: receiving a port switching instruction, wherein the port switching instruction includes a target port; In response to the port switching instruction, at a first moment, the voltage between the first common electrode and the first pixel electrode is adjusted to a first preset voltage; at the first moment, the voltage between the second common electrode and the second pixel electrode is a second preset voltage; the first preset voltage is used to enable the spatial light modulator to output the light signal projected by the lens assembly to a position outside the preset port; At a second moment, controlling the second common electrode and the second pixel electrode to generate a third preset voltage; At a third moment, a fourth preset voltage is controlled to be generated between the first common electrode and the first pixel electrode; the fourth preset voltage and the third preset voltage are used to enable the spatial light modulator to output the optical signal projected by the lens assembly to the target port.

21. A method for controlling a spatial light modulator, characterized in that: The spatial light modulator is a spatial light modulator in a wavelength selective switch as claimed in claim 16; the method comprises: receiving a signal attenuation instruction, wherein the signal attenuation instruction includes an attenuation parameter, wherein the attenuation parameter represents a preset attenuation degree of the optical signal; In response to the signal attenuation instruction, controlling the first common electrode and the first pixel electrode to generate a first target voltage; and controlling the second common electrode and the second pixel electrode to generate a second target voltage; The first target voltage and the second target voltage are used to enable the spatial light modulator to output the incident optical signal to the target port; the first target voltage is used to cause the optical signal output to the target port to attenuate the energy of the optical signal to the preset attenuation degree relative to the incident optical signal.

22. An optical communication device, characterized in that: The method comprises the spatial light modulator according to any one of claims 1 to 10, or comprises the wavelength selective switch according to claim 16.

23. An optical communication system, characterized in that: Comprising the optical communication device as claimed in claim 22.

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