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

Abstract

The embodiment of the invention discloses a spatial light modulator, a wavelength selection switch, optical communication equipment and a system, and relates to the technical field of optical communication, and the spatial light modulator comprises a first modulation assembly and a second modulation assembly which are sequentially arranged along 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. Liquid crystal molecules in the first liquid crystal layer are periodically arranged in a fan-column shape in a plane perpendicular to the incident direction of an optical signal. 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 super surface layer, a reflecting layer and a CMOS silicon-based backboard which are sequentially arranged in the specific direction. And pixel electrodes in the second pixel electrode array are electrically connected with the CMOS silicon-based back plate. The spatial light modulator has a polarization-independent phase response characteristic, and when the spatial light modulator is applied to a wavelength selective switch, output port switching of optical signals can be rapidly achieved without crosstalk.

Description

Technical Field

[0001] This application relates to the field of optical communication technologies, and in particular, to a spatial light modulator, a wavelength selective switch, an optical communication device, and a system. Background Art

[0002] An optical communication network realizes flexible configuration and free scheduling of the wavelengths of optical signals for up / down and through wavelengths at each optical network node through a reconfigurable optical add-drop multiplexer (ROADM) and an optical cross-connect (OXC). A wavelength selective switch (WSS), also known as a wavelength selective switch, as a core component of a ROADM device or an OXC device, is used to output an optical signal of any one or more wavelengths in an input wavelength division multiplexing (WDM) signal (such as a multi-wavelength optical signal) to any output port, thereby realizing functions such as dynamic port switching and energy balance (such as signal attenuation control) for each wavelength of optical signal in an optical fiber link.

[0003] Generally, the WSS realizes the above functions based on technologies such as microelectromechanical mirrors (MEMS), liquid crystal on silicon (LCoS), liquid crystal (LC), digital micro-mirror devices (DMD), etc. Among them, the LCoS-based WSS has many advantages such as flexible grid, small volume, no mechanical vibration, and high reliability, and thus has become the mainstream technology of the WSS. However, when using an LCoS device as a beam deflection element (or called an optical switching engine) in the WSS, due to the edge field effect of the LCoS, stray light is generated when the beam is deflected, and then, during the port switching process, the stray light beam is likely to enter other ports as a crosstalk signal, that is, transient crosstalk is generated.

[0004] Therefore, for an LCoS-based WSS, how to avoid the transient crosstalk accompanying port switching has become a technical problem to be solved urgently. Summary of the Invention

[0005] Embodiments of the present application provide a spatial light modulator, a wavelength selective switch, an optical communication device and a system, and the main purpose is to provide a spatial light modulator that is polarization independent and can quickly switch the optical signal transmission direction, 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 port switching. On the other hand, the wavelength selective switch can also have polarization independent characteristics, and has the advantages of simple optical path and easy implementation, and low polarization dependent loss. On the other hand, without complex algorithms, the wavelength selective switch can achieve attenuation processing of optical signals.

[0006] In a first aspect, embodiments of the present application provide a spatial light modulator, and the spatial light modulator has polarization independent characteristics. The spatial light modulator may specifically include a first modulation component and a second modulation component sequentially arranged in a specific direction, so that an incident optical signal can sequentially pass through the first modulation component and the second modulation component. The specific direction may be, for example, the incident direction of the optical signal. Among them, 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 both sides of the first liquid crystal layer; the liquid crystal molecules in the first liquid crystal layer are arranged in a periodic fan-shaped column in a plane perpendicular to the incident direction of the optical signal. Specifically, the liquid crystal molecules in the first liquid crystal layer are periodically arranged in a preset direction, and the azimuth angle of the liquid crystal molecules within one period changes continuously and linearly by 180°; the preset direction is perpendicular to the incident direction of the optical signal. The second modulation component includes a second common electrode, a second pixel electrode array and a second liquid crystal layer located therebetween, and further includes a metasurface layer, a reflection layer and a CMOS silicon substrate backplane sequentially arranged on the side of the second liquid crystal layer away from the first liquid crystal layer in a specific direction. The pixel electrodes in the second pixel electrode array are electrically connected to the CMOS silicon substrate backplane.

[0007] In the above 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 optical 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 optical 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 optical signal passing through the metasurface layer. The reflection layer is used to reflect the optical signal emitted from the metasurface layer. The CMOS silicon substrate backplane is used to configure the second voltage.

[0008] Since both the first modulation component and the second modulation component can deflect the transmission direction of the optical signal by adjusting the state of the internal liquid crystal, when the above spatial light modulator is applied to a wavelength selective switch, port switching can be quickly achieved through the cooperation of the first modulation component and the second modulation component. During the port switching process, the second modulation component only undergoes one configuration change, that is, through "single-step switching", the port switching is achieved, so it has a relatively fast switching speed.

[0009] In addition, since the liquid crystal molecules in the first liquid crystal layer are periodically arranged in a preset direction within the plane perpendicular to the incident direction of the optical signal (such as the XY plane), and the azimuth angle of the liquid crystal molecules within one period changes continuously and linearly by 180°. Therefore, looking down at the XY plane, the first liquid crystal layer forms a strip grating, and when the light beam passes through the first liquid crystal layer, it has a geometric phase. 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 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 polarization independence. That is, for incident light beams with any polarization state, the deflection of the transmission direction of the light beam can be achieved. In addition, when a voltage is applied to the first liquid crystal layer (the first voltage is greater than zero), according to the magnitude of the voltage value, the liquid crystal molecules in the first liquid crystal layer can exhibit different states. When a first voltage (greater than zero, with a driving electric field formed) is applied to the first liquid crystal layer, ideally, except for the liquid crystal molecules near the alignment layer, the long axes of other liquid crystal molecules are perpendicular to the XY plane, or rather, the inclination angle of their long axes relative to the XY plane is 90° or nearly 90°. At this time, the 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 formed) is applied to the first liquid crystal layer, ideally, except for the liquid crystal molecules near the alignment layer, the inclination angle of the long axes of other liquid crystal molecules relative to the XY plane is less than 90°. At this time, the light intensity of the incident light is attenuated under the action of the first liquid crystal layer.

[0010] As a possible implementation, assume that the liquid crystal molecules are periodically arranged along a preset direction in the XY plane, and the azimuth angle of the liquid crystal molecules changes continuously within one period by 180°, and the director n(x) of the liquid crystal is a function of the coordinate variable x and satisfies

[0011] n(x) = [sin(πx / Λ), cos(πx / Λ), 0]

[0012] where the range of x is 0 - Λ. Looking down at the XY plane, the first liquid crystal layer forms a strip grating, Λ is the grating period, and the x-axis direction is the direction of the grating period.

[0013] In the above 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 in the first direction into the second direction, and convert the polarization direction of the optical signal passing through the metasurface layer from the second direction into the first direction; the first direction is orthogonal to the second direction. Furthermore, the second modulation component has a polarization-independent phase response characteristic. Whether for the optical signal polarized in the first direction or the second direction, during the entire process from incidence on the second modulation component to final emission, the same phase modulation can be obtained once. Since the optical signal with any other polarization state in the incident optical signal can always be decomposed into a combination of the optical component with the first polarization state and the optical component with the first polarization state, and each optical component of each polarization state also only obtains the phase modulation once, the second modulation component has a polarization-independent phase response characteristic.

[0014] 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 anymore. Therefore, the structure of the wavelength selective switch can be simplified, and the device volume, optical path complexity, and polarization-dependent loss can be reduced.

[0015] In a possible implementation manner of the first aspect, in this spatial light modulator, the second pixel electrode array is formed in the reflection layer. For example, the second pixel electrode array can be specifically implemented as a pixelated metal layer that has a reflective effect on light, or rather, the second pixel electrode array has a light reflection function. In this implementation manner, the second pixel electrode array is formed in the reflection layer, or rather, is formed integrally with the metal material for light reflection.

[0016] In another possible implementation manner of the first aspect, in this spatial light modulator, the second pixel electrode array is disposed between the reflection layer and the CMOS silicon-based backplane. In this implementation manner, the second pixel electrode array is independent of the reflection layer. For example, it can be disposed on the surface of the reflection layer close to the CMOS silicon-based backplane.

[0017] In a 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. By way of 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 used to electrically connect to a driving circuit, which is used to output a voltage signal to the first pixel circuit. Based on the voltage signal input by the driving circuit, the first pixel circuit outputs a voltage to the first pixel electrode and the first common electrode. The second modulation component may include a second signal interface, and the CMOS silicon-based backplane is connected to the second signal interface through a data line. The second signal interface is used to electrically connect to a driving circuit. The driving circuit is further used to output a data signal to the data line. In addition, the second common electrode may be electrically connected to the driving circuit through the second signal interface to obtain a voltage. Wherein, the driving circuit may be a circuit structure external to the spatial light modulator.

[0018] In another possible implementation of the first aspect, the above driving circuit is integrated in the spatial light modulator, and the above N signal interfaces are electrically connected to the driving circuit.

[0019] In another possible implementation of the first aspect, the spatial light modulator further includes a first counter substrate and a second counter substrate; the first counter 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 counter substrate close to the first liquid crystal layer; the second counter substrate is disposed on a side of the second liquid crystal layer away from the CMOS silicon-based backplane; the second common electrode is disposed on a surface of the second counter substrate close to the second liquid crystal layer.

[0020] 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 two sides of the first liquid crystal layer. The first alignment layer is used to anchor the liquid crystal molecules in the first liquid crystal layer close to it, causing the liquid crystal molecules close to it to have a pre-orientation. The second alignment layer is used to anchor the liquid crystal molecules in the first liquid crystal layer close to it, causing the liquid crystal molecules close to it to have a pre-orientation. Wherein, under the action of the first alignment layer and the second alignment layer, the pre-orientation generated by the liquid crystal molecules in the first liquid crystal layer closest to the first alignment layer is the same as the pre-orientation generated by the liquid crystal molecules in the first liquid crystal layer closest to the second alignment layer. That is to say, the alignment directions corresponding to the first alignment layer and the second alignment layer are the same.

[0021] 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 two sides of the second liquid crystal layer. The third alignment layer is used to anchor the liquid crystal molecules close to it in the second liquid crystal layer, so that the liquid crystal molecules close to it generate a pre-orientation. The fourth alignment layer is used to anchor the liquid crystal molecules close to it in the second liquid crystal layer, so that the liquid crystal molecules close to it generate a pre-orientation. Wherein, under the action of the third alignment layer and the fourth alignment layer, the pre-orientation generated by the liquid crystal molecules closest to the third alignment layer in the second liquid crystal layer is the same as the pre-orientation generated by the liquid crystal molecules closest to the fourth alignment layer in the second liquid crystal layer. That is to say, the alignment directions corresponding to the third alignment layer and the fourth alignment layer are the same.

[0022] In another possible implementation of the first aspect, the spatial light modulator further includes an anti-reflection layer; the anti-reflection layer is disposed on a side of the first counter substrate away from the first liquid crystal layer, and is used to increase the transmittance of the incident optical signal.

[0023] In a second aspect, an embodiment of the present application provides a method for phase modulating an optical signal, which is applied to a spatial light modulator. The spatial light modulator includes a first modulation component and a second modulation component, such as any one of the spatial light modulators mentioned in the first aspect above. The method includes:

[0024] The first modulation component receives a first optical signal with an arbitrary 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;

[0025] 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 a second preset direction;

[0026] 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.

[0027] Wherein, 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.

[0028] 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 in pairs.

[0029] 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 the first optical signal in any polarization state, and emits a second optical signal to the second modulation component by diffracting or transmitting the first optical signal, including:

[0030] A first voltage is generated between the first common electrode and the first pixel electrode array; the first liquid crystal layer receives the incident optical signal, and based on the first voltage, diffracts or transmits the first optical signal to emit a second optical signal to the second modulation component.

[0031] 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 a 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, performs phase modulation on the second optical signal, and reflects a third optical signal to the first modulation component, including:

[0032] 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, phase modulation is performed on 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, where 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 from the reflective layer, if the polarization direction of the reflected optical signal is the first direction, phase modulation is performed on the reflected optical signal based on the second voltage, and the third optical signal is emitted to the first modulation component in a second preset direction.

[0033] In a possible implementation 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.

[0034] In a third aspect, an embodiment of the present application provides a wavelength selective switch, which includes an input / output optical fiber array, a grating dispersion element, a lens assembly, and any one of the spatial light modulators provided in the first aspect above; wherein, the input / output optical fiber array includes a plurality of input / output ports; the grating dispersion element is located on the transmission path of the incident optical signal S input from the input / output port, and is configured to disperse the incident optical signal S into at least one optical signal Si, and different optical signals Si correspond to different wavelengths; the lens assembly is located on the transmission path of at least one optical signal Si, and is configured to project at least one optical signal Si to different wavelength channels of the spatial light modulator; the spatial light modulator is configured to receive at least one optical signal Si, and based on different wavelength channels, output optical signals Si of different wavelengths to different input / output ports respectively.

[0035] 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 above. The method includes:

[0036] Receiving the optical signal projected by the lens assembly;

[0037] In a first time period, based on a first preset voltage between the first common electrode and the first pixel electrode, output the optical signal 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 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 within the first time period; the preset port includes one or more input / output ports in the input / output optical fiber array;

[0038] 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, output the optical signal 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.

[0039] It can be seen from the above embodiments that by adjusting the voltage configurations 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. Among them, the change in the configuration of the second modulation component is a necessary condition for switching the output of the optical signal from the first port to the second port, and the change in the configuration of the first modulation component is aimed at deflecting the optical signal from a certain preset port to a position outside the preset port, or deflecting the optical signal from a position outside the preset port back to a certain preset port, so as to ensure 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.

[0040] For the second modulation component, during the port switching process, there is only one configuration change. Therefore, 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 with multiple phase diagrams 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 relatively fast switching speed. Moreover, since during the process of loading the final state phase plane of the liquid crystal layer in the second modulation component (i.e., in the intermediate state), the optical signal will be deflected to a position outside the preset port based on the first modulation component, it will not become a crosstalk signal and be transmitted to the effective port.

[0041] In a possible implementation manner of the fourth aspect, the port switching method further includes:

[0042] In the third time period, based on the 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 the 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 fiber array, and the first port is different from the second port.

[0043] In a fifth aspect, the embodiment of the present application further provides a method for attenuating a signal, which is applied to the spatial light modulator in the wavelength selection switch provided in the third aspect; the method includes:

[0044] The first modulation component receives the optical signal projected by the lens component;

[0045] The first modulation component projects the optical signal to the second modulation component based on the first target voltage between the first common electrode and the first pixel electrode;

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

[0047] The first modulation component projects the optical signal from the second modulation component to the 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 fiber array;

[0048] Wherein, the optical signal projected by the first modulation component to the second modulation component, and / or, the optical signal projected by the first modulation component to the target port has a preset degree of energy attenuation relative to the optical signal projected by the lens component.

[0049] It can be seen that in the embodiments of the present application, the first modulation component is used to achieve the attenuation control of the optical signal. In the related art, taking the spatial light modulator based on LCoS as an example, in the face of some application scenarios that require signal attenuation control, extremely complex algorithms are needed 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 not only achieve phase modulation but also attenuate the signal intensity. Compared with the related art, the spatial light modulator provided by the embodiments of the present application decouples the signal attenuation control from the phase modulation. For example, the first modulation component is used to achieve signal attenuation, and the second modulation component is used to achieve phase modulation. Thus, the attenuation processing of the optical signal can be achieved without complex algorithms, and the phase modulation effect is not affected at the same time.

[0050] In a sixth aspect, the embodiments of the present application further provide a control method for a spatial light modulator, where the spatial light modulator is the spatial light modulator in the wavelength selection switch described in the third aspect; the method includes:

[0051] Receiving a port switching instruction, where the port switching instruction includes a target port;

[0052] In response to the port switching instruction, at a first moment, adjusting the voltage between the first common electrode and the first pixel electrode 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 make the spatial light modulator output the optical signal projected by the lens assembly to a position other than the preset port;

[0053] At a second moment, controlling a third preset voltage to be generated between the second common electrode and the second pixel electrode;

[0054] At a third moment, controlling a fourth preset voltage 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 make the spatial light modulator output the optical signal projected by the lens assembly to the target port.

[0055] For the technical effects of the control method for the spatial light modulator provided in the sixth aspect, reference can be made to the content of the fourth aspect, which will not be elaborated here.

[0056] In a seventh aspect, the embodiments of the present application further provide a control method for a spatial light modulator, where the spatial light modulator is the spatial light modulator in the wavelength selection switch described in the third aspect; the method includes:

[0057] Receiving a signal attenuation instruction, where the signal attenuation instruction includes an attenuation parameter, and the attenuation parameter represents a preset attenuation degree of the optical signal;

[0058] In response to a signal attenuation instruction, control a first target voltage to be generated between a first common electrode and a first pixel electrode; and control a second target voltage to be generated between a second common electrode and a second pixel electrode;

[0059] The first target voltage and the second target voltage are used to cause the spatial light modulator to output an incident optical signal to a target port; the first target voltage is used to cause the optical signal output to the target port to undergo an energy attenuation of a preset attenuation degree with respect to the incident optical signal.

[0060] For the technical effects of the control method of the spatial light modulator provided in the seventh aspect, reference may be made to the content of the fifth aspect, which will not be elaborated here.

[0061] In an eighth aspect, an embodiment of the present application further provides an optical communication device, including the spatial light modulator described in any one of the first aspect, or the wavelength selection switch described in the third aspect.

[0062] In a ninth aspect, an embodiment of the present application further provides an optical communication system, including the optical communication device described in the eighth aspect.

[0063] Among the contents of the above first aspect to ninth aspect, for the technical effects brought about by any possible implementation manner in the second aspect and the third aspect, reference may also be made to the technical effects brought about by the implementation manner of the above first aspect, which will not be elaborated here. Description of the Drawings

[0064] Figure 1 It is a schematic structural diagram of an optical communication system;

[0065] Figure 2 It is a schematic structural diagram of an optical add-drop multiplexer;

[0066] Figure 3 It is a schematic structural diagram of a wavelength selection switch;

[0067] Figure 4 It is a schematic structural diagram of a spatial light modulator 40 based on LCoS;

[0068] Figure 5 It is a schematic diagram of a liquid crystal layer;

[0069] Figure 6 It is a schematic diagram of an ideal phase surface and a non-ideal phase surface formed by the liquid crystal layer;

[0070] Figure 7 It is a schematic structural diagram of a wavelength selection switch provided by an embodiment of the present application;

[0071] Figure 8 It is a schematic structural diagram of a spatial light modulator provided by an embodiment of the present application;

[0072] Figure 9 Another structural schematic diagram of the spatial light modulator provided by the embodiment of the present application;

[0073] Figure 10 A schematic diagram of the distribution of liquid crystal molecules in the first liquid crystal layer of the spatial light modulator provided by the embodiment of the present application;

[0074] Figure 11 Another schematic diagram of the distribution of liquid crystal molecules in the first liquid crystal layer of the spatial light modulator provided by the embodiment of the present application;

[0075] Figure 12 Schematic diagrams of the deflection effects of several beam transmission directions of the spatial light modulator provided by the embodiment of the present application;

[0076] Figure 13 Schematic diagram of the control method flow of the spatial light modulator provided by the embodiment of the present application. Detailed implementation manners

[0077] Next, the technical solutions in the embodiments of the present application will be described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0078] Unless otherwise defined, all scientific and technical terms used herein have the same meaning as commonly understood by those of ordinary skill in the art. In the embodiments of the present application, "at least one" means one or more, and "a plurality" means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone, where A and B may be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after. "At least one (item)" or its similar expression below refers to any combination of these items, including any combination of single item (item) or plural items (items). For example, at least one (item) of a, b or c may represent: a, b, c, a and b, a and c, b and c, or a, b and c, where a, b and c may be single or multiple. In addition, in the embodiments of the present application, the words "first", "second", etc. do not limit the quantity and order.

[0079] In addition, in the embodiments of the present application, the orientation terms such as "upper" and "lower" are defined relative to the orientation of the components shown in the accompanying drawings. It should be understood that these directional terms are relative concepts, and they are used for relative description and clarification, and they may change accordingly with the change of the orientation of the components placed in the accompanying drawings.

[0080] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0081] Before introducing the technical solutions in the embodiments of the present application, the technical terms involved in the embodiments of the present application will be introduced first.

[0082] The nominal central wavelength refers to the central wavelength corresponding to each channel in an optical fiber communication system based on wavelength division multiplexing technology. It reflects the channel spacing, spectral position, etc. of the optical signals (optical carriers) in the optical fiber communication system. Frequency and wavelength can be calculated through 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 from a nominal central wavelength according to the above formula is also called the nominal central frequency. In the embodiments of the present application, unless otherwise specified, the wavelength of the optical signal mentioned hereinafter refers to the nominal central wavelength of the optical signal.

[0083] A multi-wavelength optical signal refers to an optical signal formed by combining multiple optical signals with different nominal central wavelengths. Its spectrum contains multiple spectral segments. Generally, each spectral segment corresponds to an optical signal with a certain nominal central wavelength. The single-wavelength optical signal corresponding to the multi-wavelength optical signal refers to an optical signal with a certain nominal central wavelength.

[0084] 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 sending end can send optical signals of any wavelength in the communication band to the optical fiber.

[0085] Directionless means that each signal receiving end can receive optical signals in any direction / dimension in the optical communication system, and each signal sending end can send optical signals to the optical fiber in any direction / dimension in the optical communication system.

[0086] Contentionless means that any n directions / dimensions (1 ≤ n) in the optical communication system can send optical signals of the same wavelength to n signal receiving ends (each signal receiving end only receives one optical signal); any n signal sending ends can send optical signals of the same wavelength to the optical fiber in any n directions / dimensions in the optical fiber communication system.

[0087] Geometric Phase: The specific information of light in the spatial domain can be represented by amplitude, phase, and polarization state. Optical field control refers to the control of the amplitude, phase, and polarization state information of light to meet the requirements of the optical field in different application scenarios. Among them, the phase of light is mainly related to the path traveled during propagation, that is, the optical path, which is jointly determined by the average refractive index of the propagation medium and the geometric path, and is usually also called the dynamic phase. In addition, there is another optical phase that depends on the evolution of the polarization state of the light beam. When light passes through an anisotropic medium, another phase will be accumulated simultaneously during the evolution of the polarization state. 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.

[0088] Next, the technical solutions in the embodiments of the present application will be described in conjunction with the accompanying drawings.

[0089] Figure 1 It is a schematic structural diagram of an optical communication system 10, as Figure 1 shown. The optical communication system 10 includes an access machine room 11 and optical add-drop multiplexing systems (such as Figure 1 the optical add-drop multiplexing system 12a, the optical add-drop multiplexing system 12b, and the optical add-drop multiplexing system 12c shown). The line-side optical signal transmitted in the optical communication system 10 is output from the access machine room 11 and sequentially passes through one or more optical add-drop multiplexing systems in a predetermined direction. Among them, the line-side optical signal can be generated by the access machine room 11 or the optical signal transmitted by other optical communication systems received by the access machine room 11. And, the line-side optical signal transmitted in the optical communication system 10 is usually a multi-wavelength optical signal formed by multiplexing using wavelength division multiplexing technology to improve the communication capacity and communication rate of the optical communication system 10.

[0090] In the optical communication system as Figure 1 shown, each optical add-drop multiplexing system can act as a "relay node" for transmitting the optical signal 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). Thus, the optical add-drop multiplexing system can support the transmission of optical signals in two directions. For example, taking Figure 1 the optical add-drop multiplexing system 12b in as an example, it supports the signal transmission in the direction from the optical add-drop multiplexing system 12a to the optical add-drop multiplexing system 12b (hereinafter assumed to be "from east to west"), and at the same time supports the signal transmission in the direction from the optical add-drop multiplexing system 12c to the optical add-drop multiplexing system 12b (hereinafter assumed to be "from west to east").

[0091] In addition, each optical add / drop multiplexing system can also serve as a "signal originating node" for transmitting optical signals input by local communication devices such as optical transponder units (OTUs) on the node side to other optical add / drop multiplexing systems. Each optical add / drop multiplexing system can also serve as a "signal termination node" for transferring line-side optical signals to local communication devices on the node side. In specific implementations, the optical add / drop multiplexing system includes an optical add / drop multiplexer (OADM). The optical add / drop multiplexer includes multiple signal input / output ports, a part of which are used as wavelength-adding ports and a part of which are used as wavelength-dropping ports. The wavelength-adding ports and / or wavelength-dropping ports are connected to local communication devices. In some cases, the local communication device generates an upstream optical signal with a predetermined wavelength and transmits the upstream optical signal with the predetermined wavelength to the wavelength-adding port of the optical add / drop multiplexer. The optical add / drop multiplexing system multiplexes the upstream optical signal into the line-side optical signal, and / or the local communication device receives one or more optical signals with different wavelengths in the line-side optical signal transmitted from the wavelength-dropping port of the optical add / drop multiplexer.

[0092] Exemplarily, referring to Figure 1 the enlarged schematic diagram of the site optical layer of the optical add / drop multiplexing system 12b shown by the dashed box. Assume 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 the wavelength of λa in the line-side optical signal S1 to the local communication device. The local communication device can generate an upstream optical signal S3 with the wavelength of λb and transmit the upstream optical signal S3 to the wavelength-adding port of the optical add / drop multiplexer. The optical add / drop multiplexer multiplexes the upstream optical signal S3 with the optical signals of other wavelengths in the line-side optical signal S1 except S2 to generate a new line-side optical signal S4.

[0093] It can be seen from this that in the optical communication system 10, each optical add / drop multiplexing system needs to implement wavelength addition (add wavelength) and wavelength dropping (drop wavelength) of single-wavelength optical signals and / or multi-wavelength optical signals, and at the same time, it is also necessary to ensure non-blocking pass-through of optical signals of any wavelength. As described above, this is generally achieved by setting an optical add / drop multiplexer in the optical add / drop multiplexing system.

[0094] At present, the optical add-drop multiplexers set in optical add-drop multiplexing systems are usually reconfigurable optical add-drop multiplexers (ROADMs). ROADMs can dynamically adjust the wavelengths of the optical signals on the up-wave and down-wave, thereby improving the flexibility of the optical add-drop multiplexing system.

[0095] Figure 2 FIG. 4 is a schematic structural diagram of an optical add-drop multiplexer 20, as Figure 2 shown. A typical colorless (C), directionless (D), contentionless (C) optical add-drop multiplexer 20 includes a line-side component 21 and a client-side component 22. Among them, the line-side component 21 can receive any wavelength and any dimension (direction) of the optical signal in the communication band used by the optical communication system and transmit it to other optical add-drop multiplexing systems 12 or the client-side component 22. The client-side component 22 can demultiplex the optical signal of any wavelength from the line-side component 21 to any local communication device, and multiplex the optical signal of any wavelength generated by any local communication device to any dimension (direction) through the line-side component 21.

[0096] In a specific implementation, the line-side component 21 usually includes a plurality of wavelength selective switches (WSSs), and the plurality of wavelength selective switches are cross-connected to realize the "wavelength-independent" and "direction-independent" signal transmission of the line-side optical signals. For example, in Figure 2 the shown line-side component, specifically includes three WSSs, namely 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.

[0097] It should be noted that Figure 2 the shown optical add-drop multiplexer 20 further includes more functional devices. For example, the optical add-drop multiplexer 20 further includes an optical amplifier, and the optical amplifier is coupled to the wavelength selective switch. The optical amplifier can amplify the optical signal transmitted to the wavelength selective switch or amplify the optical signal output by the wavelength selective switch. This application will not elaborate on this.

[0098] Generally, the above functions of the WSS are implemented based on technologies such as MEMS, LCoS, LC, and DMD. Among them, the LCoS-based WSS has many advantages such as flexible grid, small volume, no mechanical vibration, and high reliability, so it has become the mainstream technology of the WSS.

[0099] For the convenience of the following description, a three-dimensional space coordinate system, that is, the X-Y-Z coordinate system, is shown in some of the drawings of the embodiments of the present application. The following combines Figure 3 to define the meanings represented by the respective coordinate axes of the three-dimensional space coordinate system in the embodiments of the present application. Figure 3 FIG. 7 is a schematic structural diagram of a wavelength selective switch 30 in the related art, and the wavelength selective switch 30 is implemented based on an LCoS device. Referring to Figure 3 as shown, the wavelength selective switch 30 includes an input / 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.

[0100] The wavelength selective switch 30 is located in the X-Y-Z coordinate system of the three-dimensional space coordinate system.

[0101] The Z-axis direction is the incident direction of the optical signal, or rather, the transmission direction of the optical signal when it is input into the wavelength selective switch 30 is parallel to or approximately parallel to the Z-axis direction within the manufacturing tolerance.

[0102] The Y-axis direction is the arrangement direction of the input / output port array in the wavelength selective switch 30, so it can also be called the port direction. Without special instructions, the schematic diagram of the port direction mentioned below refers to the schematic diagram in the YZ plane. In the schematic diagram in the YZ plane, the transmission path of the optical signal can show which port the optical signal modulated by the spatial light modulator is output through. 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 it is described that the optical signal deflects in the Y-axis direction or the port direction, it can also be understood that the optical signal deflects in the YZ plane, or rather, the transmission direction after deflection is parallel to the YZ plane.

[0103] The X-axis direction is perpendicular to both the Z-axis direction and 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. Therefore, the X-axis direction can also be referred to as 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 it is described that the optical signal deflects in the X-axis direction or the dispersion direction, it can also be understood that the optical signal deflects in the XZ plane, or the transmission direction after deflection is parallel to the XZ plane.

[0104] In Figure 3 the wavelength selective switch 30 shown, a part of the ports in the input / output port array can be used as signal input ports for receiving incident optical signals. For example, there is an optical signal S input to port Pi+1, and the transmission direction of the incident optical signal S is Figure 3 represented by the solid line with an arrow in Figure 3 the schematic diagram in the dispersion direction. A part of the ports in the input / output port array can be used as signal output ports, such as P1, P2, Pi, Pn-1, and Pn. Referring to Figure 3 the schematic diagram in the port direction in Figure 3 it can be seen that the spatial light modulator based on LCoS can output the optical signals 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 from ports P1, P2, Pi, Pn-1, or Pn, and the corresponding optical signal and its transmission direction are as

[0105] As Figure 4As shown, the LCoS-based spatial light modulator 40 includes a liquid crystal layer 41. On both sides of the liquid crystal layer 41, a plurality of pixel electrodes 42 and a common electrode 43 that are arrayed in a two-dimensional plane are respectively provided. The liquid crystal layer 41 includes a plurality of liquid crystal molecules 410. The liquid crystal molecules can perform phase modulation on an optical signal of a certain polarization state. Exemplarily, when the liquid crystal molecules in the liquid crystal layer 41 are all rod-shaped liquid crystal molecules, the liquid crystal molecules can perform phase modulation on an optical signal whose polarization direction is the same as the orientation of its long axis. When a voltage is applied between the pixel electrode 42 and the common electrode 43 on both sides of the liquid crystal layer, a driving electric field is formed between the pixel electrode 42 and the common electrode 43. The liquid crystal molecules in the liquid crystal layer 41 will change their states under the action of the driving electric field, such as deflecting, and will deflect to different degrees according to the magnitude of the electric field strength. Generally, the degree of deflection of the liquid crystal molecules can be characterized by the orientation. Here, the orientation can refer to the angle between the long axis orientation of the liquid crystal molecules and the plane of the liquid crystal layer (or the plane where the arrangement direction is located). When the orientations of the liquid crystal molecules are different, the phase modulation effect (beam deflection effect) on the optical signal may be different.

[0106] In addition, as Figure 5 shown, according to factors such as the bandwidth, the spot width corresponding to the optical signal, and the pixel electrode size, the plurality of pixel electrodes distributed in two dimensions can be grouped to obtain multiple groups of pixel electrodes. One group of pixel electrodes corresponds to one liquid crystal region and is used to drive the deflection of the liquid crystal molecules in the liquid crystal region. One liquid crystal region corresponds to one wavelength channel and is used to perform phase modulation on an optical signal of one wavelength under the action of the driving electric field by providing the phase surface required for phase modulation.

[0107] Figure 6 In A and B respectively show Figure 5 the phase surfaces formed by the liquid crystal molecules in two liquid crystal regions in Figure 6 For the LCoS-based spatial modulator, taking two consecutive liquid crystal regions as an example, it is easy to be affected by the edge field effect and it is difficult to form an ideal phase surface such as Figure 6 A in Figure 6 and usually an non-ideal phase surface such as B in Figure 6 is easily formed. As can be seen from Figure 6 B, there is phase distortion in the phase surface corresponding to a single phase period, and at the same time, in the return region before two phase periods, the phase distortion is serious. Thus, when deflecting the light beam, part of the light energy (stray light) will enter other ports as crosstalk signals.

[0108] Port switching refers to the wavelength selective switch 30 switching the optical signal in one of its wavelength channels from being output from one port to being output from another port. Generally, by adjusting the phase plane provided by the liquid crystal layer in the LCoS, the deflection angle of the outgoing light of the LCoS is adjusted to output it to the target port. Among them, the phase plane can be represented by a phase pattern. However, during the port switching process of the wavelength selective switch 30, problems such as excessive transient crosstalk or too long switching time occur.

[0109] Specifically, during the process of controlling the LCoS to switch from the initial state phase pattern (the phase pattern that can output the outgoing light to the current port) to the final state phase pattern (the phase pattern that can output the outgoing light to the target port), since the phase plane formed during the switching process is not ideal enough, a part of the outgoing light is likely to be output to the non-target port as a crosstalk signal, thus causing transient crosstalk to the non-target port.

[0110] To improve the problem of transient crosstalk, usually, between loading the initial state phase pattern and the final state phase pattern of the LCoS, multiple additional phase patterns are loaded as a transition to finally achieve outputting the outgoing light to the target port. This process can be understood as achieving port switching through "multiple-step switching". In this way, since the time for the LCoS to load the phase pattern will be increased, the port switching time of the wavelength selective switch 30 is too long, which is not conducive to the switching performance of the wavelength selective switch 30.

[0111] In addition, for the wavelength selective switch based on LCoS, since the liquid crystal layer in the LCoS can only perform phase modulation on the optical signal with the polarization direction of the first direction, most wavelength selective switches based on LCoS are configured as polarization-related architectures. For example, Figure 3 a polarization conversion unit is also provided between the collimating lens array and the grating dispersion element shown, which can specifically be composed of a Wollaston prism and a half-wave plate. The polarization conversion unit needs to generate two orthogonally polarized optical signals according to the received optical signal, where the optical signal of one polarization state is the same as the orientation direction of the LCoS, and the optical signal of the other polarization state is perpendicular to the orientation direction of the LCoS. The two 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.

[0112] In addition, for the wavelength selective switch based on LCoS, in the face of some necessary signal attenuation requirements, extremely complex algorithms are required to configure the voltages of each pixel electrode in the LCoS so that the target phase plane formed by the liquid crystal layer can not only achieve phase modulation but also attenuate the signal intensity.

[0113] In view of this, embodiments of the present application provide a spatial light modulator and a wavelength selective switch including the spatial light modulator. On the one hand, the wavelength selective switch can quickly complete port switching and avoid transient crosstalk generated during port switching. On the other hand, the wavelength selective switch can also have polarization-independent characteristics, and has the advantages of simple optical path and easy implementation, and low polarization-dependent loss. On yet another hand, without a complex algorithm, the wavelength selective switch can implement attenuation processing of optical signals.

[0114] The various implementation manners of the spatial light modulator and the wavelength selective switch provided by the embodiments of the present application will be introduced in turn below.

[0115] Figure 7 FIG. 7 is a schematic structural diagram of a wavelength selective switch 70 provided by an embodiment of the present application. The wavelength selective switch 70 includes the spatial light modulator 80 given in any of the following embodiments. As Figure 7 shown, the wavelength selective switch 70 may include an input / output optical 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 / output optical fiber array 71 includes a plurality of input / output ports, such as Figure 7 P1, P2,..., Pi, Pi+1,..., Pn-1, Pn shown in FIG. A part of the input / output ports can be used for signal input, that is, signal input ports. For example, a light signal S is input to port Pi+1, and the transmission direction of the incident light signal S is as Figure 7 shown by the solid line with an arrow in FIG. A part of the input / output ports can be used for signal output, that is, signal output ports, such as Figure 7 P1, P2, Pi, Pn-1, Pn shown in FIG. Referring to Figure 7 the schematic diagram of the wavelength selective switch 70 in the dispersion direction shown in FIG. After the incident light signal S is incident from the signal input port, a collimating lens (one in the collimating lens array 72) collimates the incident light signal S, and the grating dispersion element 73 disperses the collimated incident light signal S into multiple light signals Si with different wavelengths (i is used to identify different light signals and corresponding wavelength channels in at least one light signal), for example Figure 7 S1, S2, S3 shown in FIG. Different light signals Si have different wavelengths. Among them, 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 the light signals Si with different wavelengths onto different wavelength channels of the spatial light modulator 80. The spatial light modulator 80 is used to receive the light signal Si and output the light signals Si with different wavelengths to different input / output ports respectively based on different wavelength channels. Referring to Figure 7Schematic diagram of the wavelength selection switch 70 shown in the port direction. It can be seen that the spatial light modulator 80 can deflect the optical signal Si in the ith wavelength channel to the port Pi for output. In fact, 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 ith wavelength channel to the ports P1, P2, Pi, Pn-1 or Pn for output. The optical signal Si and its transmission direction are as Figure 7 shown by the dashed line with an arrow in

[0116] Figure 8 Schematic diagram of the structure of a spatial light modulator 80 provided by an embodiment of the present application and the corresponding optical path diagram. As Figure 8 shown, the spatial light modulator 80 can include a first modulation component 81 and a second modulation component 82. Referring to Figure 8 , the plane where the spatial light modulator 80 is located is the XY plane, and this plane can also be called the light receiving surface of the spatial light modulator 80. Taking Figure 8 the first modulation component 81 and the second modulation component 82 shown in as an example of a cuboid, the X-axis direction (the dispersion direction in the wavelength selection switch 70) can 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 selection switch 70) can 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.

[0117] Figure 8 When the spatial light modulator 80 shown is working, first, after the first modulation component 81 receives the first optical signal S1 with any polarization state projected by the lens 74, it emits the second optical signal S2 to the second modulation component 82. The transmission direction of the second optical signal S2 is the first preset 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 second optical signal S2 emitted by it can be a beam or can be divided 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 the third optical signal S3 to the first modulation component 81. The transmission direction of the third optical signal S3 is the second preset direction. Finally, the first modulation component 81 receives the third optical signal S3 from the second modulation component 82 and emits the fourth optical signal S4 to the target port. The transmission direction of the fourth optical signal S4 is the target direction, and the target port is Figure 7An input / output port of the mid-wavelength selection switch 70. Among them, 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.

[0118] As can be seen from the above embodiments, the optical signals carrying the same service information sequentially pass through the first modulation component and the second modulation component, and after being reflected by the first modulation component, pass through the first modulation component again. The mentioned target direction 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 in pairs.

[0119] In the embodiments 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 direction deflection effect of the optical signal, but it is not limited thereto.

[0120] Thus, in the embodiments 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. When the first modulation component and the second modulation component achieve the direction deflection of the optical signal based on the spatial phase modulation effect of 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 surface of the liquid crystal layer can be adjusted, and then different direction deflection effects can be achieved. Specifically, the phase surface of the liquid crystal layer can be adjusted by adjusting the intensity of the electric field in the liquid crystal layer (i.e., the electrode voltage on both sides of the liquid crystal layer).

[0121] For the convenience of description, in this article, the state of the spatial light modulator when the optical signal is deflected to the first port is called the initial state, the state of the spatial light modulator when the optical signal is deflected to the second port is called the final state, and the state between the initial state and the final state is called the intermediate state. Then, the process of the above spatial light modulator performing port switching can be described as follows:

[0122] 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.

[0123] In the intermediate state, by adjusting the configuration of the first modulation component 81, the optical signal is deflected to a position outside the preset port. During this process, since there is no edge field effect in the first modulation component 81, no transient crosstalk will be caused to any port during the deflection of the optical signal. 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 adjustment of the configuration of the second modulation component 82, since the optical signal is deflected outside the preset port, no transient crosstalk will be caused to any port.

[0124] 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.

[0125] It can be seen that through the cooperation of the first modulation component 81 and the second modulation component 82, port switching is achieved. Among them, the change in the configuration of the second modulation component 82 is a necessary condition for switching the output of the optical signal from the first port to the second port, and the change in the configuration of the first modulation component 81 is to deflect the optical signal from a certain preset port to a position outside the preset port, or deflect the optical signal from a position outside the preset port back to a certain preset port, so as to ensure that no stray light is transmitted to the preset port during the process of changing the configuration of the second modulation component 82. The preset port here can be a valid port pre-recorded for service signal transmission.

[0126] For the second modulation component 82, during the port switching process, the configuration changes only once. Therefore, 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 with multiple phase diagrams interspersed in the middle, the embodiment of the present application can complete the adjustment of the phase plane of the liquid crystal layer in the second modulation component 82 at one time, which can ensure a relatively fast switching speed. Moreover, since the optical signal will be deflected to a position outside the preset port based on the first modulation component 81 during the process of loading the final state phase plane of the liquid crystal layer in the second modulation component 82 (i.e., in the intermediate state), it will not be transmitted to the valid port as a crosstalk signal.

[0127] 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, during the above port switching process, 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 can be briefly described as:

[0128] ①At the initial state, the optical signal is deflected to the first port → ②The state of the liquid crystal inside the first modulation component 81 changes → ③The optical signal is deflected outside the preset port → ④The state of the liquid crystal inside the second modulation component 82 changes → ⑤The optical signal is still deflected outside the preset port → ⑥The state of the liquid crystal inside the first modulation component 81 changes → ⑦The optical signal is deflected to the second port.

[0129] In some scenarios of the embodiments of the present application, ②, ④, and ⑥ can be executed serially. In some 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, so as to achieve a faster port switching speed. Specifically: At 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 there is no crosstalk to other ports. After entering the intermediate state, the state of the liquid crystal inside the first modulation component 81 starts to change (i.e., ② starts to be executed). During this change process, 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 effective ports such as the first port gradually becomes smaller. When the intensity of this optical signal is small enough, even if the liquid crystal inside the first modulation component 81 has not reached the target state, but if the intensity of the possible stray light 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, ④ is executed in advance. Similarly, during the change process of the state of the liquid crystal inside the second modulation component 82, even if the liquid crystal inside the second modulation component 82 has not reached the target state, but if the possible stray light 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, ⑥ is executed in advance.

[0130] Figure 9 It is a schematic structural diagram of a spatial light modulator 80 provided by the embodiments of the present application. As Figure 9As shown, 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 both sides of the first liquid crystal layer 811. The second modulation component 82 includes a complementary metal oxide semiconductor (CMOS) silicon-based backplane 821 (hereinafter simply 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 both sides 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, and 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 in this article 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 in this article 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. Refer to Figure 9 As shown, along the incident direction of the optical 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 metasurface layer 827, the second pixel electrode array 824, and the CMOS silicon-based backplane 821 are sequentially stacked.

[0131] Figure 9In the shown spatial light modulator, the first common electrode 812 is used to generate a first voltage between the first common electrode 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 formed, and the first liquid crystal layer 811 can be deflected under the action of the first driving electric field. The deflection angle can be represented by a first orientation. Exemplarily, the first orientation can be the angle between the long axis orientation 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 the second common electrode and the second pixel electrode. When the second voltage is greater than zero, a second driving electric field is formed, and the second liquid crystal layer 822 can be deflected under the action of the second driving electric field. The deflection angle can be represented by a second orientation. Exemplarily, the second orientation can be the angle between the long axis orientation 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, and then the transmission direction of the light emitted by the first liquid crystal layer 811 changes accordingly. 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 then the transmission direction of the light emitted by 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 direction deflection effects of the optical signal are achieved.

[0132] In a possible implementation manner, 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 dot-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 transistor (TFT) electrode. The second pixel electrode array 824 includes a plurality of pixel electrodes distributed in a two-dimensional array.

[0133] In the above embodiment, each second pixel electrode is electrically connected to the CMOS silicon-based backplane 821, so that each second pixel electrode is controlled by the pixel circuit on the CMOS silicon-based backplane 821. It can be seen that the second modulation component 82 can be specifically implemented as a spatial light modulation component based on LCoS. Therefore, the spatial light modulator 80 has many advantages such as a flexible grid of LCoS, small volume, no mechanical vibration, and high reliability.

[0134] Continue to refer to Figure 9, As a possible implementation, the spatial light modulator 80 further includes a transparent first counter substrate 814 and a transparent second counter substrate 815. The first counter substrate 814 is disposed on a side of the first liquid crystal layer 811 away from the second liquid crystal layer 822, and the first common electrode 812 is disposed on a surface of the first counter substrate 814 close to the first liquid crystal layer 811. The second counter substrate 815 is disposed on a side of the second liquid crystal layer 822 away from the CMOS silicon-based backplane 821, and the second common electrode 823 is disposed on a surface of the second counter substrate 815 close to the second liquid crystal layer 822. By way of example, the first counter substrate 814 and the second counter substrate 815 form a first liquid crystal cell, and the first liquid crystal layer 811 is encapsulated in the first liquid crystal cell. The second counter substrate 815 and the CMOS silicon-based backplane 821 form a second liquid crystal cell, and the second liquid crystal layer 822 is encapsulated in the second liquid crystal cell. More specifically, the first counter substrate 814 and the second counter substrate 815 may specifically be glass plates.

[0135] Continue to refer to Figure 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 two sides of the first liquid crystal layer 811. The first alignment layer 816 is used to anchor the liquid crystal molecules in the first liquid crystal layer 811 close to it, so that the liquid crystal molecules close to it generate a pre-orientation. By way of example, the liquid crystal molecules in the first liquid crystal layer 811 close to the first alignment layer 816 may be the liquid crystal molecules in the first liquid crystal layer 811 closest to the first alignment layer 816. The second alignment layer 817 is used to anchor the liquid crystal molecules in the first liquid crystal layer 811 close to it, so that the liquid crystal molecules close to it generate a pre-orientation. By way of example, the liquid crystal molecules in the first liquid crystal layer 811 close to the second alignment layer 817 may be the liquid crystal molecules in the first liquid crystal layer 811 closest to the second alignment layer 817. Among them, under the action of the first alignment layer 816 and the second alignment layer 817, the pre-orientation generated by the liquid crystal molecules in the first liquid crystal layer 811 closest to the first alignment layer 816 is the same as the pre-orientation generated by the liquid crystal molecules in the first liquid crystal layer 811 closest to the second alignment layer 817. That is to say, the alignment directions corresponding to the first alignment layer 816 and the second alignment layer 817 are the same.

[0136] Continue to refer to Figure 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 respectively disposed on both sides of the second liquid crystal layer 822. The third alignment layer 825 is used to anchor the liquid crystal molecules in the second liquid crystal layer 822 adjacent thereto, so that the liquid crystal molecules adjacent thereto are pre-oriented. Exemplarily, 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 used to anchor the liquid crystal molecules in the second liquid crystal layer 822 adjacent thereto, so that the liquid crystal molecules adjacent thereto are pre-oriented. Exemplarily, 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. Wherein, under the action of the third alignment layer 825 and the fourth alignment layer 826, the pre-orientation generated by the liquid crystal molecules closest to the third alignment layer 825 in the second liquid crystal layer 822 is the same as the pre-orientation generated by the liquid crystal molecules closest to the fourth alignment layer 826 in the second liquid crystal layer 822. That is to say, the alignment directions corresponding to the third alignment layer 825 and the fourth alignment layer 826 are the same.

[0137] In the above embodiment, the first liquid crystal layer may be specifically implemented as a Liquid Crystal Polarization Grating Array (LCPGA), which can deflect the incident light by first-order diffraction. When the light wavelength is determined, the smaller the grating period, the larger the beam deflection angle. As a possible implementation, the thickness d of the first liquid crystal layer satisfies Δnd = λ / 2, so as to have the best diffraction efficiency. And, the thickness d of the liquid crystal layer restricted by the diffraction efficiency is much larger than the critical thickness dc of the liquid crystal layer that can be induced to be oriented.

[0138] In the embodiments of the present application, the arrangement of the liquid crystal molecules in the first liquid crystal layer may be as Figure 10 shown. The first liquid crystal layer is sandwiched between two opposing substrates, and the grating vector is parallel to the opposing substrates, that is, the XY plane. The liquid crystal molecules lie flat in the XY plane and are arranged in a periodic fan-column shape. Specifically, the azimuth angle of the liquid crystal molecules in the first liquid crystal layer changes continuously linearly in space. Assuming that the liquid crystal molecules are arranged periodically in the XY plane along a preset direction, the azimuth angle of the liquid crystal molecules changes continuously by 180° within one period. The director n(x) of the liquid crystal is a function of the coordinate variable x and satisfies

[0139] n(x) = [sin(πx / Λ), xos(πx / Λ), 0]

[0140] Among them, the range of x is 0 - Λ. Looking down at the XY plane, the first liquid crystal layer forms a strip grating, Λ is the grating period, and the x-axis direction is the direction of the grating period. When the light beam passes through the first liquid crystal layer, it has 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 deflect 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 polarization independence. That is, for incident light beams with any polarization state, the deflection of the transmission direction of the light beam can be achieved. 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 deflects 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 deflects 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 light beams with deflection directions in the grating direction are emitted; for elliptically polarized incident light beams, there are also two outgoing light beams with deflection directions in the grating direction.

[0142] In addition, when a voltage is applied to the first liquid crystal layer (the first voltage is greater than zero), according to the magnitude of the voltage value, the liquid crystal molecules in the first liquid crystal layer can present different states. Figure 11 It is a schematic diagram of the state of the liquid crystal molecules in the first liquid crystal layer when a certain voltage is applied to the first liquid crystal layer. As Figure 11 shown, when the first voltage (greater than zero, a driving electric field is formed) is applied to the first liquid crystal layer, ideally, except for the liquid crystal molecules near the alignment layer, the long axes of other liquid crystal molecules are oriented perpendicular to the XY plane, or rather, their long axis orientations relative to the XY plane are 90° or nearly 90°. At this time, the incident light can pass through the first liquid crystal layer without changing its direction. Of course, when the second voltage (greater than zero and less than the first voltage, a driving electric field is formed) is applied to the first liquid crystal layer, ideally, except for the liquid crystal molecules near the alignment layer, the long axis orientations of other liquid crystal molecules relative to the XY plane are less than 90°. At this time, the light intensity of the incident light is attenuated under the action of the first liquid crystal layer.

[0143] As mentioned above, the second modulation component 82 reflects the optical signal from the first modulation component 81, so that the optical signal is transmitted to the first modulation component 81 again, and finally output by the first modulation component 81. Based on this, in a possible implementation manner, as Figure 9As shown, the second modulation component 82 includes a reflective layer, which includes the above-mentioned 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 reflection function. In this implementation, the second pixel electrode array 824 is formed in the reflective layer, or is formed integrally with the metal material for light reflection. In another possible implementation, the second modulation component 82 further includes a reflective layer, which is disposed on the side of the second liquid crystal layer 822 away from the first liquid crystal layer 811, so as to reflect the optical 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 can be disposed, for example, on the surface of the reflective layer close to the CMOS silicon-based backplane 821.

[0144] Taking Figure 9 the shown spatial light modulator as an example, for the second modulation component 82, after receiving the optical signal from the first modulation component 81, the optical signal passes through the second counter substrate 815 and the second common electrode 823, and is transmitted to the second liquid crystal layer 822. Under the first phase modulation of the second liquid crystal layer 822, the transmission direction thereof may deflect; then, the optical signal reaches the reflective layer via the second liquid crystal layer 822; the reflective layer reflects the optical signal, so that the optical signal is emitted again via the second liquid crystal layer 822, and under the second phase modulation of the second liquid crystal layer 822, its transmission direction may deflect again and reach the first modulation component 81. It can be seen that the optical signal deflects, reflects, and deflects in sequence within the second modulation component 82.

[0145] Figure 9 In the shown spatial light modulator 80, the second common electrode 823 is disposed closer to the first liquid crystal layer 811 than 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 closer to the first liquid crystal layer 811 than the second common electrode 823, and the second common electrode 823 can be formed in the reflective layer. Or, the second pixel electrode array 824 can be disposed closer to the first liquid crystal layer 811 than the second common electrode 823, and the second common electrode 823 is independent of the reflective layer and is disposed between the reflective layer and the CMOS silicon-based backplane 821.

[0146] Continuing to refer to Figure 9, as a possible implementation, the second modulation component 82 further includes a metasurface layer 827, and the metasurface layer 827 is disposed between the reflective layer and the second liquid crystal layer 822; the metasurface layer 827 is configured to convert an optical signal with a polarization direction of a first direction into a second direction, and convert an 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 above-mentioned second modulation component 82, it is assumed that the liquid crystal molecules in the second liquid crystal layer 822 are rod-shaped liquid crystal molecules, and the major axis orientation thereof is parallel to the first direction. In one example, after the optical signal with a polarization direction of the first direction passes through the second common electrode 823, it will first enter the second liquid crystal layer 822. The liquid crystal molecules in the second liquid crystal layer 822 generate 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 first direction is parallel to the major axis orientation of the liquid crystal molecules in the second liquid crystal layer 822, the liquid crystal molecules after the orientation change can modulate the phase of the optical signal polarized in the first direction. Subsequently, the optical signal enters the metasurface layer 827, and the metasurface layer 827 converts the first direction of the polarization direction of the optical signal into the second direction. Then, after the optical signal is reflected by the reflective layer, it enters the second liquid crystal layer 822 again. Since the second direction is perpendicular to the orientation of the liquid crystal molecules in the second liquid crystal layer 822, the liquid crystal molecules after the orientation change will not perform phase modulation on the optical signal polarized in the second direction. In another example, after the optical signal with a polarization direction of the second direction passes through the second common electrode 823, it will first enter the second liquid crystal layer 822. The liquid crystal molecules in the second liquid crystal layer 822 generate 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 major axis orientation of the liquid crystal molecules in the second liquid crystal layer 822, the liquid crystal molecules after the orientation change will not perform phase modulation on the optical signal polarized in the second direction. Subsequently, the optical signal enters the metasurface layer 827, and the metasurface layer 827 converts the second direction of the polarization direction of the optical signal into the first direction. Then, after the optical signal is reflected by the reflective layer, it 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 perform phase modulation on the optical signal polarized in the second direction.

[0148] In summary, for optical signals polarized in the first direction or the second direction, during the entire process from incidence on the second modulation component 82 to final emergence, the same phase modulation can be obtained once. Since optical signals 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 of each polarization state also only obtains phase modulation once, the second modulation component has polarization-independent phase response characteristics. When such a spatial light modulator is applied to a wavelength selective switch, the structure of the wavelength selective switch will be simplified, and the device volume, optical path complexity, and polarization-dependent loss will be reduced.

[0149] Based on the spatial light modulator 80 given in the above embodiments, 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 direction deflection effects of the optical signal can be achieved. The following introduces several control modes of the spatial light modulator and the corresponding beam deflection effects.

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

[0151] In Figure 12 the example shown in B, the grating direction of the first liquid crystal layer is the X-axis direction (dispersion direction). As Figure 12As shown in Figure B, 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 optical signal is incident on the spatial light modulator along the Z-axis direction, the outgoing light deflects in the X-axis direction (or deflects in the XZ plane, or the deflected direction is parallel to the XZ plane). And, it is split into two beams under the action of the first modulation component 81. Specifically: First, the first modulation component 81 receives the optical signal, diffracts the optical signal, and emits two optical signals to the second modulation component 82. The transmission directions of the two optical signals deflect in the X direction relative to the Z-axis direction. Then, the second modulation component 82 receives the two optical signals, deflects, reflects, and deflects each optical signal in turn, and emits two optical signals to the first modulation component 81. The transmission direction of each optical signal may or may not deflect in the X-axis direction. After receiving the two optical signals, the first modulation component 81 transmits the two optical signals, and the transmission direction may or may not deflect in the X-axis direction.

[0152] In Figure 12 the example shown in Figure C, the grating direction of the first liquid crystal layer is the Y-axis direction (port direction). As Figure 12 shown in Figure C, in the third control mode, the voltage configured for the first modulation component 81 is V5, and the voltage configured for the second modulation component 82 is V6. When the optical signal is incident on the spatial light modulator along the Z-axis direction, the outgoing light deflects in the Y-axis direction (or deflects in the YZ plane, or the deflected direction is parallel to the YZ plane), and does not deflect in the X-axis direction. Specifically: First, the first modulation component 81 receives the optical signal and transmits the optical signal to the second modulation component 82, and the transmission direction is parallel to the Z-axis direction. Then, the second modulation component 82 receives the optical signal, deflects, reflects, and deflects the optical signal, and emits the optical signal to the first modulation component 81. The transmission direction of the optical signal deflects in the Y-axis direction relative to the Z-axis direction. After receiving the optical signal, the first modulation component 81 transmits the optical signal, and the transmission direction may or may not deflect in the Y-axis direction.

[0153] In Figure 12 the example shown in Figure D, the included angle between the grating direction of the first liquid crystal layer and the Y-axis direction (port direction) is greater than zero, and the included angle with the X-axis direction (dispersion direction) is greater than zero. As Figure 12As shown in Figure D, 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 direction, the outgoing light is deflected in the Y-axis direction (or deflected in the YZ plane, or the deflection direction has a component parallel to the YZ plane), and is also deflected in the X-axis direction (or deflected in the XZ plane, or the deflection direction has a component parallel to the XZ plane). In addition, it is split into two beams under the action of the first modulation component 81. Specifically: First, the first modulation component 81 receives the optical signal, diffracts the optical signal, 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. Then, the second modulation component 82 receives the two optical signals, deflects, reflects, and deflects each optical signal in sequence, and emits two optical signals to the first modulation component 81, where the transmission direction of each optical signal is deflected in the Y-axis direction. After the first modulation component 81 receives the two optical signals, it transmits the two optical signals, and the transmission direction may or may not be deflected in the X-axis direction.

[0154] The above four control modes and the corresponding beam deflection effects, as examples of the control mode and beam deflection effect of the spatial light modulator, do not constitute a limitation on the function of the spatial light modulator. It should be understood that different beam deflection effects can be achieved by configuring different voltages for the first modulation component and the second modulation component. Among them, any two of the voltages V1, V2, V3, V4, V5, V6, V7, and V8 may be the same or different, and their specific magnitudes can be designed according to the actual port switching requirements.

[0155] Continuing with the above embodiment, for the convenience of description, in this article, the time period when 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 called time period one, the time period when the spatial modulator is in the intermediate state (the state between the initial state and the final state) is called time period two, and the time period when 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 called time period three. Then, the control process of the spatial light modulator and the port switching process executed by the spatial light modulator can be described as follows (as Figure 13 shown):

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

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

[0158] Correspondingly, within the first time period, 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, the spatial light modulator outputs the optical signal to the first port.

[0159] S102. At the first moment, a port switching instruction is received. In response to the port switching instruction, the voltage between the first common electrode and the first pixel electrode array is adjusted to a third voltage, and the voltage between the second common electrode and the second pixel electrode is maintained at the second voltage.

[0160] S103. At the second moment, the voltage between the second common electrode and the second pixel electrode is adjusted to a fourth voltage, and the voltage between the first common electrode and the first pixel electrode is maintained at the third voltage.

[0161] Wherein, the first moment and the second moment are the moments within the second time period, and the first moment is earlier than the second moment. Correspondingly, within the second time period, 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, the spatial light modulator outputs the optical signal to a position outside the preset input / output port.

[0162] S104. At the third moment, a fifth voltage is generated between the first transparent common electrode and the first pixel electrode, and the voltage between the second common electrode and the second pixel electrode is maintained at the third voltage.

[0163] Wherein, the third moment is the moment within the third time period, and the third time period is later than the second time period. Correspondingly, within the third time period, 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, at the initial state (corresponding to the first time period), 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. At the intermediate state (corresponding to the second time period), 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 to a position 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 either. At the final state (corresponding to the third time period), 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. Thus, it can be seen that since the optical signal is deflected to a position outside the preset port at the intermediate state, transient crosstalk to other ports is avoided.

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

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

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

[0168] In a possible implementation, the spatial light modulator can be disposed on a flexible circuit board 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 through its data line to obtain a data signal.

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

[0170] In some embodiments, the voltages applied to the respective first pixel electrodes in the first pixel electrode array are the same. In this way, no fringe field effect will be generated between different first pixel electrodes, so that each group of liquid crystal molecules in the first liquid crystal layer can form an ideal phase surface. Furthermore, when deflecting a light beam, no crosstalk signal will be generated. Thus, it is ensured that during the intermediate state, when switching the optical signal from the first port to a port other than the preset port, no transient crosstalk will be caused to any port.

[0171] Continue to refer to Figure 9 , in some embodiments, the spatial light modulator provided in the embodiments of the present application may further include an anti-reflection layer 818; the anti-reflection layer 818 is disposed on a side of the first counter substrate 814 away from the first liquid crystal layer 811 for increasing the transmittance of the incident optical signal.

[0172] In some embodiments, the optical signal emitted from the first modulation component 81 to the second modulation component 82, and / or the optical signal emitted from the first modulation component 81 to the input / output port, experiences a preset degree of energy attenuation relative to the incident optical signal. That is to say, the first modulation component 81 can also be used to achieve 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 needed 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 not only achieve phase modulation but also attenuate the signal intensity. Compared with the related art, the spatial light modulator provided in the embodiments of the present application decouples signal attenuation control from phase modulation. For example, the first modulation component 81 is used to achieve signal attenuation, and the second modulation component 82 is used to achieve phase modulation. Thus, the attenuation processing of the optical signal can be achieved without complex algorithms, and at the same time, the phase modulation effect is not affected.

[0173] In specific applications, when a signal attenuation instruction is received, in response to the signal attenuation instruction, a first target voltage is generated between the first common electrode and the first pixel electrode, and a second target voltage is generated between the second common electrode and the second pixel electrode; wherein, the signal attenuation instruction includes an attenuation parameter, and the attenuation parameter characterizes a preset attenuation degree 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 an energy attenuation of a preset attenuation degree relative to the incident optical signal.

[0174] The embodiments of the present application further provide an optical communication device, and the optical communication device includes any one of the wavelength selection switches given in the above embodiments. The optical communication device may specifically be a wavelength-independent (colorless, C), directionless (D), contentionless (C) ROADM device or an OXC device.

[0175] The embodiments of the present application further provide an optical communication system, and the optical communication system includes any one or more of the above optical communication devices.

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

[0177] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims described above.

Claims

1. A spatial light modulator, characterized in that, It includes a first modulation component and a second modulation component arranged in sequence 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 angle of the liquid crystal molecules within one period continuously linearly changes 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 metasurface layer, a reflection 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, and are used to apply 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 metasurface layer is arranged on the side of the second liquid crystal layer away from the first liquid crystal layer, and is used to change the polarization direction of the optical signal passing through the metasurface layer; the reflection layer is located on the side of the metasurface layer away from the second liquid crystal layer, and is used to reflect the optical signal emitted by the metasurface layer; the CMOS silicon-based backplane is located on the side of the reflection layer away from the metasurface layer and is electrically connected to the pixel electrodes in the second pixel electrode array, and is used to configure 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 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 reflection layer.

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

5. The spatial light modulator according to any one of claims 1 - 4, characterized in that, It 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.

6. The spatial light modulator according to claim 5, characterized in that, It further 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 - 6, characterized in that, It further includes a first counter substrate and a second counter substrate; The first counter substrate is arranged on the side of the first liquid crystal layer away from the second liquid crystal layer; the first common electrode is arranged on the surface of the first counter substrate close to the first liquid crystal layer; The second counter substrate is arranged on the side of the second liquid crystal layer away from the CMOS silicon-based backplane; the second common electrode is arranged on the surface of the second counter substrate close to the second liquid crystal layer.

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

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

10. The spatial light modulator according to claim 8, characterized in that, It further includes an anti-reflection layer; the anti-reflection layer is disposed on a side of the first counter substrate away from the first liquid crystal layer; the anti-reflection layer is used to increase the transmittance when an optical signal is incident on 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 a first optical signal with an arbitrary 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 for 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 a first preset plane and a 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 in pairs.

13. The phase modulation method for 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 a first optical signal with an arbitrary polarization state, and emits a second optical signal to the second modulation component by diffracting or transmitting the first optical signal, including: A first voltage is generated between the first common electrode and the first pixel electrode array; The first liquid crystal layer receives the incident optical signal, and diffracts or transmits the first optical signal based on the first voltage to emit the second optical signal to the second modulation component.

14. The phase modulation method for an optical signal according to claim 13, characterized in that, 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 reflection layer, or the second modulation component further includes a reflection 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 the second optical signal from the first modulation component; if the polarization direction of the second optical signal is the first direction, phase modulation is performed on 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 reflection 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 from the reflection layer. If the polarization direction of the reflected optical signal is the first direction, phase modulation is performed on the reflected optical signal based on the second voltage, and the third optical 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 11-14, 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, Including an input / output optical fiber array, a grating dispersion element, a lens assembly, and a spatial light modulator according to any one of claims 1-10; The input / output optical fiber array includes a plurality of input / output ports; The grating dispersion element is located on the transmission path of the incident optical signal S input from the input / output port, and is configured to disperse the incident optical signal S into at least one optical signal Si, and different optical 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 configured to project the at least one optical signal Si to different wavelength channels of the spatial light modulator; The spatial light modulator is configured to receive the at least one optical signal Si, and based on the different wavelength channels, output the optical signals Si of different wavelengths to different input / output ports respectively.

17. A port switching method, characterized in that, A spatial light modulator applied to the wavelength selection switch according to claim 16; the method includes: Receiving the optical signal projected by the lens assembly; During a first time period, based on a first preset voltage between the first common electrode and the first pixel electrode, output the optical signal 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 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 within the first time period; the preset port includes one or more input / output ports in the input / output fiber array; During a second time period, based on a fourth preset voltage between the first common electrode and the first pixel electrode and the third preset voltage between the second common electrode and the second pixel electrode, output the optical signal 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 fiber array.

18. The port switching method according to claim 17, characterized in that, The method further includes: During 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, output the optical signal 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 fiber array, and the first port is different from the second port.

19. An optical signal attenuation method, characterized in that, Applied to the spatial light modulator in the wavelength selective switch as claimed in claim 16; the method includes: The first modulation component receives the optical signal projected by the lens component; The first modulation component, based on a first target voltage between the first common electrode and the first pixel electrode, emits the optical signal to the second modulation component; The second modulation component, based on a second target voltage between the second common electrode and the second pixel electrode, reflects the optical signal from the first modulation component to the first modulation component; The first modulation component, based on the first target voltage between the first common electrode and the first pixel electrode, emits the optical signal from the second modulation component to a target port; the target port is an input / output port in the input / output fiber array; Wherein, 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 control method of a spatial light modulator, characterized in that, The spatial light modulator is the spatial light modulator in the wavelength selective switch as claimed in claim 16; the method includes: Receiving a port switching instruction, the port switching instruction including a target port; In response to the port switching instruction, at a first moment, adjust the voltage between the first common electrode and the first pixel electrode 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 optical signal projected by the lens assembly to a position outside the preset port; At a second moment, control a third preset voltage to be generated between the second common electrode and the second pixel electrode; At a third moment, control a fourth preset voltage 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 cause the spatial light modulator to output the optical signal projected by the lens assembly to the target port.

21. A control method of a spatial light modulator, characterized in that, The spatial light modulator is the spatial light modulator in the wavelength selection switch according to claim 16; the method includes: Receive a signal attenuation instruction, the signal attenuation instruction includes an attenuation parameter, and the attenuation parameter characterizes a preset attenuation degree of the optical signal; In response to the signal attenuation instruction, control a first target voltage to be generated between the first common electrode and the first pixel electrode; and control a second target voltage to be generated between the second common electrode and the second pixel electrode; 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 undergo an energy attenuation of the preset attenuation degree relative to the incident optical signal.

22. An optical communication device, characterized in that It includes the spatial light modulator according to any one of claims 1-10, or includes the wavelength selection switch according to claim 16.

23. An optical communication system, characterized in that It includes the optical communication device according to claim 22.

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