LCoS device and phase modulation method of LCoS device

Abstract

The invention discloses an LCoS device and a phase modulation method of the LCoS device. The LCoS device comprises a transparent electrode, a liquid crystal layer, a metasurface layer and a back plate which are sequentially arranged from the incident end to the reflecting end. A projection included angle is formed between the long axis of the metasurface layer and the liquid crystal molecule director of the liquid crystal layer on a propagation plane; the liquid crystal layer is used for performing phase modulation on a parallel first polarization component of incident light, and the conversion metasurface is used for performing polarization state exchange on the parallel first polarization component and an orthogonal second polarization component of the incident light; the back plate is used for reflecting incident light; and the liquid crystal layer is used for performing phase modulation on the exchanged second polarization component, so that the emergent first polarization component and the emergent second polarization component are subjected to phase modulation. The metasurface layer is introduced, a polarization-dependent modulator is converted into a polarization-independent modulator through two times of liquid crystal layer passing and one time of polarization conversion, and the fundamental limitation of a traditional LCoS device is solved.

Description

Technical Field

[0001] This invention relates to the field of metasurface technology, and in particular to an LCoS device and a phase modulation method for the LCoS device. Background Technology

[0002] Liquid crystal on silicon (LCoS) devices, as important spatial light modulators, have been widely used in micro-displays, optical communications, holographic imaging, and lidar due to their high resolution, small pixel size, and excellent phase modulation capabilities. However, an inherent limitation of traditional LCoS devices lies in their polarization dependence. Due to the anisotropy of liquid crystal molecules, their director can only be deflected within a specific plane under the influence of an electric field. This means that LCoS can only effectively modulate the phase of the component of the incident light whose polarization direction is parallel to this deflection plane, while the polarization component orthogonal to it is almost unmodulated. For applications requiring incident light with arbitrary polarization states, this polarization sensitivity becomes a significant obstacle.

[0003] To address the aforementioned issues, existing technologies primarily propose two solutions. The first solution integrates two liquid crystal layers within the LCoS chip, with their pointer deflection surfaces orthogonal to each other, thereby modulating two orthogonal polarization components. However, this solution requires complex multilayer liquid crystal alignment and encapsulation processes, and places extremely high demands on the flatness and thickness uniformity of the two liquid crystal layers. Any deviation will lead to inconsistencies in the phase modulation characteristics of the two polarization channels. Furthermore, increasing the total thickness of the liquid crystal layers will increase the device's driving voltage. The second solution integrates a quarter-wave plate between the liquid crystal layer and the backplane, achieving polarization-independent modulation through polarization conversion. However, this solution is limited by the typically narrow operating bandwidth of the quarter-wave plate material itself, making it difficult to cover broadband application requirements. Simultaneously, the traditional quarter-wave plate has a large thickness (usually on the micrometer scale), which exacerbates the edge field effect of the liquid crystal layer and leads to a significant increase in the driving voltage, thereby reducing the device's modulation accuracy and optical efficiency.

[0004] Therefore, there is an urgent need in the field for a technical solution that can overcome the above-mentioned defects in order to realize a polarization-independent LCoS device with simple structure, high operating bandwidth and high modulation efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide an LCoS device and a phase modulation method for the LCoS device, aiming to solve the problem of how to realize a polarization-independent LCoS device with simple structure, high operating bandwidth and high modulation efficiency.

[0006] To solve the above-mentioned technical problems, the objective of this invention is achieved through the following technical solution: providing an LCoS device, comprising a transparent electrode, a liquid crystal layer, a metasurface layer, and a backplate arranged sequentially from the incident end to the reflecting end; the major axis of the metasurface layer and the director of the liquid crystal molecules of the liquid crystal layer have a projection angle on the propagation plane; The liquid crystal layer is configured to perform phase modulation on the first polarization component of the incident light based on the voltage generated by the backplate, wherein the first polarization component is parallel to the projection direction of the liquid crystal molecule director on the propagation surface. The conversion metasurface is configured to perform polarization state swapping on the first polarization component and the second polarization component of the incident light, wherein the second polarization component before polarization state swapping is orthogonal to the projection direction of the liquid crystal molecule's director on the propagation surface. The backplate is configured to reflect incident light; The liquid crystal layer is configured to perform phase modulation on the second polarization component after polarization state swapping, so that both the first polarization component and the second polarization component after emission are phase modulated.

[0007] Furthermore, the metasurface layer comprises multiple identical microstructure units arranged in an array, and the material of the microstructure units is a transparent material corresponding to the application wavelength of the LCoS device.

[0008] Furthermore, the material of the microstructure unit includes at least one of silicon nitride, titanium dioxide, amorphous silicon, polycrystalline silicon, gallium nitride, and chalcogenide compounds.

[0009] Furthermore, the operating band of the metasurface layer is a combined broadband of C-band and L-band; the material of the microstructure unit is amorphous silicon, and the capping layer on the amorphous silicon is silicon dioxide.

[0010] Furthermore, the major axis of the metasurface layer is the major axis of the amorphous silicon; the included angle of the projection is 45°.

[0011] Furthermore, the metasurface layer is configured to form a phase difference of π / 2 when incident light with TE orthogonal polarization and TM orthogonal polarization of the same phase passes through it.

[0012] Furthermore, the backplate is provided with a metal pixel electrode and a control circuit; the control circuit is connected to the transparent electrode and the metal pixel electrode and is used to generate voltage; The voltage is used to deflect the director of the liquid crystal molecules in a single pixel region and change the equivalent refractive index of the liquid crystal layer in the light propagation direction of the pixel region, so that the liquid crystal layer can perform phase modulation on the first polarization component of the incident light.

[0013] This invention also provides a phase modulation method for an LCoS device, applied to the LCoS device described above, comprising: When incident light passes through the transparent electrode and reaches the liquid crystal layer, the liquid crystal layer modulates the phase of the first polarization component of the incident light based on the voltage generated by the back plate. When the incident light reaches the conversion metasurface and is reflected by the back plate, the conversion metasurface swaps the polarization states of the first polarization component and the second polarization component of the incident light. When the first polarization component and the second polarization component after polarization state swapping are emitted and pass through the liquid crystal layer again, the liquid crystal layer performs phase modulation on the second polarization component after polarization state swapping so that both the emitted first polarization component and the second polarization component are phase modulated.

[0014] Furthermore, the incident light includes any one of the following polarization states: linearly polarized light, circularly polarized light, and elliptically polarized light.

[0015] Furthermore, the angle between the major axis of the metasurface layer and the projection of the liquid crystal molecule director of the liquid crystal layer onto the propagation surface is set to 45°; When incident light with TE orthogonal polarization and TM orthogonal polarization of the same phase passes through the metasurface layer, a phase difference of π / 2 is formed.

[0016] The beneficial effects of this invention are as follows: A metasurface layer is introduced on the basis of a traditional LCoS device, and a specific angle is designed between the long axis of the metasurface layer and the projection direction of the liquid crystal molecule director in the liquid crystal layer onto the light propagation plane. During operation, the liquid crystal layer is used to perform voltage-based phase modulation on the first polarization component of the incident light that is parallel to the projection direction of the liquid crystal molecule director. Simultaneously, the second polarization component, orthogonal to the projection direction, is not modulated. The function of the metasurface layer is that when the incident light passes through the metasurface layer and is reflected by the backplate, the polarization states of the first and second polarization components are interchanged. Then, when the light with the interchanged polarization states passes through the liquid crystal layer again, the previously unmodulated second polarization component (whose polarization state has now become modulated) is phase-modulated by the liquid crystal layer, while the previously modulated first polarization component (whose polarization state has now become unmodulated) remains unchanged. Finally, in the beam emitted from the device, both the first and second polarization components undergo a complete voltage-controlled phase modulation process, thereby achieving polarization-independent phase modulation of incident light with arbitrary polarization states. Based on this, by introducing a metasurface layer and utilizing two passes through the liquid crystal layer and one polarization conversion, the polarization-dependent modulator is transformed into a polarization-independent modulator. This not only achieves an ultra-high operating bandwidth not available in quarter-wave plates, but also, with a thickness of only a few hundred nanometers, avoids increasing the driving voltage and exacerbates edge field effects. This solves the fundamental limitations of traditional LCoS devices. Attached Figure Description

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

[0018] Figure 1 A schematic diagram of the structure of a conventional polarization-dependent LCoS device in the prior art; Figure 2 This is a schematic diagram of the structure of the LCoS device provided in an embodiment of the present invention; Figure 3 A three-dimensional perspective schematic diagram of the microstructure unit provided in an embodiment of the present invention; Figure 4 This is a planar perspective schematic diagram of the microstructure unit provided in an embodiment of the present invention; Figure 5 A schematic diagram of the reflectivity of two incident lights with polarization directions of x and y after passing through the metasurface layer and being reflected by the backplate, as provided in an embodiment of the present invention. Figure 6 A schematic diagram of the phase response of two incident lights with polarization directions x and y, respectively, after passing through the metasurface layer and being reflected by the backplate, as provided in an embodiment of the present invention. Figure 7 This is a schematic flowchart of the phase modulation method for an LCoS device provided in an embodiment of the present invention.

[0019] Explanation of the markings in the image: 1. Transparent electrode; 2. Liquid crystal layer; 3. Backplate; 4. Metasurface layer. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0022] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0023] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0024] Please see Figure 1 , Figure 1 A schematic diagram of the structure of a conventional polarization-dependent LCoS device provided by existing technology.

[0025] like Figure 1 As shown, a conventional polarization-dependent LCoS device in the prior art includes a transparent electrode 1, a liquid crystal layer 2, and a backplate 3 arranged sequentially from the incident end to the reflecting end; The backplate 3 contains metal pixel electrodes and a control circuit. The control circuit generates a voltage between the transparent electrode 1 and the metal pixel electrode at both ends of the pixel, causing the liquid crystal molecules in the liquid crystal layer 2 within a single pixel region to deflect with the voltage. At this time, the equivalent refractive index of the light propagation direction within the liquid crystal layer 2 of a single pixel region changes, thereby achieving phase modulation. The amount of phase modulation changes with the amount of deflection of the liquid crystal molecule pointer (i.e., the magnitude of the voltage across the pixel). Since the liquid crystal molecule pointer deflects only within the same plane under voltage, the phase modulation amount in different pixel regions will only differ according to the voltage magnitude when the polarization state of the incident light (i.e., the parallel first polarization component described below) is within this plane. When the polarization state of the incident light (i.e., the orthogonal second polarization component described below) is perpendicular to this plane, the effective refractive index of the liquid crystal layer 2 in different pixel regions remains consistent and does not change with the voltage, thus phase modulation cannot be achieved.

[0026] Please see Figure 2 , Figure 2 This is a schematic diagram of the structure of the LCoS device provided in an embodiment of the present invention. To facilitate the display of the state of the incident light after passing through the liquid crystal layer 2, the liquid crystal layer 2 and the metasurface layer 4 are separated.

[0027] like Figure 2 As shown, this embodiment of the invention provides an LCoS device, including a transparent electrode 1, a liquid crystal layer 2, a metasurface layer 4, and a backplate 3 arranged sequentially from the incident end to the reflecting end; the major axis of the metasurface layer 4 and the liquid crystal molecule director of the liquid crystal layer 2 have a projection angle on the propagation plane; The liquid crystal layer 2 is configured to perform phase modulation on the first polarization component of the incident light based on the voltage generated by the back plate 3, wherein the first polarization component is parallel to the projection direction of the liquid crystal molecule director on the propagation surface. The transformation metasurface is configured to perform polarization state interchange on the first and second polarization components of the incident light, wherein the second polarization component before polarization state interchange is orthogonal to the projection direction of the liquid crystal molecule director on the propagation surface; The backplate 3 is configured to reflect incident light; The liquid crystal layer 2 is configured to perform phase modulation on the second polarization component after polarization state swapping, so that both the first polarization component and the second polarization component after emission are phase modulated.

[0028] In this embodiment, a metasurface layer 4 is introduced based on a traditional LCoS device, and a specific angle is designed between the long axis of the metasurface layer 4 and the projection direction of the liquid crystal molecule director in the liquid crystal layer 2 onto the light propagation plane. During operation, the liquid crystal layer 2 is used to perform voltage-based phase modulation on the first polarization component of the incident light that is parallel to the projection direction of the liquid crystal molecule director. Simultaneously, the second polarization component, orthogonal to the projection direction, remains unmodulated. The function of the metasurface layer 4 is to enable the exchange of polarization states between the first and second polarization components after the incident light passes through it and is reflected by the backplate 3. Then, when the light with the exchanged polarization states passes through the liquid crystal layer 2 again, the previously unmodulated second polarization component (whose polarization state has now become modulated) is phase-modulated by the liquid crystal layer 2, while the previously modulated first polarization component (whose polarization state has now become unmodulated) remains unchanged. Ultimately, in the beam emitted from the device, both the first and second polarization components undergo a complete voltage-controlled phase modulation process, thereby achieving polarization-independent phase modulation of incident light with arbitrary polarization states.

[0029] Based on this, this embodiment introduces a metasurface layer 4, utilizing two passes through the liquid crystal layer 2 and one polarization conversion to transform the polarization-dependent modulator into a polarization-independent modulator. This not only achieves an ultra-high operating bandwidth not available in quarter-wave plates, but also, with a thickness of only a few hundred nanometers, avoids increasing the driving voltage and exacerbating edge field effects. This solves the fundamental limitations of traditional LCoS devices. Furthermore, the metasurface layer 4 is fabricated using semiconductor processes, such as deposition and etching on the backplate 3, eliminating the need for precise alignment and encapsulation of the multilayer liquid crystal, thus offering superior fabrication capabilities.

[0030] In one embodiment, the metasurface layer 4 includes a plurality of identical microstructure units arranged in an array, the microstructure units being made of a transparent material corresponding to the wavelength band used in the LCoS device.

[0031] This embodiment details the microstructure of the metasurface layer 4. The metasurface layer 4 is composed of a large number of identical microstructural units arranged in a periodic or aperiodic array; these microstructural units constitute the physical basis for the metasurface's polarization conversion function. Furthermore, the material constituting these microstructural units is a transparent material with high transmittance for the target wavelength range of the LCoS device, ensuring minimal light loss when passing through the metasurface and maintaining the high optical efficiency of the entire device.

[0032] In one embodiment, the material of the microstructure unit includes at least one selected from silicon nitride, titanium dioxide, amorphous silicon, polycrystalline silicon, gallium nitride, and chalcogenides.

[0033] This embodiment defines the specific material selection for the constituent microstructure units. These materials are selected according to the different application wavelengths. For example, silicon nitride or titanium dioxide can be used for the visible light band; amorphous silicon or polycrystalline silicon can be used for the near-infrared band; and gallium nitride or chalcogenide compounds can be used for the mid-infrared band. These materials all have excellent properties such as low optical loss and high refractive index in their respective target wavelengths, making them suitable for constructing efficient metasurface layers 4.

[0034] This embodiment provides a broad and specific range of material choices, enabling the invention to be flexibly adapted to various application scenarios from visible light to infrared, thereby enhancing the practicality and universality of the invention.

[0035] In a specific application, the working band of the metasurface layer 4 is a combined broadband of C-band and L-band; the material of the microstructure unit is amorphous silicon, and the capping layer on the amorphous silicon is silicon dioxide.

[0036] In this specific application, the operating wavelength of the device is defined as a broadband combination of the C-band and L-band, widely used in optical communication. To meet this specific broadband application requirement, amorphous silicon is preferred as the material for the microstructure unit; amorphous silicon has a suitable refractive index and low absorption loss in the near-infrared band. Simultaneously, silicon dioxide is placed on top of the amorphous silicon structure as a capping layer, which protects the amorphous silicon and optimizes its optical performance.

[0037] This specific application provides a clear, optimized, and feasible solution for applications in the field of optical communication by defining the operating band and a specific material combination (amorphous silicon and silicon dioxide), demonstrating the advantages of this invention in broadband operation.

[0038] like Figure 3 and Figure 4 In a specific application, the major axis of the metasurface layer 4 is the major axis of amorphous silicon; the projection angle is 45°.

[0039] In this specific application, the orientation and key angle parameters of the metasurface layer 4 were defined. Specifically, the major axis of the metasurface layer 4 is defined as the major axis direction A of the microstructural units (such as amorphous silicon nanopillars) that constitute it. The angle between this major axis direction A and the projection direction B of the liquid crystal molecule director on the propagation surface is set to 45° (i.e., the amorphous silicon nanopillars are placed along the periodic diagonal). This 45° angle is the optimal condition to ensure that the metasurface can act as a reflective half-wave plate and achieve complete interchange of the two orthogonal polarization components.

[0040] More specifically, after the incident light passes through the liquid crystal layer 2, it first passes through the metasurface layer 4, and is then reflected by the metal pixel electrodes in the backplate 3. The reflected light then passes through the metasurface layer 4 again. At this point, the metasurface layer 4 and the backplate 3 together constitute a reflective half-wave plate. If the angle between the major axis of the metasurface layer 4 and the two polarization components of the incident light is 45°, then the incident light... In comparison, reflected light The first polarization component whose original polarization is parallel to the projection of the liquid crystal director is in the middle. Ex It will be converted into components. Ey The original second polarization component Ey It will then be converted into components. Ex Since the metasurface layer 4 and the backplate 3 do not undergo phase modulation, the polarization-converted components at this time... Ey (i.e., original component) Ex Phase leading.

[0041] In one embodiment, the metasurface layer 4 is configured such that when the phases are the same... TE Orthogonal polarization and TM Orthogonally polarized incident light passes through it and forms π A phase difference of 2 / 2.

[0042] In this embodiment, specific requirements are proposed for metasurface layer 4 from the perspective of optical performance. This metasurface needs to be able to handle two orthogonal polarization states (typically defined as...). TE Model and TM The modulus produces a specific phase response. Specifically, when the phases are the same... TE polarized light and TM After polarized light is incident and reflected by the metasurface, a current needs to be generated between the two. π A phase difference of 2 / 2. This property makes the metasurface equivalent to a waveplate with distinct fast and slow axes in reflection mode, which is the physical principle behind its ability to perform polarization conversion.

[0043] This embodiment defines the key phase difference parameter ( π / 2), ensuring that the metasurface layer 4 can achieve the required polarization conversion function in the design, and providing clear quantitative indicators for simulation design and performance verification.

[0044] More specifically, such as Figure 5 and 6 , Figure 5 A schematic diagram of the reflectivity of two incident lights with polarization directions of x and y after passing through the metasurface layer 4 and being reflected by the back plate 3, as provided in an embodiment of the present invention. Figure 6 The polarization directions provided for the embodiments of the present invention are respectively x and y The diagram illustrates the phase response of two incident beams after passing through metasurface layer 4 and being reflected by backplate 3. It is evident that rotation of the major axis of metasurface layer 4 within its period does not affect the two fundamental properties of reflectivity and phase response. Under both orthogonal polarizations, the reflectivity is close to 1, demonstrating the low loss of metasurface layer 4. The phase difference between the two reflected beams is... π / 2, meaning that metasurface layer 4 has fast and slow axes, and the phase difference between the fast and slow axes is . π / 2.

[0045] In one embodiment, the backplate 3 is provided with a metal pixel electrode and a control circuit; the control circuit is connected to the transparent electrode 1 and the metal pixel electrode and is used to generate voltage; The voltage is used to deflect the director of the liquid crystal molecules in a single pixel region and change the equivalent refractive index of the liquid crystal layer 2 in the direction of light propagation in that pixel region, so that the liquid crystal layer 2 can perform phase modulation on the first polarization component of the incident light.

[0046] This embodiment provides a detailed explanation of the driving and modulation principles of the LCoS device. The backplane 3 integrates metal pixel electrodes and a control circuit. The control circuit generates a controllable voltage between the transparent electrode 1 and the metal pixel electrodes of each pixel. This voltage is applied to the liquid crystal layer 2, causing the director of the liquid crystal molecules within a single pixel region to deflect. This deflection of the liquid crystal molecules directly alters the equivalent refractive index experienced by light propagating in that region of the liquid crystal layer 2, thereby achieving phase modulation of a specific polarization component (i.e., the first polarization component before deflection and the second polarization component after deflection). The magnitude of the phase modulation is continuously adjustable with the magnitude of the voltage, i.e., the change in the amount of liquid crystal molecule deflection.

[0047] Please see Figure 7 , Figure 7 This is a schematic flowchart of the phase modulation method for an LCoS device provided in an embodiment of the present invention.

[0048] like Figure 7 As shown, the phase modulation method for an LCoS device includes steps S10-S30: S10. When the incident light passes through the transparent electrode 1 and reaches the liquid crystal layer 2, the liquid crystal layer 2 performs phase modulation on the first polarization component of the incident light based on the voltage generated by the back plate 3. S20. When the incident light reaches the conversion metasurface and is reflected by the back plate 3, the conversion metasurface swaps the polarization states of the first polarization component and the second polarization component of the incident light. S30. When the first polarization component and the second polarization component after polarization state swapping are emitted and pass through the liquid crystal layer 2 again, the liquid crystal layer 2 performs phase modulation on the second polarization component after polarization state swapping so that both the emitted first polarization component and the second polarization component are phase modulated.

[0049] In this embodiment, steps S10-S30 provide the complete modulation path of light in the LCoS device. Specifically, the incident light first passes through the transparent electrode 1 and enters the liquid crystal layer 2. Here, the first polarization component, which is parallel to the projection direction of the liquid crystal molecule director on the propagation surface, is subjected to spatially varying phase modulation according to the voltage distribution, while the second polarization component, which is orthogonal to the projection direction of the liquid crystal molecule director on the propagation surface, remains unchanged. Subsequently, the light reaches the metasurface layer 4 and is reflected by the back plate 3. During this process, the metasurface layer 4 and the back plate 3 work together to interchange the polarization states of the first and second polarization components. The interchanged light passes through the liquid crystal layer 2 again. At this time, the previously unmodulated second polarization component (now a moduloable polarization state) is phase modulated, while the previously modulated first polarization component (now an unmodulated polarization state) no longer changes. Finally, the outgoing light carries phase information determined by the voltage pattern, and this phase modulation effect is independent of the polarization state of the incident light.

[0050] This implementation introduces the core steps for achieving polarization-independent phase modulation from a methodological perspective, clearly explaining how to achieve polarization-independent effect by modulating two polarization components sequentially through the path of "modulation-conversion-remodulation".

[0051] In one embodiment, the incident light includes any one of linearly polarized light, circularly polarized light, and elliptically polarized light.

[0052] This embodiment clarifies the range of its ability to process the polarization state of incident light. This phase modulation method has no special requirements regarding the polarization state of the incident light; whether it is linearly polarized, circularly polarized, or elliptically polarized light, this method can effectively perform polarization-independent phase modulation. This is because light of any polarization state can be decomposed into the aforementioned first polarization component and second polarization component, and both components are ultimately modulated through the phase modulation method flow of this invention.

[0053] In one embodiment, the angle between the major axis of the metasurface layer 4 and the projection of the liquid crystal molecule director of the liquid crystal layer 2 onto the propagation surface is set to 45°; wherein, the phase is the same TE Orthogonal polarization and TM Orthogonally polarized incident light forms when passing through metasurface layer 4π A phase difference of 2 / 2.

[0054] In this embodiment, during the method execution process, the 45° angle between the major axis of the metasurface layer 4 and the projection of the liquid crystal molecule director, and the resulting... TE / TM Orthogonally polarized light π A phase difference of 2 / 2 is the technical guarantee for achieving efficient polarization conversion and ultimately achieving polarization-independent modulation. These parameters together ensure the integrity and accuracy of the polarization conversion process.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An LCoS device, characterized in that, It includes a transparent electrode, a liquid crystal layer, a metasurface layer, and a backplate arranged sequentially from the incident end to the reflecting end; the major axis of the metasurface layer and the director of the liquid crystal molecules of the liquid crystal layer have a projection angle on the propagation plane; The liquid crystal layer is configured to perform phase modulation on the first polarization component of the incident light based on the voltage generated by the backplate, wherein the first polarization component is parallel to the projection direction of the liquid crystal molecule director on the propagation surface. The conversion metasurface is configured to perform polarization state swapping on the first polarization component and the second polarization component of the incident light, wherein the second polarization component before polarization state swapping is orthogonal to the projection direction of the liquid crystal molecule's director on the propagation surface. The backplate is configured to reflect incident light; The liquid crystal layer is configured to perform phase modulation on the second polarization component after polarization state swapping, so that both the first polarization component and the second polarization component after emission are phase modulated.

2. The LCoS device according to claim 1, characterized in that, The metasurface layer comprises multiple identical microstructure units arranged in an array, and the material of the microstructure units is a transparent material corresponding to the application wavelength of the LCoS device.

3. The LCoS device according to claim 2, characterized in that, The materials of the microstructure units include at least one of silicon nitride, titanium dioxide, amorphous silicon, polycrystalline silicon, gallium nitride, and chalcogenide compounds.

4. The LCoS device according to claim 2, characterized in that, The operating band of the metasurface layer is a combined broadband of C-band and L-band; the material of the microstructure unit is amorphous silicon, and the capping layer on the amorphous silicon is silicon dioxide.

5. The LCoS device according to claim 4, characterized in that, The major axis of the metasurface layer is the major axis of the amorphous silicon; the included angle of the projection is 45°.

6. The LCoS device according to claim 1, characterized in that, The metasurface layer is configured to form a phase difference of π / 2 when incident light with TE orthogonal polarization and TM orthogonal polarization of the same phase passes through it.

7. The LCoS device according to claim 1, characterized in that, The backplate is provided with a metal pixel electrode and a control circuit; the control circuit is connected to the transparent electrode and the metal pixel electrode and is used to generate voltage. The voltage is used to deflect the director of the liquid crystal molecules in a single pixel region and change the equivalent refractive index of the liquid crystal layer in the light propagation direction of the pixel region, so that the liquid crystal layer can perform phase modulation on the first polarization component of the incident light.

8. A phase modulation method for an LCoS device, applied to the LCoS device as described in any one of claims 1 to 7, characterized in that, include: When incident light passes through the transparent electrode and reaches the liquid crystal layer, the liquid crystal layer modulates the phase of the first polarization component of the incident light based on the voltage generated by the back plate. When the incident light reaches the conversion metasurface and is reflected by the back plate, the conversion metasurface swaps the polarization states of the first polarization component and the second polarization component of the incident light. When the first polarization component and the second polarization component after polarization state swapping are emitted and pass through the liquid crystal layer again, the liquid crystal layer performs phase modulation on the second polarization component after polarization state swapping so that both the emitted first polarization component and the second polarization component are phase modulated.

9. The phase modulation method for the LCoS device according to claim 8, characterized in that, The incident light includes any one of the following polarization states: linearly polarized light, circularly polarized light, and elliptically polarized light.

10. The phase modulation method for the LCoS device according to claim 8, characterized in that, Also includes: The angle between the major axis of the metasurface layer and the projection of the liquid crystal molecule director of the liquid crystal layer onto the propagation surface is set to 45°. When incident light with TE orthogonal polarization and TM orthogonal polarization of the same phase passes through the metasurface layer, a phase difference of π / 2 is formed.

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