CN119024603A

CN119024603A - Spatial Light Modulator

Info

Publication number: CN119024603A
Application number: CN202310611825.6A
Authority: CN
Inventors: 吕达; 梁栋; 张军平
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2023-05-25
Filing date: 2023-05-25
Publication date: 2024-11-26

Abstract

The present application relates to the field of optical processing, and to a spatial light modulator. The spatial light modulator comprises: a first substrate and a second substrate arranged opposite to each other, a first liquid crystal layer, a transparent common electrode and a second liquid crystal layer are sequentially arranged between the first substrate and the second substrate, and a plurality of metasurface units are embedded in the first liquid crystal layer. The first liquid crystal layer is configured to phase modulate the incident light with a preset discrete phase according to the metasurface unit. The second liquid crystal layer is configured to continuously phase modulate the incident light within a preset continuous phase range. The sum of the preset discrete phase and the preset continuous phase range includes at least [0,2π]. By setting a stacked structure of a liquid crystal metasurface, the first liquid crystal layer embedded in the metasurface unit ensures high transmittance when realizing discrete phase modulation, and the second liquid crystal layer of the pure liquid crystal layer realizes continuous phase modulation in a small range, which reduces the box thickness of the liquid crystal layer, thereby improving the light modulation efficiency of the spatial light modulator.

Description

Spatial light modulator

Technical Field

The embodiment of the application relates to the field of optical processing, in particular to a spatial light modulator.

Background

Spatial Light Modulators (SLMs) are a class of devices that can modulate optical signals, including changing the amplitude, phase, or polarization properties of light. Depending on the mode of operation, SLMs include reflective SLMs and transmissive SLMs.

A transmissive SLM typically comprises upper and lower transparent electrodes and a liquid crystal layer between the upper and lower transparent electrodes, the phase modulation of the light being achieved by a phase difference caused by the light being transmitted in the liquid crystal.

Currently, transmissive SLMs require the use of a larger cell thickness in order to achieve phase modulation in the 2 pi range. However, a larger cell thickness results in a longer response time of the liquid crystal, exacerbates the fringe field effect of the liquid crystal, and results in a decrease in the light modulation efficiency of the SLM.

Disclosure of Invention

The application provides a spatial light modulator, which improves the light modulation efficiency of the spatial light modulator.

In a first aspect, there is provided a spatial light modulator comprising: the transparent display device comprises a first substrate, a second substrate, a first liquid crystal layer, a transparent common electrode and a second liquid crystal layer, wherein the first substrate and the second substrate are oppositely arranged; the first liquid crystal layer is configured to enable incident light rays to perform phase modulation of preset discrete phases according to the super-surface unit; the second liquid crystal layer is configured to enable incident light rays to perform continuous phase modulation within a preset continuous phase range; wherein the sum of the predetermined discrete phase and the predetermined continuous phase range includes at least [0,2 pi ].

The spatial light modulator provided in the first aspect is configured as a stacked structure of a plurality of liquid crystal layers on a liquid crystal-super surface, wherein the first liquid crystal layer is a liquid crystal layer embedded in a super surface unit, and can realize discrete phase modulation of a preset discrete phase. The second liquid crystal layer is a pure liquid crystal layer, and can realize continuous phase modulation of a preset continuous phase range. The phase modulation depth of at least 2 pi range is divided into a form of discrete phase plus continuous phase, so that the pure liquid crystal layer reduces the range of continuous phase modulation, reduces the cell thickness of the liquid crystal layer, reduces the response time of liquid crystal and weakens the fringe field effect. The liquid crystal layer embedded in the super surface unit can also ensure high transmittance when discrete phase modulation is realized. By the laminated structure of the liquid crystal super surfaces of the first liquid crystal layer and the second liquid crystal layer, continuous phase modulation of at least 2 pi is realized, and the light modulation efficiency of the spatial light modulator is improved.

In one possible implementation, the plurality of super surface units are micro-nano structures periodically arranged in the first liquid crystal layer.

In a possible implementation manner, a plurality of super surface units are arranged in a matrix in the first liquid crystal layer, and the distance between two adjacent super surface units is the same.

In one possible implementation, the super surface unit is a hollow three-dimensional structure.

In one possible implementation, the super surface unit is a cylindrical solid structure.

In one possible implementation, the outer ring radius of the cylindrical three-dimensional structure is 165 nanometers, the inner ring radius is 65 nanometers, and the height is 135 nanometers; the distance between two adjacent cylindrical three-dimensional structures is 465 nanometers.

In one possible implementation, the subsurface unit is monocrystalline silicon, polycrystalline silicon, titanium dioxide, silicon nitride or gallium nitride, or gold or silver.

In a possible implementation, the spatial light modulator further comprises a first electrode; the first electrode is arranged on one side of the first substrate close to the first liquid crystal layer and corresponds to the position of the super-surface unit.

In one possible implementation, the first electrodes are stripe-shaped electrodes, and the stripe-shaped electrodes are arranged in rows or columns.

In a possible implementation, each strip electrode corresponds to at least one row of supersurface elements or at least one column of supersurface elements.

In a possible implementation manner, each strip electrode corresponds to M rows of super surface units or M columns of super surface units, and the super surface units corresponding to the N strip electrodes construct a phase surface according to a phase gradient of 2 pi/N; wherein M and N are positive integers. The deflection of the light beam with the working wavelength at a specific angle can be realized.

In one possible implementation, N has a value of 4, 6 or 8.

In a possible implementation, the spatial light modulator further includes a second electrode disposed on a side of the second substrate adjacent to the second liquid crystal layer.

In one possible implementation, the first electrode and the second electrode are transparent electrodes. A transmissive spatial light modulator may be implemented.

In one possible implementation, the first electrode or the second electrode is an opaque electrode. A reflective spatial light modulator may be implemented.

In a possible implementation, both sides of the first liquid crystal layer and both sides of the second liquid crystal layer are provided with liquid crystal molecular alignment layers, respectively.

In one possible implementation, the first substrate and the second substrate are transparent substrates. A transmissive spatial light modulator may be implemented.

In a possible implementation, the common electrode is quartz glass with transparent metal oxide or conductive polymer deposited on both sides.

In one possible implementation, the preset discrete phase is greater than or equal to two.

In one possible implementation, the preset discrete phases include 0 and pi.

In one possible implementation, the predetermined continuous phase range includes [0, pi ].

In a second aspect, there is provided an optical device comprising: a first spatial light modulator and a diaphragm; the first spatial light modulator is a spatial light modulator provided in the first aspect. The electronic control diaphragm is positioned on the central axis of the first spatial light modulator and positioned on the light emergent side of the first spatial light modulator.

In a third aspect, there is provided an optical device comprising: a first spatial light modulator and a second spatial light modulator; the first spatial light modulator and the second spatial light modulator are the spatial light modulators provided in the first aspect, and axes of the first spatial light modulator and the second spatial light modulator coincide.

In a possible implementation, the first spatial light modulator and the second spatial light modulator are arranged orthogonally in the direction of propagation of the light beam.

In a possible implementation, the first and second electrodes in the first and second spatial light modulators are transparent electrodes.

Drawings

FIG. 1 is a schematic diagram of a structure of a reflective SLM provided by the related art;

FIG. 2 is a schematic diagram of a structure of a transmissive SLM according to the related art;

FIG. 3 is a schematic diagram of the working principle of the liquid crystal under the action of an electric field according to the embodiment of the present application;

FIG. 4 is a schematic diagram of a spatial light modulator according to an embodiment of the present application;

FIG. 5 is a schematic diagram of the spatial light modulator of FIG. 4 when a voltage is applied;

FIG. 6 is a set of schematic diagrams of individual pixels of the spatial light modulator of FIG. 4;

FIG. 7 is a schematic diagram of another embodiment of a spatial light modulator according to the present application;

FIG. 8 is an enlarged schematic view of the transparent common electrode in FIGS. 4 to 7;

FIG. 9 is a top view of a subsurface unit arrangement provided by an embodiment of the present application;

FIG. 10 is a set of top views of cross-sections of a subsurface unit provided by embodiments of the present application;

FIG. 11 is a schematic illustration of the dimensions of a subsurface unit provided in an embodiment of the present application;

FIG. 12 is a schematic illustration of the super surface unit of the size shown in FIG. 11 operating in a Huygens condition;

FIG. 13 is a schematic diagram of a set of positions of a first electrode and a super surface unit according to an embodiment of the present application;

FIG. 14 is a schematic diagram of beam steering principle when the spatial light modulator according to the embodiment of the present application employs different phase gradients;

FIG. 15 is a schematic view of an optical device according to an embodiment of the present application;

FIG. 16 is a schematic view of another configuration of an optical device according to an embodiment of the present application;

Fig. 17 is a schematic diagram of another structure of an optical device according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings. The specific methods of operation, functional descriptions, etc. in the method embodiments may also be applied in the apparatus embodiments or the system embodiments.

First, concepts related to the embodiments of the present application will be described.

1. Spatial Light Modulator (SLM), reflective SLM, transmissive SLM

Spatial light modulators are key devices in the fields of real-time optical information processing, adaptive optics, optical computing, optical neural networks, displays, etc., for example, SLMs can be used as optical phased arrays or tunable beam deflection devices, and can be applied to all-solid-state scanning scenes of laser radars, imaging or projection, beam splitting, beam steering, laser beam shaping, laser pulse shaping, coherent wavefront modulation, phase modulation, optical tweezers, holographic projection, etc.

The spatial light modulator may implement light wave modulation based on control signals, loading information on a one-or two-dimensional light field. The optical wave modulation may include: modulating the amplitude, phase, polarization state of the light field, or converting incoherent light to coherent light, etc.

Depending on the manner in which the control signals are input, the spatial light modulator may include an optical addressing (OA-SLM) spatial light modulator and an electrical addressing (EA-SLM) spatial light modulator.

The application relates to an electrically-addressed spatial light modulator, wherein a control signal is an electric drive signal, and mainly relates to phase modulation of light waves.

The spatial light modulator may include a reflective SLM and a transmissive SLM according to an outgoing mode of outgoing light.

Illustratively, fig. 1 is a schematic structural diagram of a reflective SLM provided in the related art, and shows a schematic sectional structure of the reflective SLM. As shown in fig. 1, the reflective SLM may comprise, in a top-to-bottom direction as currently shown: a top substrate 11, a top electrode 12, an alignment layer (ALIGNMENT LAYER) 13, a liquid crystal layer (liquid crystal) 14, a reflective coating (REFLECTIVE COATING) 15, a bottom electrode 16, and a bottom substrate 17. The ellipses in the liquid crystal layer 14 represent liquid crystals, which are also referred to as liquid crystal molecules. The material of the top substrate 11 may include Glass (Glass), polycarbonate (polycarbonate, PC), or the like. The top electrode 12 may be a transparent electrode. The alignment layer 13 is used to align the liquid crystal molecules in a predetermined direction and angle, and may be formed by rubbing, for example, by coating a glass surface with an organic polymer film such as Polyimide (PI) and rubbing at a high speed. The bottom electrode 16 may include a complementary metal oxide semiconductor (complementary metal oxide semiconductor, CMOS) circuit.

Reflective SLMs are based on liquid crystal on silicon (liquid crystal on silicon, LCoS) technology, employing CMOS circuits of silicon as the substrate for the reflective liquid crystal. The CMOS chip is polished flat and then acts as a mirror, and incident light is transmitted through the top substrate 11, the top electrode 12 and the liquid crystal layer 14, and is reflected from the chip surface after dimming. The top electrode 12 and the bottom electrode 16 can apply voltage to the liquid crystal pixel unit, change the orientation of the liquid crystal, change the equivalent refractive index of the liquid crystal, realize the phase modulation of the incident light beam by utilizing the birefringence characteristic of the liquid crystal, and have higher reflectivity, for example, can be more than 70%. Since the reflective SLM is based on a reflective optical path, the designed reflective optical path may be complex, which is disadvantageous for system integration and miniaturization.

Illustratively, fig. 2 is a schematic structural diagram of a transmissive SLM provided in the related art, showing a schematic sectional structure of the transmissive SLM. As shown in fig. 2, the transmissive SLM may comprise, in a top-to-bottom direction as currently shown: a top transparent substrate 21, a top transparent electrode 22, an upper alignment layer 23, a liquid crystal layer 24, a lower alignment layer 25, a bottom transparent electrode 26, and a bottom transparent substrate 27. The materials of the top transparent substrate 21 and the bottom transparent substrate 27 may include glass, polycarbonate, and the like.

The transmissive SLM adopts a structure in which liquid crystal is embedded in upper and lower transparent electrodes, different voltages can be applied to the liquid crystal pixel unit through the top transparent electrode 22 and the bottom transparent electrode 26, the orientation of the liquid crystal is changed, the equivalent refractive index of the liquid crystal is changed, and the phase modulation of an incident light beam is realized by utilizing the birefringent characteristic of the liquid crystal. Compared with a reflective SLM, a transmissive SLM does not need to design a complex reflective light path, and is easy to integrate.

2. Working principle of liquid crystal and thickness of liquid crystal box

Fig. 3 is a schematic diagram illustrating an operation principle of a liquid crystal according to an embodiment of the present application under an electric field.

The voltage is applied to the two ends of the liquid crystal, so that the orientation angle of the liquid crystal can be changed, the effective refractive index of the liquid crystal is changed, and the phase modulation of the optical signal is realized.

Referring to fig. 2 and 3 (a), a three-dimensional coordinate system, which is identified as an x-axis, a y-axis, and a z-axis, is established from a horizontal two-dimensional plane and a normal line of the top transparent substrate 21 or the bottom transparent substrate 27, and directions of the z-axis indicate normal line directions. The oval shape in (a) in fig. 3 represents liquid crystal. The liquid crystal has a long axis and a short axis, the extraordinary refractive index of the long axis of the liquid crystal is denoted as n _e, the extraordinary refractive index of the short axis of the liquid crystal is denoted as n _o, and θ represents the orientation angle.

Fig. 3 (b) to (d) show different values of the alignment angle after the voltage is applied across the liquid crystal. As shown in (b) of fig. 3, the orientation angle θ is 0 °, the liquid crystals are vertically aligned, the incident light propagates along the z-axis, the electric field direction E is the positive z-axis direction, and the phase accumulation after the transmission of the incident light is relatively small. As shown in fig. 3 (c), the orientation angle θ is 45 °. As shown in (d) of fig. 3, the alignment angle θ is 90 °, the liquid crystals are laterally aligned, and the phase accumulation after transmission of the incident light is relatively large. The liquid crystal responds differently to light at different orientations and the phase modulation achieved is also different.

The effective refractive index n _eff (θ) of the liquid crystal is referred to as formula one. The effective refractive index is the effective refractive index along the z-axis direction.

As can be seen from equation one, the effective refractive index of the liquid crystal is related to the orientation angle θ, the refractive index n _e of the long axis of the liquid crystal, and the refractive index n _o of the short axis of the liquid crystal.

The phase modulation can be realized by using a phase difference caused when light is transmitted in the liquid crystal. Phase modulation rangeSee formula two.

Wherein n _eff represents the effective refractive index of the liquid crystal, see formula one. d represents the cell thickness, i.e. the thickness of the liquid crystal layer. Lambda represents the operating wavelength of the light.

As can be seen from the formula two, the phase modulation range is related to the thickness d of the liquid crystal cell, the operating wavelength λ of the light, and the variation range of the effective refractive index n _eff of the liquid crystal. The larger the thickness d of the liquid crystal cell, the larger the variation range of the effective refractive index n _eff of the liquid crystal, the smaller the working wavelength lambda of the light, and the larger the phase modulation range.

Let n _o＝1.5,n_e =1.75 be selected. By applying a voltage across the liquid crystal, the effective refractive index n _eff (θ) of the liquid crystal varies between 1.5 and 1.75 according to equation one, ranging from Δn=n _e-n_o =1.75 to 1.5=0.25. Assuming that the operating wavelength of the light is λ=850 nm and the cell thickness d=1.7 um, the liquid crystal layer can provide a continuous phase retardation in the range of 0-pi, in particular,

In summary, in order to achieve continuous phase modulation in the 2 pi range, a larger cell thickness d is required for the same liquid crystal parameters and light parameters.

3. Super surface, super surface unit, equiphase surface

The super surface is an artificial material based on a sub-wavelength structure, and can realize the regulation and control of the characteristics of electromagnetic wave polarization, amplitude, phase, polarization mode, propagation mode and the like. In the regulation of the phase by the super surface, the equiphase surface determines the propagation direction of the electromagnetic wave. The equiphase plane refers to a plane composed of points in space with the same phase. By controlling the phase of electromagnetic wave, the functions of beam deflection, superlens focusing, superholography, vortex light generation, coding, stealth, phantom and the like can be realized.

The material of the super surface unit can be dielectric material, such as monocrystalline silicon, polycrystalline silicon, titanium dioxide, silicon nitride or gallium nitride. The material of the super surface unit may also be a metal material, for example, gold or silver.

In the present application, a supersurface, also referred to as a supersurface unit, refers to a micro-nano structure having sub-wavelengths. Depending on the type of spatial light modulator, the relevant parameters of the light waves and the relevant parameters of the liquid crystal, the shape and size of the super surface unit can be designed such that the super surface unit operates in huygens condition (huygens' condition).

4. Huygens condition (huygens' condition)

The super surface can generate an electric dipole and a magnetic dipole with spatial transformation, and can excite the electric dipole resonance and the magnetic dipole resonance at the same time, and the existence of the resonance can generate reflection, transmission, diffraction and resonance absorption with different conditions for light waves with different frequencies.

When the electric dipole and the magnetic dipole generated by the super-surface unit have the same resonance intensity and are completely overlapped on the spectral line, reflection of light can be completely canceled and transmittance close to 100% can be obtained. At this time, after the light passes through the super surface unit, a phase jump occurs, and the light works in huygens condition.

For the spatial light modulator, the refractive index of the environment where the super surface unit is located can be changed by controlling the orientation of the liquid crystal through voltage under the Huygens condition, so that the wave band of resonance and the magnitude of phase mutation can be changed.

In the related art, for a transmissive spatial light modulator such as the structure shown in fig. 2, a transmissive SLM needs to use a large cell thickness in order to achieve a phase modulation depth in the range of 2pi. But a larger cell thickness creates two problems. One problem is that the response time of the liquid crystal becomes long. The response time of the liquid crystal under an electric field τ=t ²γ/kπ², where t represents the cell thickness, γ represents the viscosity of the liquid crystal, k represents the effective elastic constant of the liquid crystal, and the response time of the liquid crystal is proportional to the square of the cell thickness t, which limits the application of transmissive SLM in high-speed scenarios. Moreover, the spatial light modulator has a larger pixel size and lower modulation resolution. Another problem is that a larger cell thickness exacerbates the fringe field effect of the liquid crystal, i.e. the required return difference between liquid crystal pixel cells increases, reducing the refractive efficiency. The above problems result in the low light modulation efficiency of current commercial spatial light modulators.

The embodiment of the application provides a spatial light modulator which is designed into a laminated structure of a plurality of liquid crystal layers on a liquid crystal-super surface. The spatial light modulator includes a first liquid crystal layer and a second liquid crystal layer. The first liquid crystal layer is embedded with a plurality of super-surface units, so that discrete phase modulation of a preset discrete phase can be realized. The second liquid crystal layer is a pure liquid crystal layer, and can realize continuous phase modulation of a preset continuous phase range. The phase modulation depth of at least 2 pi range is divided into a form of discrete phase plus continuous phase, so that the continuous phase modulation range of the pure liquid crystal layer is reduced, and the cell thickness of the pure liquid crystal layer is reduced. The thickness of each layer of liquid crystal is reduced, so that the response time of the liquid crystal is reduced, and the fringe field effect of the liquid crystal is weakened. The liquid crystal layer embedded in the super surface unit can also ensure high transmittance when discrete phase modulation is achieved. By the laminated structure of the liquid crystal super surfaces of the first liquid crystal layer and the second liquid crystal layer, continuous phase modulation of at least 2 pi is realized, and the light modulation efficiency of the spatial light modulator is improved.

The technical scheme of the application is described in detail below through specific examples.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

In the embodiments of the present application, the words "first," "second," and the like are used to distinguish between the same item or similar items that have substantially the same function and function, and are merely used to clearly describe the technical solutions of the embodiments of the present application, and are not to be construed as indicating or implying relative importance or implying that the number of technical features indicated is indicated.

In the embodiments of the present application, the meaning of "plurality" is two or more, and the meaning of "at least two" is two or more, unless explicitly defined otherwise.

In the embodiments of the present application, the azimuth or positional relationship indicated by the terms "upper", "lower", etc. are based on the azimuth or positional relationship shown in the drawings, and are merely for convenience of description and simplification of description, and are not indicative or implying that the apparatus or element referred to must have a specific azimuth, be constructed and operated in a specific azimuth, and thus should not be construed as limiting the present application.

Fig. 4 is a schematic structural diagram of a spatial light modulator according to an embodiment of the present application, fig. 5 is a schematic diagram of the spatial light modulator of fig. 4 when a voltage is applied, fig. 6 is a group of schematic diagrams of individual pixels of the spatial light modulator of fig. 4, specifically, (a) in fig. 6 shows a structure of an individual pixel, and (b) in fig. 6 shows a schematic diagram of the spatial light modulator when a voltage is applied to an individual pixel, and fig. 7 is another schematic structural diagram of the spatial light modulator according to an embodiment of the present application. Fig. 4 to 6 show a transmissive spatial light modulator, and fig. 7 shows a reflective spatial light modulator.

As shown in fig. 4 to 7, the spatial light modulator provided in this embodiment may include:

The first substrate 41 and the second substrate 42 are arranged oppositely, a first liquid crystal layer 43, a transparent common electrode 44 and a second liquid crystal layer 45 are sequentially arranged between the first substrate 41 and the second substrate 42, and a plurality of super surface units 46 are embedded in the first liquid crystal layer 43.

The first liquid crystal layer 43 is configured to subject the incident light to a phase modulation of a preset discrete phase according to the super surface unit 46.

The second liquid crystal layer 45 is configured to subject the incident light to continuous phase modulation within a preset continuous phase range. Wherein the sum of the predetermined discrete phase and the predetermined continuous phase range includes at least [0,2 pi ].

The spatial light modulator provided in this embodiment structurally includes two liquid crystal layers, in which one liquid crystal layer is embedded with a super surface unit 46, and the other liquid crystal layer is of a pure liquid crystal structure, so as to form a multi-liquid crystal laminated layer structure of liquid crystal-super surface. For convenience of distinction, the liquid crystal layer embedded with the super surface unit 46 is referred to as a first liquid crystal layer 43, the substrate adjacent to the first liquid crystal layer 43 is referred to as a first substrate 41, the other liquid crystal layer is referred to as a second liquid crystal layer 45, and the substrate adjacent to the second liquid crystal layer 45 is referred to as a second substrate 42. A transparent common electrode 44 is disposed between the first liquid crystal layer 43 and the second liquid crystal layer 45, and the transparent common electrode 44 is a common electrode for the first liquid crystal layer 43 and the second liquid crystal layer 45 and allows light to be transmitted.

The liquid crystal included in the first liquid crystal layer 43 and the second liquid crystal layer 45 may be selected from liquid crystal molecules having a birefringence, such as E7 or E44 liquid crystal, and the like. The liquid crystal included in the first liquid crystal layer 43 and the second liquid crystal layer 45 may be the same liquid crystal or may be different liquid crystals.

Alternatively, the first substrate 41 and the second substrate 42 are transparent substrates, allowing light to be transmitted. For example, the first substrate 41 and the second substrate 42 may be made of high-transmittance quartz glass or polymer materials. At this time, the spatial light modulator may be a transmissive spatial light modulator.

Alternatively, fig. 8 is an enlarged schematic view of the transparent common electrode in fig. 4 to 7. As shown in fig. 8, the transparent common electrode 44 may include a transparent substrate 441 and electrode layers 442 on both sides of the transparent substrate 441. For example, the transparent substrate 441 is quartz glass, and the electrode layer 442 is formed by depositing transparent metal oxide, such as Indium Tin Oxide (ITO), on both sides of the quartz glass.

The spatial light modulator provided in this embodiment may be a transmissive spatial light modulator or a reflective spatial light modulator. The reflective spatial light modulator can be formed based on the transmissive spatial light modulator by modifying the structure and materials of part of the layers. The present embodiment is not limited to the light entrance side and the light exit side of the spatial light modulator. When the spatial light modulator is a transmissive spatial light modulator, the light incident side may be the first substrate 41 and the light emitting side may be the second substrate 42, or the light incident side may be the second substrate 42 and the light emitting side may be the first substrate 41. When the spatial light modulator is a reflective spatial light modulator, the light entrance side and the light exit side may be the first substrate 41, or the light entrance side and the light exit side may be the second substrate 42.

The operation principle of the spatial light modulator according to the present embodiment will be described below using the spatial light modulator as a transmissive spatial light modulator, taking the first substrate 41 as the light incident side and the second substrate 42 as the light emitting side as examples, based on the vertical and horizontal directions shown in fig. 4 to 6.

As shown in fig. 5, the spatial light modulator shows 4 pixels, identified as1 st pixel to 4 th pixel from left to right, with 1 st pixel shown in fig. 6. The size of the pixels is related to the distribution of the super surface units 46. The transparent common electrode 44 is grounded. The first substrate 41 is a light incident side, and incident light passes through the first liquid crystal layer 43 and then passes through the second liquid crystal layer 45. By applying voltages to the first liquid crystal layer 43 and the second liquid crystal layer 45, respectively, the alignment angle of the liquid crystals in the first liquid crystal layer 43 and the second liquid crystal layer 45 can be controlled, thereby phase modulating the light. For example, voltages applied to 1 st pixel to 4 th pixel of the first liquid crystal layer 43 are respectively marked asThe voltages applied to the 1 st pixel to the 4 th pixel of the second liquid crystal layer 45 are respectively marked as Alternatively, the voltage applied to the first liquid crystal layer 43 may be controlled individually, and the voltage applied to the second liquid crystal layer 45 may be controlled individually. Alternatively, voltages applied to different pixels in the first liquid crystal layer 43 and the second liquid crystal layer 45 may be controlled separately. For example, the number of the cells to be processed,The values of (2) may be the same or different. Similarly, the number of the devices to be used in the system, The values of (2) may be the same or different.

By applying a voltage to the first liquid crystal layer 43, the orientation angle of the liquid crystal in the first liquid crystal layer 43 can be adjusted. Furthermore, the first liquid crystal layer 43 has the super-surface unit 46 embedded therein, and the super-surface unit 46 can be designed to be suitable in shape and size according to the characteristics of the super-surface unit 46 and the parameters of the incident light, so that the super-surface unit 46 can work under huygens condition (huygens' condition), that is, the electric dipole and the magnetic dipole generated by the super-surface unit 46 have the same resonance intensity, and the electric dipole and the magnetic dipole overlap on the spectral line. At this time, after the light passes through the super surface unit 46, a sudden change of the preset discrete phase value is generated, so that the incident light realizes the discrete phase modulation of the preset discrete phase, and simultaneously, the incident light shows high transmittance.

The incident light enters the second liquid crystal layer 45 after undergoing discrete phase modulation of the first liquid crystal layer 43. The second liquid crystal layer 45 is a pure liquid crystal layer, and continuous phase modulation of light can be achieved by using a phase difference caused when light is transmitted in the liquid crystal. By applying a voltage to the second liquid crystal layer 45, an orientation angle of liquid crystal in the second liquid crystal layer 45 can be adjusted, and a cell thickness of the second liquid crystal layer 45 can be designed according to parameters such as a refractive index of liquid crystal in the second liquid crystal layer 45 and parameters of incident light, so that incident light can be subjected to continuous phase modulation within a preset continuous phase range.

For example.

For example, the first liquid crystal layer 43 may perform phase modulation of 2 discrete phases of 0 and pi/2, and the second liquid crystal layer 45 may perform continuous phase modulation of [0,3 pi/2 ], and then, through the first liquid crystal layer 43 and the second liquid crystal layer 45, continuous phase modulation of [0+0,0+3 pi/2 ] to [ pi/2+0, pi/2+3 pi/2 ] may be performed, i.e., continuous phase modulation of [0,2 pi ] may be realized.

For another example, the first liquid crystal layer 43 may perform phase modulation of 2 discrete phases of 0 and pi, and the second liquid crystal layer 45 may perform continuous phase modulation of [0, pi ], and then, through the first liquid crystal layer 43 and the second liquid crystal layer 45, continuous phase modulation of [0+0, 0+pi ] to [ pi+0, pi+pi ] may be performed, that is, continuous phase modulation of [0,2 pi ] may be realized.

For another example, the first liquid crystal layer 43 may perform phase modulation of 0 and pi 2 discrete phases, and the second liquid crystal layer 45 may perform continuous phase modulation of [0,3 pi/2 ], and then, through the first liquid crystal layer 43 and the second liquid crystal layer 45, continuous phase modulation of [0+0,0+3 pi/2 ] to [ pi+0, pi+3 pi/2 ] may be performed, i.e., continuous phase modulation of [0,5 pi/2 ] may be realized.

It can be seen that by providing a stacked structure of liquid crystal-super-surface multi-liquid crystal layers, the pure liquid crystal layer achieves continuous phase modulation, the liquid crystal layer embedded in the super-surface unit achieves discrete phase modulation, dividing the phase of at least 2 pi range into a form of discrete phase plus continuous phase. Thus, the pure liquid crystal layer reduces the range of continuous phase modulation, reduces the cell thickness of the pure liquid crystal layer, thus reducing the response time of the liquid crystal and weakening the fringe field effect. The cell thickness of the liquid crystal layer embedded in the super surface unit is further reduced, and high transmittance is ensured when discrete phase modulation is realized. The light modulation efficiency of the spatial light modulator is improved through the laminated structure of the super surface of the liquid crystal. Moreover, by embedding the super-surface unit in the first liquid crystal layer, the size of the pixel is related to the distribution of the super-surface unit, the pixel size is reduced, the resolution is improved, the phase modulation function is finer in space, and support is provided for realizing a larger deflection range when the spatial light modulator is used as an optical deflector.

Optionally, the preset discrete phases are greater than or equal to two.

Alternatively, the preset discrete phases are two. In this implementation, the number of preset discrete phases is small, and implementation is easy.

Alternatively, the preset discrete phases include 0 and pi.

Alternatively, when the preset discrete phase includes 0 and pi, the preset continuous phase range includes [0, pi ]. At this time, the spatial light modulator can realize continuous phase modulation in the [0,2 pi ] range. See, for example, the previous description of the principles of operation of the liquid crystal. Assuming that n _o＝1.5,n_e =1.75 of the liquid crystal in the second liquid crystal layer 45 and the operating wavelength λ=850 nm of the light, continuous phase modulation in the [0, pi ] range can be achieved when the cell thickness d of the second liquid crystal layer 45 is 1.7 um.

Optionally, as shown in fig. 4 to 7, the spatial light modulator further includes a first electrode 51. The first electrode 51 is disposed on a side of the first substrate 41 near the first liquid crystal layer 43 and corresponds to a position of the super surface unit 46.

For example, as shown in fig. 4 to 6, the first electrode 51 may be a transparent metal oxide such as ITO or tin antimony oxide (antimony tin oxide, ATO), or a conductive polymer, deposited on the first substrate 41. At this time, the first electrode is a transparent electrode.

Alternatively, as shown in fig. 4 to 7, the spatial light modulator further includes a second electrode 52, and the second electrode 52 is disposed on a side of the second substrate 42 adjacent to the second liquid crystal layer 45.

For example, as shown in fig. 4 to 7, the second electrode 52 may be a transparent metal oxide, such as ITO or ATO, or a conductive polymer, deposited on the second substrate 42. At this time, the second electrode is a transparent electrode.

Alternatively, the first electrode 51 may be a transparent electrode or an opaque electrode. The second electrode 52 may be a transparent electrode or an opaque electrode. The first electrode 51 and the second electrode 52 cannot be opaque electrodes at the same time.

When the first electrode 51 and the second electrode 52 are both transparent electrodes, the spatial light modulator is a transmissive spatial light modulator, as shown in fig. 4 to 6.

Reflective spatial light modulators can also be designed based on the phase distribution mechanism described above (discrete plus continuous). When one of the first electrode 51 and the second electrode 52 is a transparent electrode and the other electrode is an opaque electrode, the spatial light modulator is a reflective spatial light modulator. For example, as shown in fig. 7, the first electrode 51 is an opaque electrode, and the second electrode 52 is a transparent electrode. Alternatively, the substrate corresponding to the opaque electrode of the first electrode 51 and the second electrode 52 is an opaque substrate. For example, as shown in fig. 7, the first electrode 51 corresponds to the first substrate 41, the first substrate 41 is an opaque substrate, and the second substrate 42 is a transparent substrate.

The opaque electrode can adopt opaque metals such as gold, silver, copper, aluminum and the like as the electrode, so that one-dimensional linear array addressing is realized. Or the opaque electrode can adopt a silicon-based CMOS control circuit of static random-access memory (SRAM) or dynamic random memory (DYNAMIC RAM, DRAM) as an electrode driving circuit to realize two-dimensional pixel addressing.

It will be appreciated that in a reflective spatial light modulator, the incident light passes through twice the path length in the spatial light modulator, and the ray path can be seen in fig. 7. Thus, if the same phase modulation range is achieved, including at least 2 pi, as compared to a transmissive spatial light modulator, a reflective spatial light modulator can employ a smaller cell thickness than the first liquid crystal layer and the second liquid crystal layer in the transmissive spatial light modulator, thereby increasing the modulation speed. The reflective spatial light modulator may also employ the same cell thickness as the first and second liquid crystal layers in the transmissive spatial light modulator to achieve a greater phase modulation depth.

Alternatively, as shown in fig. 4 to 7, both sides of the first liquid crystal layer 43 and both sides of the second liquid crystal layer 45 are provided with liquid crystal molecule alignment layers 61, respectively.

The liquid crystal molecular alignment layer 61 is used to determine the alignment of liquid crystal molecules at the interface, and may be made of Polyimide (PI) material, rubbed to a desired alignment, or photo-alignment layer material, such as AtA-2 material.

The shape, size, material and distribution of the super surface units 46 are described below.

The plurality of super surface units 46 embedded in the first liquid crystal layer 43 are micro-nano structures periodically arranged in the first liquid crystal layer 43.

Micro-nano structures are micro-structures on the nanometer scale. The periodic arrangement means that the super surface units 46 of different regions in the first liquid crystal layer 43 may have the same arrangement, which includes, but is not limited to, at least one of the following: the number of the super surface units 46, the shape of the super surface units 46, the size of the super surface units 46, the arrangement pattern, or the distance between different super surface units 46.

The super surface unit 46 is embedded in the first liquid crystal layer 43, and the super surface unit has an anchoring effect on the orientation of the liquid crystal, so that the regulating and controlling capability of the liquid crystal in the first liquid crystal layer is enhanced by the super surface unit with a micro-nano structure, the liquid crystal is in a periodic arrangement like the super surface unit, and the pixel resolution is improved. Moreover, the cell thickness of the first liquid crystal layer embedded in the super surface unit is further reduced, so that the fringe field effect is weakened, and the modulation efficiency of pixels in the spatial light modulator is improved.

Optionally, the super surface units 46 are arranged in rows and/or columns in the first liquid crystal layer 43, the distances between different rows being the same and/or the distances between different columns being the same.

Alternatively, a plurality of the super surface units 46 are arranged in a matrix in the first liquid crystal layer 43, and the distances between two adjacent super surface units 46 are the same.

For example. Fig. 9 is a top view of a subsurface unit arrangement provided by an embodiment of the present application. As shown in fig. 9, the super surface units embedded in the first liquid crystal layer are arranged in a matrix. The two-dimensional plane of the first substrate 41 may be divided into square regions with uniform sizes, and the super surface units 46 embedded in the first liquid crystal layer correspond to the positions of the square regions one by one, and the centers of the super surface units 46 coincide with the centers of the square regions. Taking the upper left corner adjacent 4 subsurface units 46 as an example, they are identified as subsurface unit A1 through subsurface unit A4, respectively. The distance between the super surface unit A1 and the super surface unit A2 and the super surface unit A3 is the same, which may be referred to as the period of the super surface unit, and may be denoted as P, which is the single pixel size of the spatial light modulator.

Alternatively, the super surface unit 46 may be a non-hollow structure. The shape of the metasurface unit 46 may be a cube, a cuboid, a cylinder, a sphere, an ellipsoid, a cone, or a truncated cone.

Alternatively, the super surface unit 46 may be a hollow structure. The outer surface of the super surface unit 46 may be square, cuboid, cylinder, sphere, ellipsoid, cone or truncated cone, and the hollow portion of the super surface unit 46 may be square, cuboid, cylinder, sphere, ellipsoid, cone or truncated cone.

The shape of the super surface unit is exemplified below in connection with fig. 10. FIG. 10 is a set of top views of cross-sections of a super surface unit 46 provided by an embodiment of the present application.

As shown in fig. 10 (a), the outer surface of the super surface unit is square in shape and the hollow portion is cylindrical in shape. As shown in fig. 10 (b), the outer surface of the super surface unit is cylindrical in shape and the hollow portion is square in shape. As shown in (c) of fig. 10, the outer surface shape and the hollow portion shape of the super surface unit are both cubes. As shown in (d) of fig. 10, the outer surface shape and the hollow portion shape of the super surface unit are both cylindrical, and the super surface unit is specifically a cylindrical three-dimensional structure.

Alternatively, the material of the subsurface unit 46 may be a dielectric material, for example, including but not limited to at least one of the following: monocrystalline silicon, polycrystalline silicon, titanium dioxide, silicon nitride or gallium nitride.

Alternatively, the material of the super surface unit 46 may be a metallic material, for example, including but not limited to at least one of the following: gold or silver.

Alternatively, the dielectric material and the metal material may be selected to be high refractive index materials with small absorption loss in the operating band.

The dimensions of the super-surface cell operating in huyghen condition will be described below with reference to fig. 11, in which the super-surface cell is a cylindrical three-dimensional structure, made of monocrystalline silicon, and the operating wavelength λ of light waves is 850nm, and the thickness t of the liquid crystal cell of the first liquid crystal layer is 1000 nm.

Fig. 11 (a) is a cross-sectional view showing a partial structure of a single pixel of the spatial light modulator, including: a first substrate 41, a first electrode 51, a first liquid crystal layer 43, a super surface unit 46, and a transparent common electrode 44. The oval in the figure represents liquid crystal. The cell thickness t=1000 nm of the first liquid crystal layer. The height of the supersurface element 46 is denoted as H. Fig. 11 (b) shows the cross-sectional shape of the super surface unit 46, and the corresponding square area of the super surface unit 46 on the first substrate 41 is denoted as an area 411, and the period of the super surface unit 46 is denoted as P (see the related description of fig. 9). The outer radius of the super surface unit 46 is denoted as R and the diameter is 2R, and the hollow inner ring radius is denoted as R and the diameter is 2R. Let the height h=135 nm of the supersurface unit, the period p=465 nm of the supersurface unit, the inner ring radius r=65 nm of the supersurface unit, and the outer ring radius r=165 nm of the supersurface unit. At this size, the single pixel size of the spatial light modulator is p=465 nm.

FIG. 12 is a schematic diagram of the super surface unit of the size shown in FIG. 11 operating in a Huygens condition. Fig. 12 (a) shows a change in transmittance versus an alignment angle θ of the liquid crystal in the first liquid crystal layer, the horizontal axis represents the alignment angle θ of the liquid crystal in rad (radian), and the vertical axis represents the transmittance. Fig. 12 (b) shows a change relation between the phase and the alignment angle θ of the liquid crystal in the first liquid crystal layer, and the horizontal axis represents the alignment angle θ of the liquid crystal in rad (radian) and the vertical axis represents the phase modulation change. Fig. 12 (c) shows that the alignment angle θ of the liquid crystal in the first liquid crystal layer is 0 °, and the phase change at this time is specified to be 0. Fig. 12 (d) shows that the alignment angle θ of the liquid crystal in the first liquid crystal layer is 90 °, and it can be determined from fig. 12 (b) that the phase change at this time is pi.

The alignment angle θ=90° of the liquid crystal in the first liquid crystal layer in the initial state can be made by the treatment of the liquid crystal molecular alignment layers on both sides of the first liquid crystal layer. By applying a voltage to the liquid crystal in the first liquid crystal layer, the voltage direction coincides with the light transmission direction, and the orientation angle of the liquid crystal can be changed. According to (a) in fig. 12 and (b) in fig. 12, the electromagnetic field simulation results show that the above-mentioned shape and size parameters of the super-surface unit can be operated in huygens condition, the resonances of electric dipoles and magnetic dipoles generated by the super-surface unit overlap each other, and the super-surface unit resonates with incident light polarized in the x direction of 850nm wavelength, exhibiting high transmittance.

It should be noted that the shapes and dimensions of the super surface units shown in fig. 10 and fig. 11 are only examples, when the working wavelengths of the light rays are different, the thicknesses of the liquid crystal cells of the first liquid crystal layer are different, and when the spatial light modulator adopts transmission type working or reflection type working, the shapes and dimensions of the super surface units are different, the design needs to be calculated according to the actual situation, the overall structure of the device can be scaled, and n, k values of the super surface units under the working wave bands of the different light rays need to be considered, n represents the refractive index, and k represents the extinction coefficient.

Alternatively, the first electrodes 51 are stripe-shaped electrodes, and the stripe-shaped electrodes are arranged in rows or columns.

In this implementation, since the plurality of super surface units 46 are periodically arranged in the first liquid crystal layer 43, when the plurality of super surface units 46 are arranged in a matrix, the first electrodes 51 may be arranged in rows or columns, so that voltages are applied in rows or columns to realize one-dimensional linear array addressing, finely control the orientation angle of the liquid crystals in the first liquid crystal layer, and realize phase modulation.

Optionally, each strip electrode corresponds to at least one row of supersurface elements 46 or at least one column of supersurface elements 46.

For example. Fig. 13 is a set of schematic diagrams showing positions of the first electrode corresponding to the super surface unit according to an embodiment of the present application, which shows a top view of a part of the structure of the spatial light modulator, including the first substrate 41, the first electrode 51, and the super surface unit 46. The two-dimensional planar coordinate system of the first substrate 41 includes an x-axis and a y-axis. The x-axis direction is assumed to be the row and the y-axis direction is assumed to be the column.

As shown in fig. 13 (a), the first electrodes 51 are arranged in columns in the y-axis direction, and the first electrodes 51 are stripe-shaped electrodes, each stripe-shaped electrode corresponding to a column of the super surface units 46.

As shown in (b) of fig. 13, the first electrodes are arranged in rows in the x-axis direction, the first electrodes are stripe-shaped electrodes, and each stripe-shaped electrode corresponds to a row of super surface units.

As shown in (c) of fig. 13, the first electrodes are arranged in columns in the y-axis direction, and the first electrodes are stripe electrodes, each stripe electrode corresponding to two columns of super surface units.

As shown in (d) of fig. 13, the first electrodes are arranged in rows in the x-axis direction, and the first electrodes are stripe electrodes, each stripe electrode corresponding to two rows of super surface units.

It can be understood that the fewer rows or columns of the super surface unit corresponding to each strip electrode, the finer the alignment angle of the liquid crystal in the first liquid crystal layer can be controlled, and the phase adjustment effect is improved.

It should be noted that the second electrode 52 is similar to the first electrode 51 in shape and arrangement, and will not be described here again.

Alternatively, the first electrode 51 is a strip electrode, each strip electrode corresponds to M rows of the super surface units 46 or M columns of the super surface units 46, and the super surface units 46 corresponding to the N strip electrodes construct a phase plane according to a phase gradient of 2n/N. Wherein M and N are positive integers.

In this implementation, the phase difference provided by each pixel cell can be controlled individually by programming the voltage applied to each pixel in the spatial light modulator, which can be used as an optical phased array or beam deflection device to effect dynamic deflection of the beam. According to the actual use scene and the processing condition limit, N pixels can be selected as one period, each pixel corresponds to M rows or M columns of super-surface units, and the same voltage control is applied.

As illustrated in connection with fig. 14. Assume that N has a value of 4, 6 or 8.

Theoretical deflection directionWhere lambda represents the wavelength of the incident light,Representing the phase gradient values.

As shown in (a) of fig. 14, n=4, and a phase plane is constructed from a phase gradient of 2pi/4=pi/2, with 4 pixels for each period. By simulating the transmission deflection direction of the normally incident light, the deflection direction of the first-order diffraction light is approximately 27 degrees, and the deflection angle is obviously improved.

Similarly, as shown in (b) of fig. 14, n=6, and a phase plane is constructed from a phase gradient of 2pi/6=pi/3, with each period corresponding to 6 pixels. By simulating the transmission deflection direction of normally incident light, the deflection direction of first order diffracted light was approximately 17.7 °.

As shown in (c) of fig. 14, n=8, and a phase plane is constructed from a phase gradient of 2pi/8=pi/4, with 8 pixels for each period. By simulating the transmission deflection direction of normally incident light, the deflection direction of first order diffracted light was approximately 13.2 °.

The application further provides an optical device based on the embodiment shown in fig. 4-14.

Fig. 15 is a schematic structural diagram of an optical device according to an embodiment of the present application. As shown in fig. 15, the optical device includes: a first spatial light modulator and a diaphragm. The diaphragm is located on the central axis of the first spatial light modulator and located on the light emergent side of the first spatial light modulator.

The structure, material, size and principle of the first spatial light modulator can be referred to the spatial light modulator provided in the above embodiment of the present application, and will not be described herein.

Alternatively, the first spatial light modulator may be a transmissive spatial light modulator or a reflective spatial light modulator.

In particular, when the spatial light modulator is used as an optical phased array or a beam deflection device to realize large-angle beam steering, the problem that 0-order diffracted light is stronger exists. The 0 th order diffraction light refers to a light beam directly transmitted when the light passes through the device, and the 1 st order diffraction light refers to a diffraction light beam generated after the light is modulated by the device. In general, when the deflection angle is greater than 20 °, the intensity of 0 th order diffracted light may be greater than that of 1 st order diffracted light.

To solve this problem, in the present embodiment, the light-emitting side of the first spatial light modulator is provided with a diaphragm. The aperture means a device that plays a limiting role on the light beam in the optical system. The diaphragm is located on the central axis of the first spatial light modulator and has a certain distance from the first spatial light modulator, and the value of the distance is not limited in this embodiment, and is set according to practical situations.

When the deflection angle is more than 20 degrees, the diaphragm is closed to block 0-order diffraction light. When the deflection angle is smaller than 20 degrees, the diaphragm is opened, and the first-order diffraction light is emitted.

Alternatively, the diaphragm may be an electronically controlled diaphragm.

The application further provides an optical device based on the embodiment shown in fig. 4 to 14, which is used for solving the problem that 0-order diffracted light is strong.

Fig. 16 is a schematic view of another structure of an optical device according to an embodiment of the present application. As shown in fig. 16, the optical device includes: a first spatial light modulator and a second spatial light modulator. The second spatial light modulator is positioned on the light-emitting side of the first spatial light modulator.

The structure, material, size and principle of the first spatial light modulator and the second spatial light modulator can be referred to the spatial light modulator provided in the above embodiment of the present application, and will not be described herein.

The 0 th order diffracted light and the 1 st order diffracted light refer to the related descriptions in the embodiment shown in fig. 15, and are not described herein.

In this embodiment, the incident light passes through the first spatial light modulator before passing through the second spatial light modulator. The second spatial light modulator has a certain distance from the first spatial light modulator, and the value of the distance is not limited in this embodiment, and is set according to practical situations. The 0-order diffraction light emitted by the first spatial light modulator enters the second spatial light modulator, and the second spatial light modulator modulates the 0-order diffraction light emitted by the first spatial light modulator again, so that the energy of the 0-order diffraction light is reduced, and the 1-order diffraction efficiency is improved.

Optionally, the axes of the first spatial light modulator and the second spatial light modulator are coincident, so that the modulation effect of the 0-order diffracted light can be improved.

Alternatively, the number of second spatial light modulators may be at least one. When the number of the second spatial light modulators is plural, the second spatial light modulators are sequentially arranged on the light emitting side of the first spatial light modulator, and the 0 th order diffracted light is sequentially subjected to multi-level modulation.

Alternatively, the first spatial light modulator may be a transmissive spatial light modulator or a reflective spatial light modulator. To simplify the optical path, the first spatial light modulator employs a transmissive spatial light modulator. The second spatial light modulator is a transmissive spatial light modulator.

Fig. 17 is a schematic diagram of another structure of an optical device according to an embodiment of the present application. As shown in fig. 17, the optical device includes: the first spatial light modulator and the second spatial light modulator are in coincidence in axis, and are arranged orthogonally in the beam propagation direction.

The spatial light modulator may implement one-dimensional linear array electrodes, for example, the first electrode 51 and the second electrode 52 are stripe-shaped electrodes, and may be arranged in rows or columns, see fig. 13. In order to achieve the two-dimensional beam deflection capability, in this embodiment, two spatial light modulators, referred to as a first spatial light modulator and a second spatial light modulator, may be used, which are orthogonally arranged in the beam propagation direction, and as shown in fig. 17, the first spatial light modulator may achieve scanning in the x-axis direction, and the second spatial light modulator may achieve scanning in the y-axis direction, thereby achieving the scanning capability in both directions, and the transmitted light may cover the taper range.

In this embodiment, the first spatial light modulator and the second spatial light modulator are transmissive spatial light modulators.

The foregoing is merely illustrative of specific embodiments of the present application, and the scope of the embodiments of the present application is not limited thereto, and any person skilled in the art will readily appreciate variations or substitutions within the scope of the embodiments of the present application.

Claims

1. A spatial light modulator, comprising:

A first substrate and a second substrate are arranged opposite to each other, a first liquid crystal layer, a transparent common electrode and a second liquid crystal layer are arranged in sequence between the first substrate and the second substrate, and a plurality of super surface units are embedded in the first liquid crystal layer;

The first liquid crystal layer is configured according to the metasurface unit to cause incident light to undergo phase modulation with a preset discrete phase;

The second liquid crystal layer is configured to cause the incident light to undergo continuous phase modulation within a preset continuous phase range; wherein the sum of the preset discrete phase and the preset continuous phase range at least includes [0, 2π].

2. The spatial light modulator according to claim 1 is characterized in that the multiple super-surface units are micro-nano structures periodically arranged in the first liquid crystal layer.

3. The spatial light modulator according to claim 2 is characterized in that the multiple super-surface units are arranged in a matrix in the first liquid crystal layer, and the distance between two adjacent super-surface units is the same.

4. The spatial light modulator according to claim 2 or 3, further comprising a first electrode;

The first electrode is disposed on a side of the first substrate close to the first liquid crystal layer and corresponds to a position of the super surface unit.

5 . The spatial light modulator according to claim 4 , wherein the first electrodes are strip electrodes, and the strip electrodes are arranged in rows or columns.

6 . The spatial light modulator according to claim 5 , wherein each of the strip electrodes corresponds to at least one row of the metasurface units or at least one column of the metasurface units.

7 . The spatial light modulator according to claim 4 , further comprising a second electrode, wherein the second electrode is arranged on a side of the second substrate close to the second liquid crystal layer.

8 . The spatial light modulator according to claim 7 , wherein the first electrode and the second electrode are transparent electrodes.

9 . The spatial light modulator according to claim 7 , wherein the first electrode or the second electrode is an opaque electrode.

10 . The spatial light modulator according to claim 1 , wherein liquid crystal molecule alignment layers are respectively disposed on both sides of the first liquid crystal layer and on both sides of the second liquid crystal layer.

11 . The spatial light modulator according to claim 8 , wherein the first substrate and the second substrate are transparent substrates.

12. The spatial light modulator according to any one of claims 1 to 11, characterized in that the preset discrete phases are greater than or equal to two.

13 . The spatial light modulator according to claim 12 , wherein the preset discrete phases include 0 and π.

14 . The spatial light modulator according to claim 13 , wherein the preset continuous phase range includes [0, π].