Spatial light modulator, control method, and light-modulation apparatus

Abstract

The embodiments of the present application relate to the technical field of light regulation and control. Provided are a spatial light modulator, a control method, and a light-modulation apparatus, which are used for ameliorating the problem in the related art of a liquid crystal on silicon being unable to preserve data in the case of sudden power failure. The spatial light modulator comprises a liquid crystal layer, a light source layer and a first light-filtering layer, wherein the material of the liquid crystal layer comprises a photosensitive liquid crystal, and the photosensitive liquid crystal can modulate incident light under the irradiation of modulated light; the light source layer is disposed on one side of the liquid crystal layer and comprises a plurality of light-emitting pixels arranged in an array; and the first light-filtering layer is disposed between the liquid crystal layer and the light source layer, and the light-filtering layer is used for transmitting the modulated light and reflecting the incident light. The spatial light modulator can be applied to a light-modulation apparatus.

Description

A spatial light modulator, a control method and a light modulation device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on December 15, 2023, with application number 202311745634.5 and application name “A spatial light modulator, control method and light modulation device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of light control technology, and in particular to a spatial light modulator, a control method, and a light modulation device. Background Art

[0003] A spatial light modulator (SLM) is a programmable device that controls the spatial distribution of light, including its phase, amplitude, polarization, and coherence. It is widely used in optical communication scheduling and switching, optical metrology, optical imaging, and laser processing. Liquid Crystal on Silicon (LCoS) is a common spatial light modulator that includes a CMOS (Complementary Metal Oxide Semiconductor) substrate, a transparent cover, and a liquid crystal layer. The CMOS substrate and the transparent cover are positioned relative to each other, and the liquid crystal layer is positioned between the CMOS substrate and the transparent cover. During operation, an electric field is applied to the liquid crystal layer to change the properties of the liquid crystal molecules, thereby modulating the light incident on the liquid crystal layer.

[0004] However, in silicon-based liquid crystal, the modulation state of the liquid crystal layer in response to incident light corresponds to the applied electric field. When the applied electric field disappears or changes, the modulation state will also change. Therefore, in the face of a sudden power outage, the modulation state will change, and the data cannot be maintained to maintain the modulation state. This is a volatile spatial light modulator.

[0005] Summary of the Invention

[0006] The embodiments of the present application provide a spatial light modulator, a control method, and a light modulation device, which are used to improve the problem in the related art that silicon-based liquid crystal cannot retain data when facing a sudden power outage.

[0007] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0008] In a first aspect, an embodiment of the present application provides a spatial light modulator, which includes a liquid crystal layer, a light source layer and a first filter layer, wherein the material of the liquid crystal layer includes photosensitive liquid crystal, and the photosensitive liquid crystal can modulate the incident light under the irradiation of modulated light; the light source layer is arranged on one side of the liquid crystal layer, and includes a plurality of light-emitting pixels; the first filter layer is arranged between the liquid crystal layer and the light source layer, and the filter layer is used to transmit the modulated light and reflect the incident light.

[0009] In the spatial light modulator provided in the embodiments of the present application, the liquid crystal layer utilizes photosensitive liquid crystals. Under the influence of modulated light, the photosensitive liquid crystals can modulate incident light. Furthermore, after the liquid crystal layer completes modulation, its modulation state remains unchanged until it is irradiated with new modulated light, thereby suspending power to the light source layer. Therefore, compared to silicon-based liquid crystals used in related technologies, the spatial light modulator in the embodiments of the present application can reduce the power supply time to the light source layer, that is, the control power consumption time used to control the liquid crystal layer, thereby reducing power consumption. Furthermore, the liquid crystal layer can maintain its pre-power-off modulation state in the event of an unexpected power outage, demonstrating its non-volatile nature.

[0010] On the other hand, in the spatial light modulator provided in the embodiments of the present application, the size of the modulated pixel is affected by the luminescent pixel. However, since the luminescent pixel only needs to emit modulated light of a fixed wavelength and only needs to control the luminescence time and luminescence intensity, the light-emitting device and pixel driving circuit are relatively simple, resulting in a smaller size of the luminescent pixel. This, in turn, also allows for a smaller size of the modulated pixel, which facilitates the miniaturization of the modulated pixel design. Such a design can, on the one hand, meet the requirements for extremely small pixels (less than 5 microns) in some scenarios; on the other hand, more modulated pixels can be arranged in the same area, achieving an increase in pixel density, which is beneficial for improving the performance of the spatial light modulator.

[0011] In addition, in the spatial light modulator provided in the embodiment of the present application, the modulation frequency is affected by the light source layer, and the upper limit of the light emission frequency of the light source layer is very high, which is conducive to improving the modulation frequency of the spatial light modulator; for example, when Micro LED is used as the light-emitting pixel, the response frequency of Micro LED is in the GHz level, so the upper limit of the modulation frequency of the spatial light modulator reaches the GHz level, and the response time is in the ns level, which has obvious advantages.

[0012] In some embodiments, liquid crystal molecules in the photosensitive liquid crystal are arranged in a spiral structure; the modulated light emitted by the luminous pixel includes a first modulated light and a second modulated light; the pitch of the spiral structure in the photosensitive liquid crystal increases under the irradiation of the first modulated light; the pitch of the spiral structure in the photosensitive liquid crystal decreases under the irradiation of the second modulated light.

[0013] In the spatial light modulator provided in the embodiment of the present application, a photosensitive chiral liquid crystal in which liquid crystal molecules are arranged into a spiral structure and the pitch of the spiral structure is adjustable under the action of modulated light can be selected as the photosensitive liquid crystal, such as a photoresponsive cholesteric liquid crystal, which can modulate the incident light by controlling the pitch of the spiral structure through modulated light.

[0014] In some embodiments, the light-emitting pixel includes a first sub-pixel and a second sub-pixel arranged adjacent to each other in a direction parallel to the liquid crystal layer, the first sub-pixel is used to emit a first modulated light, and the second sub-pixel is used to emit a second modulated light.

[0015] The first sub-pixel and the second sub-pixel both include a light-emitting device and a pixel driving circuit; the light-emitting device is at least one of a semiconductor laser, an organic light-emitting diode, a quantum dot light-emitting diode, a sub-millimeter light-emitting diode, and a micro light-emitting diode; the pixel driving circuit is electrically connected to the light-emitting device and is used to drive the light-emitting device to emit light.

[0016] In the spatial light modulator provided in the embodiments of the present application, a luminescent pixel emits a first modulated light and a second modulated light through two independent sub-pixels. This design facilitates the arrangement and formation of the luminescent pixels, as well as their light emission control. Furthermore, the luminescent pixels can be configured in a variety of different pixel structures, providing excellent adaptability to various application scenarios and manufacturing processes.

[0017] In some embodiments, a light-emitting pixel includes a light-emitting device and a pixel driving circuit. The light-emitting device emits a first modulated light and a second modulated light when driven by different driving signals. The pixel driving circuit is electrically connected to the light-emitting device and is used to drive the light-emitting device to emit the first modulated light or the second modulated light. This design allows the emission positions of the first modulated light and the second modulated light in the light-emitting pixel to coincide with each other, and also allows the illumination positions of the first modulated light and the second modulated light emitted by the same light-emitting pixel on the liquid crystal layer to coincide with each other, thereby achieving more precise light control. Furthermore, this design helps reduce the area occupied by the light-emitting pixel, thereby reducing the pixel size of the modulated pixel and facilitating the miniaturization of the modulated pixel. This enables a spatial light modulator using this design to adapt to applications with extremely small pixels.

[0018] In some embodiments, the spatial light modulator further includes a second filter layer disposed on the side of the liquid crystal layer away from the light source layer, configured to transmit the incident light and reflect the modulated light. This design prevents the modulated light from being emitted along with the reflected incident light, thus preventing the modulated light from interfering with the incident light.

[0019] In some embodiments, the wavelength of the incident light is between 1350 nm and 1700 nm, and the wavelength of the modulated light is between 300 nm and 650 nm. The incident light and the modulated light are of different wavelengths, and the difference between the wavelengths is relatively large. This design can effectively achieve the bandpass selection effect of the first filter layer, while also reducing the difficulty and cost of selecting the first filter layer.

[0020] In some embodiments, the spatial light modulator further includes an alignment layer disposed between the light source layer and the filter layer. The alignment layer comprises multiple optical coupling structures, each corresponding to a light-emitting pixel, for coupling the modulated light emitted by the pixel to corresponding positions on the liquid crystal layer. By providing an alignment layer with optical coupling structures, the position of the modulated light on the liquid crystal layer can be precisely controlled. Furthermore, the divergence angle of the modulated light can be controlled, reducing edge light leakage and improving focusing efficiency.

[0021] In some embodiments, the optical coupling structure is a microlens, which protrudes from the light-emitting pixel toward the liquid crystal layer; or, the optical coupling structure is a light guide column, which is a columnar structure extending between the light-emitting pixel and the liquid crystal layer, and the material of the light guide column includes an optical waveguide material; or, the optical coupling structure is a closed retaining wall, and the material of the closed retaining wall includes a light-shielding material, and the closed retaining wall is arranged around the light-emitting pixel and surrounds a light channel extending between the light-emitting pixel and the liquid crystal layer.

[0022] In the spatial light modulator provided in the embodiment of the present application, the optical coupling structure in the alignment layer can select a variety of different types of structures, which has good adaptability and can match different application scenarios and manufacturing processes.

[0023] In some embodiments, the spatial light modulator further includes a polarization-selective layer located on the side of the liquid crystal layer away from the first filter layer. The polarization orientation of the polarization-selective layer is consistent with the polarization state of the liquid crystal layer's modulation response. This design can act as a polarization filter, thereby improving the spatial light modulator's modulation efficiency of incident light.

[0024] In some embodiments, the photosensitive liquid crystal is a photoresponsive blue phase liquid crystal, and the lattice constant and / or lattice direction of the photoresponsive blue phase liquid crystal changes under the irradiation of modulated light.

[0025] In the spatial light modulator provided in the embodiment of the present application, a photoresponsive blue phase liquid crystal can be selected as a photosensitive liquid crystal. By utilizing the special optical properties of the photoresponsive blue phase liquid crystal, the modulation of the incident light can be achieved by modulating the light to control the lattice constant and / or lattice direction.

[0026] In some embodiments, the photosensitive liquid crystal is a photoresponsive ferroelectric liquid crystal or a photoresponsive smectic liquid crystal. In the spatial light modulator provided in the embodiments of the present application, the photosensitive liquid crystal in the liquid crystal layer can be selected from a variety of different types of liquid crystals, which have good adaptability and can be matched to different application scenarios and manufacturing processes.

[0027] In a second aspect, embodiments of the present application also provide a light modulation device, comprising the spatial light modulator described in the first aspect and an incident light source configured to generate incident light for irradiating the spatial light modulator. Alternatively, the light modulation device comprises the spatial light modulator described in the first aspect and an optical transmission device configured to receive the incident light and project it onto the spatial light modulator.

[0028] The technical effects that can be achieved by the light modulation device provided in the embodiments of the present application are the same as the technical effects that can be achieved by the spatial light modulator in any of the above embodiments, and will not be repeated here.

[0029] On the third aspect, an embodiment of the present application also provides a control method for a spatial light modulator, wherein the spatial light modulator includes a liquid crystal layer, a light source layer and a first filter layer, the material of the liquid crystal layer includes photosensitive liquid crystal, and the photosensitive liquid crystal can modulate the incident light under the irradiation of modulated light; the light source layer is arranged on one side of the liquid crystal layer, and includes a plurality of light-emitting pixels; the light-emitting pixels are used to generate modulated light to irradiate the liquid crystal layer; the first filter layer is arranged between the liquid crystal layer and the light source layer, and the filter layer is used to transmit the modulated light and reflect the incident light.

[0030] The spatial light modulator includes a plurality of modulation pixels, and the modulation pixels include a light-emitting pixel and a liquid crystal portion of the liquid crystal layer corresponding to the light-emitting pixel.

[0031] The control method includes:

[0032] Obtaining the target modulation state and current modulation state of the modulated pixel;

[0033] According to the difference between the target modulation state and the current modulation state, the light-emitting pixels in the modulation pixels are controlled to emit modulated light.

[0034] In some embodiments, in a spatial light modulator, liquid crystal molecules in a photosensitive liquid crystal are arranged in a helical structure.

[0035] The modulated light emitted by the luminous pixel includes a first modulated light and a second modulated light; the pitch of the spiral structure in the photosensitive liquid crystal increases under the irradiation of the first modulated light; the pitch of the spiral structure in the photosensitive liquid crystal decreases under the irradiation of the second modulated light.

[0036] In the control method, controlling a light-emitting pixel in a modulated pixel to emit modulated light according to a difference between a target modulation state and a current modulation state includes:

[0037] Acquire a first pitch and a second pitch corresponding to a target modulation state and a current modulation state, respectively;

[0038] According to the difference between the first pitch and the second pitch, the light-emitting pixel is controlled to emit the first modulated light or the second modulated light.

[0039] In some embodiments, obtaining a first pitch and a second pitch corresponding to a target modulation state and a current modulation state, respectively, includes:

[0040] querying a lookup table based on the target modulation state and the current modulation state;

[0041] The lookup table records the correspondence information between the modulation relationship and the pitch.

[0042] In some embodiments, the spatial light modulator is a phase-type spatial light modulator, and in the control method, the target modulation state and the current modulation state are the target phase and the current phase, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG1 is a front view of a silicon-based liquid crystal provided by the related art;

[0044] FIG2 is a cross-sectional view of a silicon-based liquid crystal provided by the related art;

[0045] FIG3 is a schematic structural diagram of a spatial light modulator provided in an embodiment of the present application;

[0046] FIG4 is a schematic structural diagram of a photoresponsive cholesteric liquid crystal provided in an embodiment of the present application;

[0047] FIG5 is a graph showing the relationship between modulation amplitude and pitch generated by the photoresponsive cholesteric liquid crystal according to an embodiment of the present application for incident light of 1550 nm;

[0048] FIG6 is a graph showing the relationship between the modulation phase and the pitch of the photoresponsive cholesteric liquid crystal provided in an embodiment of the present application for incident light of 1550 nm;

[0049] FIG7 is a diagram showing a principle of forming a phase diagram according to an embodiment of the present application;

[0050] FIG8 is a schematic structural diagram of a spatial light modulator provided in an embodiment of the present application;

[0051] FIG9 is a schematic structural diagram of a light-emitting pixel provided in an embodiment of the present application;

[0052] FIG10 is a schematic structural diagram of another spatial light modulator provided in an embodiment of the present application;

[0053] FIG11 is a schematic structural diagram of a light-emitting pixel in another spatial light modulator provided in an embodiment of the present application;

[0054] FIG12 is a schematic structural diagram of another spatial light modulator provided in an embodiment of the present application;

[0055] FIG13 is a schematic structural diagram of another spatial light modulator provided in an embodiment of the present application;

[0056] FIG14 is a schematic structural diagram of another spatial light modulator provided in an embodiment of the present application;

[0057] FIG15 is a schematic structural diagram of another spatial light modulator provided in an embodiment of the present application;

[0058] FIG16 is a flow chart of a method for controlling a spatial light modulator provided in an embodiment of the present application;

[0059] FIG17 is a flow chart of another method for controlling a spatial light modulator provided in an embodiment of the present application;

[0060] FIG18 is a flow chart of another method for controlling a spatial light modulator provided in an embodiment of the present application;

[0061] FIG19 is a schematic structural diagram of an optical modulation device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0062] A spatial light modulator (SLM) is a programmable device that controls the spatial distribution of light, including its phase, amplitude, polarization, and coherence. It is widely used in optical communication scheduling and switching, optical metrology, optical imaging, and laser processing. A spatial light modulator comprises a one- or two-dimensional array of multiple modulating pixels, each of which can be controlled by a signal. When a beam of incident light strikes the SLM, these modulating pixels divide the incident light into several parts. Each modulating pixel is controlled to control the corresponding portion of the incident light, thereby changing the spatial distribution of the incident light.

[0063] Liquid Crystal on Silicon (LCoS), also known as liquid crystal on silicon (LCoS), is a common spatial light modulator. Figure 1 shows a front view of a LCS 100A, as described in related art. As shown in Figure 1 , LCS 100A includes a pixel array comprising a plurality of modulated pixels (Pixels) 110 arranged in multiple rows and columns. For example, the rows of the pixel array are oriented horizontally, while the columns are oriented vertically.

[0064] Figure 2 is a cross-sectional view of a silicon-based liquid crystal 100A provided by the related art. As shown in Figure 2, the silicon-based liquid crystal 100A includes a CMOS (Complementary Metal Oxide Semiconductor) substrate 103, a liquid crystal layer 102 and a transparent cover 101, wherein the CMOS substrate 103 and the transparent cover 101 are arranged opposite to each other, and the liquid crystal layer 102 is arranged between the oppositely arranged CMOS substrate 103 and the transparent cover 101.

[0065] The CMOS substrate 103 includes a pixel circuit and a metal reflector. The pixel circuit is fabricated using a CMOS process on a silicon wafer. After the pixel circuit is fabricated, the silicon wafer is ground flat using a lapping technique and coated with a metal layer that serves as the metal reflector. The metal reflector is typically made of aluminum and is used to reflect incident light. The pixel circuit in the CMOS substrate 103 includes a pixel driver circuit corresponding to the modulated pixel 110. The pixel driver circuit includes a first electrode 105. The transparent cover 101 is provided with a second electrode 104 on the side adjacent to the CMOS substrate 103.

[0066] When the silicon-based liquid crystal 100A having the above structure is working, a first voltage is applied to the first electrode 105 and a second voltage is applied to the second electrode 104. When the first voltage is different from the second voltage, an electric field with a certain voltage difference can be generated between the first electrode 105 and the second electrode 104. Under the action of the electric field, the properties of the liquid crystal molecules in the portion of the liquid crystal layer 102 located between the first electrode 105 and the second electrode 104 will change, thereby being able to modulate the light passing through the liquid crystal portion.

[0067] In phase-modulated LCOS 100A, under the influence of an electric field, the liquid crystal molecules in the liquid crystal layer 102 located between the first electrode 105 and the second electrode 104 deflect. The deflection angle is related to the voltage difference between the first and second voltages. Due to the birefringence of the liquid crystal molecules, the deflection produces a certain amount of phase retardation; different deflection angles correspond to different amounts of phase retardation. Therefore, phase modulation of light can be achieved by applying different voltage differences between the first and second electrodes 105, 104.

[0068] The above description of LCOS 100A indicates that it modulates light by applying an electric field to the liquid crystal layer 102. The applied electric field corresponds to the modulation state; when the applied electric field disappears or changes, the modulation state also changes. Furthermore, due to the operating characteristics of liquid crystals, AC power supply is required for control. Therefore, the pixel circuit in LCOS 100A uses a level-flipping drive method to control the liquid crystal layer 102. During the drive process, the voltage applied to the first electrode 105 and the second electrode 104 must be continuously refreshed.

[0069] Based on the above reasons, the LCOS 100A in the related art has at least the following deficiencies:

[0070] On the one hand, the silicon-based liquid crystal 100A of the related art will change its modulation state when faced with a sudden power outage, making it impossible to maintain data and maintain normal operation, thus belonging to a volatile spatial light modulator 100. On the other hand, in order to maintain the current modulation state, the silicon-based liquid crystal 100A needs to maintain the voltage difference applied between the first electrode 105 and the second electrode 104 during the continuous refresh drive process; thus, the silicon-based liquid crystal 100A has the problem of high device power consumption. On the other hand, in order to maintain the voltage difference applied between the first electrode 105 and the second electrode 104 during the continuous refresh drive process, a complex pixel driving circuit is required. However, the complex pixel driving circuit will lead to an increase in the occupied area, which will limit the reduction of the modulation pixel 110 in the silicon-based liquid crystal 100A, which is not conducive to the miniaturization of the modulation pixel 110 and makes it difficult to meet the requirements of extremely small pixels (less than 5 microns) in some scenarios.

[0071] Based on this, embodiments of the present application provide a spatial light modulator, a control method, and a light modulation device to improve the above-mentioned problems.

[0072] The following will describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0073] In the following embodiments of the present application, the terms "first," "second," etc. are used for convenience of description only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0074] In the embodiments of the present application, "up", "down", "left" and "right" are not limited to being defined relative to the orientation of the components schematically placed in the drawings. It should be understood that these directional terms may be relative concepts. They are used for relative descriptions and clarifications, and may change accordingly according to changes in the orientation of the components in the drawings.

[0075] In the embodiments of the present application, unless the context requires otherwise, throughout the specification and claims, the term "including" is to be interpreted as open and inclusive, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "exemplarily" or "some examples" and the like are intended to indicate that the specific features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present application. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0076] As used herein, "about," "substantially," or "approximately" includes the stated value and an average value that is within an acceptable range of deviation from the particular value as determined by one of ordinary skill in the art taking into account the measurements in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0077] As used herein, "parallel", "perpendicular", and "equal" include the situations described and situations similar to the situations described, and the range of the similar situations is within an acceptable deviation range, wherein the acceptable deviation range is as determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, wherein the acceptable deviation range of approximate parallelism can be, for example, a deviation within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, wherein the acceptable deviation range of approximate perpendicularity can also be, for example, a deviation within 5°. "Equal" includes absolute equality and approximate equality, wherein the acceptable deviation range of approximate equality can be, for example, that the difference between the two equals is less than or equal to 5% of either one.

[0078] It will be understood that when a layer or element is referred to as being on another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may be present therebetween.

[0079] In the embodiments of the present application, exemplary embodiments are described with reference to cross-sectional views and / or plan views and / or equivalent circuit diagrams as idealized exemplary drawings. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are conceivable. Therefore, the exemplary embodiments should not be interpreted as being limited to the shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing. For example, an etched region shown as a rectangle will typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shapes of regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0080] An embodiment of the present application provides a spatial light modulator 100, as shown in Figure 3, the spatial light modulator 100 includes a substrate 2, a light source layer 3, a first filter layer 1 and a liquid crystal layer 102 stacked in a first direction; wherein the liquid crystal layer 102 is used to receive incident light incident from a side away from the substrate 2, and to modulate the incident light by controlling changes in the properties of the liquid crystal molecules; the modulated incident light will be emitted from the liquid crystal layer 102 to the side of the liquid crystal layer 102 away from the substrate 2.

[0081] In the spatial light modulator 100 provided in the embodiment of the present application, the liquid crystal material of the liquid crystal layer 102 is photosensitive liquid crystal, which refers to a liquid crystal material that can change the characteristics of liquid crystal molecules under the stimulation of modulated light of a specific wavelength; thus, the modulation of the incident light can be achieved by irradiating the liquid crystal layer 102 with modulated light.

[0082] In some embodiments, the photosensitive liquid crystal can be a photosensitive chiral liquid crystal, which can be formed by adding photoresponsive chiral molecules to the liquid crystal. The photoresponsive chiral molecules include a chiral center and a photoresponsive group (also known as a photoswitch). The chiral center transfers the molecular chirality to the liquid crystal, inducing the liquid crystal molecules to self-assemble to form a helical structure. The photoresponsive group can undergo a photoisomerization reaction under the stimulation of modulated light, changing the spatial structure of the chiral molecules, thereby changing the characteristics of the helical structure, such as the pitch and helical direction, to achieve modulation of the incident light.

[0083] The following text will use photoresponsive cholesteric liquid crystal as an example to illustrate the working principle of photosensitive chiral liquid crystal. Obviously, the spatial light modulator 100 provided in the embodiment of the present application is not limited to the use of photoresponsive cholesteric liquid crystal. Any photosensitive chiral liquid crystal that can change the characteristics of the spiral structure by modulating light irradiation to achieve incident light modulation can be used, such as ferroelectric nematic liquid crystal, twisted grain boundary liquid crystal and smectic liquid crystal.

[0084] Cholesteric phase is a type of liquid crystal phase. Cholesteric liquid crystal (Cholesteric liquid crystal), also known as chiral nematic liquid crystal, is a "soft" photonic crystal with a periodic spiral structure.

[0085] As shown in Figure 4, the liquid crystal molecules in cholesteric liquid crystals self-assemble into layers. Within each layer, the liquid crystal molecules are aligned parallel to a specific direction, with their long axes parallel to the plane of the layer. The liquid crystal molecules between adjacent layers rotate by a certain angle (approximately 15°) along the layer normal, forming a periodic helical structure. Pitch (abbreviated as p) and helical direction (handedness) are two important parameters that characterize the helical structure in cholesteric liquid crystals. Pitch refers to the interlayer spacing of the liquid crystal molecules in the helical structure when the helical axis rotates 360°. Helical direction refers to the direction of rotation of the molecules between layers in the helical structure, which can be divided into left-handed and right-handed helices.

[0086] Cholesteric liquid crystals, a self-assembled periodic helical structure similar to a one-dimensional photonic crystal, can produce the following unique optical properties. On the one hand, the periodic helical structure produces Bragg reflection, which can selectively reflect incident light; only light incident in the reflection window is reflected. On the other hand, cholesteric liquid crystals can selectively reflect circularly polarized light with the same helical direction as their own; that is, cholesteric liquid crystals with right-handed helices only reflect right-handed circularly polarized light, and cholesteric liquid crystals with left-handed helices only reflect left-handed circularly polarized light. In other words, the helical direction of the helical structure in the cholesteric liquid crystal determines the circular polarization of the reflected light.

[0087] Photoresponsive cholesteric liquid crystals (LCs) are those whose helical pitch can be induced to change in response to external light. Adding photoresponsive chiral molecules to nematic LCs is a common method for preparing them. These chiral molecules undergo photoisomerization in response to light of a specific wavelength, altering the spatial structure of the chiral molecules and thereby changing the helical pitch in the LC.

[0088] In this paper, light that can cause the helical pitch of a photoresponsive cholesteric liquid crystal to change is referred to as modulated light. The modulated light includes a first modulated light and a second modulated light of different wavelengths. As shown in Figure 4, when the photoresponsive cholesteric liquid crystal is irradiated by the first modulated light, the pitch of its helical structure increases, and the greater the irradiation dose, the greater the increase in pitch. When the photoresponsive cholesteric liquid crystal is irradiated by the second modulated light, the pitch of its helical structure decreases, and the greater the irradiation dose, the greater the decrease in pitch.

[0089] For different photoresponsive cholesteric liquid crystals, the first modulated light and the second modulated light are usually different; according to the photoresponsive cholesteric liquid crystal actually used, the first modulated light and the second modulated light of appropriate wavelengths can be selected to control the pitch.

[0090] The photoresponsive cholesteric liquid crystal can achieve the purpose of moving the reflection window of Bragg reflection by controlling the pitch; by moving the reflection window, the amplitude modulation of the incident light and the phase modulation of the incident light are achieved.

[0091] Combined with the above description, it can be seen that cholesteric liquid crystal can produce Bragg reflection. According to the Bragg reflection law λ = n × p (where n is the average refractive index of the liquid crystal matrix and p is the pitch), it can be seen that the central wavelength λ of the reflection window of Bragg reflection is directly related to the pitch p of the spiral structure; therefore, the photoresponsive cholesteric liquid crystal can move the reflection window of Bragg reflection by changing the pitch.

[0092] Light of different wavelengths reflected in the reflective window has different reflectivities. Incident light of the same wavelength can fall into different reflective windows and have different reflectivities when reflected in these windows. Therefore, photoresponsive cholesteric liquid crystals can modulate the amplitude of incident light by changing the pitch of the helical structure while simultaneously shifting the Bragg reflective window.

[0093] In addition, spin-orbit coupling also exists in cholesteric liquid crystals. The reflected light of Bragg reflection is given a geometric phase related to the arrangement of the helical axis. The reflected light of different wavelengths in the reflection window has different reflection phases. Incident light of the same wavelength can be located in different reflection windows and have different reflection phases when reflected in different reflection windows. Therefore, photoresponsive cholesteric liquid crystals can change the reflection phase of the incident light by changing the helical pitch while moving the reflection window of Bragg reflection, thereby achieving phase modulation of the incident light.

[0094] The relationship between the modulation amplitude, modulation phase and pitch of the photoresponsive cholesteric liquid crystal to the incident light can be calculated according to the formula, or obtained through experiments, simulations, etc. FIG5 is a graph showing the relationship between the modulation amplitude and pitch generated by the photoresponsive cholesteric liquid crystal provided in an embodiment of the present application for incident light of 1550 nm, and FIG6 is a graph showing the relationship between the modulation phase and pitch generated by the photoresponsive cholesteric liquid crystal provided in an embodiment of the present application for incident light of 1550 nm. It should be noted that although FIG5 and FIG6 are relationship curves generated for incident light of 1550 nm, for incident light of other wavelengths, their changing trends are basically the same. Therefore, based on this, the relationship characteristics between the modulation amplitude, modulation phase and pitch of the photoresponsive cholesteric liquid crystal to the incident light can be obtained.

[0095] As can be seen in Figure 5, in the middle section of the modulation amplitude-pitch relationship curve, the modulation amplitude remains essentially constant as the pitch changes. In the sections before and after the middle section, the modulation amplitude changes with the pitch, and in certain pitch variation intervals, the modulation amplitude can change from 0 to 1. A corresponding relationship between the modulation amplitude and pitch can be established, allowing amplitude modulation to be performed using the sections before and after the middle section.

[0096] It can be seen from the modulation phase-pitch relationship curve shown in Figure 6 that the modulation phase changes with the pitch. In certain pitch change intervals, the modulation phase can change within the range of 2π; thus, a corresponding relationship between the modulation phase and the pitch can be established, and on this basis, the purpose of changing the modulation phase by modulating the pitch can be achieved.

[0097] 5 and 6 , it can be seen that in the middle section of the modulation amplitude-pitch relationship curve, the modulation amplitude is basically constant as the pitch changes; during the same pitch change process, the modulation phase changes smoothly with the pitch, and the change range is -π to π; therefore, based on this change characteristic, the amplitude modulation and phase modulation can be decoupled to form a pure phase modulation phase-type spatial light modulator 100, and a phase modulation depth of 2π can be achieved.

[0098] In the following description, a phase-type spatial light modulator 100 formed using a photoresponsive cholesteric liquid crystal is used as an example to illustrate the solution. As can be seen from the above description, modulated light is used to change the pitch of the photoresponsive cholesteric liquid crystal. Combining the relationship between the modulation phase and the pitch, the relationship between the modulation phase and the modulation phase can be obtained as follows:

[0099] When the photoresponsive cholesteric liquid crystal is irradiated with the first modulated light, the pitch increases and the modulation phase increases; the greater the irradiation dose, the greater the magnitude of the increase in pitch and modulation phase. When the photoresponsive cholesteric liquid crystal is irradiated with the second modulated light, the pitch decreases and the modulation phase decreases; the greater the irradiation dose, the greater the magnitude of the decrease in pitch and modulation phase.

[0100] It can be seen from this that, under the action of modulated light, the photoresponsive cholesteric liquid crystal can achieve phase modulation of the incident light by controlling the pitch.

[0101] When the spatial light modulator 100 is in operation, a phase pattern with a specific phase distribution can be formed by applying specific phases to different locations in the liquid crystal layer 102. Different phase patterns can achieve different functions. For example, as shown in FIG7 , by periodically applying a phase pattern with a phase distribution of 0-2π, the function of a blazed grating can be achieved, and the deflection of a light beam can be controlled by the blazed grating.

[0102] Please refer to Figures 3 and 8. The spatial light modulator 100 provided in an embodiment of the present application is provided with a light source layer 3 on the side of the liquid crystal layer 102 close to the substrate 2; the light source layer 3 includes a plurality of light-emitting pixels 4, where the plurality of light-emitting pixels 4 can be arranged in an array to form a one-dimensional array or a two-dimensional array.

[0103] Each luminescent pixel 4 generates modulated light that illuminates the liquid crystal layer 102. The properties of the liquid crystal molecules in the portion of the liquid crystal layer 102 illuminated by the modulated light change, thereby modulating the incident light. Furthermore, different luminescent pixels 4 correspond to different regions of the liquid crystal layer 102. The luminescent pixels 4 and the corresponding regions of the liquid crystal layer 102 together form a modulated pixel 110 in the spatial light modulator 100.

[0104] Corresponding to the light-emitting pixels 4 in the light source layer 3 , the spatial light modulator 100 includes a one-dimensional or two-dimensional pixel array formed by arranging a plurality of modulation pixels 110 .

[0105] Please continue to refer to Figure 8. The light source layer 3 may include a light-emitting layer 31 and a driving circuit layer 32, wherein the light-emitting layer 31 includes a light-emitting device for forming a light-emitting pixel 4, and the light-emitting device may be an LD (Laser Diode), an OLED (Organic Light-Emitting Diode), a QLED (Quantum Dot Light Emitting Diodes), a Mini LED (sub-millimeter light-emitting diode) or a Micro LED (micro light-emitting diode), etc.; the embodiment of the present application does not limit the type of the light-emitting device.

[0106] The driving circuit layer 32 includes a pixel driving circuit electrically connected to the light emitting device, and the pixel driving circuit is used to drive the light emitting device electrically connected thereto to emit light; the pixel driving circuit and the light emitting device together constitute a light emitting pixel 4 .

[0107] In other embodiments, the light source layer 3 may also be a liquid crystal display (LCD) device, that is, the liquid crystal display device provides modulated light to the liquid crystal layer 102 .

[0108] As described above, in this embodiment, liquid crystal layer 102 utilizes photoresponsive cholesteric liquid crystals. These photoresponsive cholesteric liquid crystals can control the helical pitch under the illumination of the first modulated light and the second modulated light. Correspondingly, the light-emitting pixels 4 in light source layer 3 are configured to emit both the first modulated light and the second modulated light.

[0109] As shown in FIG9 , in this embodiment, the luminescent pixel 4 includes a first sub-pixel 41 and a second sub-pixel 42. The first sub-pixel 41 and the second sub-pixel 42 are arranged adjacent to each other along a second direction perpendicular to the first direction. That is, the first sub-pixel 41 and the second sub-pixel 42 are arranged adjacent to each other in a plane parallel to the liquid crystal layer 102. The first sub-pixel 41 is configured to emit a first modulated light, and the second sub-pixel 42 is configured to emit a second modulated light. During operation of the spatial light modulator 100, the first or second modulated light can be generated by controlling the operation of the first or second sub-pixel 41 or 42 in the luminescent pixel 4 to illuminate the liquid crystal layer 102, thereby controlling the helical pitch in the photoresponsive cholesteric liquid crystal. Furthermore, the luminous intensity and luminous duration of the first or second sub-pixel 41 or 42 can be controlled to adjust the luminous dose of the first or second modulated light, thereby regulating the amplitude of the helical pitch variation in the photoresponsive cholesteric liquid crystal.

[0110] It should be noted that a single luminous pixel 4 can only emit the first modulated light or the second modulated light at the same time, and cannot emit both the first modulated light and the second modulated light at the same time. However, for the entire spatial light modulator 100, the luminous states of different luminous pixels 4 at the same time are independent of each other, and some luminous pixels 4 may emit the first modulated light while others may emit the second modulated light.

[0111] As can be seen from the above description, the spatial light modulator 100 includes both incident light and modulated light directed toward the liquid crystal layer 102. The incident light is directed toward the liquid crystal layer 102 on the side of the liquid crystal layer 102 away from the substrate 2, while the modulated light is directed toward the liquid crystal layer 102 on the side of the liquid crystal layer 102 closer to the substrate 2. To achieve independent control and isolation of the incident light and the modulated light, as shown in Figures 3 and 8, the spatial light modulator 100 provided in the embodiment of the present application is further provided with a first filter layer 1.

[0112] The first filter layer 1 is a bandpass selective filter layer, selectively transmitting light within a certain wavelength range and selectively reflecting light within another wavelength range. In this embodiment, the first filter layer 1 is disposed between the liquid crystal layer 102 and the light source layer 3, for example, in close proximity to the side of the liquid crystal layer 102 near the light source layer 3. The first filter layer 1 efficiently reflects incident light (e.g., with a reflectivity exceeding 85%) and efficiently transmits modulated light emitted by the light source layer 3 (e.g., with a transmittance exceeding 85%).

[0113] To effectively achieve the bandpass selection effect of the first filter layer 1 and to reduce the difficulty in selecting the first filter layer 1, the incident light and the modulated light should be of different wavelengths, and the wavelength difference between the two should be as large as possible. For example, the wavelength of the incident light is 1350nm to 1700nm, and the wavelength of the modulated light is 300nm to 650nm.

[0114] In this embodiment, the incident light may be infrared light, and the first modulated light and the second modulated light may be ultraviolet light.

[0115] In some embodiments, as shown in FIG10 , the spatial light modulator 100 further includes a second filter layer 5 . The second filter layer 5 is disposed on a side of the liquid crystal layer 102 away from the substrate 2 , for example, in close proximity to the side of the liquid crystal layer 102 away from the light-emitting layer 31 . The second filter layer 5 can efficiently reflect the modulated light (e.g., with a reflectivity of 85% or greater) and efficiently transmit the incident light modulated by the liquid crystal layer 102 (e.g., with a transmittance of 85% or greater). The provision of the second filter layer 5 prevents the modulated light from being emitted along with the modulated incident light, thereby improving the modulation effect and optical performance of the spatial light modulator 100 .

[0116] Continuing with Figures 3, 8, and 10, the spatial light modulator 100 provided in this embodiment of the present application further includes a substrate 2. This substrate 2 is disposed on a side of the light source layer 3 away from the liquid crystal layer 102. The substrate 2 is a plate-like structure perpendicular to the first direction and is used to support other structures disposed thereon. It also serves to dissipate heat. For example, the substrate 2 can be a ceramic substrate such as alumina or aluminum nitride.

[0117] The spatial light modulator 100 having the above-described structure includes a liquid crystal layer 102 and a light source layer 3. The liquid crystal layer 102 utilizes photoresponsive cholesteric liquid crystals, and the light source layer 3 generates modulated light that acts upon the photoresponsive cholesteric liquid crystals. Under the illumination of the modulated light, the liquid crystal layer 102 can achieve phase modulation of the incident light. By controlling the emission of the light-emitting pixels 4 in the light source layer 3, a phase pattern with a specific phase distribution can be formed in the liquid crystal layer 102, thereby achieving phase programming. By loading different phase patterns, the spatial light modulator 100 can achieve different functions.

[0118] Because the liquid crystal layer 102 utilizes a photoresponsive cholesteric liquid crystal, after the phase diagram is loaded, the phase diagram remains unchanged until it is irradiated with new modulated light, thereby stopping the power supply to the light source layer 3. With this design, compared to the silicon-based liquid crystal 100A in the related art, the spatial light modulator 100 in the embodiment of the present application can reduce the power supply time to the light source layer 3, that is, reduce the control power consumption time used to control the liquid crystal layer 102, thereby achieving the purpose of reducing power consumption; furthermore, the liquid crystal layer 102 can maintain the phase diagram before the power failure in the event of an unexpected power failure, thereby maintaining the modulation state unchanged, and having non-volatile characteristics.

[0119] On the other hand, as can be seen from the above description, the silicon-based liquid crystal 100A in the related art cannot be made very small due to the complex pixel driving circuit, making it difficult to meet the requirements of extremely small pixels (less than 5 microns) in some scenarios. In contrast to the related art, in the spatial light modulator 100 provided in the embodiment of the present application, the size of the modulating pixel 110 is affected by the light-emitting pixel 4. However, since the light-emitting pixel 4 only needs to emit modulated light of a fixed wavelength and only needs to control the light-emitting time and light-emitting intensity, the light-emitting device and pixel driving circuit are relatively simple, resulting in a smaller size of the light-emitting pixel 4. In turn, the size of the modulating pixel 110 can also be smaller, which is conducive to the miniaturization design of the modulating pixel 110. Such a design can, on the one hand, meet the requirements of extremely small pixels (less than 5 microns) in some scenarios; on the other hand, more modulating pixels 110 can be arranged in the same area, achieving an increase in pixel density, which is conducive to improving the performance of the spatial light modulator 100.

[0120] In addition, the silicon-based liquid crystal 100A in the related art requires a level-flipping drive method to control the liquid crystal layer 102, but this drive method will restrict the increase in the modulation frequency. For example, the modulation frequency of the silicon-based liquid crystal 100A in the related art is generally around 100 Hz and will not exceed 200 Hz. In the spatial light modulator 100 provided in the embodiment of the present application, the modulation frequency is affected by the light source layer 3, and the upper limit of the light emission frequency of the light source layer 3 is very high. For example, when Micro LEDs are used as light-emitting pixels 4, the response frequency of Micro LEDs is in the order of GHz. Therefore, the modulation frequency upper limit of the spatial light modulator 100 reaches the order of GHz, and the response time is in the order of nanoseconds, which has obvious advantages.

[0121] The present embodiment also provides a schematic structural diagram of another spatial light modulator 100. This spatial light modulator 100 differs from the spatial light modulator 100 of the aforementioned embodiment in the light-emitting pixel 4. As shown in FIG11 , in this embodiment, the light-emitting device in the light-emitting pixel 4 employs a pixel structure capable of being controlled to emit first and second modulated lights of different wavelengths, such as a stacked Micro LED light-emitting chip. Different drive signals are input to the light-emitting device via a pixel driver circuit to control the light-emitting device to emit first and second modulated lights of different wavelengths. This design allows the emission locations of the first and second modulated lights in the light-emitting pixel 4 to coincide, and also allows the first and second modulated lights emitted by the same light-emitting pixel 4 to coincide with each other on the liquid crystal layer 102, thereby enabling more precise light control. Furthermore, this design helps reduce the area occupied by the light-emitting pixel 4, thereby reducing the pixel size of the modulating pixel 110 and facilitating a miniaturized design of the modulating pixel 110. This enables the spatial light modulator 100 employing this design to adapt to applications involving extremely small pixels.

[0122] Figure 12 is a structural schematic diagram of another spatial light modulator 100 provided in an embodiment of the present application. As shown in Figure 12, the difference between this spatial light modulator 100 and the spatial light modulator 100 in the above embodiment is that an alignment layer 6 is provided between the light source layer 3 and the first filter layer 1. The alignment layer 6 has an optical coupling structure 61 corresponding one-to-one to the light-emitting pixel 4. The optical coupling structure 61 is used to enable the modulated light emitted by the light-emitting pixel 4 to be accurately coupled to the corresponding part of the liquid crystal layer 102, so that the modulation position of the modulated light on the liquid crystal layer 102 can be accurately controlled; and the alignment layer 6 can also control the divergence angle of the modulated light, reduce edge leakage, and improve focusing efficiency.

[0123] Exemplarily, as shown in Figure 12, the alignment layer 6 includes a microlens array, which includes a plurality of microlenses arranged in an array. The microlenses are optical coupling structures 61 set corresponding to the light-emitting pixels 4 in the alignment layer 6; the arrangement of the microlenses in the microlens array is the same as the arrangement of the light-emitting pixels 4 in the light source layer 3.

[0124] The microlenses are lens structures that protrude toward the liquid crystal layer 102. The lens surface of the lens structure near the liquid crystal layer 102 can be spherical or aspherical. The focal length of each microlens in the microlens array can be uniform or slightly different (with a fluctuation of plus or minus <10%). The liquid crystal layer 102 can be located at the focal point of the microlens or out of focus.

[0125] During operation, the modulated light emitted by the luminous pixel 4 is first diffused and then converged through the microlens to reduce the mode field radius on the liquid crystal layer 102, so that the modulated light emitted by the luminous pixel 4 can be accurately converged to the specified position of the liquid crystal layer 102; and it can prevent the modulated light emitted by one luminous pixel 4 from affecting other positions in the liquid crystal layer 102, thereby reducing crosstalk and light leakage between the luminous pixels 4.

[0126] As another example, as shown in FIG13 , the optical coupling structure 61 can be a light guide column formed of a waveguide material. The light guide column is a columnar structure extending between the light-emitting pixel 4 and the liquid crystal layer 102. The light guide columns corresponding to adjacent light-emitting pixels 4 are spaced apart. In this case, the spacing can be through a gap, or through a material with a different refractive index from the light guide column, or through a light-shielding material. This design can confine the light emitted by the light-emitting pixel 4 to be transmitted within the light guide column, so that the modulated light emitted by the light-emitting pixel 4 can be accurately focused at a designated location in the liquid crystal layer 102. It can also prevent the modulated light emitted by one light-emitting pixel 4 from affecting other locations in the liquid crystal layer 102, thereby reducing crosstalk and light leakage between the light-emitting pixels 4.

[0127] As another example, as shown in Figure 14, the optical coupling structure 61 can be a closed baffle made of a shading material, which is arranged around the light-emitting pixel 4 and surrounds an optical channel extending between the light-emitting pixel 4 and the liquid crystal layer 102; thereby, the modulated light emitted by the light-emitting pixel 4 can be limited to be transmitted in the optical channel formed by the closed baffle. In this way, the light emitted by the light-emitting pixel 4 can be limited to be transmitted in the closed baffle, so that the modulated light emitted by the light-emitting pixel 4 can be accurately converged to a specified position of the liquid crystal layer 102; and the modulated light emitted by one light-emitting pixel 4 can be prevented from affecting other positions in the liquid crystal layer 102, thereby reducing crosstalk and light leakage between the light-emitting pixels 4.

[0128] FIG15 is a schematic diagram of the structure of another spatial light modulator 100 provided in an embodiment of the present application. As shown in FIG15 , this spatial light modulator 100 differs from the spatial light modulator 100 in the aforementioned embodiment in that a polarization-selective layer 7 is provided on the side of the liquid crystal layer 102 away from the substrate 2. Exemplarily, the polarization-selective layer 7 is directly attached to the surface of the liquid crystal layer 102 away from the substrate 2.

[0129] The polarization-selective layer 7 can be made of liquid crystal materials, organic materials, and micro-nano structures. Its polarization orientation is consistent with the polarization state of the modulation response of the underlying liquid crystal layer 102. Its function is to perform polarization filtering on the incident light. The incident light can be a mixture of light with any polarization state, and is not required to be a specific linearly polarized light or circularly polarized light. When the incident light passes through the polarization-selective layer 7, only light with the polarization state corresponding to the polarization-selective layer 7 can be transmitted into the liquid crystal layer 102, and the liquid crystal layer 102 modulates the incident light in response to the polarization state. After being modulated by the liquid crystal layer 102, the incident light is reflected, and its polarization is not modulated in the liquid crystal layer 102. The incident light reflected by the liquid crystal layer 102 can directly pass through the polarization-selective layer 7, completing the modulation effect of the entire incident light.

[0130] In the above embodiments, the scheme is exemplified by taking the case where the photosensitive liquid crystal adopts a photoresponsive cholesteric liquid crystal and the spatial light modulator 100 is a phase-type spatial light modulator 100 as an example, but the spatial light modulator 100 provided in the embodiments of the present application is not limited thereto.

[0131] In some embodiments, the photosensitive liquid crystal may also be any other liquid crystal material that can change the properties of liquid crystal molecules by modulating light to achieve modulation of the spatial distribution of the incident light, such as phase, amplitude, polarization, and coherence.

[0132] Exemplarily, the photosensitive liquid crystal may be a light-responsive blue phase liquid crystal, wherein the liquid crystal molecules in the blue phase liquid crystal (BPLC) are subjected to the helical twisting force provided by the chiral dopant, and not only undergo helical twisting in the axial direction of the helical axis, but also twist in the direction perpendicular to the helical axis, and eventually self-assemble to form double twisted cylinders, which are double helical structures different from the single helix in the cholesteric phase liquid crystal. According to the different arrangements of the double twisted cylinders, blue phase liquid crystals can be roughly divided into: blue phase I (BPⅠ), blue phase II (BPⅡ) and blue phase III (BPⅢ). Among them, BPⅠ has a body-centered cubic structure, BPⅡ has a simple cubic structure, and BPⅢ has an amorphous structure.

[0133] Photoresponsive blue phase liquid crystal refers to a blue phase liquid crystal that can change the properties of the liquid crystal molecules under light stimulation by incorporating synthetic photosensitive molecules into the blue phase liquid crystal host. For example, in the case where the photosensitive molecule is azobenzene, the isomerization of azobenzene can be used to change the pitch length of the photonic band gap, thereby changing the lattice constant; it can also trigger a phase transition of the double twisted cylindrical arrangement phase, thereby changing its lattice direction. It can be seen from this that photoresponsive blue phase liquid crystal can change the lattice constant and / or lattice direction of the photonic crystal (blue phase liquid crystal) under the action of modulated light, thereby controlling the Bragg reflection characteristics and achieving a shift in the reflection center wavelength, thereby achieving modulation of the incident light.

[0134] As another example, the photosensitive liquid crystal can also be a photoresponsive ferroelectric liquid crystal, a photoresponsive smectic liquid crystal, or other liquid crystal material that can change the properties of liquid crystal molecules by modulating light to achieve modulation of the spatial distribution of the incident light, such as phase, amplitude, polarization, and coherence.

[0135] In other embodiments, based on the control characteristics of the photosensitive liquid crystal in the liquid crystal layer 102 on the incident light, the spatial light modulator 100 may be a phase-type, amplitude-type, or phase-amplitude-type spatial light modulator 100 .

[0136] The spatial light modulator 100 employing the above-described design includes a light source layer 3 and a liquid crystal layer 102. The light source layer 3 generates modulated light that acts on the liquid crystal layer 102. The liquid crystal layer 102 utilizes photosensitive liquid crystals, which, under the influence of the modulated light, can modulate the incident light. Furthermore, after completing modulation, the liquid crystal layer 102 maintains its modulation state until it is irradiated with new modulated light, thereby suspending power to the light source layer 3. Compared to the silicon-based liquid crystal 100A of the related art, the spatial light modulator 100 in the embodiment of the present application can reduce the power supply time to the light source layer 3, that is, the control power consumption time used to control the liquid crystal layer 102, thereby reducing power consumption. Furthermore, the liquid crystal layer 102 can maintain its pre-power-off modulation state in the event of an unexpected power outage, demonstrating its non-volatile nature.

[0137] On the other hand, in the spatial light modulator 100 provided in the embodiment of the present application, the size of the modulating pixel 110 is affected by the light-emitting pixel 4. However, since the light-emitting pixel 4 only needs to emit modulated light of a fixed wavelength and only needs to control the emission time and intensity, the light-emitting device and pixel driving circuit are relatively simple, resulting in a smaller size of the light-emitting pixel 4. In turn, the size of the modulating pixel 110 can also be smaller, which is conducive to the miniaturization of the modulating pixel 110. Such a design can, on the one hand, meet the requirements of some scenarios for extremely small pixels (less than 5 microns); on the other hand, more modulating pixels 110 can be arranged in the same area, achieving an increase in pixel density, which is beneficial to improving the performance of the spatial light modulator 100.

[0138] In addition, in the spatial light modulator 100 provided in the embodiment of the present application, the modulation frequency is affected by the light source layer 3, and the upper limit of the light emission frequency of the light source layer 3 is very high. For example, when Micro LED is used as the light-emitting pixel 4, the response frequency of Micro LED is in the order of GHz. Therefore, the upper limit of the modulation frequency of the spatial light modulator 100 reaches the order of GHz, and the response time is in the order of ns, which has obvious advantages.

[0139] The present embodiment also provides a control method for the spatial light modulator 100, which can be used to control the spatial light modulator 100 in the above embodiment. As shown in FIG16 , the control method 200 includes:

[0140] Step S100: Acquire the target modulation state and current modulation state of the modulated pixel.

[0141] As can be seen from the above description of the spatial light modulator 100, the luminescent pixel 4 and the liquid crystal portion corresponding to the luminescent pixel 4 in the liquid crystal layer 102 together form a modulated pixel 110 in the spatial light modulator 100. The spatial light modulator 100 includes a one-dimensional or two-dimensional pixel array formed by a plurality of modulated pixels 110. The modulation state of the spatial light modulator 100 is the combination of the modulation states of all modulated pixels 110 in the pixel array. In a given modulation state of the spatial light modulator 100, the modulation states of all modulated pixels 110 in the pixel array are independent of each other, and the modulation states of different modulated pixels 110 can be the same or different. During the modulation process of the spatial light modulator 100, the modulation of each modulated pixel 110 in the pixel array is also independent. In other words, during the modulation process of the spatial light modulator 100, each modulated pixel 110 is modulated individually according to the modulation requirements of the spatial light modulator 100. When all modulated pixels 110 in the pixel array are modulated, the spatial light modulator 100 has completed modulation.

[0142] For example, when the spatial light modulator 100 forms a target phase diagram with a specific phase distribution, each modulated pixel 110 in the pixel array needs to be independently phase modulated according to the target phase diagram. When all the modulated pixels 110 in the pixel array have completed phase modulation, the spatial light modulator 100 has formed the required target phase diagram.

[0143] In step S100, the target modulation state of the modulating pixel 110 refers to the modulation state that the modulating pixel 110 needs to achieve during the modulation task. When all the modulating pixels 110 in the pixel array reach the target modulation state, modulation of the spatial light modulator 100 is achieved. The current modulation state of the modulating pixel 110 refers to the modulation state of the modulating pixel 110 before the modulation task begins.

[0144] For a modulation pixel 110 in a phase-type spatial light modulator, the target modulation state refers to the modulation phase that the modulation pixel 110 needs to achieve in the modulation task, and the current modulation state refers to the modulation phase of the modulation pixel 110 before the modulation task begins. For a modulation pixel 110 in an amplitude-type spatial light modulator 100, the target modulation state refers to the modulation amplitude that the modulation pixel 110 needs to achieve in the modulation task, and the current modulation state refers to the modulation amplitude of the modulation pixel 110 before the modulation task begins.

[0145] The target modulation state of the modulated pixel 110 can be directly obtained from the relevant parameters of the modulation task of the spatial light modulator 100 .

[0146] The current modulation state of the modulated pixel 110 can be obtained through the memory storage of the spatial light modulator 100. That is, during operation, the spatial light modulator 100 will record and update the modulation state of each modulated pixel 110 in the pixel array, so that the current modulation state can be directly read when it is needed.

[0147] The current modulation state of the modulation pixel 110 can also be obtained by optical measurement.

[0148] Step S200: controlling the light-emitting pixels in the modulation pixels to emit modulated light according to the difference between the target modulation state and the current modulation state.

[0149] Through step S100, the target modulation state and current modulation state of the modulation pixel 110 can be obtained. Based on the difference between the target modulation state and the current modulation state, the luminescent pixel 4 in the modulation pixel 110 can be controlled to emit modulated light. Under the irradiation of the modulated light, the liquid crystal portion in the modulation pixel 110 can change the liquid crystal molecular properties, thereby converting the modulation pixel 110 from the current modulation state to the target modulation state, completing the modulation task of the modulation pixel 110. During the modulation process of the modulation pixel 110, the transition time between the target modulation state and the current modulation state can also be controlled by controlling the luminescence time and luminescence intensity of the luminescent pixel 4. After the modulation task of the modulation pixel 110 is completed, the luminescent pixel 4 can be controlled to stop working. The liquid crystal portion in the modulation pixel 110 will maintain the converted modulation state until it is irradiated with new modulated light.

[0150] When all the modulated pixels 110 in the pixel array are converted to the target modulation state, the spatial light modulator 100 completes the modulation task.

[0151] In the case where the photosensitive liquid crystal is a photoresponsive cholesteric liquid crystal, the liquid crystal molecules in the photoresponsive cholesteric liquid crystal are arranged in a spiral structure, and the pitch of the spiral structure can be increased or decreased by irradiating the first modulated light and the second modulated light. Based on this, as shown in FIG17 , the above step S200 may include:

[0152] Step S210: Acquire a first pitch and a second pitch corresponding to a target modulation state and a current modulation state, respectively.

[0153] As described above, the relationship between the modulation amplitude, modulation phase, and pitch of the photoresponsive cholesteric liquid crystal to incident light can be calculated using a formula or obtained through experiments, simulations, etc. Therefore, the first and second pitches corresponding to the target modulation state and the current modulation state can be obtained, respectively.

[0154] In some embodiments, step S210 may include:

[0155] Based on the target modulation state and the current modulation state, a lookup table is queried; wherein the lookup table (abbreviated as LUT) records the correspondence relationship information between the modulation relationship and the pitch.

[0156] Step S220: controlling the light-emitting pixel to emit the first modulated light or the second modulated light according to the difference between the first pitch and the second pitch.

[0157] After obtaining the first pitch and the second pitch through step S210, the difference between the first pitch and the second pitch can be calculated. When the difference is greater than zero, it means that the pitch needs to be controlled to increase, so the light-emitting pixel 4 can be controlled to emit the first modulated light; when the difference is less than zero, it means that the pitch needs to be controlled to decrease, so the light-emitting pixel 4 can be controlled to emit the second modulated light.

[0158] The control method 200 will be exemplarily described below by taking the spatial light modulator 100 using a photoresponsive cholesteric liquid crystal for phase control as an example.

[0159] As shown in FIG18 , the control method 200 may include:

[0160] Step S10: Acquire the target phase and current phase of the modulated pixel.

[0161] The target phase of the modulated pixel 110 is is the phase that the modulated pixel 110 needs to reach during the phase modulation process. It can be directly obtained from the target phase diagram. When the phases of all modulated pixels 110 are modulated to the target phase After that, a target phase diagram that meets the modulation requirements can be formed.

[0162] The current phase of the modulated pixel 110 It is the actual phase of the modulated pixel 110 before the modulation operation begins; this phase can be obtained based on the storage information of the spatial light modulator 100, that is, the spatial light modulator 100 records and updates the phase of the modulated pixel 110 at any time during operation, so that the current phase of the modulated pixel 110 can be obtained.

[0163] The current phase of the modulated pixel 110 It can also be obtained through optical measurement and other methods.

[0164] Step S20: Acquire the corresponding first pitch and second pitch according to the target phase and the current phase.

[0165] From the above description, it can be known that the corresponding relationship between the modulation phase of the light-responsive cholesteric liquid crystal to the incident light and the pitch can be calculated by formula, or obtained by experiment, simulation, etc. and the current phase After that, the first pitch P_1 and the second pitch P_2 corresponding to the two can be obtained respectively.

[0166] In this embodiment, before the modulation operation begins, the relationship curve between pitch and modulation phase is calibrated by computational simulation and preliminary experiments for incident light of possible wavelengths, forming a lookup table that records the corresponding relationship between modulation phase and pitch. During the modulation operation, the phase corresponding to the target can be obtained by querying the lookup table according to the wavelength of the incident light. and the current phase Corresponding first pitch P_1 and second pitch P_2.

[0167] Step S30: controlling the light-emitting pixel to emit the first modulated light or the second modulated light according to the difference between the first pitch and the second pitch.

[0168] After obtaining the target phase through step S20 and the current phase After respectively corresponding the first pitch P_1 and the second pitch P_2, the pitch difference ΔP between the first pitch P_1 and the second pitch P_2 can be obtained, ΔP=P_1-P_2.

[0169] When the pitch difference ΔP is greater than 0, it indicates that the pitch needs to be increased. Based on the above description, it can be seen that the light-emitting pixel 4 can be controlled to emit the first modulated light. When the pitch difference ΔP is less than 0, it indicates that the pitch needs to be reduced. Based on the above description, it can be seen that the light-emitting pixel 4 can be controlled to emit the second modulated light. During the light control process, the light emission time and light intensity can also be controlled, and the change amplitude and change time of the pitch adjustment process can be controlled.

[0170] When the pitch variation reaches ΔP, the phase of the modulated pixel 110 is converted to the target phase, the modulation work is completed, and the light source layer 3 can be controlled to stop emitting light.

[0171] The present application also provides an optical modulation device, as shown in part (a) of FIG19 . The optical modulation device 300 includes the spatial light modulator 100 as described in the above embodiment, and an incident light source 310; the incident light source 310 is used to generate incident light that is irradiated onto the spatial light modulator 100. As shown in part (b) of FIG19 , in other embodiments, the optical modulation device 300 includes the spatial light modulator 100 as described in the above embodiment, and an optical transmission device 320; the optical transmission device 320 is used to receive the incident light and project the incident light onto the spatial light modulator 100. The above optical modulation device 300 can be used in the fields of optical communication scheduling and switching, optical metrology, optical imaging, laser processing, etc.

[0172] For example, the optical modulation device 300 can be a wavelength selective switch (WSS) used for optical communication scheduling and switching. The wavelength selective switch includes an optical fiber array and a spatial light modulator 100. The optical fiber array belongs to the optical transmission device 320 mentioned above. The incident light is irradiated to the spatial light modulator 100 through the optical fiber array. The spatial light modulator 100 can achieve deflection control of the incident light by modulating the incident light, thereby achieving the purpose of controlling the incident light to be emitted from the target port of the optical fiber array.

[0173] For another example, the light modulation device 300 may be a picture generation unit (PGU) for optical imaging. The PGU includes an illumination light source, a spatial light modulator 100, and a projection lens. The illumination light source provides an illumination beam for the spatial light modulator 100. The spatial light modulator 100 modulates the illumination beam to form imaging light containing image information, which is then projected to a target location via the projection lens. The illumination light source and illumination beam are referred to as the incident light source 310 and incident light, respectively, as described above.

[0174] The technical effects that can be achieved by the light modulation device 300 provided in the embodiment of the present application are the same as the technical effects that can be achieved by the spatial light modulator 100 in any of the above embodiments, and will not be repeated here.

[0175] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A spatial light modulator, characterized in that: include: A liquid crystal layer, wherein the material of the liquid crystal layer includes photosensitive liquid crystal, and the photosensitive liquid crystal modulates the incident light under the irradiation of modulated light; A light source layer, which is arranged on one side of the liquid crystal layer and includes a plurality of light-emitting pixels; the light-emitting pixels are used to generate the modulated light for irradiating the liquid crystal layer; as well as A first filter layer is disposed between the liquid crystal layer and the light source layer, and is used for transmitting the modulated light and reflecting the incident light.

2. The spatial light modulator according to claim 1, characterized in that The liquid crystal molecules of the photosensitive liquid crystal are arranged in a spiral structure; The modulated light emitted by the light-emitting pixel includes a first modulated light and a second modulated light; The pitch of the spiral structure in the photosensitive liquid crystal increases under the irradiation of the first modulated light; The pitch of the spiral structure in the photosensitive liquid crystal becomes smaller under the irradiation of the second modulated light.

3. The spatial light modulator according to claim 2, characterized in that The light-emitting pixel includes a first sub-pixel and a second sub-pixel arranged adjacent to each other in a direction parallel to the liquid crystal layer, the first sub-pixel is used to emit the first modulated light, and the second sub-pixel is used to emit the second modulated light; The first sub-pixel and the second sub-pixel each include a light emitting device and a pixel driving circuit; The light emitting device is at least one of a semiconductor laser, an organic light emitting diode, a quantum dot light emitting diode, a sub-millimeter light emitting diode and a micro light emitting diode; The pixel driving circuit is electrically connected to the light emitting device and is used to drive the light emitting device to emit light.

4. The spatial light modulator according to claim 2, characterized in that The light-emitting pixel comprises a light-emitting device and a pixel driving circuit, and the light-emitting device emits the first modulated light and the second modulated light under the driving of different driving signals; The pixel driving circuit is electrically connected to the light emitting device, and is used to drive the light emitting device to emit the first modulated light or the second modulated light.

5. The spatial light modulator according to any one of claims 1 to 4, characterized in that: The spatial light modulator further comprises a second filter layer; the second filter layer is arranged on a side of the liquid crystal layer away from the light source layer, and is used for transmitting the incident light and reflecting the modulated light.

6. The spatial light modulator according to any one of claims 1 to 5, characterized in that: The wavelength of the incident light is 1350nm to 1700nm, and the wavelength of the modulated light is 300nm to 650nm.

7. The spatial light modulator according to claim 1, wherein: The spatial light modulator further comprises an alignment layer, wherein the alignment layer is arranged between the light source layer and the filter layer; The alignment layer includes a plurality of light coupling structures, and the light coupling structures correspond to the light-emitting pixels one by one, and are used to couple the modulated light emitted by the light-emitting pixels to corresponding positions of the liquid crystal layer.

8. The spatial light modulator according to claim 7, characterized in that The optical coupling structure is a microlens, and the microlens protrudes from the light-emitting pixel toward the liquid crystal layer; Alternatively, the optical coupling structure is a light guide column, which is a columnar structure extending between the light-emitting pixel and the liquid crystal layer, and the material of the light guide column includes an optical waveguide material; Alternatively, the optical coupling structure is a closed retaining wall, the material of the closed retaining wall includes a light shielding material, the closed retaining wall is arranged around the light-emitting pixel, and surrounds a light channel extending between the light-emitting pixel and the liquid crystal layer.

9. The spatial light modulator according to any one of claims 1 to 8, characterized in that: The spatial light modulator further comprises a polarization selection layer, and the polarization selection layer is located on a side of the liquid crystal layer away from the first filter layer; The polarization orientation of the polarization selection layer is consistent with the polarization state of the modulation response of the liquid crystal layer.

10. The spatial light modulator according to claim 1, wherein: The photosensitive liquid crystal is a light-responsive blue phase liquid crystal. When the light-responsive blue phase liquid crystal is irradiated by the modulated light, the lattice constant and / or lattice direction of the liquid crystal changes.

11. The spatial light modulator according to claim 1, characterized in that: The photosensitive liquid crystal is a photoresponsive ferroelectric liquid crystal or a photoresponsive smectic liquid crystal.

12. A light modulation device, characterized in that: The light modulation device comprises: A spatial light modulator as claimed in any one of claims 1 to 11; and An incident light source, the incident light source is used to generate incident light to irradiate the spatial light modulator; Alternatively, the light modulation device comprises: A spatial light modulator as claimed in any one of claims 1 to 11; and An optical transmission device is used to receive incident light and project the incident light to the spatial light modulator.

13. A method for controlling a spatial light modulator, characterized in that: The spatial light modulator comprises a liquid crystal layer, a light source layer and a first filter layer, the material of the liquid crystal layer comprises photosensitive liquid crystal, and the photosensitive liquid crystal can modulate the incident light under the irradiation of modulated light; The light source layer is arranged on one side of the liquid crystal layer, and includes a plurality of light-emitting pixels; the light-emitting pixels are used to generate the modulated light irradiated to the liquid crystal layer; The first filter layer is disposed between the liquid crystal layer and the light source layer, and is used to transmit the modulated light and reflect the incident light; The spatial light modulator comprises a plurality of modulation pixels, wherein the modulation pixels comprise the light-emitting pixels and a liquid crystal portion of the liquid crystal layer corresponding to the light-emitting pixels; The control method comprises: Obtaining a target modulation state and a current modulation state of a modulated pixel; According to the difference between the target modulation state and the current modulation state, the light-emitting pixels in the modulation pixels are controlled to emit modulated light.

14. The control method according to claim 13, characterized in that: In the spatial light modulator, liquid crystal molecules in the photosensitive liquid crystal are arranged in a spiral structure; The modulated light emitted by the light-emitting pixel includes a first modulated light and a second modulated light; The pitch of the spiral structure in the photosensitive liquid crystal increases under the irradiation of the first modulated light; The pitch of the spiral structure in the photosensitive liquid crystal becomes smaller under the irradiation of the second modulated light; In the control method, controlling the light-emitting pixels in the modulated pixels to emit modulated light according to the difference between the target modulation state and the current modulation state includes: Acquire a first pitch and a second pitch corresponding to the target modulation state and the current modulation state respectively; According to the difference between the first pitch and the second pitch, the light-emitting pixel is controlled to emit the first modulated light or the second modulated light.

15. The control method according to claim 14, characterized in that: The acquiring of the first pitch and the second pitch corresponding to the target modulation state and the current modulation state respectively comprises: Based on the target modulation state and the current modulation state, querying a lookup table; The lookup table records the correspondence information between the modulation relationship and the pitch.

16. The control method according to claim 14 or 15, characterized in that: The spatial light modulator is a phase-type spatial light modulator. In the control method, the target modulation state and the current modulation state are the target phase and the current phase, respectively.

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