Spatial light modulator, control method and light modulation device

Abstract

The embodiment of the invention provides a spatial light modulator, a control method and a light modulation device, relates to the technical field of light regulation and control, and is used for solving the problem that in the related technology, liquid crystal on silicon cannot keep data under the condition of sudden power failure. 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 incident light under the irradiation of modulated light; the light source layer is arranged on one side of the liquid crystal layer and comprises a plurality of light-emitting pixels arranged in an array mode. The first filter layer is arranged between the liquid crystal layer and the light source layer, and the filter layer is used for transmitting modulated light and reflecting incident light. The spatial light modulator can be applied to a light modulation device.

Description

Technical Field

[0001] This application relates to the field of optical modulation technology, and in particular, to a spatial light modulator, a control method, and an optical modulation device. Background Art

[0002] A spatial light modulator (SLM for short) is a programmable device that modulates the spatial distribution of the phase, amplitude, polarization, coherence, etc. of light, and is widely used in fields such as optical communication scheduling and switching, optical metrology, optical imaging, and laser processing. Liquid Crystal on Silicon (LCoS for short) is a common spatial light modulator, which includes a CMOS (Complementary Metal Oxide Semiconductor) substrate, a transparent cover plate, and a liquid crystal layer. Among them, the CMOS substrate and the transparent cover plate are arranged opposite to each other, and the liquid crystal layer is arranged between the CMOS substrate and the transparent cover plate. During operation, the characteristics of the liquid crystal molecules are changed by applying an electric field to the liquid crystal layer, thereby realizing the function of modulating the light incident on the liquid crystal layer.

[0003] However, in Liquid Crystal on Silicon, there is a corresponding relationship between the modulation state of the liquid crystal layer for incident light and the applied electric field. When the applied electric field disappears or changes, the modulation state also changes. Therefore, in the face of a sudden power failure, the modulation state will change and it is impossible to maintain the data to keep the modulation state, belonging to a volatile spatial light modulator. Summary of the Invention

[0004] Embodiments of this application provide a spatial light modulator, a control method, and an optical modulation device, which are used to improve the problem that the Liquid Crystal on Silicon in the related art cannot retain data in the face of a sudden power failure.

[0005] To achieve the above object, the embodiments of this application adopt the following technical solutions:

[0006] In a first aspect, an embodiment of this application provides a spatial light modulator, which includes a liquid crystal layer, a light source layer, and a first filter layer. Among them, the material of the liquid crystal layer includes photosensitive liquid crystal, and the photosensitive liquid crystal can realize the modulation of incident light under the irradiation of modulation 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 modulation light and reflect incident light.

[0007] In the spatial light modulator provided by the embodiments of the present application, the liquid crystal layer uses photosensitive liquid crystal, and the photosensitive liquid crystal can modulate the incident light under the action of the modulating light; and after the liquid crystal layer completes the modulation, before being irradiated by new modulating light, its modulation state remains unchanged, so that the power supply to the light source layer can be stopped. Therefore, compared with the liquid crystal on silicon in the related art, the spatial light modulator in the embodiments of the present application can reduce the power supply time to the light source layer, that is, reduce the control power consumption time for controlling the liquid crystal layer, thereby achieving the purpose of reducing power consumption; and, the liquid crystal layer can maintain the modulation state before power failure when power failure occurs accidentally, and has the characteristic of non-volatility.

[0008] On the other hand, in the spatial light modulator provided by the embodiments of the present application, the size of the modulation pixel is affected by the light-emitting pixel. However, since the light-emitting pixel only needs to emit modulating light of a fixed wavelength and only needs to control the light-emitting time and light-emitting intensity; therefore, the light-emitting device and the pixel driving circuit are relatively simple, so that the size of the light-emitting pixel is small; furthermore, the size of the modulation pixel can also be small; thus, it is beneficial to the miniaturized design of the modulation pixel. Designed in this way, on the one hand, it can meet the requirements for extremely small pixels (less than 5 micrometers) in some scenarios; on the other hand, more modulation pixels can be arranged in the same area, realizing an increase in pixel density, which is beneficial to improving the performance of the spatial light modulator.

[0009] In addition, in the spatial light modulator provided by the embodiments of the present application, the modulation frequency is affected by the light source layer, and the upper limit of the light-emitting frequency of the light source layer is very high, which is beneficial to improving the modulation frequency of the spatial light modulator; for example, when using Micro LED as the light-emitting pixel, the response frequency of the Micro LED is in the GHz range, so that the upper limit of the modulation frequency of the spatial light modulator reaches the GHz range, and the response time is in the ns level, having obvious advantages.

[0010] In some embodiments, the liquid crystal molecules in the photosensitive liquid crystal are arranged in a helical structure; the modulating light emitted by the light-emitting pixel includes first modulating light and second modulating light; the pitch of the helical structure in the photosensitive liquid crystal becomes larger under the irradiation of the first modulating light; the pitch of the helical structure in the photosensitive liquid crystal becomes smaller under the irradiation of the second modulating light.

[0011] In the spatial light modulator provided by the embodiments of the present application, a photosensitive chiral liquid crystal with a helical structure in which the liquid crystal molecules are arranged and the pitch of the helical structure is adjustable under the action of the modulating light can be selected as the photosensitive liquid crystal, such as a photo-responsive cholesteric liquid crystal, and the modulation of the incident light is realized by controlling the pitch in the helical structure with the modulating light.

[0012] 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 the first modulating light, and the second sub-pixel is used to emit the second modulating light.

[0013] Both the first sub-pixel and the second sub-pixel 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 submillimeter 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.

[0014] In the spatial light modulator provided in the embodiment of the present application, the light-emitting pixel emits first modulation light and second modulation light through two independent sub-pixels respectively; such a design is beneficial to the arrangement and formation of the light-emitting pixel and is also beneficial to the light emission control of the light-emitting pixel. In addition, the light-emitting pixel can select a variety of different pixel structures, has good adaptability, and can match different application scenarios and manufacturing processes.

[0015] In some embodiments, the light-emitting pixel includes a light-emitting device and a pixel driving circuit. The light-emitting device emits first modulation light and second modulation light under the drive of different drive signals; the pixel driving circuit is electrically connected to the light-emitting device and is used to drive the light-emitting device to emit first modulation light or second modulation light. Such a design can make the emission positions of the first modulation light and the second modulation light in the light-emitting pixel coincide, and also make the irradiation positions of the first modulation light and the second modulation light emitted by the same light-emitting pixel on the liquid crystal layer coincide, so that the light regulation is more precise. And it is beneficial to reduce the occupied area of the light-emitting pixel, thereby facilitating the reduction of the pixel size of the modulation pixel and facilitating the miniaturized design of the modulation pixel; enabling the spatial light modulator adopting the above design to adapt to the application scenario of extremely small pixels.

[0016] In some embodiments, the spatial light modulator further includes a second filter layer; the second filter layer is disposed on the side of the liquid crystal layer away from the light source layer and is used to transmit incident light and reflect modulation light. Such a design can avoid the modulation light from being emitted together with the reflected incident light and avoid the interference of the modulation light on the incident light.

[0017] In some embodiments, the wavelength of the incident light is 1350 nm to 1700 nm, and the wavelength of the modulation light is 300 nm to 650 nm. The incident light and the modulation light select different wavelengths, and the wavelength difference between the two is large. Such a design can better achieve the band-pass selection effect of the first filter layer and at the same time reduce the selection difficulty and cost of the first filter layer.

[0018] 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 includes a plurality of optical coupling structures, and the optical coupling structures correspond to the light-emitting pixels one by one, and are configured to couple the modulated light emitted by the light-emitting pixels to corresponding positions of the liquid crystal layer. By providing the alignment layer with optical coupling structures, the modulation position of the modulated light on the liquid crystal layer can be precisely controlled; moreover, the divergence angle of the modulated light can also be controlled, reducing edge light leakage and improving the focusing efficiency.

[0019] In some embodiments, the optical coupling structure is a microlens that protrudes from the light-emitting pixel toward the liquid crystal layer; alternatively, the optical coupling structure is a light guide column, and the light guide column 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 barrier, and the material of the closed barrier includes a light-shielding material, and the closed barrier is disposed around the light-emitting pixel and surrounds to form a light channel extending between the light-emitting pixel and the liquid crystal layer.

[0020] In the spatial light modulator provided in the embodiments of the present application, the optical coupling structures in the alignment layer can select various different types of structures, with good adaptability, and can match different application scenarios and manufacturing processes.

[0021] In some embodiments, the spatial light modulator further includes a polarization selection layer located on the 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. Such a design can play a role in polarization filtering, which is beneficial to improving the modulation efficiency of the spatial light modulator for incident light.

[0022] In some embodiments, the photosensitive liquid crystal is a light-responsive blue phase liquid crystal, and under the irradiation of the modulated light, the lattice constant and / or the lattice direction of the light-responsive blue phase liquid crystal change.

[0023] In the spatial light modulator provided in the embodiments of the present application, a light-responsive blue phase liquid crystal can be selected as the photosensitive liquid crystal, and by utilizing the special optical properties of the light-responsive blue phase liquid crystal and controlling the lattice constant and / or the lattice direction through the modulated light, the modulation of the incident light can be achieved.

[0024] In some embodiments, the photosensitive liquid crystal is a light-responsive ferroelectric liquid crystal or a light-responsive 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 select various different types of liquid crystals, with good adaptability, and can match different application scenarios and manufacturing processes.

[0025] In a second aspect, embodiments of the present application also provide an optical modulation device, which includes a spatial light modulator as described in the embodiments of the first aspect, and an incident light source; the incident light source is configured to generate incident light that irradiates the spatial light modulator. Alternatively, the optical modulation device includes a spatial light modulator as described in the embodiments of the first aspect, and an optical transmission device; the optical transmission device is configured to receive the incident light and project the incident light onto the spatial light modulator.

[0026] The technical effects that can be achieved by the optical modulation device provided in the embodiments of the present application are the same as those that can be achieved by the spatial light modulator in any of the above embodiments, and will not be elaborated here.

[0027] In a third aspect, embodiments of the present application further provide a control method for a spatial light modulator. 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 incident light under the irradiation of modulation light; the light source layer is disposed on one side of the liquid crystal layer and includes a plurality of light-emitting pixels; the light-emitting pixels are configured to generate modulation light that irradiates the liquid crystal layer; the first filter layer is disposed between the liquid crystal layer and the light source layer, and the filter layer is configured to transmit the modulation light and reflect the incident light.

[0028] The spatial light modulator includes a plurality of modulation pixels, and each modulation pixel includes a light-emitting pixel and a liquid crystal portion of the liquid crystal layer corresponding to the light-emitting pixel.

[0029] The control method includes:

[0030] Obtaining the target modulation state and the current modulation state of the modulation pixel;

[0031] According to the difference between the target modulation state and the current modulation state, controlling the light-emitting pixel in the modulation pixel to emit modulation light.

[0032] In some embodiments, in the spatial light modulator, the liquid crystal molecules in the photosensitive liquid crystal are arranged in a helical structure.

[0033] The modulation light emitted by the light-emitting pixel includes first modulation light and second modulation light; the pitch of the helical structure in the photosensitive liquid crystal becomes larger under the irradiation of the first modulation light; the pitch of the helical structure in the photosensitive liquid crystal becomes smaller under the irradiation of the second modulation light.

[0034] In the control method, according to the difference between the target modulation state and the current modulation state, controlling the light-emitting pixel in the modulation pixel to emit modulation light includes:

[0035] Obtaining a first pitch and a second pitch respectively corresponding to the target modulation state and the current modulation state;

[0036] According to the difference between the first pitch and the second pitch, controlling the light-emitting pixel to emit the first modulation light or the second modulation light.

[0037] In some embodiments, obtaining a first pitch and a second pitch corresponding to a target modulation state and a current modulation state respectively includes:

[0038] Querying a look-up table based on the target modulation state and the current modulation state;

[0039] Wherein, the look-up table records the correspondence information between the modulation relationship and the pitch.

[0040] In some embodiments, 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A front view of a liquid crystal on silicon provided for the related art;

[0042] Figure 2 A cross-sectional view of a liquid crystal on silicon provided for the related art;

[0043] Figure 3 A schematic structural diagram of a spatial light modulator provided by an embodiment of the present application;

[0044] Figure 4 A schematic structural diagram of a light-responsive cholesteric liquid crystal provided by an embodiment of the present application;

[0045] Figure 5 A relationship curve graph of modulation amplitude - pitch generated by the light-responsive cholesteric liquid crystal provided by an embodiment of the present application for incident light of 1550 nm;

[0046] Figure 6 A relationship curve graph of modulation phase - pitch generated by the light-responsive cholesteric liquid crystal provided by an embodiment of the present application for incident light of 1550 nm;

[0047] Figure 7 A schematic diagram of the formation principle of a phase diagram provided by an embodiment of the present application;

[0048] Figure 8 A schematic structural diagram of a spatial light modulator provided by an embodiment of the present application;

[0049] Figure 9 A schematic structural diagram of a light-emitting pixel provided by an embodiment of the present application;

[0050] Figure 10 A schematic structural diagram of another spatial light modulator provided by an embodiment of the present application;

[0051] Figure 11 A schematic structural diagram of a light-emitting pixel in yet another spatial light modulator provided by an embodiment of the present application;

[0052] Figure 12 Schematic diagram of another spatial light modulator provided by an embodiment of the present application;

[0053] Figure 13 Schematic diagram of yet another spatial light modulator provided by an embodiment of the present application;

[0054] Figure 14 Schematic diagram of yet another spatial light modulator provided by an embodiment of the present application;

[0055] Figure 15 Schematic diagram of yet another spatial light modulator provided by an embodiment of the present application;

[0056] Figure 16 Flowchart of a control method for a spatial light modulator provided by an embodiment of the present application;

[0057] Figure 17 Flowchart of another control method for a spatial light modulator provided by an embodiment of the present application;

[0058] Figure 18 Flowchart of another control method for a spatial light modulator provided by an embodiment of the present application;

[0059] Figure 19 Schematic diagram of the structure of an optical modulation device provided by an embodiment of the present application. Detailed implementation manners

[0060] A spatial light modulator (Spatial Light Modulator, abbreviated as SLM) is a programmable device that can regulate the spatial distribution of the phase, amplitude, polarization, coherence, etc. of light; it is widely used in fields such as optical communication scheduling and switching, optical metrology, optical imaging, and laser processing. The spatial light modulator includes a one-dimensional or two-dimensional pixel array composed of multiple modulation pixels, and each modulation pixel can be controlled by a signal. When a beam of incident light irradiates the spatial light modulator, these modulation pixels will divide the incident light into several parts, and control each modulation pixel to control the corresponding part of the incident light, thereby changing the spatial distribution of the incident light.

[0061] Liquid Crystal on Silicon (abbreviated as LCoS), also known as liquid crystal on silicon, is a common spatial light modulator. Figure 1 Front view of a liquid crystal on silicon 100A provided by the related art, as Figure 1 shown, the liquid crystal on silicon 100A includes a pixel array, and the pixel array includes a plurality of modulation pixels (Pixel) 110 arranged in a multi-row and multi-column array, so as to Figure 1Taking the orientation shown as an example, the row direction of the pixel array is the horizontal direction, and the column direction is the vertical direction.

[0062] Figure 2 FIG. is a cross-sectional view of a liquid crystal on silicon 100A provided by the related art. As Figure 2 shown, the liquid crystal on silicon 100A includes a CMOS (Complementary Metal Oxide Semiconductor) substrate 103, a liquid crystal layer 102, and a transparent cover plate 101. Among them, the CMOS substrate 103 and the transparent cover plate 101 are disposed opposite to each other, and the liquid crystal layer 102 is disposed between the relatively disposed CMOS substrate 103 and the transparent cover plate 101.

[0063] The CMOS substrate 103 includes a pixel circuit and a metal mirror. The pixel circuit is formed by using a CMOS process on a silicon wafer. After the pixel circuit is fabricated, the silicon wafer is polished by a grinding technique and plated with a metal layer serving as a metal mirror. The metal mirror is usually prepared from metal aluminum to reflect incident light. The pixel circuit in the CMOS substrate 103 includes a pixel driving circuit corresponding to the modulation pixel 110, and the pixel driving circuit includes a first electrode 105. The transparent cover plate 101 is provided with a second electrode 104 on a side close to the CMOS substrate 103.

[0064] When the liquid crystal on silicon 100A having the above structure operates, 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 and the second voltage are different, 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 characteristics of the liquid crystal molecules in the part of the liquid crystal layer 102 between the first electrode 105 and the second electrode 104 will change, so that the light passing through this liquid crystal part can be modulated.

[0065] For the phase-type liquid crystal on silicon 100A, under the action of the electric field, the liquid crystal molecules in the part of the liquid crystal layer 102 between the first electrode 105 and the second electrode 104 will deflect, and the deflection angle is related to the voltage difference between the first voltage and the second voltage. Due to the birefringence effect of the liquid crystal molecules, the deflection of the liquid crystal molecules will generate a certain amount of phase delay; moreover, different deflection angles correspond to different amounts of phase delay. Therefore, the phase modulation of light can be achieved by applying different voltage differences between the first electrode 105 and the second electrode 104.

[0066] From the above description of the liquid crystal on silicon 100A, it can be known that the liquid crystal on silicon 100A realizes the modulation of light by applying an electric field to the liquid crystal layer 102. There is a corresponding relationship between the applied electric field and the modulation state. When the applied electric field disappears or changes, the modulation state also changes. In addition, due to the working characteristics of the liquid crystal, it is necessary to use an AC power supply for control. Therefore, the pixel circuit in the liquid crystal on silicon 100A uses a level inversion driving method to control the liquid crystal layer 102, and the voltage values applied to the first electrode 105 and the second electrode 104 need to be continuously refreshed during the driving process.

[0067] For the above reasons, the liquid crystal on silicon 100A in the related technology has at least the following deficiencies:

[0068] On the one hand, when the related technology liquid crystal on silicon 100A faces a sudden power failure, the modulation state will change, so that it cannot maintain the data to work normally, and it belongs to a volatile spatial light modulator 100. On the other hand, in order to maintain the current modulation state, the liquid crystal on silicon 100A needs to maintain the voltage difference between the first electrode 105 and the second electrode 104 unchanged during the continuous refreshing driving process; this leads to the problem of high device power consumption of the liquid crystal on silicon 100A. On the other hand, in order to maintain the voltage difference between the first electrode 105 and the second electrode 104 unchanged during the continuous refreshing driving process, a complex pixel driving circuit needs to be set; and the complex pixel driving circuit will lead to an increase in the occupied area, thus restricting the reduction of the modulation pixel 110 in the liquid crystal on silicon 100A, which is not conducive to the miniaturization of the modulation pixel 110 and is difficult to meet the requirements for extremely small pixels (less than 5 micrometers) in some scenarios.

[0069] Based on this, the embodiments of the present application provide a spatial light modulator, a control method and an optical modulation device to improve the above problems.

[0070] Next, the technical solutions in the embodiments of the present application will be described with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0071] Hereinafter, in the embodiments of the present application, the terms "first", "second", etc. are only for convenience of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more.

[0072] In the embodiments of the present application, the terms "upper", "lower", "left", and "right" are not limited to being defined based on the orientation of the components shown in the drawings. It should be understood that these directional terms can be relative concepts, which are used for relative description and clarification, and they can change accordingly with the change of the orientation of the components shown in the drawings.

[0073] In the embodiments of the present application, unless otherwise required by the context, throughout the specification and claims, the term "comprising" is interpreted as an open and inclusive meaning, 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", etc. are intended to indicate that the specific features, structures, materials or characteristics related to the embodiment or example are included in at least one embodiment or example of the present application. The schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics can be included in any one or more embodiments or examples in any appropriate manner.

[0074] As used herein, "about", "substantially" or "approximately" includes the stated value and the average value within an acceptable deviation range of the specific value, where the acceptable deviation range is determined by those of ordinary skill in the art considering the measurement being discussed and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system).

[0075] As used herein, "parallel", "perpendicular", "equal" include the stated situation and situations similar to the stated situation, and the range of the similar situations is within an acceptable deviation range, where the acceptable deviation range is determined by those of ordinary skill in the art considering the measurement being discussed and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallel and approximate parallel, and the acceptable deviation range of approximate parallel can be, for example, within 5° deviation; "perpendicular" includes absolute perpendicular and approximate perpendicular, and the acceptable deviation range of approximate perpendicular can also be, for example, within 5° deviation. "Equal" includes absolute equality and approximate equality, and the acceptable deviation range of approximate equality can be, for example, that the difference between the two equal values is less than or equal to 5% of either one of them.

[0076] It should be understood that when a layer or element is referred to as being on another layer or substrate, it can be that the layer or element is directly on the other layer or substrate, or there can also be an intermediate layer between the layer or element and the other layer or substrate.

[0077] 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 enlarged for clarity. Therefore, variations in the shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances can be envisioned. Thus, the exemplary embodiments should not be construed as being limited to the shapes of the regions shown herein, but include shape deviations caused by, for example, manufacturing. For example, an etched region shown as rectangular will generally have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shape of the regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0078] Embodiments of the present application provide a spatial light modulator 100, as Figure 3 shown, 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 configured to receive incident light incident from a side away from the substrate 2 and, by controlling changes in the characteristics of liquid crystal molecules, achieve the effect of modulating the incident light; 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.

[0079] In the spatial light modulator 100 provided by the embodiments of the present application, the liquid crystal material of the liquid crystal layer 102 is a photosensitive liquid crystal, and a photosensitive liquid crystal 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 incident light can be modulated by irradiating the liquid crystal layer 102 with modulated light.

[0080] In some embodiments, the photosensitive liquid crystal can be a photosensitive chiral liquid crystal, and the photosensitive chiral liquid crystal can be formed by adding a photo-responsive chiral molecule to the liquid crystal. The photo-responsive chiral molecule includes a chiral center and a photo-responsive group (also known as a photoswitch, Photoswitch). The chiral center transfers the molecular chirality to the liquid crystal, inducing the self-assembly of liquid crystal molecules to form a helical structure. The photo-responsive group can undergo a photoisomerization reaction under the stimulation of modulated light, changing the spatial structure of the chiral molecule, thereby changing the characteristics of the helical structure, such as the pitch and the helical direction, to achieve the modulation of the incident light.

[0081] Hereinafter, taking a photo-responsive cholesteric liquid crystal as an example, the working principle of the photosensitive chiral liquid crystal will be exemplarily described. Obviously, the spatial light modulator 100 provided by the embodiments of the present application is not limited to using a photo-responsive cholesteric liquid crystal. Any photosensitive chiral liquid crystal that can change the characteristics of the helical structure by irradiating with modulated light to achieve the modulation of the incident light can be used, such as ferroelectric nematic liquid crystal, twisted grain boundary phase liquid crystal, and smectic liquid crystal, etc.

[0082] The cholesteric phase is a type of liquid crystal phase. Cholesteric liquid crystal, also known as chiral nematic liquid crystal, is a kind of "soft" photonic crystal with a periodic helical structure.

[0083] As Figure 4 shown, in cholesteric liquid crystal, the liquid crystal molecules self-assemble into layers. Inside the layer, the liquid crystal molecules are arranged parallel to each other in a certain direction, and the long axis of the molecules is parallel to the layer plane. Between adjacent layers, the liquid crystal molecules rotate by a certain angle (about 15°) along the layer normal direction, thus forming a periodic helical structure. The pitch (abbreviated as p) and the handedness are two important parameters characterizing the helical structure in cholesteric liquid crystal. Among them, the pitch refers to the layer spacing in the helical structure where the orientation of the liquid crystal molecules rotates 360° along the helical axis; the handedness refers to the direction of the rotation of the interlayer molecules in the helical structure, which is divided into left-handed helix and right-handed helix.

[0084] This self-assembled periodic helical structure of cholesteric liquid crystal, similar to a one-dimensional photonic crystal, can produce the following unique optical properties. On the one hand, the periodic helical structure will produce Bragg reflection, thus enabling selective reflection of incident light; only the incident light within the reflection window can be reflected. On the other hand, cholesteric liquid crystal can selectively reflect circularly polarized light with the same helical direction as itself; that is, the right-handed helical cholesteric liquid crystal only reflects right-handed circularly polarized light, and the left-handed helical cholesteric liquid crystal only reflects left-handed circularly polarized light. That is to say, the helical direction of the helical structure in cholesteric liquid crystal determines the circular polarization of the reflected light.

[0085] Light-responsive cholesteric liquid crystal refers to cholesteric liquid crystal whose helical structure pitch can be induced to change under the stimulation of an external light source. Adding light-responsive chiral molecules to nematic liquid crystal is a common method for preparing light-responsive cholesteric liquid crystal. The light-responsive chiral molecules undergo a photoisomerization reaction under the stimulation of light with a specific wavelength, changing the spatial structure of the chiral molecules, thereby achieving the purpose of changing the pitch in cholesteric liquid crystal.

[0086] In this article, the light that can cause the pitch change in light-responsive cholesteric liquid crystal is called modulation light. The modulation light includes a first modulation light and a second modulation light with different wavelengths. Among them, as Figure 4 shown, when the light-responsive cholesteric liquid crystal is irradiated with the first modulation light, the pitch of its helical structure will become larger, and the greater the irradiation dose, the greater the amplitude of the pitch increase. When the light-responsive cholesteric liquid crystal is irradiated with the second modulation light, the pitch of its helical structure will become smaller, and the greater the irradiation dose, the greater the amplitude of the pitch decrease.

[0087] For different light-responsive cholesteric liquid crystals, the first modulation light is usually different, and the second modulation light is usually different; the first modulation light and the second modulation light with appropriate wavelengths can be selected according to the actually used light-responsive cholesteric liquid crystal to control the pitch.

[0088] By controlling the pitch, the light-responsive cholesteric liquid crystal can achieve the purpose of moving the reflection window of Bragg reflection; by moving the reflection window, amplitude modulation of the incident light and phase modulation of the incident light can be achieved.

[0089] Combined with the above description, it can be known that cholesteric liquid crystals 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), the central wavelength λ of the reflection window of Bragg reflection is directly related to the pitch p of the helical structure; therefore, the light-responsive cholesteric liquid crystal can move the reflection window of Bragg reflection by changing the pitch.

[0090] In the reflection window, the reflectivities of reflected lights with different wavelengths are different. The incident light with the same wavelength can be in different reflection windows, and the reflectivities are different when reflected in different reflection windows. Therefore, the light-responsive cholesteric liquid crystal can change the amplitude of the incident light while moving the reflection window of Bragg reflection by changing the pitch, so as to achieve amplitude modulation of the incident light.

[0091] In addition, there is also a spin-orbit coupling effect in cholesteric liquid crystals. The reflected light of Bragg reflection is given a geometric phase related to the arrangement of the helical axis. The reflection phases of reflected lights with different wavelengths in the reflection window are different; the incident light with the same wavelength can be in different reflection windows, and the reflection phases are different when reflected in different reflection windows. Therefore, the light-responsive cholesteric liquid crystal can change the reflection phase of the incident light while moving the reflection window of Bragg reflection by changing the pitch, so as to achieve phase modulation of the incident light.

[0092] The relationships between the modulation amplitude, modulation phase of the incident light and the pitch of the light-responsive cholesteric liquid crystal can be obtained by calculation according to the formula, or can be obtained by means such as experiments and simulations. Figure 5 This is the relationship curve graph of modulation amplitude - pitch generated by the light-responsive cholesteric liquid crystal provided by the embodiment of the present application for incident light of 1550 nm. Figure 6 This is the relationship curve graph of modulation phase - pitch generated by the light-responsive cholesteric liquid crystal provided by the embodiment of the present application for incident light of 1550 nm; it should be noted that although Figure 5 and Figure 6It is a relationship curve generated for incident light at 1550 nm. However, for incident light of other wavelengths, the change trend is basically the same. Therefore, based on this, the relationship characteristics among the modulation amplitude, modulation phase, and pitch of the light-responsive cholesteric liquid crystal for incident light can be obtained.

[0093] As can be seen Figure 5 from it, in the middle section of the modulation amplitude-pitch relationship curve, the modulation amplitude is basically in a constant state with the change of the pitch. In the parts on both sides before and after the middle section, the modulation amplitude changes with the change of the pitch. In some pitch change intervals, the modulation amplitude can change from 0 to 1; and the corresponding relationship between the modulation amplitude and the pitch can be established. Therefore, the parts on both sides of the relationship curve can be used for amplitude modulation.

[0094] As can be seen Figure 6 from the shown modulation phase-pitch relationship curve, the modulation phase changes with the change of the pitch. In some pitch change intervals, the modulation phase can change within the range of 2π; thus, the corresponding relationship between the modulation phase and the pitch can be established, and based on this, the purpose of changing the modulation phase by modulating the pitch can be achieved.

[0095] Combining Figure 5 and Figure 6 it can be seen that in the middle section of the modulation amplitude-pitch relationship curve, the modulation amplitude is basically in a constant state with the change of the pitch; during the same pitch change process, the modulation phase changes gently with the pitch, and the change interval is from -π to π; therefore, based on this change characteristic, the decoupling of amplitude modulation and phase modulation can be achieved, forming a phase-type spatial light modulator 100 with pure phase modulation, and a phase modulation depth of 2π can be achieved.

[0096] In the following description, the phase-type spatial light modulator 100 formed by using the light-responsive cholesteric liquid crystal will be taken as an example to illustrate the solution exemplarily. It can be known from the above description that the modulation light is used to change the pitch of the light-responsive cholesteric liquid crystal; combining the relationship between the modulation phase and the pitch, the relationship between the modulation light and the modulation phase can be obtained as:

[0097] When the light-responsive cholesteric liquid crystal is irradiated with the first modulation light, the pitch will increase and the modulation phase will also increase; and the greater the irradiation dose, the greater the change amplitudes of the pitch and the modulation phase. When the light-responsive cholesteric liquid crystal is irradiated with the second modulation light, the pitch will decrease and the modulation phase will also decrease; and the greater the irradiation dose, the greater the decrease amplitudes of the pitch and the modulation phase.

[0098] It can be seen from this that the light-responsive cholesteric liquid crystal can achieve phase modulation of incident light by controlling the pitch under the action of the modulation light.

[0099] When the spatial light modulator 100 is operating, a phase map with a specific phase distribution can be formed by loading specific phases at different positions of the liquid crystal layer 102. Different functions can be achieved through different phase maps. For example, as Figure 7 shown, by periodically loading a phase map with a 0-2π phase distribution, the function of a blazed grating can be achieved, and the deflection of the light beam can be controlled through the blazed grating.

[0100] Please refer to Figure 3 and Figure 8 , in the spatial light modulator 100 provided by the embodiments of the present application, a light source layer 3 is provided 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, and here the plurality of light-emitting pixels 4 can be arranged in an array to form a one-dimensional array or a two-dimensional array.

[0101] Each light-emitting pixel 4 can generate modulated light that irradiates the liquid crystal layer 102. The characteristics of the liquid crystal molecules in the part of the liquid crystal layer 102 irradiated by the modulated light will change, so as to achieve the purpose of modulating the incident light. Moreover, different light-emitting pixels 4 correspond to different regions in the liquid crystal layer 102, and a part of the corresponding regions of the light-emitting pixels 4 and the liquid crystal layer 102 together form a modulation pixel 110 in the spatial light modulator 100.

[0102] 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.

[0103] 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. Among them, the light-emitting layer 31 includes light-emitting devices for forming the light-emitting pixels 4, and the light-emitting devices can be LD (Laser Diode, semiconductor laser), OLED (Organic Light-Emitting Diode, organic light-emitting diode), QLED (Quantum Dot Light Emitting Diodes, quantum dot light-emitting diode), Mini LED (sub-millimeter light-emitting diode) or Micro LED (micro light-emitting diode), etc.; the embodiments of the present application do not limit the type of the light-emitting device.

[0104] 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 form a light-emitting pixel 4.

[0105] In some other embodiments, the light source layer 3 may also adopt a liquid crystal display (LCD), that is, the modulated light is provided for the liquid crystal layer 102 through the liquid crystal display.

[0106] According to the above description, in this embodiment, the liquid crystal layer 102 adopts a light-responsive cholesteric liquid crystal. Under the irradiation of the first modulated light and the first modulated light, the light-responsive cholesteric liquid crystal can achieve the control of the pitch. Correspondingly, the light-emitting pixel 4 in the light source layer 3 is a pixel structure capable of emitting the first modulated light and the second modulated light.

[0107] As Figure 9 shown, in this embodiment, the light-emitting 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 the second direction, and the second direction is 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 used to emit the first modulated light, and the second sub-pixel 42 is used to emit the second modulated light. When the spatial light modulator 100 works, the first modulated light or the second modulated light irradiated on the liquid crystal layer 102 can be generated by controlling the operation of the first sub-pixel 41 or the second sub-pixel 42 in the light-emitting pixel 4, so as to achieve the control of the pitch in the light-responsive cholesteric liquid crystal; and, the light dose of the first modulated light or the second modulated light can also be adjusted by controlling the light-emitting intensity and light-emitting time of the first sub-pixel 41 and the second sub-pixel 42, so as to achieve the regulation of the pitch change amplitude in the light-responsive cholesteric liquid crystal.

[0108] It should be noted that for a light-emitting pixel 4, only the first modulated light or the second modulated light can be emitted at the same time, and the first modulated light and the second modulated light cannot be emitted simultaneously. For the entire spatial light modulator 100, the light-emitting states of different light-emitting pixels 4 are independent of each other at the same time. Some light-emitting pixels 4 may emit the first modulated light, and some light-emitting pixels 4 may emit the second modulated light.

[0109] According to the above description, the spatial light modulator 100 simultaneously includes incident light and modulated light irradiated on the liquid crystal layer 102. The incident light irradiates the liquid crystal layer 102 on the side away from the substrate 2, and the modulated light irradiates the liquid crystal layer 102 on the side close to the substrate 2. In order to achieve the independent regulation and isolation of the incident light and the modulated light, as Figure 3 and Figure 8 shown, a first filter layer 1 is also provided in the spatial light modulator 100 provided by the embodiment of the present application.

[0110] The first filter layer 1 is a band-pass selective filter layer, which has the characteristic of 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, closely disposed on the side of the liquid crystal layer 102 close to the light source layer 3. The first filter layer 1 can efficiently reflect (for example, the reflectivity is above 85%) the incident light, and the reflectivity reaches above 85%; and efficiently transmit (for example, the transmittance is above 85%) the modulated light emitted by the light source layer 3.

[0111] In order to better achieve the band-pass selection effect of the first filter layer 1 and at the same time reduce the difficulty of selecting the first filter layer 1, the incident light and the modulated light should be selected with different wavelengths, and the wavelength difference between the two should be as large as possible. For example, the wavelength of the incident light is from 1350 nm to 1700 nm, and the wavelength of the modulated light is from 300 nm to 650 nm.

[0112] In this embodiment, the incident light can be selected as infrared light, and the first modulated light and the second modulated light can be selected as ultraviolet light.

[0113] In some embodiments, as Figure 10 shown, the spatial light modulator 100 further includes a second filter layer 5. The second filter layer 5 is disposed on the side of the liquid crystal layer 102 away from the substrate 2, for example, closely disposed on the side of the liquid crystal layer 102 away from the light-emitting layer 31. The second filter layer 5 can efficiently reflect (for example, the reflectivity is above 85%) the modulated light and efficiently transmit (for example, the transmittance is above 85%) the incident light modulated by the liquid crystal layer 102. By providing the second filter layer 5, the modulated light can be prevented from exiting together with the modulated incident light, which is beneficial to improving the modulation effect and optical performance of the spatial light modulator 100.

[0114] Please continue to refer to Figure 3 、 Figure 8 and Figure 10 , the spatial light modulator 100 provided by the embodiment of the present application further includes a substrate 2. The substrate 2 is disposed on the side of the light source layer 3 away from the liquid crystal layer 102, and is a plate-like structure perpendicular to the first direction, for carrying other structures disposed above; and can also play a heat dissipation effect. Exemplarily, the substrate 2 can be a ceramic substrate 2 such as alumina or aluminum nitride.

[0115] In the spatial light modulator 100 having the above structure, a liquid crystal layer 102 and a light source layer 3 are included; the liquid crystal layer 102 employs a light-responsive cholesteric liquid crystal, and the light source layer 3 can generate modulated light acting on the light-responsive cholesteric liquid crystal; under the irradiation of the modulated light, the liquid crystal layer 102 can realize the phase modulation function of incident light. By controlling the light emission of the light-emitting pixels 4 in the light source layer 3, a phase map with a specific phase distribution can be formed in the liquid crystal layer 102, that is, the function of phase programming is realized; the spatial light modulator 100 can realize different functions by loading different phase maps.

[0116] Since the liquid crystal layer 102 employs a light-responsive cholesteric liquid crystal, after the phase map is loaded, before being irradiated by new modulated light, the phase map will remain unchanged, so that the power supply to the light source layer 3 can be stopped. Designed in this way, compared with the liquid crystal on silicon 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 for controlling the liquid crystal layer 102, thereby achieving the purpose of reducing power consumption; moreover, the liquid crystal layer 102 can maintain the phase map before power failure when power failure occurs accidentally, so that the modulation state can be maintained unchanged, having the characteristic of non-volatility.

[0117] On the other hand, as can be seen from the above description, due to the complex pixel driving circuit in the liquid crystal on silicon 100A in the related art, the modulation pixels 110 cannot be made very small, so it is difficult to meet the requirements for extremely small pixels (less than 5 micrometers) 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 modulation pixels 110 is affected by the light-emitting pixels 4. However, since the light-emitting pixels 4 only need to emit modulated light of a fixed wavelength and only need to control the light emission time and light emission intensity; therefore, the light-emitting device and the pixel driving circuit are relatively simple, so that the size of the light-emitting pixels 4 is small; furthermore, the size of the modulation pixels 110 can also be small; thus, it is beneficial to the miniaturization design of the modulation pixels 110. Designed in this way, on the one hand, it can meet the requirements for extremely small pixels (less than 5 micrometers) in some scenarios; on the other hand, more modulation pixels 110 can be arranged in the same area, increasing the pixel density, thereby being beneficial to improving the performance of the spatial light modulator 100.

[0118] In addition, the liquid crystal on silicon 100A in the related art needs to use a level inversion driving method to control the liquid crystal layer 102. However, this driving method restricts the improvement of the modulation frequency. For example, the modulation frequency of the liquid crystal on silicon 100A in the related art is generally about 100 Hz and will not exceed 200 Hz. In the spatial light modulator 100 provided in the embodiments 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 using a Micro LED as the light-emitting pixel 4, the response frequency of the Micro LED is in the GHz order of magnitude. Therefore, the upper limit of the modulation frequency of the spatial light modulator 100 reaches the GHz order of magnitude, and the response time is in the ns level, which has obvious advantages.

[0119] The embodiments of the present application also provide a schematic structural diagram of another spatial light modulator 100. The difference between this spatial light modulator 100 and the spatial light modulator 100 in the above embodiments lies in the light-emitting pixel 4. As Figure 11 shown, in this embodiment, the light-emitting device in the light-emitting pixel 4 adopts a pixel structure capable of being controlled to emit first modulation light and second modulation light with different wavelengths, such as a stacked Micro LED light-emitting chip. Different driving signals are input to the light-emitting device through the pixel driving circuit to control the light-emitting device to emit first modulation light and second modulation light with different wavelengths. With such a design, the emission positions of the first modulation light and the second modulation light in the light-emitting pixel 4 can be made to coincide, and the irradiation positions of the first modulation light and the second modulation light emitted by the same light-emitting pixel 4 on the liquid crystal layer 102 can also be made to coincide, so that the light regulation is more precise. Moreover, it is beneficial to reduce the occupied area of the light-emitting pixel 4, which is beneficial to reducing the pixel size of the modulation pixel 110 and is beneficial to the miniaturized design of the modulation pixel 110; the spatial light modulator 100 adopting the above design can adapt to application scenarios with extremely small pixels.

[0120] Figure 12 This is a schematic structural diagram of another spatial light modulator 100 provided by the embodiments of the present application. As Figure 12 shown, the difference between this spatial light modulator 100 and the spatial light modulator 100 in the above embodiments 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 modulation 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 modulation light on the liquid crystal layer 102 can be accurately controlled; moreover, the alignment layer 6 can also control the divergence angle of the modulation light, reduce edge light leakage, and improve the focusing efficiency.

[0121] Exemplarily, as Figure 12As shown, the alignment layer 6 includes a microlens array. The microlens array includes a plurality of microlenses arranged in an array. The microlenses are optical coupling structures 61 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.

[0122] The microlens is a lens structure protruding towards the liquid crystal layer 102. The lens surface of the lens structure close to the liquid crystal layer 102 can be a spherical surface or an aspherical surface. The focal lengths of each microlens in the microlens array can be the same or slightly different (floating plus or minus <10%). The liquid crystal layer 102 can be located at the focal point of the microlens or at a defocused position.

[0123] During operation, the modulated light emitted by the light-emitting pixel 4 first diffuses and then converges through the microlens to reduce the mode field radius on the liquid crystal layer 102, so that the modulated light emitted by the light-emitting pixel 4 can accurately converge to the specified position on the liquid crystal layer 102. And it can avoid the modulated light emitted by one light-emitting pixel 4 from affecting other positions in the liquid crystal layer 102, thereby reducing crosstalk and light leakage between the light-emitting pixels 4.

[0124] Another example is, as Figure 13 shown, 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 arranged at intervals. At this time, the interval can be an air gap, or can be separated by a material with a refractive index difference from the light guide column, or can also be separated by a light-shielding material. Designed in this way, the light emitted by the light-emitting pixel 4 can be restricted to be transmitted in the light guide column, so that the modulated light emitted by the light-emitting pixel 4 can accurately converge to the specified position on the liquid crystal layer 102. And it can avoid the modulated light emitted by one light-emitting pixel 4 from affecting other positions in the liquid crystal layer 102, thereby reducing crosstalk and light leakage between the light-emitting pixels 4.

[0125] Another example is, as Figure 14 shown, the optical coupling structure 61 can be an enclosed retaining wall made of a light-shielding material. The enclosed retaining wall is arranged around the light-emitting pixel 4 and encloses and forms a light channel extending between the light-emitting pixel 4 and the liquid crystal layer 102. Thus, the modulated light emitted by the light-emitting pixel 4 can be restricted to be transmitted in the light channel surrounded by the enclosed retaining wall. In this way, the light emitted by the light-emitting pixel 4 can be restricted to be transmitted in the enclosed retaining wall, so that the modulated light emitted by the light-emitting pixel 4 can accurately converge to the specified position on the liquid crystal layer 102. And it can avoid the modulated light emitted by one light-emitting pixel 4 from affecting other positions in the liquid crystal layer 102, thereby reducing crosstalk and light leakage between the light-emitting pixels 4.

[0126] Figure 15FIG. 0 is a schematic structural diagram of another spatial light modulator 100 provided by an embodiment of the present application, as Figure 15 shown. The difference between this spatial light modulator 100 and the spatial light modulator 100 in the above embodiment is that a polarization selection layer 7 is provided on the side of the liquid crystal layer 102 away from the substrate 2. Exemplarily, the polarization selection layer 7 is directly attached to the surface of the liquid crystal layer 102 on the side away from the substrate 2.

[0127] The polarization selection layer 7 can be a liquid crystal material, an organic material, a micro-nano structure, etc. Its polarization orientation is consistent with the polarization state of the modulation response of the underlying liquid crystal layer 102, and its function is to perform polarization filtering on the incident light. The incident light can be light with any mixed polarization state, and it is not required to be a specific linearly polarized light or circularly polarized light. When the incident light passes through the polarization selection layer 7, only the light with the polarization state corresponding to the polarization selection layer 7 can be transmitted into the liquid crystal layer 102, and the liquid crystal layer 102 performs a modulation response on the incident light with this 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 selection layer 7 to complete the modulation effect of the entire incident light.

[0128] In the above embodiments, taking the photosensitive liquid crystal as a light-responsive cholesteric liquid crystal and the spatial light modulator 100 as a phase-type spatial light modulator 100 as an example, the solution is exemplarily described. However, the spatial light modulator 100 provided by the embodiments of the present application is not limited thereto.

[0129] In some embodiments, the photosensitive liquid crystal can also adopt any other liquid crystal material that can change the characteristics of liquid crystal molecules by modulating light to achieve modulation of the spatial distribution of the phase, amplitude, polarization, coherence, etc. of the incident light.

[0130] Exemplarily, the photosensitive liquid crystal can be a light-responsive blue phase liquid crystal. Among them, in the blue phase liquid crystal (Blue phase liquid crystal, abbreviated as BPLC), under the action of the helical twisting force provided by the chiral dopant, the liquid crystal molecules will not only twist helically along the helical axis direction, but also twist in the direction perpendicular to the helical axis, and finally self-assemble into double-twisted cylinders. The double-twisted cylinders are double-helical structures different from the single helix in cholesteric liquid crystals. According to the different arrangements of the double-twisted cylinders, the blue phase liquid crystal can be roughly divided into: blue phase I (BP I), blue phase II (BP II), and blue phase III (BP III). Among them, BP I has a body-centered cubic structure, BP II is a simple cubic structure, and BP III is an amorphous structure.

[0131] A light-responsive blue phase liquid crystal refers to a blue phase liquid crystal obtained by doping a synthesized photosensitive molecule into a blue phase liquid crystal matrix, which can change the characteristics of liquid crystal molecules under light stimulation. For example, when the photosensitive molecule is azobenzene, the pitch length of the photonic bandgap can be changed by the isomerization of azobenzene, thereby changing the lattice constant; or the phase transition of the double-twisted cylindrical arrangement phase can be induced, thereby changing its lattice direction. It can be seen from this that under the action of modulated light, the light-responsive blue phase liquid crystal can change the lattice constant and / or lattice direction of the photonic crystal (blue phase liquid crystal), thereby controlling the Bragg reflection characteristics and realizing the shift of the reflection center wavelength, so as to realize the modulation of incident light.

[0132] Another exemplary photosensitive liquid crystal can also be a light-responsive ferroelectric liquid crystal, a light-responsive smectic liquid crystal, etc., which can change the characteristics of liquid crystal molecules by modulating light to realize the modulation of the spatial distribution of the phase, amplitude, polarization, coherence, etc. of incident light.

[0133] In some other embodiments, based on the regulation characteristics of the photosensitive liquid crystal in the liquid crystal layer 102 on incident light, the spatial light modulator 100 can be a phase-type, amplitude-type or phase-amplitude-type spatial light modulator 100.

[0134] In the spatial light modulator 100 adopting the above design, it includes a light source layer 3 and a liquid crystal layer 102; the light source layer 3 can generate modulated light acting on the liquid crystal layer 102, and the liquid crystal layer 102 uses a photosensitive liquid crystal, which can realize the modulation of incident light under the action of the modulated light; and after the liquid crystal layer 102 completes the modulation, before being irradiated by new modulated light, its modulation state will remain unchanged, so that the power supply to the light source layer 3 can be stopped. Compared with the liquid crystal on silicon 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 for controlling the liquid crystal layer 102, thereby achieving the purpose of reducing power consumption; and, the liquid crystal layer 102 can maintain the modulation state before power failure when power failure occurs accidentally, and has the characteristic of non-volatility.

[0135] On the other hand, in the spatial light modulator 100 provided in the embodiment of the present application, the size of the modulation 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; therefore, the light-emitting device and the pixel driving circuit are relatively simple, so that the size of the light-emitting pixel 4 is small; furthermore, the size of the modulation pixel 110 can also be small; thus, it is beneficial to the miniaturized design of the modulation pixel 110. Designed in this way, on the one hand, it can meet the requirements for extremely small pixels (less than 5 micrometers) in some scenarios; on the other hand, more modulation pixels 110 can be arranged in the same area, realizing an increase in pixel density, which is beneficial to improving the performance of the spatial light modulator 100.

[0136] In addition, in the spatial light modulator 100 provided in the embodiments 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 the Micro LED is on 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 at the ns level, which has obvious advantages.

[0137] The embodiments of the present application also provide a control method for the spatial light modulator 100, which can be used to control the spatial light modulator 100 in the above embodiments; as Figure 16 shown, the control method 200 includes:

[0138] Step S100: Obtain the target modulation state and the current modulation state of the modulation pixel.

[0139] As can be seen from the above description of the spatial light modulator 100, the light-emitting pixel 4 and the liquid crystal part corresponding to the light-emitting pixel 4 in the liquid crystal layer 102 together form a modulation pixel 110 in the spatial light modulator 100. The spatial light modulator 100 includes a one-dimensional or two-dimensional pixel array formed by arranging a plurality of modulation pixels 110. The modulation state of the spatial light modulator 100 is a combination of the modulation states of all the modulation pixels 110 in the pixel array; in a certain modulation state of the spatial light modulator 100, the modulation states of all the modulation pixels 110 in the pixel array are independent of each other, and the modulation states of different modulation pixels 110 can be the same or different. During the modulation process of the spatial light modulator 100, the modulation of each modulation pixel 110 in the pixel array is also independent. That is to say, during the modulation process of the spatial light modulator 100, separate modulation needs to be performed on each modulation pixel 110 according to the modulation requirements of the spatial light modulator 100. When all the modulation pixels 110 in the pixel array are modulated, the spatial light modulator 100 is also modulated.

[0140] Exemplarily, when the spatial light modulator 100 forms a target phase diagram with a specific phase distribution, independent phase modulation needs to be performed on each modulation pixel 110 in the pixel array according to the target phase diagram. When all the modulation pixels 110 in the pixel array are phase-modulated, the spatial light modulator 100 forms the required target phase diagram.

[0141] In step S100, the target modulation state of modulation pixel 110 refers to the modulation state that modulation pixel 110 needs to achieve in the modulation task. After all modulation pixels 110 in the pixel array reach the target modulation state, the modulation of spatial light modulator 100 can be realized. The current modulation state of modulation pixel 110 refers to the modulation state that modulation pixel 110 is in before the modulation task starts.

[0142] For modulation pixel 110 in a phase-type spatial light modulator, the target modulation state refers to the modulation phase that modulation pixel 110 needs to achieve in the modulation task, and the current modulation state refers to the modulation phase that modulation pixel 110 is in before the modulation task starts; for a modulation pixel 110 in amplitude-type spatial light modulator 100, the target modulation state refers to the modulation amplitude that modulation pixel 110 needs to achieve in the modulation task, and the current modulation state refers to the modulation amplitude that modulation pixel 110 is in before the modulation task starts.

[0143] Regarding the target modulation state of modulation pixel 110, it can be directly obtained from the relevant parameters of the modulation task of spatial light modulator 100.

[0144] Regarding the current modulation state of modulation pixel 110, it can be obtained through the memory storage of spatial light modulator 100. That is, during the operation of spatial light modulator 100, it will record and update the modulation state of each modulation pixel 110 in the pixel array, so that it can be directly read when the current modulation state needs to be obtained.

[0145] Regarding the current modulation state of modulation pixel 110, it can also be obtained by means of optical measurement.

[0146] Step S200: Control 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.

[0147] Through step S100, the target modulation state and the current modulation state of modulation pixel 110 can be obtained. According to the difference between the target modulation state and the current modulation state, the light-emitting pixels 4 in modulation pixel 110 can be controlled to emit modulated light. Under the irradiation of the modulated light, the liquid crystal part in modulation pixel 110 can change the characteristics of liquid crystal molecules, so that modulation pixel 110 is converted from the current modulation state to the target modulation state, completing the modulation task of modulation pixel 110. During the modulation process of modulation pixel 110, the conversion time between the target modulation state and the current modulation state can also be controlled by controlling the light-emitting time and light-emitting intensity of light-emitting pixels 4. After the modulation task of modulation pixel 110 is completed, the light-emitting pixels 4 can be controlled to stop working. The liquid crystal part in modulation pixel 110 will maintain the converted modulation state until it is irradiated by new modulated light.

[0148] After 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.

[0149] In the case where the photosensitive liquid crystal is a light-responsive cholesteric liquid crystal, the liquid crystal molecules in the light-responsive cholesteric liquid crystal are arranged in a helical structure. By irradiating the first modulation light and the second modulation light, the pitch can be increased and decreased. Based on this, as Figure 17 shown, the above step S200 may include:

[0150] Step S210: Obtain a first pitch and a second pitch corresponding to the target modulation state and the current modulation state, respectively.

[0151] As can be known from the above description, the relationship between the modulation amplitude, modulation phase and pitch of the incident light by the light-responsive cholesteric liquid crystal can be calculated according to the formula, or can be obtained by means of experiments, simulations, etc. Therefore, according to the target modulation state and the current modulation state, a first pitch and a second pitch corresponding to the two can be obtained.

[0152] In some embodiments, step S210 may include:

[0153] Based on the target modulation state and the current modulation state, query the look-up table; wherein, the look-up table (abbreviated as LUT) records the corresponding relationship information between the modulation relationship and the pitch.

[0154] Step S220: Control the light-emitting pixel to emit the first modulation light or the second modulation light according to the difference between the first pitch and the second pitch.

[0155] 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 increased, so the light-emitting pixel 4 can be controlled to emit the first modulation light; when the difference is less than zero, it means that the pitch needs to be decreased, so the light-emitting pixel 4 can be controlled to emit the second modulation light.

[0156] Hereinafter, taking the phase control of the spatial light modulator 100 using the light-responsive cholesteric liquid crystal as an example, the control method 200 will be exemplarily described.

[0157] As Figure 18 shown, the control method 200 may include:

[0158] Step S10: Obtain the target phase and the current phase of the modulated pixel.

[0159] Among them, the target phase of the modulated pixel 110 is the phase that the modulated pixel 110 needs to reach during the phase modulation process. The target phase It can be directly obtained from the target phase diagram. When the phases of all modulation pixels 110 are modulated to the target phase a target phase diagram that meets the modulation requirements can be formed.

[0160] The current phase of the modulation pixel 110 is the actual phase of the modulation pixel 110 before the start of the modulation operation; this phase can be obtained according to the stored information of the spatial light modulator 100, that is, the spatial light modulator 100 records and updates the phase of the modulation pixel 110 at any time during operation, so that the current phase of the modulation pixel 110 can be obtained.

[0161] The current phase of the modulation pixel 110 can also be obtained by means of optical measurement or the like.

[0162] Step S20: Obtain the corresponding first pitch and second pitch according to the target phase and the current phase.

[0163] As can be seen from the above description, the correspondence between the modulation phase of the light-responsive cholesteric liquid crystal to the incident light and the pitch can be obtained by calculation, or by means of experiments, simulations, etc. Therefore, after obtaining the target phase and the current phase through step S10, the corresponding first pitch P_1 and second pitch P_2 can be obtained for the two.

[0164] In this embodiment, before the start of the modulation operation, for incident light of possible wavelengths, the relationship curve between the pitch and the modulation phase is calibrated by means of calculation simulation and pre-experiment, etc., to form a look-up table recording the correspondence between the modulation phase and the pitch. During the modulation operation, according to the wavelength of the incident light, the corresponding first pitch P_1 and second pitch P_2 for the target phase and the current phase can be obtained by querying the look-up table.

[0165] Step S30: Control the light-emitting pixel to emit the first modulation light or the second modulation light according to the difference between the first pitch and the second pitch.

[0166] After obtaining the corresponding first pitch P_1 and second pitch P_2 for the target phase and the current phase respectively through step S20, the pitch difference ΔP between the first pitch P_1 and the second pitch P_2 can be obtained, ΔP = P_1 - P_2.

[0167] When the pitch difference ΔP is greater than 0, it indicates that the pitch needs to be increased. Based on the above description, it is possible to control the light-emitting pixel 4 to emit the first modulation light. When the pitch difference ΔP is less than 0, it indicates that the pitch needs to be decreased. Based on the above description, it is possible to control the light-emitting pixel 4 to emit the second modulation light. During the process of controlling light emission, it is also possible to control the light emission time and light emission intensity to control the change amplitude and change time of the pitch adjustment process.

[0168] When the pitch change amount reaches ΔP, the phase of the modulation pixel 110 is converted to the target phase, and the modulation work is completed. It is possible to control the light source layer 3 to stop emitting light.

[0169] The embodiment of the present application also provides an optical modulation device, as Figure 19 shown in part (a). The optical modulation device 300 includes the spatial light modulator 100 described in the above embodiment, and an incident light source 310. The incident light source 310 is used to generate incident light that irradiates the spatial light modulator 100. As Figure 19 shown in part (b), in some other embodiments, the optical modulation device 300 includes the spatial light modulator 100 described in the above embodiment, and an optical transmission device 320. The optical transmission device 320 is used to receive incident light and project the incident light onto the spatial light modulator 100. The above optical modulation device 300 can be a device applied to fields such as optical communication scheduling and switching, optical metrology, optical imaging, and laser processing.

[0170] For example, the optical modulation device 300 can be a wavelength selective switch (abbreviated as WSS) 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 described above. The incident light irradiates the spatial light modulator 100 through the optical fiber array. The spatial light modulator 100 can control the deflection of the incident light through modulation of the incident light, so as to achieve the purpose of controlling the incident light to exit from the target port of the optical fiber array.

[0171] Another example is that the optical modulation device 300 can be a picture generation unit (abbreviated as PGU) for optical imaging. The picture generation unit includes an illumination light source, a spatial light modulator 100, and a projection lens. The illumination light source is used to provide an illumination beam for the spatial light modulator 100. The spatial light modulator 100 forms imaging light containing image information by modulating the illumination beam, and the imaging light is projected onto the target position through the projection lens. Here, the illumination light source and the illumination beam respectively belong to the incident light source 310 and the incident light described above.

[0172] The technical effects achievable by the optical modulation device 300 provided in the embodiments of the present application are the same as those achievable by the spatial light modulator 100 in any of the above embodiments, and will not be elaborated here.

[0173] The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claimed rights.

Claims

1. A spatial light modulator, characterized in that, Comprising: A liquid crystal layer, the material of the liquid crystal layer comprising photosensitive liquid crystal, and the photosensitive liquid crystal realizes modulation of incident light under irradiation of modulated light; A light source layer, the light source layer is disposed 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; And A first filter layer, the first filter layer is disposed 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.

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 helical structure; The modulated light emitted by the light-emitting pixels includes first modulated light and second modulated light; The pitch of the helical structure in the photosensitive liquid crystal becomes larger under irradiation of the first modulated light; The pitch of the helical structure in the photosensitive liquid crystal becomes smaller under irradiation of the second modulated light.

3. The spatial light modulator according to claim 2, characterized in that, The light-emitting pixels include 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; Both the first sub-pixel and the second sub-pixel 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 submillimeter 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 pixels include 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 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 includes a second filter layer; the second filter layer is disposed on a side of the liquid crystal layer away from the light source layer and is used to transmit the incident light and reflect 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 from 1350 nm to 1700 nm, and the wavelength of the modulated light is from 300 nm to 650 nm.

7. The spatial light modulator according to claim 1, characterized in that, The spatial light modulator further includes an alignment layer, and the alignment layer is disposed between the light source layer and the filter layer; The alignment layer includes a plurality of optical coupling structures, and the optical 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, the light guide column 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 barrier, the material of the closed barrier includes a light-shielding material, the closed barrier is disposed around the light-emitting pixel, and a light channel extending between the light-emitting pixel and the liquid crystal layer is surrounded and formed.

9. The spatial light modulator according to any one of claims 1 to 8, characterized in that, The spatial light modulator further includes 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, characterized in that, The photosensitive liquid crystal is a photo-responsive blue phase liquid crystal. Under the irradiation of the modulation light, the lattice constant and / or lattice direction of the photo-responsive blue phase liquid crystal change.

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

12. An optical modulation device, characterized in that, The optical modulation device includes: A spatial light modulator as described in any one of claims 1 to 11; and An incident light source for generating incident light that irradiates the spatial light modulator. Alternatively, the optical modulation device includes: A spatial light modulator as described in any one of claims 1 to 11; and An optical transmission device for receiving incident light and projecting the incident light onto the spatial light modulator.

13. A control method for a spatial light modulator, characterized in that, 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 a photosensitive liquid crystal, and the photosensitive liquid crystal can modulate the incident light under the irradiation of the modulation light. The light source layer is disposed 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 modulation light that irradiates the liquid crystal layer. The first filter layer is disposed between the liquid crystal layer and the light source layer, and the filter layer is used to transmit the modulation light and reflect the incident light. The spatial light modulator includes a plurality of modulation pixels, and each modulation pixel includes the light-emitting pixel and the liquid crystal portion corresponding to the light-emitting pixel in the liquid crystal layer. The control method includes: Obtaining the target modulation state and the current modulation state of the modulation pixel. Controlling the light-emitting pixel in the modulation pixel to emit modulation light according to the difference between the target modulation state and the current modulation state.

14. The control method according to claim 13, characterized in that, In the spatial light modulator, the liquid crystal molecules in the photosensitive liquid crystal are arranged in a helical structure. The modulation light emitted by the light-emitting pixel includes a first modulation light and a second modulation light. The pitch of the helical structure in the photosensitive liquid crystal becomes larger under the irradiation of the first modulation light. The pitch of the helical structure in the photosensitive liquid crystal becomes smaller under the irradiation of the second modulation light. In the control method, the step of controlling the light-emitting pixel in the modulation pixel to emit modulation light according to the difference between the target modulation state and the current modulation state includes: Obtaining a first pitch and a second pitch respectively corresponding to the target modulation state and the current modulation state. Controlling the light-emitting pixel to emit the first modulation light or the second modulation light according to the difference between the first pitch and the second pitch.

15. The control method according to claim 14, characterized in that, The step of obtaining a first pitch and a second pitch respectively corresponding to the target modulation state and the current modulation state includes: Querying a look-up table based on the target modulation state and the current modulation state. Wherein, the look-up 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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