Transmission-type high-damage-threshold liquid crystal light addressing spatial light modulator

Abstract

The utility model discloses a transmission-type high-damage-threshold liquid crystal light addressing spatial light modulator, and relates to the technical field of spatial light modulators. The light addressing spatial light modulator sequentially comprises a substrate, a transparent conductive layer, a first PI orientation layer, a liquid crystal layer, a spacer, a second PI orientation layer, a light guide layer, a first anti-reflection film and a second anti-reflection film from top to bottom. The transparent conductive layer and the light guide layer are made of the same material, namely a gallium nitride material or a gallium oxide material with a conductive characteristic and a photoconductive characteristic, so that the irradiation resistance of high-energy-density laser and high-average-power laser is enhanced; and the problems of cracking caused by inconsistent thermal expansion of different materials, light beam modulation caused by a reflection mode and the like are solved. As the sizes of the materials such as gallium nitride and gallium oxide reach 150mm, the aperture limitation of the materials such as BSO and BGO is solved, and large-aperture light transmission is realized.

Description

Technical Field

[0001] The utility model belongs to the field of liquid crystal spatial light modulators, in particular to a transmission-type liquid crystal spatial light modulator with high damage threshold, wide spectrum and large clear aperture. Background Art

[0002] Liquid crystal spatial light modulators (LCSLMs) are advanced light field manipulation devices capable of dynamically adjusting laser characteristics, such as amplitude, phase, and polarization. They have important applications in beam shaping for large laser devices and are also used as image generation devices in laser additive manufacturing.

[0003] Light-addressable liquid crystal spatial light modulators (LALICs) eliminate the need for pixel electrodes and therefore do not affect the existing optical path. Compared to common transmissive electrically addressed spatial light modulators (such as thin-film transistors (TFTs)) and reflective electrically addressed spatial light modulators (such as liquid crystal on silicon (LCoS)), LALLICs avoid the low aperture ratio issues caused by components such as non-transparent electrodes in TFT modulators, while also avoiding the optical path distortion caused by the black grid effect in LCoS modulators.

[0004] However, when light-addressable liquid crystal spatial light modulators (LALMs) are used in large-scale laser devices and in processing fields such as additive manufacturing, their laser damage threshold (LDT) is a critical performance metric. Currently, the transparent conductive layer material, indium tin oxide (ITO), has a low LDT. This not only results in a low LDT for LLMs overall, limiting their application in high-power laser devices, but also has strong absorption in the infrared band, making it susceptible to heating after laser irradiation, causing heat to accumulate within the liquid crystal layer. Because liquid crystals are extremely sensitive to operating temperature, LLMs struggle to operate stably for extended periods of time under high-power laser irradiation, and may even fail.

[0005] In response to the above problems, the prior art has proposed a variety of solutions. For example, patent document CN113126373B uses gallium nitride (GaN) instead of ITO as a transparent conductive film material to improve the ability of the spatial light modulator to resist laser damage. However, since there is currently no effective method to combine GaN with the commonly used photoconductive material BSO, if BSO is to be used as the photoconductive layer, then GaN cannot be used for the transparent conductive layer. Therefore, this high damage threshold spatial light modulator can only be used as a reflective type and cannot be used as a transmissive type. However, reflective devices have very high requirements for the residual reflectivity coating and flatness processing accuracy of the liquid crystal window substrate, and are prone to problems such as large spectral distortion and large wavefront distortion. Moreover, the Fabry-Perot effect in the reflective spatial light modulator cannot be avoided, resulting in spectral modulation and time domain modulation problems. Due to the size of the BSO crystal, it is currently difficult to increase the aperture of the optically addressable spatial light modulator.

[0006] Patent document CN115113429A combines sapphire with a photoconductive layer through hydroxide-catalyzed bonding, significantly improving the heat dissipation efficiency of the photoconductive layer in an OASLM and addressing the thermal deposition issue under high-power lasers. However, this approach does not fundamentally address the low thermal conductivity of BSO crystals. Similarly, due to the size of BSO crystals, increasing the aperture of optically addressable spatial light modulators is currently difficult.

[0007] Patent document CN114594633A uses gallium nitride as a transparent conductive material and zinc oxide thin film as a photoconductor. Compared with the liquid crystal box used in traditional liquid crystal spatial light modulators, this combination improves the tolerance to high-energy lasers, but the manufacturing process is complex and the technical implementation is difficult.

[0008] Patent document CN116736584A adopts plasma electrodes to replace the commonly used transparent conductive film layer, which not only enables the optically addressed spatial light modulator to operate in transmission mode, but also realizes the high damage threshold characteristics of the device. However, due to the narrow gap between the photoconductive layer and the liquid crystal layer, there are high processing requirements, and precise control of discharge parameters is also required to maintain the stability of the plasma.

[0009] Although patent document US20240142814A1 uses an ultra-wide bandgap semiconductor to replace the original BSO crystal as a photoconductor, thereby improving the laser radiation resistance of the overall device, its conductive layer is plated on the photoconductor using ITO thin film, so that ITO still limits the laser radiation resistance of the overall device.

[0010] In summary, while existing technologies have improved the laser damage threshold and performance of light-addressable liquid crystal spatial light modulators (LALMs), limitations remain in material bonding, processing precision, manufacturing processes, and the inherent properties of the materials themselves. Therefore, developing new transparent conductive materials and optimizing structural designs to increase the laser damage threshold, reduce processing complexity, and enhance overall performance have become key areas for advancing LAM technology. Utility Model Content

[0011] The purpose of the present utility model is to overcome the defects of existing devices and provide a new structure, in which the traditional ITO transparent electrode and BSO photoconductive layer are replaced by high thermal conductivity laser radiation resistant materials such as gallium nitride or gallium oxide that have both photoconductive and conductive properties, so that the thermal conductivity of the materials on both sides of the liquid crystal is equivalent, avoiding the deformation or even cracking problems introduced during the liquid crystal box packaging process, realizing the transmission modulation function, and improving the yield of the liquid crystal light valve while increasing the laser damage threshold.

[0012] The utility model is realized through the following technical solutions:

[0013] A high damage threshold liquid crystal optically addressable spatial light modulator comprises, from top to bottom, a substrate, a transparent conductive layer, a first PI alignment layer, a liquid crystal layer encapsulated by spacers, a second PI alignment layer, and a light guide layer. The light guide layer is coated with a first anti-reflection and anti-reflection coating and a second anti-reflection and anti-reflection coating on its upper and lower surfaces. The light guide layer and the transparent conductive layer are both made of the same material, possessing both optical and electrical properties, and a thermal conductivity greater than 3 (W / m·K).

[0014] At room temperature, pure gallium nitride (GaN) has low conductivity, making it unsuitable for use as a transparent conductive film. Therefore, it requires doping with materials such as silicon, magnesium, or carbon. Low carrier concentration and high carrier mobility are key considerations. The liquid crystal layer is encapsulated between the first and second alignment layers via spacers. GaN serves not only as a conductive layer but also as a photoconductive layer. Due to GaN's absorption spectrum, the photoconductive layer can be illuminated with addressing light in the 200nm to 360nm range. GaN's transmission spectrum covers wavelengths from 1µm to 5µm. Therefore, when using GaN as a light-addressable liquid crystal light valve, the addressing light wavelength can be from 200nm to 360nm, while the readout light can be from lasers in the 1µm to 5µm range. GaN can be fabricated in sizes ranging from two, four, six, and even eight inches, enabling the fabrication of optically addressable spatial light modulators with apertures larger than 40mm x 40mm. This overcomes the size limitations of existing photoconductive materials such as BSO and BGO.

[0015] Optionally, the photoconductive layer and the transparent conductive layer are both made of the same gallium nitride material.

[0016] Preferably, the gallium nitride material is n-type silicon-doped gallium nitride film, p-type magnesium-doped gallium nitride film, n-type

[0017] Silicon gallium nitride single crystal, p-type magnesium-doped gallium nitride single crystal or undoped gallium nitride single crystal, the n-type silicon-doped gallium nitride thin film, p-type magnesium-doped gallium nitride thin film, n-type silicon-doped gallium nitride single crystal, p-type magnesium-doped gallium nitride single crystal or undoped gallium nitride single crystal, the carrier concentration is 1×1018cm-3 to 1×1020cm-3, the thickness of the n-type or p-type gallium nitride thin film is 1um to 5um, and the thickness of the n-type, p-type or undoped gallium nitride single crystal is 0.5mm to 5mm.

[0018] Gallium oxide is an ultra-wide bandgap semiconductor material characterized by chemical stability, corrosion resistance, high mechanical strength, and stable performance at high temperatures. It exhibits high transparency in the visible and ultraviolet regions, particularly in the ultraviolet and blue regions, a property not possessed by traditional transparent conductive materials. Therefore, β-Ga2O3 single crystals can be used as transparent conductive materials. A liquid crystal layer is encapsulated between the first and second alignment layers via spacers. Gallium oxide serves not only as a conductive layer but also as a photoconductive layer. Based on the absorption spectrum of gallium oxide, the addressing wavelength can be in the 200nm to 270nm range, while the readout wavelength can cover the 500nm to 1.5µm range. Gallium oxide can be fabricated in sizes ranging from two inches, four inches, and six inches, enabling the fabrication of optically addressable spatial light modulators with apertures larger than 40mm x 40mm. This overcomes the size limitations of existing BSO and BGO photoconductive materials.

[0019] Optionally, the photoconductive layer and the transparent conductive layer are both made of the same gallium oxide material.

[0020] Preferably, the gallium oxide material is a gallium oxide thin film or a gallium oxide single crystal. Among the six crystal phases of α, β, γ, δ, ε, and κ, the β crystal phase is used, and the carrier concentration is 1×10 15 cm -3 ~1×10 18 cm -3 The thickness of the gallium oxide film is 1um~5um, and the thickness of the gallium oxide single crystal is 0.5mm~5mm.

[0021] Furthermore, the liquid crystal layer is a twisted nematic type with a twist angle ranging from 0° to 90°; and the thickness d of the liquid crystal layer satisfies the following conditions: Where Δn is the birefringence of the liquid crystal, and λ is the wavelength of the light to be modulated.

[0022] In the light modulation application of the high damage threshold liquid crystal light addressing spatial light modulator provided by the present invention, the wavelength band of the addressing light is within the range of 200 nm to 365 nm.

[0023] Preferably, the addressing light adopts blue-violet light controlled by LCOS, or Micro-Led emits single blue-violet light, or DMD controls blue-violet light.

[0024] In the device, the upper and lower surfaces of the light guide layer are coated to reduce reflection and increase transmittance, reduce the mutual interference of reflected light caused by Fresnel diffraction, and prevent unnecessary light beam modulation.

[0025] The addressing light used in this invention is blue light or ultraviolet light. LCOS or DMD can be used to modulate the addressing light, or LEDs or MicroLEDs can be used directly as the addressing light. The materials mentioned above are not limited to gallium nitride and gallium oxide; other materials that possess both photoconductive and conductive properties, as well as high thermal conductivity, are also within the scope of this invention.

[0026] The wavelength of the readout light applicable to the utility model mainly depends on the transmittance of materials such as gallium nitride and gallium oxide used for both the light-guiding layer and the conductive layer.

[0027] The anti-reflection and anti-reflection film used in the present invention can use silicon dioxide film and magnesium fluoride film to match the refractive index of gallium nitride to reduce the reflection of visible light and near-infrared bands; it can also be a multi-layer film, using titanium oxide as a high-refractive index layer and then matching silicon dioxide as a low-refractive layer.

[0028] The above materials are not limited to silicon dioxide, magnesium fluoride and titanium oxide materials. Other materials that have anti-reflection and anti-transmission properties in the visible light and infrared light bands are also within the scope of the utility model.

[0029] When the high damage threshold liquid crystal light addressing spatial light modulator is in the off state, the voltage of the liquid crystal layer (4) is the threshold voltage U th , its threshold voltage U th is a function of temperature, expressed as Among them U th is the threshold voltage, m is a parameter related to the elastic coefficient of the liquid crystal, T is the real-time temperature of the liquid crystal, Tc is the clearing point temperature of the liquid crystal, and β is the material constant of the liquid crystal, where the threshold voltage U th It will decrease as the temperature rises, and temperature monitoring and closed-loop control systems are required to maintain a stable γ curve.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] By using gallium nitride (GaN) in the transparent conductive layer, the overall laser damage threshold of the optically addressed liquid crystal spatial light modulator (SLM) is improved, leveraging its high laser damage threshold of 1.67 J / cm², compared to ITO's 0.467 J / cm². Replacing the commonly used BSO light-conducting crystal with GaN avoids the difficulty of bonding GaN thin films to BSO, thus achieving a transmissive, high-damage-threshold SLM. Compared to reflective structures, this SLM offers advantages such as reduced spectral and wavefront distortion.

[0032] The utility model uses gallium oxide material in the transparent conductive layer, and takes advantage of the high laser damage threshold of gallium oxide material of 3.44J / cm^2, which is higher than that of ITO at 0.467J / cm^2. 2, improving the overall laser damage threshold of the optically addressed liquid crystal spatial light modulator. Replacing the commonly used BSO light-conducting crystal with gallium oxide avoids the difficulty of bonding gallium nitride thin films to BSO, thus achieving a transmissive, high-damage threshold spatial light modulator. Compared to reflective structures, it offers advantages such as reduced spectral and wavefront distortion.

[0033] The optical waveguide material used in this invention optimizes the problem that BSO crystals, BGO crystals and other crystals cannot currently grow large-diameter crystals. Currently, BSO crystals can reach 3 inches, while gallium nitride or gallium oxide can be used to make large-diameter crystals. Gallium nitride single crystals can reach 6 inches or even 8 inches, and gallium oxide single crystals can also reach 6 inches.

[0034] The thermal conductivity of BSO crystal is 0.006 W / cm×K, while the thermal conductivity of gallium nitride is 1.3 W / cm×K and that of gallium oxide is 0.11 W / cm×K, all of which are higher than BSO crystal, thus improving the low thermal conductivity of BSO crystal. Therefore, using materials such as gallium nitride and gallium oxide instead of BSO can improve the laser radiation resistance of optically addressable spatial light modulators. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the high damage threshold optically addressed spatial light modulator of the utility model.

[0036] Figure 2 Schematic diagram of implementing amplitude modulation for an optically addressable spatial light modulator. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the embodiments and drawings, but the scope of protection of the present invention shall not be limited thereby.

[0038] Example 1

[0039] As attached Figure 1 As shown, a high damage threshold optically addressable spatial light modulator includes, from top to bottom, a substrate 1, a transparent conductive layer 2, a first PI orientation layer 3, a liquid crystal layer 4 encapsulated by a spacer 5, a second PI orientation layer 6, and a light guide layer 7. The upper and lower surfaces of the light guide layer 7 are respectively coated with a first anti-reflection and anti-reflection film 8 and a second anti-reflection and anti-reflection film 9.

[0040] The lower surface of the substrate 1 is coated with a transparent conductive layer 2 and a first PI orientation layer 3 in sequence; the upper surface of the light guide layer 7 coated with a first anti-reflection and anti-reflection film 8 is coated with a second PI orientation layer 6; the liquid crystal layer 4 encapsulated by the spacer 5 is glued to the substrate 1 and the light guide layer 7 and then filled.

[0041] The method for preparing the above-mentioned optically addressable spatial light modulator with a high damage threshold comprises the following steps:

[0042] Step 1. A transparent conductive layer 2 and a first PI orientation layer 3 are sequentially deposited on the lower surface of the substrate 1; a first anti-reflection and anti-reflection film 8 and a second PI orientation layer 6 are sequentially deposited on the upper surface of the photoconductive layer 7, and a second anti-reflection and anti-reflection film 9 is deposited on the lower surface of the photoconductive layer 7.

[0043] Step 2: Use the glue dispensed with the doped spacers 5 to bond and solidify the substrate 1 and the optical guide layer 7 to form a parallel flat plate box with a fixed gap.

[0044] Step 3: Fill the parallel plate box with the liquid crystal layer 4 through the filling port.

[0045] Step 4: First, vacuum press the parallel flat box filled with the liquid crystal layer 4 using a vacuum packaging machine, and then use ultraviolet light to cure for 30 seconds to complete the box making.

[0046] The thickness of the substrate 1 is 0.3 mm, 0.4 mm or 0.5 mm, preferably 0.5 mm, and the material may be a light-transmitting material such as sapphire or K9 glass.

[0047] The transparent conductive layer 2 is a gallium nitride transparent conductive film or a gallium nitride single crystal, which can be any of the following materials: (1) a thin film layer of 1 μm to 5 μm thick coated with silicon-doped gallium nitride (n-type doping), the carrier concentration of which is 1×10 18 cm -3 ~1×10 20 cm -3 , select: 1×10 18 cm -3 , 5um;

[0048] (2) A thin film layer with a thickness of 1um to 5um is coated with magnesium-doped gallium nitride (p-type doping), and the carrier concentration of magnesium-doped gallium nitride is 1×10 18 cm -3 ~1×10 20 cm -3 , select: 1×10 18 cm -3 , 5um;

[0049] (3) The thickness of the n-type silicon-doped gallium nitride single crystal is 0.5 mm to 5 mm, and the carrier concentration of the silicon-doped gallium nitride is 1×10 18 cm -3 ~1×10 20 cm -3 , select: 1×10 18 cm -3 , select: 1×10 18 cm -3 , 1mm;

[0050] (4) The thickness of the p-type Mg-doped GaN single crystal is 0.5 mm to 5 mm, and the carrier concentration of the Mg-doped GaN is 1×10 18 cm -3 ~1×10 20 cm -3 , select: 1×10 18 cm -3 , 1mm;

[0051] (5) The thickness of the undoped gallium nitride single crystal is 0.5 mm to 5 mm, and the carrier concentration is 1×10 18 cm -3 ~1×10 20 cm -3 , select: 1×10 18 cm -3 , 1mm.

[0052] The thickness of the light guide layer 7 is 0.5 mm to 5 mm, preferably 1 mm, and is made of the same material as the transparent conductive layer 2 .

[0053] The first anti-reflection and anti-reflection film 8 and the second anti-reflection and anti-reflection film 9 are made of silicon dioxide, with a film thickness of 3 to 5 μm. Their specific performance indicators are: a thickness of 3 μm, a transmittance of 95%, and a reflectivity of 3%.

[0054] The thickness d of the liquid crystal layer 4 is controlled by applying spacers 5 at the edge of the liquid crystal cell. The specific indicator is: the thickness d is 4.071 μm.

[0055] When the optically addressed spatial light modulator is of amplitude type, the liquid crystal layer 4 operates in a twisted nematic mode.

[0056] The first PI alignment layer 3 and the second PI alignment layer 6 can be made of polyimide material with a thickness of 250 nm to 125 μm, preferably 500 nm.

[0057] In light modulation applications, the wavelength of the modulated laser is 1053nm, and the liquid crystal light addressing spatial light modulator is amplitude type; the wavelength of the addressing light is: 250nm

[0058] A dichroic mirror 13 is provided behind the high damage threshold liquid crystal light addressable spatial light modulator;

[0059] The dichroic mirror 13 has a reflectivity of higher than 90% for addressing light in the wavelength range of 200nm to 360nm with 45-degree incidence, and can also set the bandwidth of the central wavelength of 45-degree incidence within the range of 0.4um to 1.5um as needed. The transmittance of the light beam with a spectral width of ±0.5um is higher than 80%.

[0060] The liquid crystal layer 4 is a twisted nematic liquid crystal with a twist angle range of 0° to 90°. The liquid crystal thickness d and the liquid crystal birefringence Δn satisfy The wavelength λ is 1053 nm, the birefringence Δn is 0.224, the thickness d is 4.071 μm, and the twist angle is selected as 90°.

[0061] like Figure 2 As shown, wires are further connected to the GaN transparent conductive layer 2 and the GaN photoconductive layer 7, and a voltage of 40V is applied. Then, 250nm addressing light is reflected by the dichroic mirror 13 and irradiated onto the photoconductive layer 7 to achieve addressing. When the incident light passes through the optically addressable spatial light modulator, it is amplitude modulated, and the output light is the modulated output light.

[0062] The effective value of the voltage is between 10V and 200V, the frequency is between 50Hz and 1000Hz, and both the voltage amplitude and the frequency are adjustable. Specifically, 40V is selected and the frequency is set at 800Hz.

[0063] Example 2

[0064] As attached Figure 1 As shown, a high damage threshold optically addressable spatial light modulator includes, from top to bottom, a substrate 1, a transparent conductive layer 2, a first PI orientation layer 3, a liquid crystal layer 4 encapsulated by a spacer 5, a second PI orientation layer 6, and a light guide layer 7. The upper and lower surfaces of the light guide layer 7 are respectively coated with a first anti-reflection and anti-reflection film 8 and a second anti-reflection and anti-reflection film 9.

[0065] The lower surface of the substrate 1 is coated with a transparent conductive layer 2 and a first PI orientation layer 3 in sequence; the upper surface of the light guide layer 7 coated with a first anti-reflection and anti-reflection film 8 is coated with a second PI orientation layer 6; the liquid crystal layer 4 encapsulated by the spacer 5 is glued to the substrate 1 and the light guide layer 7 and then filled.

[0066] The method for preparing the above-mentioned optically addressable spatial light modulator with a high damage threshold comprises the following steps:

[0067] Step 1. A transparent conductive layer 2 and a first PI orientation layer 3 are sequentially deposited on the lower surface of the substrate 1; a first anti-reflection and anti-reflection film 8 and a second PI orientation layer 6 are sequentially deposited on the upper surface of the photoconductive layer 7, and a second anti-reflection and anti-reflection film 9 is deposited on the lower surface of the photoconductive layer 7.

[0068] Step 2: Use the glue dispensed with the doped spacers 5 to bond and solidify the substrate 1 and the optical guide layer 7 to form a parallel flat plate box with a fixed gap.

[0069] Step 3: Fill the parallel plate box with the liquid crystal layer 4 through the filling port.

[0070] Step 4: First, vacuum press the parallel flat box filled with the liquid crystal layer 4 using a vacuum packaging machine, and then use ultraviolet light to cure for 30 seconds to complete the box making.

[0071] The thickness of the substrate 1 is 0.3 mm, 0.4 mm or 0.5 mm, preferably 0.5 mm, and the material may be a light-transmitting material such as sapphire or K9 glass.

[0072] The transparent conductive layer 2 is a gallium oxide conductive transparent film or a gallium oxide single crystal, which can be made of any of the following materials: (1) an undoped gallium oxide conductive transparent film with a thickness of 1 μm to 5 μm and a carrier concentration of 1×10 15 cm -3 ~1×10 18 cm -3 , select: 3um, 1×10 15 cm -3 ;

[0073] (2) The thickness of the gallium oxide single crystal is 0.5 mm to 5 mm, and the carrier concentration is 1×10 15 cm -3 ~1×10 18 cm -3 , select: 1mm, 1×10 15 cm -3 .

[0074] The thickness of the light guide layer 7 is 0.5 mm to 5 mm, preferably 1 mm, and is made of the same material as the transparent conductive layer 2 .

[0075] The first anti-reflection and anti-reflection film 8 and the second anti-reflection and anti-reflection film 9 can be made of silicon dioxide, with a film thickness of 3 to 5 μm. Their specific performance indicators are: a thickness of 3 μm, a transmittance of 95%, and a reflectivity of 3%.

[0076] The thickness d of the liquid crystal layer 4 is controlled by applying spacers 5 at the edge of the liquid crystal cell. The specific indicator is: the thickness d is 4.071 μm.

[0077] The liquid crystal layer 4 is a twisted nematic liquid crystal with a twist angle range of 0° to 90°. The liquid crystal thickness d and the liquid crystal birefringence Δn satisfy The wavelength λ is 1053 nm, the birefringence Δn is 0.224, the thickness d is 4.071 μm, and the twist angle is selected as 90°.

[0078] When the optically addressed spatial light modulator is of amplitude type, the liquid crystal layer 4 operates in a twisted nematic mode.

[0079] The first alignment layer 3 and the second alignment layer 6 can be made of polyimide materials.

[0080] In the light modulation application, the wavelength of the modulated laser is 1053nm, and the liquid crystal light addressing spatial light modulator is an amplitude type; the wavelength band of the addressing light is: 250nm;

[0081] In light modulation applications, a dichroic mirror 13 is provided behind the high damage threshold liquid crystal light addressable spatial light modulator;

[0082] The dichroic mirror 13 has a reflectivity of higher than 90% for addressing light in the wavelength range of 200nm to 270nm with 45-degree incidence, and can set the bandwidth of the central wavelength of 45-degree incidence within the range of 0.4um to 1.5um as needed. The transmittance of the light beam with a spectral width of ±0.5um is higher than 80%.

[0083] like Figure 2 As shown, wires are connected to the gallium oxide transparent conductive layer and the gallium oxide photoconductive layer, and a voltage of 40V is applied. Then, 250nm addressing light is reflected by the dichroic mirror 13 and irradiated onto the photoconductive layer to achieve addressing. When the incident light passes through the optically addressable spatial light modulator, it is amplitude modulated, and the output light is the modulated output light.

[0084] The effective value of the voltage is between 10V and 200V, the frequency is between 50Hz and 1000Hz, and both the voltage amplitude and the frequency are adjustable. Specifically, 40V is selected and the frequency is set at 800Hz.

[0085] Example 1:

[0086] Substrate: Choose a glass substrate with high light transmittance.

[0087] Transparent conductive layer: n-type silicon-doped gallium nitride film with a thickness of 2um and a carrier concentration of 5×1018cm-3 is used to ensure it has good conductivity and light transmittance.

[0088] The first PI alignment layer is coated on the transparent conductive layer and is used to control the alignment of liquid crystal molecules.

[0089] Liquid crystal layer: Twisted nematic liquid crystal is used with a twist angle of 45°. The thickness d is calculated according to the formula d = (λΔn) / (2π), where λ is 550nm (visible light band) and Δn is the birefringence of the liquid crystal, ensuring that the liquid crystal layer effectively modulates visible light.

[0090] Second PI alignment layer: coated under the liquid crystal layer, and works together with the first PI alignment layer to maintain the stable orientation of the liquid crystal molecules.

[0091] Light guide layer: It also uses n-type silicon-doped gallium nitride film with a thickness of 2um. The upper and lower surfaces are coated with silicon dioxide film and magnesium fluoride film as anti-reflection and anti-reflection films to reduce the interference of reflected light and improve the transmittance.

[0092] By building a transmissive modulation performance test system and measuring parameters such as the spectral distortion and wavefront distortion of the modulator in transmissive mode, it can be seen that the overall laser damage threshold of the optically addressed liquid crystal spatial light modulator of the present invention is significantly improved, and the problem of deformation and even cracking caused by thermal deposition during the liquid crystal box packaging process is effectively solved. The transmissive structure has the advantages of small spectral distortion and small wavefront distortion, which improves the performance of the modulator.

Claims

1. A transmissive high damage threshold liquid crystal optically addressable spatial light modulator, characterized in that: From top to bottom, the substrate comprises a substrate (1), a transparent conductive layer (2), a first PI orientation layer (3), a liquid crystal layer (4) encapsulated by a spacer (5), a second PI orientation layer (6), and a light guide layer (7). The upper and lower surfaces of the light guide layer (7) are respectively coated with a first anti-reflection and anti-reflection film (8) and a second anti-reflection and anti-reflection film (9). The light guide layer (7) and the transparent conductive layer (2) are both made of the same material having both optical and conductive properties and a thermal conductivity greater than 3 (W / m·K).

2. The transmissive high damage threshold liquid crystal optically addressable spatial light modulator according to claim 1, characterized in that The photoconductive layer (7) and the transparent conductive layer (2) are both made of the same gallium nitride material, and the gallium nitride material is selected from one of n-type silicon-doped gallium nitride thin film, p-type magnesium-doped gallium nitride thin film, n-type silicon-doped gallium nitride single crystal, p-type magnesium-doped gallium nitride single crystal or undoped single crystal, and the carrier concentration is 1×10 18 cm -3 ~1×10 20 cm -3 The thickness of n-type or p-type gallium nitride film is 1um to 5um, and the thickness of n-type, p-type or undoped gallium nitride single crystal is 0.5mm to 5mm.

3. The transmissive high damage threshold liquid crystal optically addressable spatial light modulator according to claim 1, wherein: The photoconductive layer (7) and the transparent conductive layer (2) are both made of the same gallium oxide material. The gallium oxide material is a gallium oxide thin film or a gallium oxide single crystal, and is in a β-crystalline phase with a carrier concentration of 1×1015 cm -3 to 1×1018cm -3 The thickness of the gallium oxide film is 1um to 5um, and the thickness of the gallium oxide single crystal is 0.5mm to 5mm.

4. The transmissive high damage threshold liquid crystal optically addressable spatial light modulator according to any one of claims 1 to 3, wherein: The liquid crystal layer (4) is a twisted nematic type with a twist angle ranging from 0° to 90°; the thickness d of the liquid crystal layer (4) satisfies the following conditions: Where Δn is the birefringence of the liquid crystal, and λ is the wavelength of the light to be modulated.

5. A high damage threshold liquid crystal optically addressable spatial light modulator according to any one of claims 1 to 3, characterized in that: In optical modulation applications, the wavelength of the addressing light is in the range of 200nm to 365nm.

6. The high damage threshold liquid crystal optically addressable spatial light modulator according to claim 5, characterized in that: In optical modulation applications, the addressing light uses blue-violet light controlled by LCOS, single blue-violet light emitted by Micro-Led, or blue-violet light controlled by DMD.

7. The high damage threshold liquid crystal optically addressable spatial light modulator according to any one of claims 1 to 3, characterized in that: The anti-reflection and anti-reflection film uses silicon dioxide film and magnesium fluoride film to match the refractive index of gallium nitride to reduce the reflection of visible light and near-infrared bands; or it is a multi-layer film, using titanium oxide as a high refractive index layer and then matching silicon dioxide as a low refractive index layer.

8. The high damage threshold liquid crystal optically addressable spatial light modulator according to any one of claims 1 to 3, characterized in that: The light aperture is larger than 40mm×40mm, which solves the size limitation of the original BSO and BGO optical waveguide materials.

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