Transmissive high-damage-threshold liquid crystal optically addressed spatial light modulator

Abstract

A transmissive high-damage-threshold liquid crystal optically addressed spatial light modulator. The optically addressed spatial light modulator sequentially comprises, from top to bottom, a substrate (1), a transparent conductive layer (2), a first PI alignment layer (3), a liquid crystal layer (4), spacers (5), a second PI alignment layer (6), and a photoconductive layer (7). The upper surface and the lower surface of the photoconductive layer (7) are coated with a first anti-reflection and transmittance-enhanced film (8) and a second anti-reflection and transmittance-enhanced film (9), respectively. The transparent conductive layer (2) and the photoconductive layer (7) are made of a same material, i.e., a gallium nitride material or a gallium oxide material possessing optical properties and conductive properties, which enhances irradiation resistance to high-energy-density lasers and high-average-power lasers, and solves the problem of cracking caused by inconsistent thermal expansion of different materials, the problem of beam modulation caused by a reflective mode, etc. The size of the gallium nitride material or the gallium oxide material can reach 150 mm, solving an aperture limitation of materials such as BSO and BGO and achieving large-aperture light transmission.

Description

A transmissive high-damage threshold liquid crystal light-addressed spatial light modulator TECHNICAL FIELD

[0001] The utility model belongs to liquid crystal spatial light modulator field, concretely is a kind of transmissive high-damage threshold wide spectrum big light aperture liquid crystal spatial light modulator. BACKGROUND

[0002] Liquid crystal spatial light modulator is an advanced light field regulation device, with the ability to dynamically adjust laser characteristics, such as amplitude, phase and polarization state adjustment. It has important applications in beam shaping of large laser devices, in addition, in the field of laser additive manufacturing, it is used as an image generation device.

[0003] In the light-addressed liquid crystal spatial light modulator, it does not need to use pixel electrodes, so it will not affect the original optical path. Compared with the common transmissive electrically-addressed spatial light modulator (such as thin film transistor, TFT) and reflective electrically-addressed spatial light modulator (such as liquid crystal on silicon, LCoS), the light-addressed liquid crystal spatial light modulator avoids the low aperture ratio problem caused by non-transparent electrodes and other components in the TFT modulator, and also avoids the optical path distortion caused by the black grid effect in the LCoS modulator.

[0004] However, the laser damage threshold of the light-addressed liquid crystal spatial light modulator is an important performance indicator when it is applied in large laser devices and additive manufacturing and other processing fields. At present, the transparent conductive layer material - indium tin oxide (ITO) has a low laser damage threshold, which not only leads to a low overall laser damage threshold of the light-addressed liquid crystal spatial light modulator, limiting its application in high-power laser devices, but also has strong absorption in the infrared band, and is easily heated after laser irradiation, causing heat accumulation inside the liquid crystal layer. Since liquid crystals are extremely sensitive to operating temperature, this causes the light-addressed spatial light modulator to be difficult to work stably for a long time or even fail under high-power laser irradiation.

[0005] To solve the above problems, the prior art proposes various solutions. Patent document CN113126373B uses gallium nitride (GaN) instead of ITO as a transparent conductive film material to improve the laser damage resistance of the spatial light modulator. However, since there is currently no effective method to combine GaN with the commonly used photoconductive material BSO, if BSO is used as the photoconductive layer, the transparent conductive layer cannot use GaN. 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, the reflective device has high requirements for the residual reflectivity coating of the liquid crystal window substrate and the flatness processing precision, and is 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, leading to problems of spectral modulation and time-domain modulation. Due to the size limitation of the BSO crystal, it is currently difficult to increase the light-detecting aperture of the spatial light modulator.

[0006] Patent document CN115113429A combines sapphire with the photoconductive layer through a hydroxide catalytic bonding method, which can significantly improve the heat dissipation efficiency of the photoconductive layer in the OASLM and improve the heat deposition problem of the OASLM under high-power laser. However, it does not fundamentally solve the problem of low thermal conductivity of the BSO crystal. Similarly, due to the size limitation of the BSO crystal, it is currently difficult to increase the light-detecting aperture of the spatial light modulator.

[0007] Patent document CN114594633A uses gallium nitride as a transparent conductive material and zinc oxide film as a photoconductor. Compared with the liquid crystal cell used in the traditional liquid crystal spatial light modulator, this combination improves the resistance to high-energy laser. However, the manufacturing process is complex and difficult to implement.

[0008] Patent document CN116736584A uses a plasma electrode to replace the commonly used transparent conductive film layer, which not only allows the light-addressed spatial light modulator to work in transmissive mode, but also achieves high damage threshold characteristics of the device. However, due to the narrow gap between the photoconductive layer and the liquid crystal layer, the processing requirements are high, and precise control of discharge parameters is required to maintain the stability of the plasma.

[0009] Patent document US20240142814A1 uses a super-wide-bandgap semiconductor to replace the original BSO crystal as a photoconductor, improving the overall device's resistance to laser irradiation. However, the conductive layer uses ITO film coated on the photoconductor, which limits the overall device's resistance to laser irradiation.

[0010] In summary, although the prior art improves the laser damage threshold and performance of the light-addressed liquid crystal spatial light modulator to a certain extent, there are still limitations in material combination, machining precision, manufacturing process and performance of the material itself, etc. Therefore, developing new transparent conductive materials and optimizing the structure design to improve the laser damage threshold, reduce the processing difficulty and improve the overall performance become the key direction to promote the development of the light-addressed liquid crystal spatial light modulator technology.

[0011] Practical new

[0012] The utility model discloses a new structure to overcome the existing device defects, replaces the traditional ITO transparent electrode and BSO light guide layer with gallium nitride or gallium oxide etc. high thermal conductivity laser irradiation resistant material that has light guide characteristic and conductive characteristic simultaneously, makes the heat conduction performance of liquid crystal both sides material be equivalent, avoids the deformation even the rupture problem introduced in the liquid crystal cell packaging process, realizes the transmission type modulation function, improves the laser damage threshold and improves the finished product rate of liquid crystal light valve.

[0013] The utility model discloses a new structure to overcome the existing device defects, replaces the traditional ITO transparent electrode and BSO light guide layer with gallium nitride or gallium oxide etc. high thermal conductivity laser irradiation resistant material that has light guide characteristic and conductive characteristic simultaneously, makes the heat conduction performance of liquid crystal both sides material be equivalent, avoids the deformation even the rupture problem introduced in the liquid crystal cell packaging process, realizes the transmission type modulation function, improves the laser damage threshold and improves the finished product rate of liquid crystal light valve.

[0014] A kind of high damage threshold liquid crystal light-addressed spatial light modulator, from top to bottom sequentially include substrate, transparent conductive layer, first PI orientation layer, liquid crystal layer encapsulated by interval, second PI orientation layer, light guide layer, the first anti-reflection film and second anti-reflection film are coated on the upper and lower surfaces of the light guide layer respectively;The light guide layer and transparent conductive layer are all same kind of material that has light characteristic and conductive characteristic simultaneously and thermal conductivity is greater than 3 (W / m·K);

[0015] At room temperature, the conductivity of pure gallium nitride material is low, and it is not suitable as a transparent conductive film material, so it needs to be doped, and materials such as silicon, magnesium or carbon can be selected, and low carrier concentration and high carrier mobility need to be considered. The liquid crystal layer is encapsulated between the first orientation layer and the second orientation layer by the spacer. Gallium nitride not only serves as a conductive layer, but also as a light guide layer. The light guide layer can use 200-360 nm wavelength addressing light to irradiate gallium nitride according to the absorption spectrum of gallium nitride. The transmission spectrum of gallium nitride covers 1-5 um, so using gallium nitride as a light-addressed liquid crystal light valve, the addressing light wavelength can use 200-360 nm light; The readout light can cover 1-5 um band laser. The size of gallium nitride can reach two inches, four inches, six inches or even eight inches, so a light-addressed spatial light modulator with a light aperture larger than 40mm*40mm can be made. The size limitation of the original BSO and BGO light guide materials is solved.

[0016] Optionally, the light guide layer and the transparent conductive layer are both made of the same gallium nitride material.

[0017] Preferably, the gallium nitride material is an n-type silicon-doped gallium nitride thin film, a p-type magnesium-doped gallium nitride thin film, or an n-type doped gallium nitride thin film.

[0018] Gallium nitride (GaN) silicon single crystal, p-type magnesium-doped GaN single crystal, or undoped GaN single crystal, wherein the n-type GaN silicon-doped film, p-type magnesium-doped GaN film, n-type GaN silicon-doped single crystal, p-type magnesium-doped GaN single crystal, or undoped GaN single crystal has a carrier concentration of 1×10¹⁸ cm⁻³ to 1×10²⁰ cm⁻³, the thickness of the n-type or p-type GaN film is 1µm to 5µm, and the thickness of the n-type, p-type, or undoped GaN single crystal is 0.5mm to 5mm.

[0019] Gallium oxide (GaO) is an ultra-wide bandgap semiconductor material with stable chemical properties, resistance to corrosion, high mechanical strength, stable performance at high temperatures, and high transparency in the visible and ultraviolet light regions, especially in the ultraviolet and blue light regions. This is a characteristic not found in traditional transparent conductive materials, thus β-Ga2O3 single crystals can serve as transparent conductive materials. The liquid crystal layer is encapsulated between the first and second alignment layers using spacers. Gallium oxide not only functions as a conductive layer but also as a photoconductor layer. Based on the absorption spectrum of gallium oxide, the addressing light wavelength can use the 200nm–270nm band; the readout light can cover the 500nm–1.5µm laser band. Gallium oxide can be manufactured in sizes of two inches, four inches, and six inches, thus enabling the fabrication of optically addressed spatial light modulators with apertures larger than 40mm × 40mm. This overcomes the size limitations of traditional BSO and BGO photoconductor materials.

[0020] Optionally, the light-conducting layer and the transparent conductive layer are both made of the same gallium oxide material.

[0021] Preferably, the gallium oxide material is a gallium oxide thin film or a gallium oxide single crystal, and among the six crystal phases α, β, γ, δ, ε, and κ, the β crystal phase is used, with a carrier concentration of 1×10⁻⁶. 15 cm -3 ~1×10 18 cm -3 The thickness of gallium oxide thin films is 1µm to 5µm, and the thickness of gallium oxide single crystals is 0.5mm to 5mm.

[0022] Furthermore, the liquid crystal layer is of a twisted nematic type with a twist angle ranging from 0° to 90°; the thickness d of the liquid crystal layer satisfies the following condition: Where Δn is the birefringence of the liquid crystal and λ is the wavelength of the light to be modulated.

[0023] In optical modulation applications, the high damage threshold liquid crystal optical addressing spatial light modulator provided by this invention addresses light in the range of 200nm to 365nm.

[0024] Preferably, the addressing light uses LCOS-controlled blue-violet light, or Micro-LED emits a single blue-violet light, or DMD-controlled blue-violet light.

[0025] In the device described, a coating is applied to the upper and lower surfaces of the photoconductor layer. This coating is used to reduce reflection and increase light transmission, thereby reducing the interference between reflected light caused by Fresnel diffraction and preventing unnecessary beam modulation.

[0026] The addressing light used in this invention is blue light or ultraviolet light. It can be modulated using LCOS or DMD, or directly used as the addressing light from sources such as LEDs or Micro LEDs. The materials mentioned are not limited to gallium nitride and gallium oxide; other materials possessing both photoconductivity and electrical conductivity, as well as high thermal conductivity, are also within the scope of this invention.

[0027] The applicable readout wavelength of this invention mainly depends on the transmittance of materials such as gallium nitride and gallium oxide, which are used as both photoconductive and conductive layers.

[0028] The antireflection and anti-reflection film used in this invention can be made of silicon dioxide film and magnesium fluoride film to match the refractive index of gallium nitride, in order to reduce the reflection of visible light and near-infrared bands; or it can be a multilayer film, which can use titanium oxide as a high refractive index layer and then match silicon dioxide as a low refractive index layer.

[0029] The aforementioned materials are not limited to silicon dioxide, magnesium fluoride, and titanium dioxide; other materials that simultaneously possess anti-reflection and anti-reflection properties in both visible and infrared light bands are also within the scope of this utility model.

[0030] When the high-damage-threshold liquid crystal optical 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 It is a function that changes with temperature, expressed as: U th U 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. th The gamma curve will decrease as the temperature rises, requiring temperature monitoring and a closed-loop control system to maintain a stable gamma curve.

[0031] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0032] By using gallium nitride material in the transparent conductive layer, the higher laser damage threshold of 1.67 J / cm^2 of the gallium nitride material is utilized to improve the overall laser damage threshold of the light-addressed liquid crystal spatial light modulator compared with 0.467 J / cm2 of ITO. The commonly used BSO photoconductive crystal is replaced by gallium nitride, which avoids the problem that the gallium nitride film is difficult to be combined with BSO, and thus a transmissive, high damage threshold spatial light modulator is realized, and compared with the reflective structure, the transmissive spatial light modulator has the advantages of small spectral distortion and small wavefront distortion.

[0033] The utility model discloses in transparent conductive layer uses gallium oxide material, utilizes the higher laser damage threshold of 3.44J / cm^2 of gallium oxide material, compared with 0.467J / cm 2 , improve the overall laser damage threshold of light-addressed liquid crystal spatial light modulator. The commonly used BSO photoconductive crystal is replaced by gallium oxide, which avoids the problem that the gallium nitride film is difficult to be combined with BSO, and thus a transmissive, high damage threshold spatial light modulator is realized, and compared with the reflective structure, the transmissive spatial light modulator has the advantages of small spectral distortion and small wavefront distortion.

[0034] The light guide material used in the utility model optimizes the problem that the current BSO crystal, BGO crystal and the like cannot grow large aperture crystals. At present, the BSO crystal can reach 3 inches, and the gallium nitride or gallium oxide can be made into large aperture crystals. The gallium nitride single crystal can reach 6 inches or even 8 inches, and the gallium oxide single crystal can also reach 6 inches.

[0035] The thermal conductivity of the BSO crystal is 0.006 W / cm×K, and the thermal conductivity of the gallium nitride is 1.3 W / cm×K, and the thermal conductivity of the gallium oxide is 0.11 W / cm×K, all of which are higher than the thermal conductivity of the BSO crystal, thereby optimizing the problem of low thermal conductivity of the BSO crystal. Therefore, the laser irradiation resistance of the light-addressed spatial light modulator can be improved by using the gallium nitride, the gallium oxide and the like instead of the BSO. BRIEF DESCRIPTION OF DRAWINGS

[0036] Fig. 1 is a structural schematic view of the high damage threshold light-addressed spatial light modulator according to the utility model.

[0037] Fig. 2 is a schematic view of the amplitude modulation of the light-addressed spatial light modulator. DETAILED DESCRIPTION

[0038] The utility model will be further described below in combination with the embodiments and the drawings, but the protection scope of the utility model should not be limited thereto.

[0039] Embodiment 1

[0040] As shown in Fig. 1, a high-damage-threshold light-addressed spatial light modulator comprises, from top to bottom, a substrate 1, a transparent conductive layer 2, a first PI alignment layer 3, a liquid crystal layer 4 encapsulated by spacers 5, a second PI alignment layer 6, and a light guide layer 7, the upper and lower surfaces of the light guide layer 7 being coated with a first anti-reflection coating 8 and a second anti-reflection coating 9, respectively.

[0041] The lower surface of the substrate 1 is coated with the transparent conductive layer 2 and the first PI alignment layer 3 in sequence, the upper surface of the light guide layer 7 coated with the first anti-reflection coating 8 is coated with the second PI alignment layer 6, and the liquid crystal layer 4 encapsulated by the spacers 5 is filled by dispensing after the substrate 1 and the light guide layer 7 are adhered.

[0042] The preparation method of the high-damage-threshold light-addressed spatial light modulator comprises the following steps:

[0043] Step 1. The lower surface of the substrate 1 is coated with the transparent conductive layer 2 and the first PI alignment layer 3 in sequence, the upper surface of the light guide layer 7 is coated with the first anti-reflection coating 8 and the second PI alignment layer 6 in sequence, and the lower surface of the light guide layer 7 is coated with the second anti-reflection coating 9.

[0044] Step 2. The substrate 1 and the light guide layer 7 are adhered and cured by dispensing the doped spacers 5 to form a parallel flat box with fixed gaps.

[0045] Step 3. The liquid crystal layer 4 is filled in the parallel flat box through a filling port.

[0046] Step 4. The parallel flat box filled with the liquid crystal layer 4 is vacuum-pressed by a vacuum packaging machine, and then cured by ultraviolet light for 30 seconds to complete the box.

[0047] The thickness of the substrate 1 is 0.3 mm or 0.4 mm or 0.5 mm, and is preferably 0.5 mm. The material can be sapphire or K9 glass or other light-transmitting materials.

[0048] The transparent conductive layer 2 is a gallium nitride transparent conductive film or a gallium nitride single crystal, and is any one of the following materials:

[0049] (1) a thin film layer with a thickness of 1 um to 5 um coated with silicon-doped gallium nitride (n-type doping), the carrier concentration of the silicon-doped gallium nitride being 1×10 18 cm -3 - 1×10 20 cm -3 , preferably 1×10 18 cm -3 , and 5 um;

[0050] (2) a thin film layer with a thickness of 1 um to 5 um coated with magnesium-doped gallium nitride (p-type doping), the carrier concentration of the magnesium-doped gallium nitride being 1×10 18 cm -3 - 1×1020 cm -3 , 1 x 10 18 cm -3 , 5um;

[0051] (3) The thickness of the n-type silicon-doped gallium nitride single crystal is 0.5mm-5mm, and the carrier concentration of the silicon-doped gallium nitride is 1 x 10 18 cm -3 -1 x 10 20 cm -3 , 1 x 10 18 cm -3 , 1 x 10 18 cm -3 , 1mm;

[0052] (4) The thickness of the p-type magnesium-doped gallium nitride single crystal is 0.5mm-5mm, and the carrier concentration of the magnesium-doped gallium nitride is 1 x 10 18 cm -3 -1 x 10 20 cm -3 , 1 x 10 18 cm -3 , 1mm;

[0053] (5) The thickness of the undoped gallium nitride single crystal is 0.5mm-5mm, and the carrier concentration is 1 x 10 18 cm -3 -1 x 10 20 cm -3 , 1 x 10 18 cm -3 , 1mm.

[0054] The thickness of the light guide layer 7 is 0.5mm-5mm, and is preferably 1mm.

[0055] The first anti-reflection film 8 and the second anti-reflection film 9 are made of silicon dioxide, and the thickness of the film layer is 3-5um, and the specific performance indicators are: the thickness is 3um, the transmittance is 95%, and the reflectance is 3%.

[0056] The thickness d of the liquid crystal layer 4 is controlled by applying a spacer 5 to the edge part of the liquid crystal cell, and the thickness is controlled by the thickness of the spacer 5, and the specific indicators are: the thickness d is 4.071um.

[0057] When the optical addressing spatial light modulator is amplitude type, the liquid crystal layer 4 works in the twisted nematic mode.

[0058] The first PI alignment layer 3 and the second PI alignment layer 6 can be polyimide material, and the thickness is 250nm-125um, and is preferably 500nm.

[0059] In the light modulation application, the wavelength of the modulated laser is 1053nm, and the liquid crystal light-addressed spatial light modulator is amplitude type; the wavelength of the addressing light is 250nm

[0060] A dichroic mirror 13 is arranged behind the high-damage-threshold liquid crystal light-addressed spatial light modulator.

[0061] The dichroic mirror 13 has a reflectivity of more than 90% for the 45-degree incident addressing light of the 200nm-360nm wavelength band, and a transmittance of more than 80% for the 45-degree incident light beam with a center wavelength that can be set in the range of 0.4um-1.5um and a spectral width of ±0.5um.

[0062] The liquid crystal layer 4 is a twisted nematic liquid crystal with a twist angle in the range of 0°-90°, and the liquid crystal thickness d and the liquid crystal birefringence Δn satisfy the relationship of d=λ / (2Δn sin(θ / 2)) The wavelength λ is 1053nm, the birefringence Δn is 0.224, the thickness d is 4.071um, and the twist angle is selected as 90°.

[0063] As shown in FIG. 2, further connecting a wire and applying a voltage of 40V to the gallium nitride transparent conductive layer 2 and the gallium nitride photoconductive layer 7, then the 250nm addressing light is reflected by the dichroic mirror 13 and irradiated onto the photoconductive layer 7 to achieve addressing. The incident light is amplitude-modulated after passing through the light-addressed spatial light modulator, and the output light is the modulated output light.

[0064] The effective value of the voltage is between 10V and 200V, and the frequency is between 50Hz and 1000Hz, and the voltage amplitude and frequency are adjustable, and are specifically selected as 40V and 800Hz.

[0065] Embodiment 2

[0066] As shown in FIG. 1, a high-damage-threshold light-addressed spatial light modulator includes, from top to bottom, a substrate 1, a transparent conductive layer 2, a first PI alignment layer 3, a liquid crystal layer 4 encapsulated by spacers 5, a second PI alignment layer 6, and a photoconductive layer 7, and the upper and lower surfaces of the photoconductive layer 7 are coated with a first anti-reflection coating 8 and a second anti-reflection coating 9, respectively.

[0067] The lower surface of the substrate 1 is sequentially coated with the transparent conductive layer 2 and the first PI alignment layer 3; the upper surface of the photoconductive layer 7 coated with the first anti-reflection coating 8 is coated with the second PI alignment layer 6; and the liquid crystal layer 4 encapsulated by the spacers 5 is filled after being attached to the substrate 1 and the photoconductive layer 7 by point gluing.

[0068] The preparation method of the above-mentioned high-damage-threshold light-addressed spatial light modulator includes the following steps:

[0069] Step 1. Plating transparent conductive layer 2 and first PI alignment layer 3 on the lower surface of substrate 1 in turn; plating first anti-reflective film 8 and second PI alignment layer 6 on the upper surface of light guide layer 7 in turn, and plating second anti-reflective film 9 on the lower surface of light guide layer 7.

[0070] Step 2. Using dispensing of doped spacers 5 to adhere and cure substrate 1 and light guide layer 7, forming a gap-fixed parallel flat box.

[0071] Step 3. Fill the liquid crystal layer 4 through the filling port to fill the parallel flat box.

[0072] Step 4. First, use a vacuum packaging machine to vacuum press the parallel flat box filled with liquid crystal layer 4, and then use ultraviolet light to cure for 30 seconds to complete the box.

[0073] The thickness of the substrate 1 is 0.3mm or 0.4mm or 0.5mm, and the material can be sapphire or K9 glass or other light-transmitting materials.

[0074] The transparent conductive layer 2 is a gallium oxide conductive transparent film or a gallium oxide single crystal, which is any of the following materials:

[0075] (1) Undoped gallium oxide conductive transparent film, thickness 1um-5um, carrier concentration 1×10 15 cm -3 -1×10 18 cm -3 , selected: 3um, 1×10 15 cm -3 ;

[0076] (2) Gallium oxide single crystal thickness 0.5mm-5mm, carrier concentration 1×10 15 cm -3 -1×10 18 cm -3 , selected: 1mm, 1×10 15 cm -3 .

[0077] The thickness of the light guide layer 7 is 0.5mm-5mm, selected: 1mm and prepared with the same material as the transparent conductive layer 2.

[0078] The first anti-reflective film 8 and the second anti-reflective film 9 can be a film made of silicon dioxide, with a film thickness of 3-5um, and the specific performance indicators are: thickness 3um, transmittance 95%, reflectance 3%.

[0079] The thickness d of the liquid crystal layer 4 is controlled by applying spacers 5 to the edge part of the liquid crystal box, and the thickness is controlled by the thickness of the spacers, and the specific index is: d thickness 4.071um.

[0080] The liquid crystal layer 4 is a twisted nematic liquid crystal, the twist angle is in the range of 0°-90°, and 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 um, and the twist angle is selected as 90°.

[0081] When the optical addressing spatial light modulator is an amplitude type, the liquid crystal layer 4 works in a twisted nematic mode.

[0082] The first alignment layer 3 and the second alignment layer 6 can be polyimide materials.

[0083] In the optical modulation application, the wavelength of the modulated laser is 1053 nm, and the liquid crystal optical addressing spatial light modulator is an amplitude type; the wavelength band of the addressing light is: 250 nm;

[0084] In the optical modulation application, a dichroic mirror 13 is arranged behind the high damage threshold liquid crystal optical addressing spatial light modulator;

[0085] The dichroic mirror 13 has a reflectivity of the addressing light of 200 nm to 270 nm at an incident angle of 45 degrees higher than 90%, and a transmittance of the light beam of the center wavelength which can also be set in a bandwidth range of 0.4 um to 1.5 um according to needs, and a spectral width of ±0.5 um higher than 80%.

[0086] As shown in FIG. 2, further connecting a lead wire and applying a voltage of 40 V to the gallium oxide transparent conductive layer and the gallium oxide photoconductive layer, then the 250 nm addressing light is reflected by the dichroic mirror 13 and irradiated to the photoconductive layer to achieve addressing. The incident light is amplitude-modulated after passing through the optical addressing spatial light modulator, and the output light is the modulated output light.

[0087] The effective value of the voltage is between 10 V and 200 V, the frequency is between 50 Hz and 1000 Hz, and the voltage amplitude and the frequency are adjustable, and specifically selected as 40 V and the frequency is set at 800 Hz.

[0088] Embodiment 1:

[0089] Substrate: a glass substrate with high light transmittance is selected.

[0090] Transparent conductive layer: an n-type silicon-doped gallium nitride film with a thickness of 2 um and a carrier concentration of 5×1018cm-3 is adopted to ensure good conductivity and light transmittance.

[0091] First PI alignment layer: coated on the transparent conductive layer, used for controlling the orientation of the liquid crystal molecules.

[0092] Liquid crystal layer: twisted nematic liquid crystal is adopted, the twist angle is 45 degrees, and the thickness d is calculated according to the formula d=(lambda Delta n) / (2pi), wherein lambda is 550nm (visible light band), and Delta n is the birefringence of the liquid crystal, so that the effective modulation of the liquid crystal layer to visible light is ensured.

[0093] Second PI alignment layer: coated below the liquid crystal layer, cooperates with the first PI alignment layer to maintain the stable orientation of the liquid crystal molecules.

[0094] Light guide layer: n-type silicon-doped gallium nitride film is also adopted, the thickness is 2um, and the upper and lower surfaces are respectively coated with a silicon dioxide film and a magnesium fluoride film as an antireflection film, so that the interference of reflected light is reduced, and the light transmittance is improved.

[0095] By building a transmission type modulation performance test system, the spectral distortion and wavefront distortion of the modulator in the transmission mode are measured, it is known that the overall laser damage threshold of the light addressing liquid crystal spatial light modulator is obviously improved, the deformation and even the rupture problem caused by thermal deposition in the liquid crystal box packaging process is effectively solved, the transmission type structure has the advantages of small spectral distortion and small wavefront distortion, and the performance of the modulator is improved.

Claims

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

2. The transmissive high damage threshold liquid crystal light addressing spatial light modulator according to claim 1, characterized in that The light guide layer (7) and the transparent conductive layer (2) are both gallium nitride materials, which are selected from one of n-type silicon-doped gallium nitride film, p-type magnesium-doped gallium nitride 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 the n-type or p-type gallium nitride 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.

3. The transmissive high damage threshold liquid crystal light addressing spatial light modulator according to claim 1, wherein, The light guide layer (7) and the transparent conductive layer (2) are both gallium oxide materials, the gallium oxide material is a gallium oxide film or a gallium oxide single crystal, and is a beta crystal phase, the carrier concentration is 1x1015cm -3 -1x1018cm -3 -3, the thickness of the gallium oxide film is 1um-5um, and the thickness of the gallium oxide single crystal is 0.5mm-5mm.

4. The transmissive high damage threshold liquid crystal light addressing spatial light modulator according to any one of claims 1 to 3, characterized in that The liquid crystal layer (4) is a twisted nematic type, and the twist angle ranges from 0° to 90°; the thickness d of the liquid crystal layer (4) satisfies the following condition: 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 addressed spatial light modulator according to any one of claims 1 to 3, characterized in that, In the light modulation application, the wavelength of the addressing light is in the range of 200nm-365nm.

6. A high damage threshold liquid crystal optically addressed spatial light modulator according to claim 5, wherein, In the light modulation application, the addressing light is 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 light addressing spatial light modulator according to any one of claims 1 to 3, wherein, The anti-reflection film 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 band; it can also be a multilayer film using titanium oxide as a high refractive index layer and matching silicon dioxide as a low refractive layer.

8. The high damage threshold liquid crystal light addressing spatial light modulator according to any one of claims 1 to 3, wherein, The light aperture is greater than 40mm*40mm, solving the size limitation of the original BSO and BGO light guide materials.

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