A high laser damage threshold reflective light-addressable liquid crystal spatial light modulator for 1053 nm linearly polarized light

Abstract

A high laser damage threshold reflective light-addressed liquid crystal spatial light modulator for 1053nm linear polarized light beam shaping, the structure of which includes a computer-controlled LCoS type electrically addressed spatial light modulator, a polarization beam splitter, a polarizer, a liquid crystal box, an analyzer, and an AC stabilized power supply, wherein the liquid crystal box includes a transparent conductive film anti-reflection film layer, a transparent conductive film substrate layer, a first transparent conductive layer, a liquid crystal orientation layer, a liquid crystal layer, an orientation element, a reflective film layer, a light-conducting layer, and a second transparent conductive layer. By changing the transparent conductive layer material of the light-transmitting part in the liquid crystal box from ITO to gallium nitride material, the present invention achieves an improvement in the damage threshold of high-energy lasers compared to the liquid crystal box used in the existing liquid crystal spatial light modulator, which is conducive to the application of beam shaping in high-power laser devices.

Description

Technical Field

[0001] The invention belongs to the field of liquid crystal devices, and in particular relates to a high laser damage threshold reflective light-addressed liquid crystal spatial light modulator for 1053nm linearly polarized light. Background Art

[0002] Liquid crystal spatial light modulator (LC-SLM) is an optical device that can dynamically control the amplitude, phase and polarization state of the light field in real time, and has important applications in beam shaping of large laser devices. For example, in the NIF device in the United States, the OMEGA-EP device, the LMJ device in Europe, and the "Shenguang III" device in China, the liquid crystal spatial light modulator is used for pre-shielding of damage points, pre-compensation of beam intensity, and improving the uniformity of beam intensity.

[0003] In LC-SLM, the light-addressed liquid crystal spatial light modulator is a spatial light modulator that does not require pixel electrodes and does not affect the original light path. Compared with the common transmissive electrically addressed spatial light modulator based on thin film transistor (TFT) and the reflective electrically addressed spatial light modulator based on liquid crystal on silicon (LCoS), it avoids the low aperture ratio of TFT spatial light modulator due to components such as non-transparent electrodes, and avoids the optical path distortion caused by the black grid effect and other reasons of LCoS spatial light modulator.

[0004] When light-addressable liquid crystal spatial light modulators are used in large laser devices, their laser damage threshold is an important performance indicator. However, the laser damage threshold of indium tin oxide (ITO), the transparent conductive layer material currently used, is low, which makes the overall laser damage threshold of light-addressable liquid crystal spatial light modulators low, limiting their application in high-power laser devices. Therefore, how to improve the damage threshold of transparent conductive films and thus improve the laser damage threshold of light-addressable liquid crystal spatial light modulators has become an important research topic for relevant researchers.

[0005] Prior to the present invention, the research team has proposed a high laser damage threshold reflective light-addressable liquid crystal spatial light modulator for 1053nm linearly polarized light, but its liquid crystal box structure has a problem that the reflective film layer hinders the transmission of electrical signals between the photoconductive layer and the second conductive film layer. Summary of the invention

[0006] The purpose of the present invention is to provide a reflective light-addressable spatial light modulator, so as to obtain a higher laser damage threshold while ensuring its laser response performance. In the existing light-addressable spatial light modulator, the ITO material used in the transparent conductive layer of the liquid crystal box has a low laser damage threshold. By changing the transparent conductive layer material of the part through which light passes from ITO to gallium nitride material, the laser damage performance of the spatial light modulator can be improved while ensuring the performance of the spatial light modulator. On this basis, the present invention further adjusts the structure of the liquid crystal box in the device, and simplifies the structure of the spatial light modulator device while improving the electrical signal transmission of the liquid crystal box.

[0007] In order to achieve the above technical objectives, the technical solutions provided by the present invention are as follows:

[0008] A high laser damage threshold reflective optically addressed liquid crystal spatial light modulator for 1053nm linear polarized light comprises a polarization beam splitter (420-680nm), an LCoS type electrically addressed spatial light modulator controlled by a computer, a polarizer, a liquid crystal box, an analyzer and an AC voltage stabilized power supply. The liquid crystal box is characterized in that the liquid crystal box is composed of a transparent conductive film anti-reflection film layer, a transparent conductive film substrate layer, a first transparent conductive layer, a first liquid crystal orientation layer, a liquid crystal layer, an orienter, a second liquid crystal orientation layer, a reflective film layer, a photoconductive layer and a second transparent conductive layer. The first transparent conductive layer and the second transparent conductive layer are made of different materials. The photoconductive layer also serves as the substrate layer of the second transparent conductive layer and is made of a material different from that of the transparent conductive film substrate layer. The reflective film layer is located between the second liquid crystal orientation layer (47) and the photoconductive layer. The reflective film layer and the second transparent conductive layer are respectively coated on both sides of the photoconductive layer. An AC voltage stabilized power supply is connected between the first transparent conductive layer and the second transparent conductive layer. The orienter is located between the first liquid crystal orientation layer and the second liquid crystal orientation layer and surrounds the liquid crystal layer.

[0009] After the readout light is incident from the transparent conductive film anti-reflection film layer, it is transmitted in sequence through the transparent conductive film base layer, the first transparent conductive layer, the first liquid crystal orientation layer, the liquid crystal layer, and the second liquid crystal orientation layer, and then reflected by the reflective film layer (48) and returned to the original path and output;

[0010] After the writing light is incident from the second transparent conductive layer, it modulates the electrical signal on the photoconductive layer and then returns along the original path after being reflected by the reflective film layer (48);

[0011] The first transparent conductive layer has a transmittance of >70% for 1053nm polarized light and a damage threshold of >1J / cm for 1053nm pulse light with a pulse width of 10ns. 2 .

[0012] The transparent conductive film uses n-type doped gallium nitride or p-type doped gallium nitride, wherein the n-type doped gallium nitride uses a carrier concentration of 1*1018 cm -3 ~1*10 19 cm -3 The thickness of the p-type doped gallium nitride is 0.3mm to 0.5mm, and the carrier concentration of the p-type doped gallium nitride is 1*10 18 cm -3 ~1*10 19 cm -3 The magnesium-doped gallium nitride has a thickness of 0.3mm to 0.5mm.

[0013] The second transparent conductive layer is a transparent conductive layer.

[0014] The material used for the second transparent conductive layer is indium tin oxide.

[0015] The material used for the optical guide layer is bismuth silicate (BSO).

[0016] The principle of the present invention is as follows:

[0017] Since the laser damage threshold of gallium nitride materials is higher than that of ITO materials commonly used for transparent conductive layers, the laser damage threshold of the reflective light-addressed liquid crystal spatial light modulator is improved by replacing ITO with gallium nitride materials in the transparent conductive layer of the light-passing part of the reflective light-addressed liquid crystal spatial light modulator. By changing the position of the reflective film layer in the liquid crystal box from between the photoconductive layer and the second transparent conductive layer to between the liquid crystal orientation layer and the photoconductive layer and on the same side of the photoconductive layer and the second transparent conductive layer, the transmission of electrical signals between the photoconductive layer and the second transparent conductive layer is improved, and since the writing light and the reading light are incident in different directions, the device no longer needs to include a dichroic mirror and a read-out light exit window, simplifying the overall structure of the liquid crystal spatial light modulator.

[0018] Compared with the prior art, the advantages and features of the present invention are:

[0019] Based on the use of gallium nitride material in the transparent conductive layer in the optical path of the spatial light modulator, the higher laser damage threshold of the gallium nitride material is used to improve the overall laser damage threshold of the light-addressable liquid crystal spatial light modulator, thereby broadening the application range of the light-addressable liquid crystal spatial light modulator in high-energy laser devices. By changing the position of the reflective film layer in the liquid crystal box, the electrical signal transmission between the photoconductive layer and the second transparent conductive layer is improved, and the overall structure of the liquid crystal spatial light modulator is simplified. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of the reflective light-addressable liquid crystal spatial light modulator of the present invention. In the figure, 1-polarization beam splitter (420-680nm), 2-LCoS type electrically addressable spatial light modulator controlled by a computer, 3-polarizer, 4-liquid crystal box, 5-analyzer, 6-AC stabilized power supply.

[0021] Figure 2 It is a structural diagram of the liquid crystal box of the reflective light-addressed liquid crystal spatial light modulator in an embodiment of the present invention. In the figure, 41-transparent conductive film anti-reflection film layer, 42-transparent conductive film base layer, 43-first transparent conductive layer, 44-first liquid crystal orientation layer, 45-liquid crystal layer, 46-orientation element, 47-second liquid crystal orientation layer, 48-reflective film layer, 49-photoconductive layer, 410-second transparent conductive layer.

[0022] Figure 3 This is an example diagram of an experimental optical path for intensity modulation of 1053nm linear polarized light using an embodiment of the present invention. In the figure, A-1053nm linear polarized light source, B-aperture, C-polarizer, D-embodiment 1, E, F-lens group, G-analyzer, H-CCD, I-AC regulated power supply, and J-computer. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with embodiments and drawings, but the protection scope of the present invention shall not be limited thereby:

[0024] Figure 1 It is a schematic diagram of the structure of the high damage threshold reflective light-addressable liquid crystal spatial light modulator in the present invention. As can be seen from the figure, the structure of the high damage threshold reflective light-addressable liquid crystal spatial light modulator in the present invention includes: a polarization beam splitter (420-680nm) 1, a LCoS type electrically addressed spatial light modulator 2 controlled by a computer, a polarizer 3, a liquid crystal box 4, an analyzer 5, and an AC stabilized power supply 6. As can be seen from the figure, the liquid crystal box 4 is placed at an angle. After the 480nm blue LED writing light is input, it passes through the LCoS type electrically addressed spatial light modulator 2 and has a binary intensity distribution with a pixel structure. It is then irradiated onto the liquid crystal box 4 through the polarization beam splitter 1, and the light signal modulated by the LCoS type electrically addressed spatial light modulator 2 is converted into an electrical signal, and the 1053nm linearly polarized readout light, after passing through the polarizer 3, is injected from the other side of the liquid crystal box 4, and is modulated by the liquid crystal box 4 and then emitted through the analyzer 5. The polarization direction of the polarizer 3 and the analyzer 5 is parallel to the polarization direction of the 1053nm linearly polarized readout light.

[0025] Figure 24 is a structural diagram of a liquid crystal cell 4 in a high damage threshold reflective light-addressed liquid crystal spatial light modulator according to an embodiment of the present invention. As can be seen from the figure, the structure of the liquid crystal cell 4 includes: a transparent conductive film anti-reflection film layer 41, a transparent conductive film base layer 42, a first transparent conductive layer 43, a first liquid crystal orientation layer 44, a liquid crystal layer 45, an orientation element 46, a second liquid crystal orientation layer 47, a reflective film layer 48, a photoconductive layer 49, and a second transparent conductive layer 410. Among them, the reflective film layer 48 and the second transparent conductive layer 410 are respectively coated on both sides of the photoconductive layer 49. After the readout light is incident from the transparent conductive film anti-reflection film layer 41 of the liquid crystal cell 4, it is transmitted through the transparent conductive film base layer 42, the first transparent conductive layer 43, the first liquid crystal orientation layer 44, the liquid crystal layer 45, and the second liquid crystal orientation layer 47 in sequence, and then it is reflected by the reflective film layer 48 and then it returns to the original path and is output. The write light is incident from the second transparent conductive layer 410, modulates the electrical signal on the photoconductive layer 49, and then it is reflected by the reflective film layer 48 and then it returns to the original path. The orientation element 46 is located between the first liquid crystal orientation layer 44 and the second liquid crystal orientation layer 47 , surrounds the liquid crystal layer 45 , and plays a role in fixing the width of the liquid crystal layer 45 .

[0026] An AC regulated power source 6 is connected between the first transparent conductive layer 43 and the second transparent conductive layer 410 .

[0027] like Figure 1 As shown, the liquid crystal box is placed at an angle in the light path to prevent the incident light of the liquid crystal box from overlapping with the outgoing light.

[0028] The first transparent conductive layer 43 and the second transparent conductive layer 410 are made of different materials.

[0029] The liquid crystal layer 45 is a 90° twisted nematic liquid crystal, and the thickness d of the liquid crystal layer and the birefringence Δn of the liquid crystal satisfy

[0030] The material of the photoconductive layer 49 should meet the following requirements: 1. The conductivity increases with the intensity of the 480nm writing light, but has nothing to do with the intensity of the 1053nm reading light; 2. The transmittance of the 1053nm linear polarized light is higher than 65%; 3. It can be used as the base layer of the reflective film layer 48 and the second transparent conductive layer 410. This material is generally bismuth silicate (BSO).

[0031] The AC regulated power supply connected between the first transparent conductive layer 43 and the second transparent conductive layer 410 has a frequency of 100 Hz to 1000 Hz, and its operating voltage is determined according to the following principle: when there is no writing light irradiating the photoconductive layer 49 of the liquid crystal box 4, the partial pressure of the liquid crystal layer 45 is less than its threshold voltage; when there is writing light irradiating the photoconductive layer (49) of the liquid crystal box 4, the partial pressure of the liquid crystal layer 45 is greater than its saturation voltage.

[0032] The first transparent conductive layer 43 in the liquid crystal cell 4 has a transmittance of >70% for 1053nm polarized light, and a damage threshold of >1J / cm2 for 1053nm pulse light with a pulse width of 10ns. 2 The material used is doped gallium nitride material, generally silicon-doped gallium nitride (n-type doping) or magnesium-doped gallium nitride (p-type doping). The carrier concentration of silicon-doped gallium nitride is 1*10 18 cm -3 ~1*10 19 cm -3 , with a thickness of 0.3mm to 0.5mm. The carrier concentration of the magnesium-doped gallium nitride used is 1*10 18 cm -3 ~1*10 19 cm -3 , thickness is 0.3mm~0.5mm.

[0033] The second transparent conductive layer 410 in the liquid crystal cell 4 can generally be made of ITO material.

[0034] Figure 3 This is an experimental optical path diagram for intensity modulation of 1053nm linear polarized light using Example 1, including a 1053nm linear polarized light source A, an aperture B, a polarizer C, Example 1D, a lens E, a lens F, an analyzer G, a CCD (H), and a computer I, wherein the directions of the polarizer C and the analyzer G are parallel to the polarization direction of the light source.

Claims

1. A high laser damage threshold reflective optically addressed liquid crystal spatial light modulator for 1053 nm linearly polarized light, comprising a polarization beam splitter (1) for a wavelength of 420-680 nm, a computer-controlled LCoS type electrically addressed spatial light modulator (2), a polarizer (3), a liquid crystal cell (4), an analyzer (5) and an AC regulated power supply (6), characterized in that: The liquid crystal box (4) is composed of a transparent conductive film anti-reflection film layer (41), a transparent conductive film base layer (42), a first transparent conductive layer (43), a first liquid crystal orientation layer (44), a liquid crystal layer (45), an orientation element (46), a second liquid crystal orientation layer (47), a reflective film layer (48), a photoconductive layer (49), and a second transparent conductive layer (410); the first transparent conductive layer (43) and the second transparent conductive layer (410) are made of different materials; the photoconductive layer (49) also serves as the base layer of the second transparent conductive layer (410) and is made of a material different from that of the transparent conductive film base layer (42); the reflective film layer (48) is located between the second liquid crystal orientation layer (47) and the photoconductive layer (49); an AC regulated power supply (6) is connected between the first transparent conductive layer (43) and the second transparent conductive layer (410); the orientation element (46) is located between the first liquid crystal orientation layer (44) and the second liquid crystal orientation layer (47) and surrounds the liquid crystal layer (45); The first transparent conductive layer (43) is an n-type silicon-doped gallium nitride film or a p-type magnesium-doped gallium nitride film.

2. The reflective light-addressable liquid crystal spatial light modulator according to claim 1, characterized in that: After the readout light is incident from the transparent conductive film anti-reflection film layer (41), it is transmitted in sequence through the transparent conductive film base layer (42), the first transparent conductive layer (43), the first liquid crystal orientation layer (44), the liquid crystal layer (45), and the second liquid crystal orientation layer (47), and then it is reflected by the reflective film layer (48) and returns to the original path and is output; After the writing light is incident from the second transparent conductive layer (410), it modulates the electrical signal on the photoconductive layer (49) and then returns along the original path after being reflected by the reflective film layer (48).

3. The reflective light-addressable liquid crystal spatial light modulator according to claim 1, characterized in that: The first transparent conductive layer (43) has a transmittance of >70% for 1053nm polarized light and a damage threshold of >1J / cm for 1053nm pulse light with a pulse width of 10ns. 2 .

4. The reflective light-addressable liquid crystal spatial light modulator according to any one of claims 1 to 3, characterized in that: The carrier concentration of the first transparent conductive layer (43) is 1*10 18 cm -3 ~1*10 19 cm -3 , the thickness is 0.3~0.5mm.

5. The reflective light-addressable liquid crystal spatial light modulator according to any one of claims 1 to 3, characterized in that: The second transparent conductive layer (410) is a transparent conductive layer.

6. The reflective light-addressable liquid crystal spatial light modulator according to any one of claims 1 to 5, characterized in that: The material used for the second transparent conductive layer (410) is indium tin oxide (ITO).

7. The reflective light-addressable liquid crystal spatial light modulator according to any one of claims 1 to 5, characterized in that: The material used for the optical guide layer (49) is bismuth silicate (BSO).

Images