A temperature-tuned RGB cholesteric liquid crystal laser and its preparation method

Abstract

The present invention discloses a temperature-tuned RGB cholesteric liquid crystal laser and a preparation method thereof. The structure of the temperature-tuned RGB cholesteric liquid crystal laser includes an optical resonant cavity, and the optical resonant cavity sequentially includes a first reflective layer, a perovskite quantum dot layer, and a second reflective layer from bottom to top; wherein, the first reflective layer includes a cholesteric liquid crystal layer and a polymer protective layer disposed on the cholesteric liquid crystal layer; the cholesteric liquid crystal layer has fluidity; the polymer protective layer does not have fluidity. The present invention has excellent properties such as low laser threshold, high radiation intensity, and good repeatability, and can emit red, green, and blue lasers with specific reflection center wavelengths of the liquid crystal reflective layer at different temperatures, having good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, and particularly to a temperature-tuned RGB cholesteric liquid crystal laser and a preparation method thereof. Background Art

[0002] A laser generally consists of three parts: a pump source, a resonant cavity, and a gain medium.

[0003] An optical resonant cavity in the F-P mode is usually composed of two relatively arranged reflective layers. As a one-dimensional photonic crystal, cholesteric liquid crystal (CLC) has the property of Bragg reflection, can selectively reflect light of a specific wavelength, and also has a certain transmittance. Since CLC molecules self-assemble into a helical structure with a certain repeatability, the molecular director rotates 360° along a normal direction, and the distance between two directors in the same direction is called the pitch of the cholesteric liquid crystal (Pitch, hereinafter referred to as P value). When the wavelength of the incident light is equal to the P value, the matching photons will be selectively reflected, generating circularly polarized reflected light of a specific wavelength with the same chirality as the CLC, which is the photonic bandgap effect of CLC. The P value of CLC at a certain temperature is determined by the following formula:

[0004]

[0005] where CX is the concentration of the chiral dopant in the liquid crystal mixture, and HTP is the helical twisting power constant of the chiral dopant. After making a thin film with a certain ratio of liquid crystal mixture, the change in temperature will also affect the pitch of CLC, and thus affect its reflection. When the pitch shortens, the reflection center blue-shifts; when the pitch increases, the reflection center red-shifts. Therefore, the reflection wavelength of the cholesteric liquid crystal reflector can be controlled by controlling the temperature to meet the requirements of the reflective layer of the tunable laser. The cholesteric liquid crystal laser prepared based on this principle has the advantages of high stability and large tuning range, and can solve some drawbacks of semiconductor lasers.

[0006] The gain medium is generally a luminescent dye or a semiconductor luminescent material. The pump source, as an external energy source, causes the gain medium to generate population inversion. The resonant cavity selects light with a certain frequency and wavelength for gain amplification. When the gain of the generated light is greater than the loss threshold, laser emission can occur on the side with lower reflectivity. Currently, the most commonly used lasers are group III-V semiconductor lasers. However, such semiconductor lasers have problems such as poor temperature characteristics, easy divergence of the output light, easy generation of noise, and relatively high synthesis costs, and are not suitable for use in some occasions. The gain medium used in liquid crystal reflective lasers is usually a luminescent dye, such as DCM and PM597. However, polymer-stabilized liquid crystal lasers with ordinary luminescent dye gain usually have a high laser threshold and low emission intensity. In contrast, perovskite materials are semiconductor materials with excellent optoelectronic properties. Among them, pure inorganic CsPbX3 materials (X is a halogen element) are suitable for large-scale preparation at low cost due to their strong resistance to water and oxygen corrosion, and the fluorescence quantum yield of perovskite quantum dots prepared with this material is relatively high, making it an ideal material suitable as the gain medium for F-P cavity lasers. Although the newly studied perovskite quantum dot-doped liquid crystal lasers can solve the drawback of high laser threshold, usually the dispersion of perovskite quantum dots doped into cholesteric liquid crystals is very poor, the obtained optical gain is poor, and the repeatability of the device is very low. In addition, perovskite quantum dot materials with different emission bands will undergo phase transitions that are not conducive to luminescence, such as decomposition, when mixed. Therefore, they have not been well applied in the field of multicolor lasers, especially in the field of tunable pure-color lasers. Thus, how to effectively combine a perovskite optical gain medium with excellent luminescence performance and a liquid crystal reflector with excellent reflection performance and thermal and electrical responses to fabricate a new type of laser remains to be explored.

[0007] In summary, there is an urgent need to develop a new technical solution to solve the problems existing in the prior art and improve the performance of the device. Summary of the Invention

[0008] Based on this, the present invention provides a temperature-tunable RGB cholesteric liquid crystal laser, which has excellent performance such as a low laser threshold, high radiation intensity, and good repeatability, and can emit red, green, and blue lasers with specific reflection center wavelengths of the liquid crystal reflection layer at different temperatures, having good application prospects.

[0009] An object of the present invention is to provide a temperature-tunable RGB cholesteric liquid crystal laser. The structure of the temperature-tunable RGB cholesteric liquid crystal laser includes an optical resonant cavity, and the optical resonant cavity sequentially includes a first reflection layer, a perovskite quantum dot layer, and a second reflection layer from bottom to top;

[0010] Among them,

[0011] The first reflection layer includes a cholesteric liquid crystal layer and a polymer protective layer provided on the cholesteric liquid crystal layer;

[0012] The cholesteric liquid crystal layer has fluidity; the polymer protective layer does not have fluidity;

[0013] The perovskite quantum dot layer includes three kinds of perovskite quantum dots, and the three kinds of perovskite quantum dots emit red light, green light and blue light respectively.

[0014] The temperature-tuned RGB cholesteric liquid crystal laser of the present invention further includes a transparent insulating substrate, and a parallel alignment layer is provided on the transparent insulating substrate;

[0015] The first reflective layer is a polymer cholesteric liquid crystal layer and an in-situ formed transparent protective layer, and the first reflective layer is provided on one surface of the parallel alignment layer;

[0016] The second reflective layer is a noble metal reflective layer and is provided on the top of the device.

[0017] Further, the optical resonator further includes a first transparent separation layer and a second transparent separation layer, and the first transparent separation layer and the second transparent separation layer are respectively adjacently provided on the perovskite quantum dot layer.

[0018] Further, the first transparent separation layer, the perovskite quantum dot layer, and the second transparent separation layer together form a planar optical waveguide.

[0019] Further, the material of the perovskite quantum dot layer is CsPbX3, wherein X is selected from one of Cl, Cl m Br 3-m 、Br、Br m I 3-m 、I, and the value of m is 0-3.

[0020] Further, the emission wavelength bands of the three kinds of perovskite quantum dots are respectively: red light: 600-700 nm, green light: 480-580 nm, blue light: 380-460 nm.

[0021] As a high-performance light-emitting material, perovskite quantum dots have high fluorescence quantum yield for all-inorganic CsPbX3 quantum dots. The threshold of amplified spontaneous emission (ASE) generated by this kind of perovskite quantum dot thin film layer is extremely low, and the full width at half maximum of the emitted light is narrow, which can reach below 20 nm, and the monochromaticity and linearity are good. Moreover, the water and oxygen tolerance of this kind of perovskite layer material is better than that of organic-inorganic hybrid perovskite materials. Therefore, it is not necessary to prepare in a glove box, which is conducive to low-cost large-scale production.

[0022] Further, the perovskite quantum dot layer includes three types of perovskite quantum dots capable of emitting amplified spontaneous emissions of red, green, and blue colors respectively, and the thickness of the optical resonator cavity is greater than the least common multiple of half of the emission peak wavelengths of the three types of perovskite quantum dots, that is, 35 μm.

[0023] Generally, the thickness setting of the optical resonator cavity needs to satisfy the resonance formula of the laser. Regarding the thickness of the optical resonator cavity as the optical path L of light propagation, the optical path generally needs to satisfy L = emission wavelength / 2 * N, where N ≥ 1 and is an integer. In some embodiments of the present invention, the thickness of the optical resonator cavity is the least common multiple of half of the emission peak wavelengths of the three types of perovskite quantum dots.

[0024] Further, the thickness of the laser body is controlled within 1.0 - 2.0 cm. Structures such as the light-transmitting substrate, the first reflective layer, the optical resonator cavity layer, and the second reflective layer in the laser body are sequentially stacked and arranged in parallel.

[0025] Further, the first reflective layer is made of a liquid crystal mixture, and the liquid crystal mixture has the following components in parts by mass: 40 - 50 parts of polymerizable liquid crystal monomers, 30 - 40 parts of nematic liquid crystals, 0.1 - 1 part of photoinitiator, 0.1 - 1 part of ultraviolet light absorbing dye, 10 - 30 parts of chiral dopants, and 1 - 10 parts of crosslinking agents.

[0026] Further, the nematic liquid crystal is selected from E7 and 5CB; the chiral dopants are selected from S81, R811, S5011, and R5011; the photoinitiator can be Irg651; the ultraviolet light absorber can be UV dye 328; the polymerizable liquid crystal monomer can be a methacrylate such as isobornyl methacrylate; the crosslinking agent can be a diacrylate such as bisphenol A ethoxylated dimethacrylate and HCM - 008.

[0027] In previous studies, the temperature response ability of cholesteric liquid crystals was based on maintaining a certain fluidity. However, the price of maintaining this fluidity was the inability to effectively construct other functional structures on its surface. Therefore, a network was often formed by adding small molecule polymerizable monomers to it, fixing it into a polymer-stabilized cholesteric liquid crystal film with a certain rigidity. However, this type of polymer-stabilized cholesteric liquid crystal film lost the ability to change the P value with changes in thermal and electrical environments, making its reflectivity also fixed. Thus, in the present invention, we proposed a technique. By adding a chiral dopant to a nematic liquid crystal to form a cholesteric phase, and adding small molecule polymerizable monomers, a crosslinking agent, an ultraviolet absorber, and a photoinitiator, and by artificially controlling the ultraviolet irradiance and with the assistance of the added ultraviolet absorber, an ultraviolet gradient from top to bottom was formed inside the precursor film. The polymerization of small molecule monomers requires ultraviolet stimulation to initiate a radical reaction. Thus, polymerization occurs under a decreasing ultraviolet intensity gradient from top to bottom. At the same time, since the monomers on the surface layer of the film are consumed, the monomers in the lower layer diffuse upward through diffusion. Eventually, a homogeneous transparent polymer film is in-situ generated on the upper surface of the cholesteric liquid crystal film, endowing a certain rigidity to the entire structure while still allowing the lower cholesteric liquid crystal layer to retain a certain fluidity, making it possible to deposit a functional film above the reflective layer subsequently.

[0028] The present invention uses a cholesteric liquid crystal layer as the first reflective layer and a noble metal reflective layer as the second reflective layer. The latter has a higher reflectivity than the cholesteric liquid crystal layer. The difference in reflectivity between the two reflective layers enables the cholesteric liquid crystal laser to not require a special design for the difference in reflectivity of the two reflective layers, and the laser is fixed to emit from the direction of the liquid crystal reflective layer. When performing temperature increase and decrease operations on the laser, when the pitch of the CLC at the current temperature, that is, the position of the reflection peak, overlaps with the ASE emission peak wavelength of one of the perovskite quantum dots (red: 700; green: 520; blue: 490), the ASE of this color will be enhanced in reflection. Through the above structural design, the laser of the present invention can generate RGB three-color lasers at different temperatures.

[0029] Further, the second reflective layer is selected from one or more metals.

[0030] Further, the metal is selected from one or more of gold, silver, platinum, magnesium, copper, and aluminum.

[0031] The noble metal reflective layer has the characteristic of high reflectivity, which can reduce the energy loss of the device. The second reflective layer is preferably silver.

[0032] Further, the material of the transparent separation layer is selected from one of polymethyl methacrylate (PMMA) and polyvinyl alcohol (PVA).

[0033] Further, the temperature-tuned RGB cholesteric liquid crystal laser further includes a pump source.

[0034] Another object of the present invention is to improve the preparation method of the above-mentioned temperature-tuned RGB cholesteric liquid crystal laser. The preparation method of the temperature-tuned RGB cholesteric liquid crystal laser includes the following steps:

[0035] S1. A planar alignment layer is provided on a glass substrate.

[0036] S2. The liquid crystal mixture is coated on the surface of the parallel alignment layer, and then the surface of the liquid crystal mixture is subjected to ultraviolet light treatment to obtain the first reflective layer.

[0037] S3. A second reflective layer is provided.

[0038] Further, the preparation method of the temperature-tuned RGB cholesteric liquid crystal laser includes the following steps:

[0039] S1. An alignment layer material is spin-coated on a light-transmissive substrate, and then parallel alignment treatment is performed to obtain a light-transmissive substrate with a parallel alignment layer.

[0040] S2. A liquid crystal mixture including nematic liquid crystal, polymerizable liquid crystal monomer, chiral dopant, ultraviolet light absorber, and photoinitiator is scrape-coated on the parallel alignment layer, and then ultraviolet light and / or visible light irradiation polymerization is performed to form a first reflective layer composed of a cholesteric liquid crystal layer and an in-situ generated polymer protection layer.

[0041] S3. A first transparent separation layer is provided on the polymer protection layer, and then a perovskite quantum dot mixture is spin-coated on the first transparent separation layer and annealed and cured to form a perovskite quantum dot layer; a second transparent separation layer is provided on the perovskite quantum dot layer, and then a second reflective layer is provided on the second transparent separation layer.

[0042] Another object of the present invention is to provide an optical device, and the optical device includes the above-mentioned temperature-tuned RGB cholesteric liquid crystal laser.

[0043] Further, the optical device is an optical device applied to the fields of photon integration, optical fiber communication, biological detection, and optical sensing.

[0044] The present invention has the following beneficial effects:

[0045] 1. When the wavelength of the ASE radiation light excited by the pump source in the perovskite quantum dot layer in the present invention just overlaps with the reflection band of the cholesteric liquid crystal layer, the radiation light generated by ASE will be continuously reflected due to the Bragg reflection of the cholesteric liquid crystal layer, and the reflected light further excites the perovskite quantum dots to generate stimulated radiation, thereby continuously achieving optical gain. When the generated optical gain is greater than the optical loss caused by reflection and refraction in the device, laser emission can be achieved. Moreover, the perovskite quantum dot layer in this cholesteric liquid crystal laser has a high fluorescence quantum yield (up to 50 - 100%), making it easier to generate ASE, and correspondingly easier to generate laser emission, which further results in a laser with higher emission intensity and lower laser threshold, and the radiation threshold is lower than that of common semiconductor lasers.

[0046] 2. After the liquid crystal mixture in the present invention is irradiated with ultraviolet light, it maintains the fluidity of the cholesteric liquid crystal film that can change the P value with the change of thermal and electrical environments. At the same time, a homogeneous solid polymer protective layer is in-situ synthesized on its surface. Therefore, other functional films can be further applied on it. Through the above structural design, the laser of the present invention not only improves the device performance but also has the function of generating RGB three-color lasers at different temperatures.

[0047] 3. After the liquid crystal mixture in the present invention is irradiated with ultraviolet light, the lower cholesteric liquid crystal film with fluidity contains a chiral dopant with a single helicity (left S / right R). Therefore, it selectively reflects the circularly polarized light component with the same helicity, enabling the circularly polarized light with the same helicity to be reflected and enhanced in the resonant cavity, resulting in the emission of circularly polarized laser with high polarization degree. Description of the Drawings

[0048] Figure 1 Shows the structural schematic diagram of the temperature-tuned RGB cholesteric liquid crystal laser of the present invention;

[0049] Figure 2 Shows the schematic diagram of stimulated radiation of the temperature-tuned RGB cholesteric liquid crystal laser of the present invention under the excitation of the pump source laser;

[0050] Reference Signs: 100 - Substrate; 200 - Parallel Alignment Layer; 300 - First Reflective Layer; 310 - Cholesteric Liquid Crystal Layer; 320 - Polymer Protective Layer; 400 - Optical Resonator; 410 - First Transparent Separation Layer; 420 - Perovskite Quantum Dot Layer; 430 - Second Transparent Separation Layer; 440 - Second Reflective Layer. Detailed Embodiments

[0051] In order to more clearly illustrate the technical solutions of the present invention, the following examples are listed. The raw materials, reactions, and post-treatment means appearing in the examples are all common raw materials on the market and technical means well-known to those skilled in the art, unless otherwise specified.

[0052] The terms "preferred", "preferably", "more preferred", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain cases. However, in the same cases or other cases, other embodiments may also be preferred. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not available, nor is it intended to exclude other embodiments from the scope of the present invention.

[0053] It should be understood that, except in any operating examples or otherwise indicated, all numbers representing the amounts of ingredients used in, for example, the specification and claims should be understood to be modified in all cases by the term "about". Therefore, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that vary depending on the desired properties to be obtained by the present invention.

[0054] Please refer to Figure 1 , Figure 1 which shows a schematic structural diagram of an embodiment of the temperature-tuned RGB cholesteric liquid crystal laser of the present invention, as Figure 1 shown, the temperature-tuned RGB cholesteric liquid crystal laser body includes a substrate 100 and an optical resonator 400; a parallel alignment layer 200 is provided on the substrate 100; the optical resonator 400 includes a first reflective layer 300, a planar optical waveguide, and a second reflective layer 440; the first reflective layer 300 is provided on the parallel alignment layer 200, and the first reflective layer 300 includes a cholesteric liquid crystal layer 310 and a polymer protective layer 320; the planar optical waveguide is provided on the first reflective layer 300, and the planar optical waveguide includes a first transparent spacer layer 410, a perovskite quantum dot layer 420, and a second transparent spacer layer 430. The first transparent spacer layer 410 is sandwiched between the perovskite quantum dot layer 420 and the first reflective layer 300 for separating the perovskite quantum dot layer 420 and the first reflective layer 300; the second transparent spacer layer 430 is sandwiched between the perovskite quantum dot layer 420 and the second reflective layer 440 for separating the perovskite quantum dot layer 420 and the second reflective layer 440.

[0055] The first reflective layer 300 can be formed by ultraviolet polymerization of a liquid crystal mixture, and the liquid crystal mixture may include the following components in parts by mass: 40-50 parts of polymerizable liquid crystal monomers, 30-40 parts of nematic liquid crystals, 0.1-1 part of photoinitiator, 0.1-1 part of ultraviolet light absorbing dye, 10-30 parts of chiral dopant, and 1-10 parts of crosslinking agent. Among them, the nematic liquid crystal can be E7 or 5CB; the chiral dopant can be S81, R811, S5011, or R5011; the photoinitiator can be Irg651; the ultraviolet light absorber can be UV dye 328; the polymerizable liquid crystal monomer can be a methacrylate such as isobornyl methacrylate; and the crosslinking agent can be a diacrylate such as bisphenol A ethoxylated dimethacrylate or HCM-008.

[0056] The perovskite quantum dot layer 420 includes three perovskite quantum dots that can respectively emit amplified spontaneous emission of red, green, and blue light. The perovskite quantum dots can be CsPbX3, where X is selected from one of Cl, Cl m Br 3-m 、Br, Br m I 3-m 、I, and the value of m is 0-3.

[0057] In some embodiments, since the cholesteric liquid crystal reflective layer is in a liquid crystal state and has a certain fluidity, to meet the subsequent spin coating operation, after obtaining the cholesteric liquid crystal reflective layer with a polymer protective layer, a small amount of photocurable glue can be dropped at the edge of its film and cured by ultraviolet light irradiation to fix the reflective layer. This operation will not change the thickness of the film and will not affect the light emission of the device.

[0058] The above polymer cholesteric liquid crystal laser can be used in conjunction with an external pump source during use. In some embodiments, the pump source can also be a component of the polymer cholesteric liquid crystal laser itself, that is, the polymer cholesteric liquid crystal laser further includes a pump source, and the pump source is used to provide pump energy for the laser body.

[0059] See Figure 2, at a certain temperature, the cholesteric liquid crystal has a certain pitch P. When the cholesteric liquid crystal laser is stimulated by an external pump pulse laser, stimulated absorption occurs in the perovskite quantum dot layer 420 in the laser. Electrons in the quantum dots at low energy levels absorb the energy supplied by the pump source and jump to high energy levels, and are in a high-energy metastable state, thus generating population inversion. At this time, quantum dots with emission wavelengths matching the pitch of the CLC at the current temperature, that is, the reflection peak position, generate ASE, and the radiation light intensity increases. The ASE wavelengths of the three kinds of quantum dots are different, located at 700 nm, 520 nm, and 490 nm respectively. Then, under the dual action of the Bragg reflection of the polymer cholesteric liquid crystal layer and the silver reflection layer, the radiation light is amplified each time it passes through the optical waveguide layer, and the radiation laser exits from the liquid crystal thin film layer with a lower reflectivity.

[0060] In the embodiments of the present invention, "parts" refers to parts by mass.

[0061] Example 1

[0062] A temperature-tunable RGB cholesteric liquid crystal laser, the structure of the temperature-tunable RGB cholesteric liquid crystal laser includes an optical resonator, and the optical resonator sequentially includes a first reflection layer, a perovskite quantum dot layer, and a second reflection layer from bottom to top; the first reflection layer includes a cholesteric liquid crystal layer and a polymer protection layer provided on the cholesteric liquid crystal layer, and the cholesteric liquid crystal layer has fluidity; the polymer protection layer does not have fluidity.

[0063] The preparation method of the above temperature-tunable RGB cholesteric liquid crystal laser includes the following steps:

[0064] S1. After cleaning and ozone treatment of the quartz glass substrate, spin-coat 5 parts of an aqueous PVA solution on the surface of the substrate, anneal at 60 °C for 1 h, and after cooling, rub the PVA surface with a velvet black cloth in the same direction to obtain a parallel alignment layer;

[0065] S2. Under yellow light conditions, dissolve 45 parts of polymerizable liquid crystal monomer isobornyl methacrylate, 5 parts of crosslinking agent bisphenol A ethoxylated dimethacrylate, 0.5 part of photoinitiator Irg651, 0.5 part of ultraviolet absorber UV328, 34 parts of nematic liquid crystal monomer E7, and 15 parts of chiral dopant S81 in dichloromethane, seal and stir at 40 °C in a brown bottle for 24 h, and then open the lid and stir for 2 h to volatilize the solvent to obtain a liquid crystal mixture;

[0066] Scrape the liquid crystal mixture on the surface of the parallel alignment layer with a 75 μm doctor blade, and then cure it under ultraviolet light (350 nm) to obtain a first reflection layer composed of a cholesteric liquid crystal layer and a polymer protection layer;

[0067] S3. Spin-coat 5 parts of PMMA aqueous solution on the surface of the polymer protective layer, anneal at 50 °C for 1 h to obtain the first transparent separation layer; then spin-coat a mixture of 420 nm three kinds of perovskite quantum dots (CsPbCl3:CsPbCl3:CsPbBr3 = 1:1:1, m / m / m) on the surface of the first transparent separation layer, anneal at 50 °C for 1 h to obtain the perovskite quantum dot layer, and then continue to spin-coat 5 parts of PMMA aqueous solution on the surface of the perovskite quantum dot layer, anneal at 50 °C for 1 h to obtain the second transparent separation layer;

[0068] Evaporate 50 nm of silver on the surface of the second transparent separation layer to prepare the second reflective layer, and obtain the temperature-tuned RGB cholesteric liquid crystal laser.

[0069] Figure 1 The structural schematic diagram of the temperature-tuned RGB cholesteric liquid crystal laser of the present invention is shown.

[0070] Figure 2 The schematic diagram of stimulated emission of the temperature-tuned RGB cholesteric liquid crystal laser of the present invention under the excitation of the pump source laser is shown.

[0071] Example 2

[0072] A temperature-tuned RGB cholesteric liquid crystal laser, the structure of the temperature-tuned RGB cholesteric liquid crystal laser includes an optical resonator, and the optical resonator sequentially includes a first reflective layer, a perovskite quantum dot layer, and a second reflective layer from bottom to top; the first reflective layer includes a cholesteric liquid crystal layer and a polymer protective layer provided on the cholesteric liquid crystal layer, and the cholesteric liquid crystal layer has fluidity; the polymer protective layer does not have fluidity;

[0073] The temperature-tuned RGB cholesteric liquid crystal laser further includes a pump source.

[0074] The preparation method of the above temperature-tuned RGB cholesteric liquid crystal laser includes the following steps:

[0075] S1. After cleaning and ozone treatment of the quartz glass substrate, spin-coat 5 parts of PVA aqueous solution on the surface of the substrate, anneal at 60 °C for 1 h, and after cooling, rub the PVA surface along the same direction with a velvet black cloth to obtain a parallel alignment layer;

[0076] S2. Under yellow light conditions, dissolve 50 parts of polymerizable liquid crystal monomer isobornyl methacrylate, 3 parts of crosslinking agent HCM-008, 0.6 parts of photoinitiator Irg651, 0.3 parts of ultraviolet absorber UV328, 38 parts of nematic liquid crystal monomer 5CB and 20 parts of chiral dopant R5011 in dichloromethane, seal and stir at 40 °C in a brown bottle for 24 h, and then open the lid and stir for 2 h to volatilize the solvent to obtain a liquid crystal mixture;

[0077] The liquid crystal mixture is doctor-bladed on the surface of the parallel alignment layer with a 75-μm doctor blade, and then cured under ultraviolet light (350 nm) to obtain a first reflective layer composed of a cholesteric liquid crystal layer and a polymer protective layer;

[0078] S3. Spin-coat 5 parts of an aqueous PMMA solution on the surface of the polymer protective layer, anneal at 50 °C for 1 h to obtain a first transparent spacer layer; then spin-coat a mixture of three perovskite quantum dots (CsPbCl3:CsPbCl3:CsPbBr3 = 1:1:1, m / m / m) with a thickness of 420 nm on the surface of the first transparent spacer layer, anneal at 50 °C for 1 h to obtain a perovskite quantum dot layer, and then continue to spin-coat 5 parts of an aqueous PMMA solution on the surface of the perovskite quantum dot layer, anneal at 50 °C for 1 h to obtain a second transparent spacer layer;

[0079] Evaporate 50 nm of silver on the surface of the second transparent spacer layer to prepare a second reflective layer, and obtain the temperature-tunable RGB cholesteric liquid crystal laser.

[0080] When the above temperature-tuned RGB cholesteric liquid crystal laser is in use, when the radiation wavelength of the amplified spontaneous emission (ASE) generated by the perovskite quantum dot layer excited by the pump source just overlaps with the reflection band of the cholesteric liquid crystal layer, the radiation light generated by the amplified spontaneous emission will be continuously reflected due to the Bragg reflection of the polymer cholesteric liquid crystal layer. The reflected light further excites the perovskite quantum dots to generate stimulated emission, and then continuously realizes optical gain. When the generated optical gain is greater than the optical loss caused by reflection and refraction in the device, laser emission can be achieved. Moreover, the perovskite quantum dot layer in this cholesteric liquid crystal laser has a high fluorescence quantum yield (up to 50-100%), which makes it easier to generate ASE, and correspondingly easier to generate laser emission, thereby resulting in a laser with higher emission intensity and lower laser threshold. The radiation threshold is lower than that of common semiconductor lasers. In addition, the thin film containing the cholesteric liquid crystal layer is used as the first reflection layer, and the noble metal reflection layer is used as the second reflection layer, which has a higher reflectivity than the polymer cholesteric liquid crystal layer. The difference in the reflectivity of the two reflection layers enables the cholesteric liquid crystal laser to not require a special differential design of the reflectivity of the two reflection layers. In the example, for the cholesteric liquid crystal layer in the first reflection layer prepared, its P value decreases with the increase in temperature, thereby reducing the center wavelength of its reflection peak. Therefore, by controlling the temperature, its reflection characteristics can be adjusted, and then in the bands belonging to the three perovskite excitation lights of RGB, which are 700nm, 520nm, and 490nm respectively, a resonant cavity is formed to generate laser light of a specific wavelength. The above temperature-tuned RGB cholesteric liquid crystal laser can be applied to the preparation of optical devices in the fields of photon integration, optical fiber communication, biological detection, and optical sensing. Therefore, the present invention also provides another optical device, including any one of the above temperature-tuned RGB cholesteric liquid crystal lasers.

[0081] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

[0082] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A temperature-tuned RGB cholesteric liquid crystal laser, characterized in that: The structure of the temperature-tuned RGB cholesteric liquid crystal laser includes an optical resonator, which successively includes a first reflective layer, a perovskite quantum dot layer, and a second reflective layer from bottom to top; Wherein, The first reflective layer includes a cholesteric liquid crystal layer and a polymer protective layer provided on the cholesteric liquid crystal layer; The cholesteric liquid crystal layer has fluidity; the polymer protective layer does not have fluidity; The perovskite quantum dot layer includes three kinds of perovskite quantum dots, and the three kinds of perovskite quantum dots emit red light, green light, and blue light respectively; The optical resonator further includes a first transparent separation layer and a second transparent separation layer, and the first transparent separation layer and the second transparent separation layer are respectively adjacent to the perovskite quantum dot layer; The first reflective layer is made of a liquid crystal mixture, and the liquid crystal mixture has the following components in parts by mass: 40-50 parts of polymerizable liquid crystal monomer isobornyl methacrylate, 30-40 parts of nematic liquid crystal E7, 0.1-1 part of photoinitiator Irg651, 0.1-1 part of ultraviolet light absorbing dye UV328, 10-30 parts of chiral dopant S81, and 1-10 parts of crosslinking agent bisphenol A ethoxylated dimethacrylate.

2. The temperature-tuned RGB cholesteric liquid crystal laser according to claim 1, characterized in that: The material of the perovskite quantum dot layer is CsPbX3, where X is selected from Cl, Cl m Br 3-m , Br, Br m I 3-m , one of I, and the value of m is 0 - 3.

3. The temperature-tuned RGB cholesteric liquid crystal laser according to claim 1, characterized in that: The emission bands of the three kinds of perovskite quantum dots are respectively red light: 600-700 nm, green light: 480-580 nm, and blue light: 380-460 nm.

4. The temperature-tuned RGB cholesteric liquid crystal laser according to claim 1, characterized in that, The thickness of the optical resonator cavity is greater than the least common multiple of half of the emission peak wavelengths of the three kinds of perovskite quantum dots.

5. The temperature-tuned RGB cholesteric liquid crystal laser according to claim 1, characterized in that: The second reflective layer is selected from one or more metals.

6. The temperature-tuned RGB cholesteric liquid crystal laser according to claim 1, wherein The temperature-tuned RGB cholesteric liquid crystal laser further includes a pump source.

7. The method for preparing the temperature-tuned RGB cholesteric liquid crystal laser according to any one of claims 1 to 6, characterized in that: The preparation method of the temperature-tuned RGB cholesteric liquid crystal laser includes the following steps: S1. A planar alignment layer is provided on a glass substrate; S2. The liquid crystal mixture is coated on the surface of the parallel alignment layer, and then the surface of the liquid crystal mixture is treated with ultraviolet light to obtain the first reflective layer; S3. A second reflective layer is provided.

8. An optical device, comprising the temperature-tuned RGB cholesteric liquid crystal laser according to any one of claims 1-7.

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