AlN-based deep ultraviolet space laser based on nuclear pumping

Abstract

The present invention relates to an AlN-based space deep ultraviolet laser based on nuclear pumping, which includes a working substance, an excitation energy source and an optical resonant cavity, wherein the working substance includes an AlN semiconductor medium capable of realizing energy level transition; the excitation energy source uses nuclear energy to directly pump the working substance to give energy to the atoms of the working substance to excite; the optical resonant cavity allows the working substance to continuously undergo stimulated radiation, while limiting the output direction of the laser; the diamond polycrystalline layer, as a heat dissipation material with high thermal conductivity, can also be used as a moderator for nuclear fuel; the diamond polycrystalline layer is sequentially stacked with an AlN-based semiconductor active region, highly enriched uranium and an AlN-based semiconductor active region to form a core-laser medium stacking unit structure, thereby forming a reactor. The present invention utilizes nuclear energy to directly pump AlN-based semiconductor materials to realize a deep ultraviolet laser with a lasing wave of 150nm-260nm, with an output power above the MW level, and at the same time, has a small size, a compact structure and good maneuverability.

Description

Technical Field

[0001] The invention relates to the technical field of high-power space lasers, and in particular to an AlN-based space deep ultraviolet laser based on nuclear pumping. Background Art

[0002] With the increasing development of space information acquisition technology, various reconnaissance and surveillance systems have the ability to monitor targets on land, sea and air in all directions, posing a major threat to various combat operations. In view of this increasingly serious photoelectric threat, the most effective countermeasure is to use high-power lasers to damage the optical system of space detectors, causing the combat performance of enemy space-based reconnaissance equipment to be reduced or even fail.

[0003] Due to its unique wavelength advantages, ultraviolet lasers have important application value in the field of future space lasers.

[0004] The wavelength of deep ultraviolet laser is below 260nm. Compared with infrared laser, its advantages are short laser wavelength, high single photon energy, high target coupling efficiency and small diffraction spot. Deep ultraviolet laser with shorter wavelength is particularly suitable for future space applications.

[0005] At present, the theoretical wavelength of ultraviolet lasers designed based on GaN-based semiconductor materials is at 265nm, and the output power is relatively low. In addition, the band gap energy of GaN of 3.4eV determines that the molecular bond energy is weaker than that of AlN, and it is difficult to dope Al in the core layer (the Al molar component is required to be very high, more than 40%), and the preparation process for growing the AlGaN active layer on a crack-free, thick, high-quality, high-aluminum-content bottom layer is very demanding. Even if the process meets the requirements, the light emission wavelength of GaN-based semiconductor material lasers is difficult to design in the deep ultraviolet band below 250nm. Summary of the invention

[0006] The purpose of the present invention is to provide an AlN-based space deep ultraviolet laser based on nuclear pumping in order to solve the above problems, so as to achieve a deep ultraviolet laser with a lasing wavelength of 150nm-260nm, an output power above MW level, and a very small size.

[0007] In order to achieve the above-mentioned object, the present invention is implemented by the following technical scheme: an AlN-based space deep ultraviolet laser based on nuclear pumping, which includes a working substance, an excitation energy source and an optical resonant cavity, wherein the working substance includes an AlN semiconductor medium capable of realizing energy level transition, and the AlN semiconductor medium and the semiconductor material constitute an AlN-based semiconductor active region; the interaction between the AlN semiconductor medium and the semiconductor material induces an ionization effect to generate electron-hole pairs, thereby performing composite luminescence in the AlN-based semiconductor active region through stimulated radiation;

[0008] The excitation energy source uses nuclear energy to directly pump the working substance to give energy to the atoms of the working substance to excite it. Neutrons, high-energy particles and rays of different energy levels generated by nuclear reactions act on the working substance, thereby achieving energy level transition of the working substance.

[0009] The optical resonant cavity allows the working substance to continuously emit stimulated radiation while limiting the output direction of the laser;

[0010] The polycrystalline layer of diamond can be used as a heat dissipation material with high thermal conductivity and as a moderator for nuclear fuel;

[0011] An AlN-based semiconductor active region, highly enriched uranium and an AlN-based semiconductor active region are sequentially stacked on the diamond polycrystalline layer to form a core-laser medium stacking unit structure, thereby forming a reactor.

[0012] Furthermore, the optical resonant cavity is a reflector array and an output mirror array placed parallel to each other on both sides of the reactor, so that the light beam generated by stimulated radiation is repeatedly reflected back and forth between the left and right lenses, generating a resonance effect and amplifying the light energy.

[0013] Furthermore, the optical resonant cavity is a second-order grating introduced on one side of the AlN-based semiconductor active region. The light beam generated by stimulated radiation is surface-emitted by the first-order grating diffraction light, and the second-order grating diffraction light oscillates along the horizontal cavity feedback to produce a resonance effect and amplify the light energy.

[0014] Furthermore, the conceptual estimated critical volume of the reactor of the core-laser medium stacking unit structure is 0.1 cubic meters and the overall weight is 2 tons.

[0015] Furthermore, the laser emits light of deep ultraviolet laser with a wavelength of 110nm-260nm.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The AlN-based space deep ultraviolet laser based on nuclear pumping of the present invention utilizes nuclear energy to directly pump AlN-based semiconductor materials. The laser wavelength of the AlN-based semiconductor laser can be designed theoretically within the range of 110nm-260nm deep ultraviolet band. The AlN-based material has good radiation resistance, high temperature resistance and environmental stability, so that it has good application prospects in the nuclear field. Neutrons, high-energy particles and various rays such as alpha rays, beta rays and gamma rays generated by nuclear reactions act on semiconductor laser media (AlN) and interact with semiconductor materials to induce physical processes such as ionization effect and displacement effect, thereby generating electron-hole pairs. The above structure forms an active region of the AlN-based semiconductor. Electrons and holes are compound-luminesced in the active region by stimulated radiation, and light is amplified along the longitudinal direction of the reactor structure to finally output laser light in the deep ultraviolet band. The design target of the space nuclear reactor is a steady-state and pulse multi-purpose reactor type, which can not only have the capability of nuclear pumping semiconductor lasers, but also meet the multi-purpose energy requirements of laser systems at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the laser principle of the present invention;

[0019] Figure 2 This is a schematic diagram of the core-laser medium stacking unit structure of the present invention;

[0020] Figure 3 This is a schematic diagram of the distributed feedback laser principle of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below in conjunction with the embodiments in the accompanying drawings, but this does not constitute any limitation to the present invention.

[0022] The present invention aims to realize high-energy-level deep ultraviolet laser by directly pumping AlN-based semiconductor materials with nuclear energy. At present, deep ultraviolet laser light sources mainly include excimer lasers, gas lasers, all-solid-state lasers or synchrotron radiation light sources generated by synchrotron accelerators. Among them, deep ultraviolet all-solid-state lasers based on nonlinear frequency conversion have attracted wide attention due to their efficiency, compactness and low system maintenance cost. The unique wavelength advantage of deep ultraviolet lasers can not only interfere with and damage ultraviolet detectors, but also interfere with and damage optical systems of space detectors in the visible light and infrared bands, truly achieving full band coverage.

[0023] Ultra-wide bandgap semiconductor material AlN material has important uses in many fields due to its wide bandgap (6.2eV), thermal stability and good thermal conductivity, low expansion coefficient, high strength, high temperature resistance, chemical corrosion resistance, high resistivity, low dielectric loss, high breakdown electric field strength (1.2×107V / cm), etc., especially it is an excellent material for the development of deep ultraviolet light sources;

[0024] The general working principle of nuclear pumping is to use the capture effect of thermal neutrons produced by nuclear reactors in laser pumping media. After the medium captures neutrons, it undergoes fission or decay and releases energy. The particles produced in the nuclear reaction process enter the laser medium with the energy released in the reaction process, and interact with the laser medium to reverse its particle number, and pump to produce lasers. Compared with other high-power lasers, nuclear reactor pumped lasers have many potential advantages: high laser output power, up to MW level; can run continuously for a long time; pump energy self-supplied, high energy storage density; small size, compact structure, good mobility; wide range of laser wavelength variation. From the current development process, nuclear pumped lasers have broad application prospects.

[0025] Based on the above theoretical reference Figure 1 , 2 As shown, an AlN-based space deep ultraviolet laser based on nuclear pumping includes a working substance, an excitation energy source and an optical resonant cavity. The working substance includes an AlN semiconductor medium capable of realizing energy level transition, and the AlN semiconductor medium and the semiconductor material constitute an AlN-based semiconductor active region; the interaction between the AlN semiconductor medium and the semiconductor material induces an ionization effect to generate electron-hole pairs, thereby performing composite light emission in the AlN-based semiconductor active region through stimulated radiation;

[0026] Excitation energy, which uses nuclear energy to directly pump the working material to give energy to the atoms of the working material to excite them. The neutrons, high-energy particles and rays of different energy levels generated by the nuclear reaction act on the working material, thereby achieving energy level transition of the working material;

[0027] The optical resonant cavity allows the working material to continuously emit stimulated radiation while limiting the output direction of the laser;

[0028] Regarding the optical resonant cavity, the resonance mode of the existing semiconductor laser can be used: the electrons of the semiconductor are excited by external energy (light energy or electrical energy) and jump from the valence band to the conduction band. When the electrons jump back from the conduction band to the valence band, the energy is released in the form of light energy. Through the reflector array and output mirror array placed parallel to each other on both sides of the reactor, the light beam generated by the stimulated radiation is repeatedly reflected back and forth between the left and right lenses, generating a resonance effect and amplifying the light energy.

[0029] Reference Figure 3As shown, the resonance mode of the distributed feedback laser can also be used: the horizontal cavity surface emitting distributed feedback laser introduces a second-order grating in the device and utilizes the diffraction characteristics of the second-order grating to achieve surface emission from the first-order diffracted light, and the second-order diffracted light is feedback oscillated along the horizontal cavity. Since the cavity of the horizontal cavity surface emitting DFB laser is longer, higher optical gain and single-mode output power can be obtained. At the same time, smaller spectral temperature drift brings higher reliability (higher surface damage threshold), and smaller divergence angle brings better beam quality. Therefore, the second-order grating introduced on one side of the AlN-based semiconductor active region can be used to introduce the first-order grating diffracted light to achieve surface emission of the light beam generated by stimulated radiation, and the second-order grating diffracted light is feedback oscillated along the horizontal cavity, producing a resonance effect and amplifying the light energy;

[0030] In order to ensure that the laser of the present invention is small in size, long in life, compact in structure and has simple laser emission conditions, a diamond polycrystalline layer is arranged outside the AlN-based semiconductor active region as a heat dissipation material with high thermal conductivity, and can also be used as a moderator for nuclear fuel; the AlN-based semiconductor active region, highly enriched uranium and the AlN-based semiconductor active region are stacked on the diamond polycrystalline layer in sequence to form a core-laser medium stacking unit structure, and then a reactor is formed. The development of military nuclear power is the internal driving force for the development of space nuclear reactor technology. The main purpose of military space nuclear reactor power sources is monitoring, tracking and strategic defense. The power demand range of most space military systems has reached the MW level, among which the power demand of the main space-based weapon systems is between 10MW-500MW. According to the power size, for space-based weapon systems, although their power demand is high, the energy pulse duration is often short. Therefore, space nuclear reactors will be the only power source option, and deep ultraviolet lasers with shorter wavelengths are more likely to pass through plasma and directly act on the surface of materials to cause serious damage. For the same optical material, the damage threshold of deep ultraviolet laser is much lower than that of visible light and infrared laser, but the damage effect is stronger. Using more efficient deep ultraviolet laser as a new band laser will be extremely disruptive in space-based applications where energy demand is very tight;

[0031] Combining the technical advantages of AlN-based semiconductor material lasers and nuclear pumping technology, we have designed nuclear pumped semiconductor ultraviolet lasers. Using nuclear pumping AlN-based materials, we can generate high-energy deep ultraviolet lasers, which can not only interfere with and damage ultraviolet detectors, but also interfere with and damage the optical systems of space detectors in the visible and infrared bands, truly achieving full band coverage. At the same time, we use space nuclear reactors to solve the power supply problem of space-based laser systems and meet the multi-purpose energy needs of space-based ultraviolet laser systems.

[0032] The above embodiments are preferred implementation modes of the present invention and are only used to facilitate the description of the present invention. They are not intended to limit the present invention in any form. Any person with ordinary knowledge in the relevant technical field, if they do not depart from the scope of the technical features of the present invention, can make equivalent embodiments by partial changes or modifications to the technical contents disclosed in the present invention, and they still fall within the scope of the technical features of the present invention without departing from the technical features of the present invention.

Claims

1. A nuclear-pumped AlN-based deep ultraviolet laser, comprising a working material, an excitation energy source, and an optical resonant cavity, characterized by: The working material includes an AlN semiconductor medium capable of achieving energy level transitions, wherein the AlN semiconductor medium and the semiconductor material constitute an AlN-based semiconductor active region; the interaction between the AlN semiconductor medium and the semiconductor material triggers an ionization effect to generate electron-hole pairs, thereby performing composite luminescence in the AlN-based semiconductor active region through stimulated radiation; The excitation energy source uses nuclear energy to directly pump the working material to give the working material atoms excitation energy. Neutrons, high-energy particles and rays of different energy levels generated by the nuclear reaction act on the working material, thereby achieving energy level transition of the working material. The optical resonant cavity allows the working substance to continuously emit stimulated radiation while limiting the output direction of the laser; A diamond polycrystalline layer is disposed outside the AlN-based semiconductor active region; the diamond polycrystalline layer serves as a heat dissipation material with high thermal conductivity and also as a moderator for nuclear fuel; An AlN-based semiconductor active region, highly enriched uranium, and an AlN-based semiconductor active region are sequentially stacked on the diamond polycrystalline layer to form a core-laser medium stacking unit structure, thereby forming a reactor.

2. The nuclear-pumped AlN-based deep ultraviolet laser according to claim 1, characterized in that: The optical resonant cavity is a reflector array and an output mirror array placed parallel to each other on both sides of the reactor, so that the light beam generated by stimulated radiation is repeatedly reflected back and forth between the left and right lenses, generating a resonance effect and amplifying the light energy.

3. The nuclear-pumped AlN-based deep ultraviolet laser according to claim 1, characterized in that: The optical resonant cavity is a second-order grating introduced on one side of the AlN-based semiconductor active area. The light beam generated by stimulated radiation is emitted from the surface by the first-order grating diffraction light, and the second-order grating diffraction light oscillates along the horizontal cavity feedback, generating a resonance effect and amplifying the light energy.

4. The nuclear-pumped AlN-based deep ultraviolet laser according to claim 1, characterized in that: The conceptual estimated critical volume of the reactor of the core-laser medium stacked unit structure is 0.1 cubic meters and the overall weight is 2 tons.

5. The nuclear-pumped AlN-based deep ultraviolet laser according to any one of claims 1 to 4, characterized in that: The laser emits light of deep ultraviolet laser with a wavelength of 110nm-260nm.

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