Hollow-core optical fiber coherent array gas laser structure

Abstract

The invention discloses a hollow-core optical fiber coherent array gas laser structure which comprises a pumping system, laser emitted by the pumping system is coupled and then enters an array hollow-core optical fiber, a first gas cavity is formed in the laser emitting end of the array hollow-core optical fiber, a micro-nano structure layer is prepared on the front end face of an emitting window of the first gas cavity, and the rear end face of the emitting window of the first gas cavity is plated with a reflecting layer. The first gas cavity can vacuumize the array hollow-core optical fiber, fill working gas and adjust the air pressure, laser entering the array hollow-core optical fiber excites the working gas to form array laser, and the array laser enters the first gas cavity, passes through the micro-nano structure layer at the front end of the emergent window and then is fed back by the reflecting layer to be injected into the array hollow-core optical fiber. And self-organizing phase locking is obtained, in-phase super-mode locking is obtained, and therefore coherent array laser output is achieved. According to the laser, working gas is filled into the hollow-core optical fiber, and a phase modulation layer is prepared by combining a gas cavity window, so that coherent array laser can be formed, and high-power intermediate infrared laser output of a single main lobe at a far-field diffraction limit is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, and in particular to a hollow-core optical fiber coherent array gas laser structure. Background Art

[0002] Mid-infrared wavelength lasers have important applications in military, biomedical, security, and atmospheric communications. Mid-infrared lasers based on rare-earth ion-doped fibers offer advantages such as compact structure, high conversion efficiency, excellent beam quality, and convenient thermal management, and have the potential to achieve portable, stable, and efficient mid-infrared laser output. However, the matrix materials and drawing processes for mid-infrared solid-doped fiber lasers are still immature, and due to limitations in nonlinear and thermal effects, achieving high-power, high-beam-quality laser output is difficult.

[0003] Currently, there are relatively few rare earth materials used to generate mid-infrared, mainly including Er 3+ 、Ho 3+ and Dy 3+ Due to the self-termination effect of doped ions, the limited output wavelength of the gain band is difficult to exceed 4μm, and the wavelength selectivity is limited. Commonly used mid-infrared glass is ZBLAN glass, whose low-loss band can reach a long wavelength of about 4.5μm, while the transmission low-loss band long wavelength of chalcogenide glass can reach about 7μm, but the solubility of rare earth ions in chalcogenide glass is low. Gas lasers use gases such as CO2, CO, and C2H2 as gain gases, which is an effective way to achieve mid-infrared output. However, traditional gas laser systems are large and bulky, and are limited by the gas cavity and the working distance, resulting in low laser efficiency.

[0004] The emergence of hollow-core fibers provides an ideal environment for the interaction between light and gas. Fiber gas lasers, which use hollow-core fibers as the laser's transmission carrier and gas molecules as the gain medium, combine the advantages of both fiber and gas lasers, offering a promising path to addressing the technical bottlenecks of traditional fiber lasers in power enhancement and wavelength expansion. However, existing fiber gas lasers typically employ a single-pass structure without a resonant cavity. This is limited by hollow-core fiber transmission losses, low concentrations of the working material, and low gain, making it difficult to achieve high-power, high-beam-quality laser output. This limits their application and makes it difficult to meet practical needs. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a hollow-core fiber coherent array gas laser structure. This laser structure can form a coherent array laser by filling the array hollow-core optical fiber with working gas and combining it with a phase modulation layer prepared by the gas cavity window. It overcomes the problems of single hollow-core fiber gas laser transmission loss, low working material concentration, low gain, etc., and obtains high-power laser output with a single main lobe at the far-field diffraction limit.

[0006] A hollow-core fiber coherent array gas laser structure includes a pumping system. Laser light emitted by the pumping system is coupled and then enters an array hollow-core fiber. A gas cavity 1 is provided at the laser output end of the array hollow-core fiber. The front end face of the output window of the gas cavity 1 is prepared with a micro-nanostructure layer, and the rear end face is plated with a reflective layer. The gas cavity 1 can evacuate the array hollow-core fiber, fill it with working gas, and adjust the gas pressure. The gas cavity 1 and the array hollow-core fiber filled with working gas form a composite resonant cavity. The laser light entering the array hollow-core fiber excites the working gas to form an array laser. The array laser light enters the gas cavity 1, is phase-modulated by the micro-nanostructure layer at the front end of the output window, and is then fed back into the array hollow-core fiber through the reflective layer to achieve in-phase supermode self-organized locking, thereby forming a coherent array laser output.

[0007] As a preferred embodiment of the above technical solution, the pumping system includes a pumping light source and a pumping light coupling system.

[0008] The pump light source is any one of a semiconductor laser, a fiber laser, a solid-state laser, an optical parametric oscillator and an optical parametric amplifier, and the wavelength of the pump light source matches the center of the absorption spectrum of the working gas;

[0009] The pump light coupling system adopts any one of a spatial coupling system and an optical fiber coupling system.

[0010] As a preferred embodiment of the above technical solution, the working gas in the array hollow-core optical fiber realizes array laser output through population inversion or stimulated Raman scattering.

[0011] As a preferred embodiment of the above technical solution, the working gas is any one of carbon dioxide gas, methane, acetylene, hydrogen, tritium gas, carbon monoxide gas, helium-neon gas, acetylene gas, and oxygen-iodine gas.

[0012] As a preferred embodiment of the above technical solution, the laser emitting end of the array hollow-core optical fiber is sealedly connected to the gas cavity, and the other end is connected to the solid-core optical fiber for packaging.

[0013] As a preferred embodiment of the above technical solution, a gas cavity 2 is provided in front of the incident end of the array hollow-core optical fiber, and the front end surface of the incident window of the gas cavity 2 is coated with a pump light anti-reflection film, and the pump light is coupled into the array hollow-core optical fiber through the incident window of the gas cavity 2.

[0014] As a preferred embodiment of the above technical solution, one or more groups of lenses and reflectors are provided between the pumping system and the incident window of the second gas chamber.

[0015] As a preferred embodiment of the above technical solution, the output end and the input end of the array hollow-core optical fiber are sealed by the gas cavity 1 and the gas cavity 2 respectively.

[0016] As a preferred embodiment of the above technical solution, the output window of the gas cavity 1 and the incident window of the gas cavity 2 are both arranged parallel to the end face of the array hollow-core optical fiber.

[0017] As a preferred embodiment of the above technical solution, the arrayed hollow-core optical fiber includes N hollow-core optical fibers arranged in a two-dimensional periodic array, and the arrangement is any one of a hexagon, a square or a cored quadrilateral.

[0018] As a preferred embodiment of the above technical solution, the micro-nano structure layer is prepared with a groove at a position corresponding to the gas core of the hollow-core optical fiber, and the groove is filled with a working gas or a light-transmitting material with a different refractive index.

[0019] As a preferred embodiment of the above technical solution, the distance between the end face of the array hollow-core optical fiber and the micro-nanostructure layer is an integer multiple or a fractional multiple of the Talbot distance.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention can form a coherent array laser by filling the array hollow-core optical fiber with working gas and combining it with a phase modulation layer prepared by the gas cavity window. It overcomes the problems of single hollow-core optical fiber gas laser transmission loss, low working material concentration, low gain, etc., and obtains high-power laser output with a single main lobe at the far-field diffraction limit.

[0022] 2. The all-fiber hollow-core fiber coherent array gas laser has a compact structure and a long operating distance. It improves the damage threshold of traditional solid optical fibers through hollow-core fibers. It has flexible selectivity in working gases and can output a rich range of wavelengths from ultraviolet to infrared.

[0023] 3. The nonlinear effect of the working gas is very weak, so the hollow-core fiber coherent array gas laser also has great advantages in narrow linewidth output at high peak power. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the first embodiment of the present invention.

[0025] Figure 2 A cross-sectional view of one type of hexagonally arranged hollow-core optical fiber array.

[0026] Figure 3 Schematic diagram of the gas cavity and exit window structure.

[0027] Figure 4 This is a schematic diagram of the second embodiment of the invention.

[0028] Figure 5 This is a cross-sectional view of a hollow-core optical fiber array consisting of multiple hollow-core optical fibers arranged in a square array.

[0029] Figure 6 Schematic diagram of the second exit window structure of the gas cavity.

[0030] The reference numerals are as follows: 1-pump system, 2-array hollow-core optical fiber, 3-gas cavity 1, 4-exit window, 5-solid-core optical fiber, 6-gas cavity 2, 7-incident window, 8-lens, 9-reflecting mirror. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0032] The present invention is described in further detail below with reference to the accompanying drawings:

[0033] Example 1: The hollow core optical fiber array in this embodiment uses multiple hollow core optical fibers arranged in an array, such as Figure 2 shown.

[0034] like Figure 1 The structure of a hollow-core fiber coherent array gas laser shown includes a pumping system 1. The laser emitted by the pumping system 1 is coupled and enters the array hollow-core fiber 2. The laser output end of the array hollow-core fiber 2 is provided with a gas cavity 3. The front end face of the output window 4 of the gas cavity 3 is prepared with a micro-nano structure layer, and the rear end face is plated with a reflective layer. The gas cavity 3 can evacuate and fill the array hollow-core fiber 2 with working gas and adjust the gas pressure. The gas cavity 3 and the array hollow-core fiber 2 filled with working gas constitute a composite resonant cavity. The laser entering the array hollow-core fiber 2 excites the working gas to form an array laser. The array laser enters the gas cavity 3 and is phase-modulated by the micro-nano structure layer at the front end of the output window 4, and then fed back into the array hollow-core fiber 2 through the reflective layer to achieve in-phase supermode self-organized locking, thereby forming a coherent array laser output.

[0035] The array hollow core optical fiber 2 is as follows Figure 2 The multiple hollow-core optical fibers shown are arranged periodically in a hexagonal pattern, and the number n of light sources in each row or column is greater than or equal to 2; the hollow-core optical fiber can be a photonic bandgap type or an antiresonant type, and the photonic bandgap type is preferably used in this embodiment; the core diameter is 10-50 μm; the hollow-core optical fiber length is 2 to 5 m; and the array period is 300-500 μm.

[0036] In this embodiment, the pumping system 1 includes a pumping light source and a pumping light coupling system.

[0037] The pump light source is any one of a semiconductor laser, a fiber laser, a solid-state laser, an optical parametric oscillator, and an optical parametric amplifier. The wavelength of the pump light source matches the center of the absorption spectrum of the working gas. In this embodiment, a 1 μm band solid-state laser is preferably used.

[0038] The pump light coupling system adopts any one of a spatial coupling system and an optical fiber coupling system.

[0039] In this embodiment, the laser emitted by the pump system 1 enters the array hollow-core fiber 2 after being coupled through the solid-core fiber 5. The solid-core fiber 5 is a solid-core fiber array with the same arrangement as the array hollow-core fiber 2. The solid-core fiber 5 corresponds one-to-one with the hollow-core fiber, and is packaged by fusion splicing or inserting the hollow-core fiber after taper. After sealing, the air pressure in the fiber is 200-1000Pa.

[0040] In this embodiment, the working gas can be: methane, hydrogen, tritium, carbon dioxide gas or other types, and methane is preferred in this embodiment; the working gas in the array hollow-core optical fiber 2 realizes array laser output through particle number inversion or stimulated Raman scattering. In this embodiment, stimulated Raman scattering is preferably used to realize array first-order Stokes laser output, and the output laser is in the 1.5μm band.

[0041] In this embodiment, the laser-emitting end of the arrayed hollow-core fiber 2 is sealed with the gas cavity 1 3, while the other end is connected to the solid-core fiber 5 for encapsulation. The gas cavity 1 3 assists in securing the arrayed hollow-core fiber 2. The window of the gas cavity 1 3 is made of a light-transmitting material corresponding to the laser wavelength band, and the reflectivity of the rear facet reflective layer meets the reflectivity required for coherent array laser oscillation.

[0042] In this embodiment, a phase modulation layer is prepared on the front end face of the output window of the gas cavity 1 3. The phase modulation layer is prepared by etching at the position corresponding to the gas core of the hollow core optical fiber. Figure 3 The micro-nanostructure shown is filled with a working gas or a light-transmitting material with a different refractive index than the window material, such as Si3N4 or CaF2. In this embodiment, the working gas is preferably filled. The front end surface of the output window of gas cavity 1 3 is coated with a reflective layer whose reflectivity meets the reflectivity required for coherent array laser oscillation.

[0043] In this embodiment, the output window of the gas cavity 1 3 and the incident window of the gas cavity 2 6 are both arranged parallel to the end face of the array hollow core fiber 2. The distance between the end face of the array hollow core fiber and the micro-nano structure layer satisfies the Talbot distance, and the calculation formula is: ZT =2nd 2 / λ, where n is the gas refractive index, d is the spacing between the hollow-core fibers in the array, and λ is the wavelength of the laser generated by the working gas. The distance between the fiber end face and the micro-nanostructure layer satisfies the Talbot distance of 2-5 mm.

[0044] It should be noted that the reflective layer on the rear end face of the exit window 4 of the gas cavity 1 3 is highly reflective to the array laser and transmissive to the pump light. In addition, a filter can be provided at the rear end of the gas cavity 1 3 , and the filter bandpass range includes the coherent array laser wavelength band but does not include the pump light band. The output wavelength of the array hollow-core fiber coherent array gas laser can cover the ultraviolet to infrared band.

[0045] Example 2: The hollow core optical fiber array 2 in this embodiment is composed of multiple hollow core optical fibers arranged in an array, such as Figure 4 shown.

[0046] The difference between this embodiment and the first embodiment is that:

[0047] A second gas cavity 6 is provided in front of the incident end of the array hollow-core optical fiber 2. The front end surface of the incident window 7 of the second gas cavity 6 is coated with a pump light anti-reflection coating. The pump light is coupled into the array hollow-core optical fiber 2 through the incident window of the second gas cavity 6. The incident window 7 of the second gas cavity 6 is also made of a light-transmitting material corresponding to the wavelength band of the pump light.

[0048] like Figure 5 As shown, the array hollow-core optical fiber 2 is a plurality of hollow-core optical fibers arranged periodically in a square, and the number n of light sources in each row or column is greater than or equal to 2; the hollow-core optical fiber can be: photonic bandgap type and antiresonance type, and the present embodiment is preferably antiresonance type; the antiresonance type hollow-core optical fiber structure can be: Kagome type, ice cream type, nodeless wheel type or other types, and the present embodiment is preferably nodeless wheel type; the core diameter is 80-90 μm; the hollow-core optical fiber length is 4 to 6 m; the array period is 300-500 μm.

[0049] In this embodiment, the working gas can be: acetylene, carbon dioxide, oxygen-iodine gas or other types, and in this embodiment, carbon dioxide is preferred; the working gas in the array hollow-core optical fiber 2 realizes array laser output through particle number inversion or stimulated Raman scattering. In this embodiment, array laser output is preferably realized through particle number inversion, and the array laser is in the 4.3μm band.

[0050] In this embodiment, the pump system 1 uses a 2μm-band OPO as a pump source, and one or more groups of lenses 8 and reflectors 9 are disposed between the pump system 1 and the incident window 7 of the second gas chamber 6. Specifically, two groups of lenses 8 are provided, one adjacent to the output end of the pump system 1 and the other adjacent to the incident end of the second gas chamber 6, with a multi-stage reflector 9 disposed between the two groups of lenses 8.

[0051] In this embodiment, the output end and the input end of the array hollow-core optical fiber 2 are sealed by the gas cavity 1 3 and the gas cavity 2 6 respectively. After sealing, the gas pressure in the optical fiber is 400-800 Pa.

[0052] The distance between the optical fiber end face and the micro-nanostructure layer satisfies the Talbot distance of 5-10 mm.

[0053] In this embodiment, the front end surface of the output window of the gas cavity 1 is prepared with a micro-nano structure layer, and the micro-nano structure layer is prepared by etching at the position corresponding to the gas core of the hollow core optical fiber. Figure 6 The groove structure shown in the figure is filled with a working gas or a light-transmitting material having a different refractive index from the window material, such as Si3N4, CaF2 and other materials. In this embodiment, the light-transmitting material having a different refractive index from the window material is preferably filled in the structure.

[0054] In this embodiment, the output window 4 of the gas cavity 1 3 and the incident window 7 of the gas cavity 2 6 are both arranged parallel to the end face of the array hollow-core optical fiber 2 .

[0055] It should be noted that

[0056] The hollow core optical fiber can be arranged in any of the two-dimensional periodic arrays such as quadrilateral, hexagonal or cored square.

[0057] The present invention forms a coherent array laser by filling the array hollow-core optical fiber 2 with a working gas and combining it with a phase modulation layer prepared by the gas cavity window. This overcomes the problems of transmission loss, low working substance concentration, and low gain of a single hollow-core optical fiber gas laser, and obtains a high-power laser output with a single main lobe at the far-field diffraction limit. The hollow-core optical fiber coherent array gas laser with an all-fiber structure has a compact structure and a long operating distance. The hollow-core optical fiber improves the damage threshold of the traditional solid optical fiber. It has flexible selectivity in terms of working gas and can output a rich range of wavelengths from ultraviolet to infrared bands. The nonlinear effect of the working gas is very weak, so the hollow-core optical fiber coherent array gas laser also has a huge advantage in narrow linewidth output at high peak power.

[0058] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A hollow-core fiber coherent array gas laser structure, characterized by: The invention comprises a pumping system, wherein the laser emitted by the pumping system is coupled and enters an array hollow-core optical fiber. A gas cavity 1 is provided at the laser output end of the array hollow-core optical fiber. The front end face of the output window of the gas cavity 1 is prepared with a micro-nano structure layer, and the rear end face is plated with a reflective layer. The gas cavity 1 can evacuate the array hollow-core optical fiber, fill it with working gas, and adjust the gas pressure. The gas cavity 1 and the array hollow-core optical fiber filled with working gas constitute a composite resonant cavity. The laser entering the array hollow-core optical fiber excites the working gas to form an array laser. The array laser enters the gas cavity 1 and is phase-modulated by the micro-nano structure layer at the front end of the output window. The array laser is then fed back into the array hollow-core optical fiber through the reflective layer to achieve in-phase supermode self-organized locking, thereby forming a coherent array laser output.

2. The hollow-core fiber coherent array gas laser structure according to claim 1, characterized in that: The pumping system includes a pumping light source and a pumping light coupling system. The pump light source is any one of a semiconductor laser, a fiber laser, a solid-state laser, an optical parametric oscillator and an optical parametric amplifier, and the wavelength of the pump light source matches the center of the absorption spectrum of the working gas; The pump light coupling system adopts any one of a spatial coupling system and an optical fiber coupling system.

3. The hollow-core fiber coherent array gas laser structure according to claim 1, characterized in that: The working gas in the array hollow-core optical fiber realizes array laser output through population inversion or stimulated Raman scattering.

4. The hollow-core fiber coherent array gas laser structure according to claim 1, characterized in that: The working gas is any one of carbon dioxide gas, methane, acetylene, hydrogen, tritium gas, carbon monoxide gas, helium-neon gas, acetylene gas, and oxygen-iodine gas; the micro-nanostructure layer is prepared with grooves at positions corresponding to the gas cores of the hollow-core optical fiber, and the grooves are filled with working gas or light-transmitting materials with different refractive indices.

5. A hollow-core fiber coherent array gas laser structure according to any one of claims 1 to 4, characterized in that: The laser emitting end of the array hollow-core optical fiber is sealedly connected to the gas cavity, and the other end is connected to the solid-core optical fiber for packaging.

6. The hollow-core fiber coherent array gas laser structure according to claim 5, characterized in that: A second gas cavity is provided in front of the incident end of the array hollow-core optical fiber. The front end surface of the incident window of the second gas cavity is plated with a pump light anti-reflection film. The pump light is coupled into the array hollow-core optical fiber through the incident window of the second gas cavity.

7. The hollow-core fiber coherent array gas laser structure according to claim 6, characterized in that: One or more groups of lenses and reflectors are provided between the pumping system and the incident window of the second gas chamber.

8. The hollow-core fiber coherent array gas laser structure according to claim 7, characterized in that: The output end and the input end of the array hollow-core optical fiber are sealed by the gas cavity 1 and the gas cavity 2 respectively.

9. The hollow-core fiber coherent array gas laser structure according to claim 6, characterized in that: The incident window of the second gas cavity is arranged parallel to the end face of the array hollow-core optical fiber.

10. The hollow-core fiber coherent array gas laser structure according to claim 1, characterized in that: The array hollow-core optical fiber includes N hollow-core optical fibers arranged in a two-dimensional periodic array, and the arrangement adopts any one of a hexagon, a square or a cored quadrilateral; the distance between the end face of the array hollow-core optical fiber and the micro-nanostructure layer is an integer multiple or a fractional multiple of the Talbot distance.

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