A composite slat laser device and method of laser generation

Abstract

The application discloses a composite slab laser device and a laser generating method, and the device comprises a composite slab, wherein the composite slab comprises at least one slab gain layer and at least one slab expansion layer which are arranged alternately along the direction of incident pump light, the incident pump light is reflected in the composite slab for multiple times, laser gain is generated in the slab gain layer, and a laser beam is output from the end face of the composite slab. The application expands the thickness size and the end face aperture of the composite slab, breaks through the limitation of the growth process of the existing laser gain medium, reduces the peak power density of the end face of the composite slab, prevents the end face from being damaged, expands the thickness size of the slab, utilizes the high thermal conductivity characteristics of the slab expansion layer, improves the overall heat conduction capacity of the slab, reduces the temperature of the slab, and realizes high-peak-power and high-beam-quality laser output.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid-state lasers. More particularly, it relates to a composite slab laser device and a method of laser generation. BACKGROUND

[0002] In the field of high energy, short pulse and high peak power lasers, the laser gain medium plays a crucial role, and the selection and design of the gain medium has a significant impact on the performance and stability of the laser. Compared with the traditional round rod laser, the slab laser has a larger heat dissipation area, can withstand higher pump power and waste heat, and can use a unique zigzag light path for laser transmission and gain to compensate for the low-order aberration caused by thermal light effects, thus producing short pulse, high peak power and large energy laser output.

[0003] In the slab laser, the damage threshold and thermal response characteristics of the slab are key factors that directly affect the working stability and life of the laser. The most commonly used gain medium for slab lasers is a laser crystal. However, due to limitations in the crystal growth process, the aperture of the crystal slab is often limited. This limitation results in a small aperture of the crystal slab, which faces challenges in terms of crystal end face damage threshold when applied to high energy and high peak power lasers. At the same time, during the output of high energy pulse laser, high power waste heat is generated inside the slab. Small size of the slab leads to high thermal power density, which in turn produces strong thermal light effect, affecting the beam quality of the output laser, and in severe cases, causing the slab to break.

[0004] In the development of slab laser oscillators, in order to obtain output laser with good beam quality, a non-stable cavity is often used as the laser resonant cavity, and the output laser is a "hollow" beam, which is very suitable for focusing using a reflective Schmidt-Cassegrain telescope. However, if the aperture of the slab in the thickness direction is small, it is difficult to obtain a hollow beam in this direction using a non-stable cavity. Therefore, in order to obtain a non-stable cavity hollow beam with high beam quality, a large aperture slab gain medium is required. However, the slab laser gain medium usually uses a large surface for heat dissipation, and the thickness direction is the main direction of heat flow. Increasing the thickness of the slab will reduce the heat dissipation capacity of the slab, resulting in an increase in the center temperature of the slab and causing more severe thermal distortion. Therefore, while expanding the aperture of the slab, the heat dissipation capacity of the slab also needs to be enhanced to obtain high beam quality laser output.

[0005] In summary, in the high-energy, short-pulse and high-peak power laser, in order to reduce the end face peak power density to below the damage threshold, increase the size of the slab to reduce the heat density, and increase the thickness direction aperture to obtain a high beam quality hollow beam, it is necessary to break through the limitation of the growth process of the laser gain medium, and develop a larger size and larger aperture slab. At the same time, in order to ensure the beam quality of the slab laser, it is also necessary to enhance the heat conduction capacity of the slab, so as to develop a large-aperture high-thermal-conductivity laser slab, and promote the development and application of laser technology. SUMMARY

[0006] The present application provides a kind of composite slab laser device and the method for generating laser to solve at least one of the problems in the prior art.

[0007] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0008] The first aspect of the present application provides a kind of composite slab laser device, which comprises a composite slab,

[0009] The composite slab comprises at least one slab gain layer and at least one slab expansion layer arranged alternately along the direction of incident pump light, the incident pump light is reflected multiple times in the composite slab, laser gain is generated in the slab gain layer, and a laser beam is output from the end face of the composite slab.

[0010] Optionally, the thermal conductivity of the material of the slab expansion layer is greater than the thermal conductivity of the material of the slab gain layer.

[0011] Optionally, the material of the slab expansion layer and the material of the slab gain layer have similar refractive indices.

[0012] Optionally, the slab gain layer and the slab expansion layer are both transparent crystal materials, and are connected by bonding; or

[0013] The slab gain layer and the slab expansion layer are both transparent ceramic materials, and are connected by sintering.

[0014] Optionally, the laser device comprises a first pump coupling structure, and the shaped first pump light is incident on the composite slab from the surface of the slab gain layer on one side of the composite slab.

[0015] Optionally, the laser device further comprises a second pump coupling structure, and the shaped second pump light is opposite to the shaped first pump light, and is incident on the composite slab from the surface of the gain layer on the other side of the composite slab.

[0016] Optionally, the composite slab is coated with a transmission film for transmitting incident pump light and a reflection film for reflecting the light beam in the composite slab on the surface of the incident pump light.

[0017] Optionally, a reflective film is coated on the surface of the composite slab away from the side of the incident pump light for reflecting the light beam in the composite slab.

[0018] Optionally, the device further comprises a cooling structure for providing cooling for the composite slab.

[0019] The second aspect of the present application provides a method for generating laser, which comprises

[0020] The pump light is shaped by the pump coupling structure and is injected into the composite slab;

[0021] The incident pump light is reflected multiple times in the composite slab and is amplified to a preset threshold in the slab gain layer, and then is output from the end face of the slab as laser.

[0022] The present application has the following advantages:

[0023] The slab gain layer and the slab expansion layer with high thermal conductivity are tightly connected by bonding or direct sintering in the present application, which expands the thickness size and the end face aperture of the composite slab, breaks through the limitation of the growth process of the existing laser gain medium, and obtains a large-aperture laser slab. In the application process, the peak power density of the end face of the composite slab is reduced, the end face damage is prevented, and the reliability and stability of the slab laser are improved. At the same time, the composite slab with an expanded end face aperture reduces the power density of waste heat, and the increase in the thickness size is conducive to generating a high-beam-quality hollow light beam through a non-stable cavity. While expanding the thickness size of the slab, the high thermal conductivity of the slab expansion layer is utilized to improve the overall heat dissipation capacity of the slab, reduce the temperature of the slab, and realize high-beam-quality laser output. BRIEF DESCRIPTION OF DRAWINGS

[0024] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0025] Figure 1 A schematic diagram of a composite slab laser device of the first embodiment of the present application is shown;

[0026] Figure 2 A comparison diagram of the temperature distribution simulation results of the composite slab laser device with the same geometric size and the single slab laser device under the same output power and cooling conditions in the first embodiment of the present application is shown;

[0027] Figure 3 A schematic diagram of a composite slab laser device of the second embodiment of the present application is shown;

[0028] Figure 4 A schematic diagram of a composite slab laser device of the third embodiment of the present application is shown. DETAILED DESCRIPTION

[0029] In order to more clearly illustrate the present application, the present application will be further described below in conjunction with preferred embodiments and the accompanying drawings. Like components are denoted by the same reference numerals in the accompanying drawings. It should be understood by those skilled in the art that the specific description below is illustrative rather than limiting, and should not limit the scope of protection of the present application.

[0030] The present application provides a large-aperture high-thermal-conductivity composite slab laser device and a laser generation method. The device tightly connects a slab gain layer and a slab expansion layer to obtain a large-aperture composite laser slab, and uses the high thermal conductivity of the material of the slab expansion layer to enhance the thermal conductivity of the slab. The device can solve the problem of excessive end face peak power density and serious thermal distortion caused by insufficient thermal conductivity of the slab due to the small aperture of the laser slab in the prior art.

[0031] The device comprises a composite slab, a first pump coupling structure and a cooling structure. The composite slab comprises at least one slab gain layer and at least one slab expansion layer arranged alternately along the direction of incident pump light. The first pump coupling structure is used to shape the first pump light and inject the shaped first pump light into the composite slab from the slab gain layer of the composite slab. The incident first pump light is reflected multiple times in the composite slab, generates laser gain in the slab gain layer, and outputs a laser beam from the end face of the composite slab. The slab gain layer is used to absorb the shaped pump light to generate laser gain and output a laser beam from the end face of the composite slab. The slab expansion layer is used to reduce the peak power density of the end face of the composite slab and improve the thermal conductivity of the composite slab to reduce the temperature of the slab. The first pump coupling structure is arranged apart from the cooling structure, and the cooling structure is tightly connected with the composite slab to provide cooling for the composite slab.

[0032] The composite slab is coated with a transmission film on the surface on the side of incident pump light for transmitting the incident pump light, and a reflection film for reflecting the light beam in the composite slab on the surface on the side away from the incident pump light. The composite slab is coated with a reflection film for reflecting the light beam in the composite slab on the surface on the side away from the incident pump light. In the composite slab, the thermal conductivity of the material of the slab expansion layer is greater than that of the material of the slab gain layer. The material of the slab expansion layer and the material of the slab gain layer have similar refractive indexes to make the light beam travel approximately in a straight line between the slab gain layer and the slab expansion layer.

[0033] When the materials of the slab gain layer and the slab expansion layer are both crystals, they are connected by bonding. Or when the materials of the slab gain layer and the slab expansion layer are both transparent ceramic materials, they are connected by sintering.

[0034] The first pump coupling structure can be a lens group or a special-shaped waveguide.

[0035] The material of the slat gain layer is a crystal or ceramic material doped with ions, specifically YAG, YVO4, sapphire, YLF, YAP and LuAG laser materials; the material of the slat extension layer is a transparent crystal or ceramic material with high thermal conductivity, specifically sapphire, diamond, aluminum nitride, silicon nitride and zinc oxide, etc., which improves the overall thermal conductivity of the first composite slat while expanding the end face diameter of the slat, and reduces the temperature of the first composite slat; the slat extension layer is doped with rare earth ions, specifically Nd 3+ 、Yb 3+ 、Tm 3+ and Ho 3+ Laser doping ions.

[0036] The cooling structure can be made of a high-thermal-conductivity metal or alloy such as copper or brass. The cooling method of the cooling structure can be conduction cooling of the composite slats by a microchannel heat sink or direct liquid cooling of the composite slats. The coolant used in the cooling structure can be a commonly used coolant such as water or ethanol.

[0037] In a specific embodiment, Figure 1 This is a schematic diagram of the composite slab laser device of this embodiment. Figure 1 As shown, the composite slab laser device includes a composite slab 11, a cooling structure 12 and a first pump coupling structure 13, wherein the composite slab 11 is a two-layer composite slab in which a slab gain layer and a slab extension layer are alternately arranged along the incident direction of the pump light, and the composite slab 11 includes a slab gain layer 11A and a slab extension layer 11B tightly combined along the thickness direction, wherein the X-axis is the length direction, the Y-axis is the thickness direction, and the Z-axis is the width direction (the Z-axis is not shown).

[0038] In this embodiment, the first pump light emitted by the pump source is shaped by the first pump coupling structure 13 and input into the composite slab 11. The shaped first pump light generates laser gain through the slab gain layer 11A in the composite slab 11, forming a laser beam. The slab expansion layer 11B increases the thickness of the composite slab 11 and expands the end face diameter of the composite slab 11, reducing the peak power density at the slab end face, preventing end face damage, and improving the reliability and stability of the slab laser. Optical resonators (not shown in the figures) are provided on both end faces of the composite slab 11. After reflecting and oscillating within the composite slab to a preset threshold, the laser beam is output through the right end face of the composite slab 11.

[0039] The slab gain layer 11A is a doped laser gain medium for absorbing the shaped pump light and providing laser gain. In the embodiment, the material of the slab gain layer 11A is Yb:YAG. The slab expansion layer 11B is undoped sapphire. The slab gain layer 11A and the slab expansion layer 11B are tightly connected by bonding. The slab gain layer 11A and the slab expansion layer 11B have similar refractive indexes. The refractive index of the slab gain layer 11A is 1.82, and the refractive index of the slab expansion layer 11B is 1.77. The light beam in the composite slab 11 travels approximately in a straight line between the slab gain layer 11A and the slab expansion layer 11B, so as to reduce the loss of the laser beam in the composite slab 11 during refraction. The thermal expansion coefficients of the slab gain layer 11A and the slab expansion layer 11B are matched in a wide temperature range, so as to prevent the composite slab 11 from deforming.

[0040] In the embodiment, the material of the cooling structure 12 is oxygen-free copper. The cooling structure 12 is internally provided with cooling liquid microchannels for cooling the composite slab 11. The pump source is a laser diode array. The first pump coupling structure 13 is an optical waveguide made of fused quartz glass.

[0041] Figure 2 FIG. 6 is a comparison diagram of temperature distribution simulation results of the composite slab laser device of the first embodiment of the present application and a conventional single-slab laser device under the same output power and cooling conditions. The composite slab 11 of the composite slab laser device includes a slab gain layer 11A made of Yb:YAG and a slab expansion layer 11B made of undoped sapphire. The single slab of the single-slab laser device is made of Yb:YAG.

[0042] In the model for calculating the temperature distribution by finite element, the size of the single slab and the composite slab is set to 100mm×30mm×10mm, wherein the size along the X-axis direction is 100mm, the size along the Y-axis direction is 10mm, and the size along the Z-axis direction is 30mm. The composite slab 11 includes a 5mm-thick slab gain layer 11A and a 5mm-thick slab expansion layer 11B. The two slabs are set to the same heat generation power and the same cooling condition. The simulation results are shown in FIG. 7. Figure 2 As shown in the figure, the maximum temperature of the composite slab 11 is about 60.8℃ at steady state due to the existence of the slab expansion layer 11B with high thermal conductivity. The maximum temperature of the single slab is about 70℃, which is nearly 10℃ higher than that of the composite slab 11.

[0043] According to the result, the composite slab laser device increases the slab expansion layer 11B compared with the single slab laser device, breaks through the limitation of the existing laser gain medium growth process, and obtains a composite slab with larger thickness size and larger end face aperture. While expanding the thickness size and end face aperture of the slab, the high thermal conductivity of the slab expansion layer 11B is used to improve the overall heat conduction capacity of the composite slab 11, reduce the temperature of the composite slab 11 itself, and solve the problem of serious thermal distortion caused by insufficient heat conduction capacity of the slab.

[0044] In one embodiment, Figure 3 The structure diagram of the composite slab laser device in the second embodiment of the present application is shown in the figure. In this embodiment, only the differences from the first embodiment are discussed, and the same parts are not discussed.

[0045] The number of layers of the slab gain layer 11A and the slab expansion layer 11B arranged in the thickness direction of the composite slab is increased, such as Figure 3 As shown in the figure, in this embodiment, the composite slab 11 is a five-layer composite slab arranged alternately along the pump light incident direction, including three slab gain layers 11A and two slab expansion layers 11B. Specifically, the composite slab 11 is arranged from top to bottom in the thickness direction (Y-axis direction) as slab gain layer 11A, slab expansion layer 11B, slab gain layer 11A, slab expansion layer 11B, and slab gain layer 11A.

[0046] The composite slab 11 is coated with a transmission film for transmitting the shaped pump light on the side of the pump light incident surface, and a reflection film for reflecting the laser beam; the surface of the composite slab 11 away from the pump light incident surface is coated with a reflection film for reflecting the light beam inside the composite slab 11. The material of the slab expansion layer 11B has a similar refractive index to that of the slab gain layer 11A, so that the light beam is reflected in a nearly straight line between the slab gain layer and the slab expansion layer.

[0047] The material of the cooling structure 12 is oxygen-free copper, and the inside is provided with a cooling liquid microchannel for conduction cooling of the composite slab through the microchannel heat sink.

[0048] This embodiment increases the thickness size and end face aperture of the composite slab, prevents the slab from being damaged, improves the stability and life of the composite slab laser, reduces the power density of the laser beam passing through the composite slab, improves the overall heat conduction capacity of the composite slab, reduces the temperature of the composite slab, and obtains a laser beam with higher peak power and higher beam quality.

[0049] In one embodiment, Figure 4 The structure diagram of the composite slab laser device in the third embodiment of the present application is shown in the figure. In this embodiment, only the differences from the first embodiment are discussed, and the same parts are not discussed.

[0050] By increasing the intensity of the incident pump light, a higher peak power and a higher quality laser beam are obtained. Figure 4 As shown in the figure, in the embodiment, the first pump coupling structure 13 and the second pump coupling structure 33 are arranged to shape the pump light emitted by the pump source respectively, and the shaped first pump light and the second pump light are injected into the composite slab 11. After the laser beam is reflected and amplified to a preset threshold value by the composite slab 11 and the optical resonant cavity, the laser beam is output through the end face on the right side of the composite slab 11.

[0051] In the embodiment, the surface of the composite slab 11 close to the first pump coupling structure 13 and the surface away from the first pump coupling structure 13 are both coated with a transmission film for transmitting the shaped pump light and a reflection film for reflecting the laser beam.

[0052] In the embodiment, the pump sources of the first pump coupling structure 13 and the second pump coupling structure 33 are the same; the first pump coupling structure 13 and the second pump coupling structure 33 are symmetrically arranged based on the composite slab 11; the first pump coupling structure 13 and the second pump coupling structure 33 are made of the same material and have the same structure, and of course can also be made of different materials and have different structures; the cooling structure 12 is arranged close to the first pump coupling structure 13 and close to the second pump coupling structure 33, and the first pump coupling structure 13 and the second pump coupling structure 33 are both arranged apart from the cooling structure 12, and the cooling mode of the cooling structure 12 is direct liquid cooling.

[0053] The embodiment increases the incident intensity of the pump light, so that more shaped pump light enters the composite slab, and the pump light providing excitation in the composite slab is increased, thereby obtaining a laser beam with higher peak power and higher beam quality.

[0054] The application also provides a method for generating laser, which comprises shaping the pump light by the pump coupling structure and injecting the shaped pump light into the composite slab; the incident pump light is reflected multiple times in the composite slab, and is amplified to a preset threshold value in the slab gain layer, and is output as laser through the end face of the slab.

[0055] The application adopts the composite slab to expand the thickness size and the end face caliber of the slab, breaks through the limitation of the existing laser gain medium growth process, obtains a large-caliber laser slab, reduces the peak power density of the end face of the slab in the application process, prevents the end face damage, and improves the reliability and stability of the slab laser. Meanwhile, the composite slab with large thickness size can reduce the power density of waste heat, and the promotion of the end face caliber is beneficial to generate a high-beam-quality hollow beam through a non-stable cavity. The application realizes the expansion of the thickness size and the end face caliber of the slab, uses the high thermal conductivity characteristics of the slab expansion layer to improve the overall heat conduction capacity of the slab, reduces the temperature of the slab, and realizes high-beam-quality laser output.

[0056] In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise expressly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0057] It should also be noted that in the description of the present application, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or equipment. Without more limitation, the element defined by the sentence "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0058] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not a limitation on the embodiments of the present application. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description, and it is impossible to enumerate all the embodiments here. Any obvious changes or variations derived from the technical solutions of the present application still fall within the protection scope of the present application.

Claims

1. A composite slab laser device, characterized in that: The device comprises composite slats, The composite slab includes at least one slab gain layer and at least one slab expansion layer alternately arranged along the incident direction of the pump light. The incident pump light is reflected multiple times in the composite slab, generating laser gain in the slab gain layer, and outputting a laser beam from the end face of the composite slab. The laser device includes a first pump coupling structure, wherein the shaped first pump light is incident on the composite slab from the slab gain layer surface on one side of the composite slab; The laser device further includes a second pump coupling structure, wherein the shaped second pump light is opposite to the shaped first pump light and is incident on the composite slab from the gain layer surface on the other side of the composite slab; The first pump coupling structure is a lens group or a special-shaped waveguide; The first pump coupling structure and the second pump coupling structure are made of the same material and have the same structure; The material of the slat extension layer is sapphire, diamond, aluminum nitride, silicon nitride and zinc oxide; The material of the slab extension layer and the material of the slab gain layer have similar refractive indexes, so that the light beam travels approximately in a straight line between the slab gain layer and the slab extension layer.

2. The laser device according to claim 1, wherein The thermal conductivity of the slat expansion layer material is greater than the thermal conductivity of the slat gain layer material.

3. The laser device according to claim 1, wherein The slat gain layer and the slat expansion layer are both made of transparent crystal materials and are connected by bonding; or The slat gain layer and the slat expansion layer are both made of transparent ceramic materials and are connected by sintering.

4. The laser device according to claim 1, wherein The composite slab is coated with a transmission film for transmitting the incident pump light and a reflection film for reflecting the light beam in the composite slab on the pump light incident surface.

5. The laser device according to claim 1, wherein The surface of the composite slab away from the incident side of the pump light is coated with a reflection film for reflecting the light beam in the composite slab.

6. The laser device according to claim 1, wherein The apparatus further comprises a cooling structure for providing cooling to the composite strip.

7. A laser generating method of a composite slab laser device according to any one of claims 1 to 6, characterized in that: The method comprises The pump light is shaped by a pump coupling structure, and the shaped pump light is injected into the composite slab; The incident pump light is reflected multiple times in the composite slab, amplified to a preset threshold in the slab gain layer, and then output as laser light through the end face of the slab.

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