Compact beam modulation laser gain module

Abstract

This invention provides a compact beam-modulated laser gain module, belonging to the field of solid-state laser technology. The gain module includes a first structural component, a second structural component, a gain medium, and heat sinks. The heat sinks have micro-phase structures on their surfaces and are respectively disposed on both end faces of the gain medium. The gain medium and heat sinks, when connected, form a laser gain core unit located within a cavity. The outer end faces of the two heat sinks are respectively connected to the inner end faces of the two second structural components, sealing off the light-transmitting areas. The first structural component, the second structural component, and the laser gain core unit, excluding the corresponding light-transmitting areas, form a sealed cooling chamber, within which a cooling medium flows. The gain module utilizes the micro-phase structures of the two heat sinks to modulate the transmitted beam, resulting in a specific intensity distribution of the transmitted beam entering the gain medium, thereby achieving higher energy extraction and better beam quality output.

Description

Technical Field

[0001] This invention relates to the field of solid-state laser technology, and more particularly to a compact beam modulation laser gain module. Background Technology

[0002] High-power all-solid-state lasers pumped by laser diodes (LDs) are currently a hot research topic in the international laser technology field, with wide applications in advanced manufacturing, precision detection, fusion research, and military applications. However, the development of high-power all-solid-state lasers has always been constrained by thermal effects. This is because during high-power pumping, the gain medium generates a large amount of unwanted heat while outputting laser light. The presence of this unwanted heat can lead to adverse effects such as thermal lensing, thermal stress, depolarization, and birefringence, resulting in decreased laser beam quality, limited output power, and even damage to the working medium, severely limiting the maximum average output power of the laser. Under these circumstances, novel thin-plate lasers with smaller thermal effects have emerged. Due to the many advantages of thin-plate lasers—such as compact structure, light weight, small size, high allowable pump power of the laser crystal, and the ability to maintain a relatively constant temperature within the crystal—they have rapidly become a research focus for research institutions both domestically and internationally.

[0003] Foreign research institutions have made significant strides in the development of thin-plate lasers, moving from conceptualization to practical application. They have designed schemes ranging from single-pass to multi-pass pumped thin plates, which have become the most widely used pumping method for thin-plate lasers. Many domestic institutions have also conducted research on multi-pass pumped thin plates. However, due to the limitation of the finite gain medium volume on the energy storage of such thin-plate lasers, research on tandem multi-plate thin-plate lasers has been carried out both domestically and internationally to achieve higher power laser output. This tandem multi-plate scheme can compensate for the insufficient energy storage of a single thin-plate laser; however, the tandem scheme generally has a more complex structure and a larger size.

[0004] To meet the requirements of higher power laser output and compact structure, especially driven by the demand for laser fusion, high-power all-solid-state lasers based on multi-plate structures have attracted widespread attention. This structure uses multiple discrete gain media plates, which can provide high gain. Waste heat in the medium can be effectively removed by blowing high-speed gas or direct liquid cooling, ensuring the normal operation of the laser. Domestic and international research on high-speed gas-cooled laser amplifiers achieves good heat dissipation by controlling the gas flow rate and temperature to match the thermal characteristics of the gain medium. Liquid direct cooling of plate-shaped solid-state laser media involves directly immersing the gain medium in the coolant. The laser directly transmits through the coolant and gain medium. Using a coolant with a matching refractive index can greatly reduce the loss of the laser passing through the coolant and gain medium. This allows for the cascading of a large number of plate-shaped gain media plates and is one of the technical routes for achieving 100 MW high-power output in solid-state lasers.

[0005] Currently, scholars both domestically and internationally have been dedicated to high-power laser output from sheet lasers. However, due to the limited gain of a single sheet laser, it is difficult to increase energy storage, power scaling and amplification are challenging, and the complex inter-sheet cascade optical systems fail to achieve a compact structure. Multi-sheet lasers are currently an effective means of achieving both high-energy output and a compact structure. As the gain medium has evolved from a single sheet to multiple sheets, the cooling method has also progressed from directly connecting the end face to a heat dissipation device (such as water or gas cooling) to direct cooling with high-speed gas and liquid. However, for the design and research of multi-sheet lasers, when using high-speed gas cooling, the instability of the fluid as the laser beam passes through the fluid channel can cause slight disturbances to the wavefront shape of the beam, affecting the laser output. Therefore, the control of the uniformity of the cooling airflow is extremely demanding, which undoubtedly increases the system's difficulty and complexity. When using direct liquid cooling, the laser passes directly through the coolant, and the flow field characteristics, thermodynamic properties, and various optical properties in the laser oscillation are coupled together, making the process complex. Although some low-frequency aberrations can be corrected with the help of active optical control technology, the beam quality still needs to be controlled by better means when high-frequency turbulence is generated in the laser beam path. Summary of the Invention

[0006] This invention provides a compact beam modulation laser gain module to solve the problem that beam wavefront interference and beam quality degradation occur when there is high-speed airflow or high-frequency turbulence in the laser light path of existing technologies; at the same time, it changes the intensity distribution of the transmitted beam by beam modulation to obtain higher energy extraction and better beam quality output.

[0007] This invention provides a compact beam modulation laser gain module, comprising:

[0008] The first structural component has a through cavity inside;

[0009] The second structural component has a light-transmitting area in the middle. The second structural component is located inside the cavity, and there are two of the second structural components.

[0010] Gain medium, used to generate laser light under the action of a pump source;

[0011] The heat sink has a micro-phase structure on its surface and is respectively disposed on both end faces of the gain medium;

[0012] The gain medium and the heat sink are connected to form a laser gain core unit. The laser gain core unit is located in the cavity. The outer end faces of the two heat sinks are respectively connected to the inner end faces of the two second structural components and enclose the light-transmitting area. The first structural component, the second structural component and the laser gain core unit, excluding the portion corresponding to the light-transmitting area, form a sealed cooling chamber. A cooling medium flows through the cooling chamber.

[0013] According to the present invention, a compact beam modulation laser gain module is provided, wherein the micro-phase structure on the outer surface of the first heat sink into which the incident beam enters is obtained by phase calculation based on the actual incident beam distribution and the beam distribution to be entered into the gain medium. The phase data is then fabricated on the heat sink by laser direct writing or photolithography. The beam distribution to be entered into the gain medium is a flat-top distribution or a saddle-shaped distribution to obtain higher energy extraction.

[0014] According to the present invention, a compact beam modulation laser gain module is provided. The micro-phase structure on the outer surface of the second heat sink after the transmission beam passes through the gain medium is obtained by phase calculation based on the actual beam distribution after passing through the gain medium and the beam distribution expected to be output by the gain module. The phase data is fabricated on the heat sink by laser direct writing or photolithography based on the phase data. The beam distribution expected to be output by the gain module is a Gaussian distribution of the fundamental mode in order to obtain better beam quality output.

[0015] According to a compact beam modulation laser gain module provided by the present invention, the gain medium and the heat sink are connected by one of the following methods: bonding, optical adhesive, or connector.

[0016] According to a compact beam modulation laser gain module provided by the present invention, a sealing ring is provided at the connection between the heat sink and the second structural component, and the sealing ring is disposed around the outer boundary of the light-transmitting area.

[0017] According to the present invention, a compact beam modulation laser gain module is provided, wherein the heat sink and the gain medium are in the shape of a square, a circle, a triangle or a polygon.

[0018] According to the present invention, a compact beam modulation laser gain module is provided, wherein the gain medium is a laser crystal material.

[0019] According to the present invention, a compact beam modulation laser gain module is provided, wherein the heat sink is made of a light-transmitting material with high thermodynamic and optical properties.

[0020] According to the present invention, a compact beam modulation laser gain module is provided, wherein the heat sink is made of sapphire, sapphire, diamond, or the substrate material of the gain medium.

[0021] According to a compact beam modulation laser gain module provided by the present invention, the upper part of the first structural member has a cooling medium inlet communicating with the cooling chamber, and the lower part of the first structural member has a cooling medium outlet communicating with the cooling chamber.

[0022] The compact beam modulation laser gain module provided by this invention comprises a first structural component, a second structural component, and a laser gain core unit, excluding the corresponding light-transmitting areas, forming a sealed cooling chamber. The laser gain core unit consists of two optical heat sinks with micro-phase structures and a gain medium, wherein the gain medium is sandwiched between the two heat sinks. The micro-phase structure of the heat sinks on both sides modulates the transmitted beam, resulting in a specific intensity distribution of the transmitted beam entering the gain medium, thereby achieving higher energy extraction and better beam quality output. The heat generated by the gain medium is partially transferred to the heat sinks on both sides via thermal conduction through the light-transmitting end faces, and then carried away by the cooling medium flowing over the surface of the heat sinks; the other part is dissipated by the outer surface of the gain medium excluding the light-transmitting end faces directly contacting the cooling medium. This achieves the purpose of efficient heat dissipation of the gain module.

[0023] The laser gain module of this invention directly fabricates the micro-phase structure with beam modulation function on the surface of the heat sink, instead of adding a single micro-phase optical element in the module. This makes the module structure more compact. At the same time, it avoids the influence of the cooling medium directly acting on the light transmission range of the gain medium on the transmitted beam, thereby achieving the purpose of high power output and efficient heat dissipation of the gain module. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a front structural cross-sectional view of the compact beam modulation laser gain module provided by the present invention;

[0026] Figure 2 This is a side view of the compact beam modulation laser gain module provided by the present invention;

[0027] Figure 3 This is a side sectional view of the first structural component.

[0028] Figure label:

[0029] 100. First structural component; 101. Cooling chamber; 102. Cooling medium inlet;

[0030] 103. Cooling medium outlet;

[0031] 200. Second structural component; 201. Light-transmitting area; 202. Sealing ring;

[0032] 300. Laser gain core unit; 301. Heat sink; 302. Gain medium;

[0033] 303. Microphase structure. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] The following is combined Figures 1-3 The present invention describes a compact beam modulation laser gain module, comprising a first structural component 100, a second structural component 200, a gain medium 302, and a heat sink 301.

[0036] The first structural component 100 has a through cavity inside; it can be understood that the first structural component 100 is a shell structure with open ends.

[0037] The second structural component 200 has a light-transmitting area 201 in the middle, the second structural component 200 is located in the cavity, and there are two second structural components 200.

[0038] The gain medium 302 is used to generate laser light under the action of a pump source;

[0039] The heat sink 301 has a micro-phase structure 303 on its surface and is disposed on both ends of the gain medium 302. The gain medium 302 and the heat sink 301 can be connected by bonding, photoresist or connector.

[0040] The gain medium 302 and the heat sink 301 are connected to form a laser gain core unit 300, which is located inside a cavity. The outer end faces of the two heat sinks 301 are respectively connected to the inner end faces of the two second structural components 200, thus sealing the light-transmitting area 201. The first structural component 100, the second structural component 200, and the laser gain core unit 300, excluding the portion corresponding to the light-transmitting area 201, form a sealed cooling chamber 101, through which a cooling medium flows. The shape or structure of the second structural component 200 is not specifically limited, as long as it can fix the laser gain core unit 300 and participate in forming the sealed cooling chamber 101.

[0041] The micro-phase structure 303 on the outer surface of the first heat sink 301 into which the incident beam enters is obtained by phase calculation based on the actual incident beam distribution and the beam distribution expected to enter the gain medium 302. The phase data is then fabricated on the heat sink 301 using laser direct writing or photolithography. The beam distribution expected to enter the gain medium 302 is a flat-top distribution, a saddle-shaped distribution, or a specific intensity distribution to obtain higher energy extraction.

[0042] After the incident beam enters the laser gain core unit 300, it begins to propagate. After passing through the gain medium 302, the propagating beam enters the micro-phase structure 303 on the outer surface of the second heat sink 301. The phase data is obtained by solving the phase problem based on the actual beam distribution after passing through the gain medium 302 and the beam distribution expected to be output by the gain module. The phase data is then fabricated on the heat sink 301 using laser direct writing or photolithography. The beam distribution expected to be output by the gain module is generally set to a fundamental mode Gaussian distribution or a specific intensity distribution to obtain better beam quality output.

[0043] In this embodiment, the two heat sinks 301 have micro-phase structures 303 only on their outer end faces corresponding to the light-transmitting areas 201. The micro-phase structures 303 can modulate the incident beam to generate a beam with a specific intensity distribution (such as a square beam, a flat-top beam, a saddle-shaped beam, etc.) and enter the gain medium 302 to obtain higher energy extraction. After being modulated by the micro-phase structure 303 of the other heat sink 301, the output beam of the laser gain core unit 300 is modulated to the required intensity distribution.

[0044] To further improve the sealing effect, a sealing ring 202 is provided at the connection between the heat sink 301 and the second structural component 200, and the sealing ring 202 is arranged around the outer boundary of the light-transmitting area 201. At the same time, the presence of the sealing ring 202 creates a gap between the heat sink 301 and the second structural component 200, increasing the heat dissipation area.

[0045] The shapes of the heat sink 301 and the gain medium 302 are not specifically limited and can be square, circular, triangular, or polygonal. Since the area of ​​the incident beam can completely cover the light transmission area 201, the areas of both the heat sink 301 and the gain medium 302 must be larger than the light transmission area 201 to ensure that the incident beam passing through the light transmission area 201 can completely pass through the heat sink 301 and the gain medium 302 during transmission.

[0046] The gain medium 302 is a laser crystal material; the choice of material for the heat sink 301 is limited. Since the heat sink 301 is in the optical path, its presence cannot affect the beam quality. The material of the heat sink 301 is a light-transmitting material with high thermodynamic and optical properties, specifically sapphire, white sapphire, diamond, or a medium optical element such as the substrate material of the gain medium 302. The thickness of each heat sink 301 can be set according to actual needs.

[0047] The upper part of the first structural member 100 is provided with a cooling medium inlet 102 communicating with the cooling chamber 101, and the lower part of the first structural member 100 is provided with a cooling medium outlet 103 communicating with the cooling chamber 101.

[0048] The cooling medium can be a gas, liquid, etc. It enters from the top of the first structural component 100, flows over the outer edge surface of the gain medium 302 (excluding the light-transmitting surfaces on both sides) and the other surfaces of the heat sink 301 (excluding the area within the sealing ring 202), and exits from the bottom of the first structural component 100, thereby providing large-scale heat dissipation for the laser gain core unit 300. Simultaneously, the two light-transmitting end faces of the gain medium 302 can also utilize the heat sinks 301 on both sides for conductive heat dissipation. Since the light-transmitting area of ​​the gain medium 302 does not directly contact the cooling medium, the influence of the cooling medium on the transmitted beam is avoided, thus achieving high power output and efficient heat dissipation of the gain module.

[0049] Driven by the demand for high-power laser output and compact structure, current high-speed gas-cooled multi-chip laser amplifiers require gain media that are graded and spaced doped or gradient-doped, which increases the difficulty and complexity of gain media preparation. On the other hand, directly liquid-cooled multi-chip lasers have problems such as complex operation process, need to control aberrations and beam quality, and relatively complex system. Compared with existing multi-chip laser amplifiers, the compact beam modulation laser gain module proposed in this invention has the advantages of no special requirements for gain media doping, simpler operation process, compact structure, high energy output and effective heat dissipation, providing a new approach and development direction for high-power output of multi-chip lasers.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compact beam modulated laser gain module, characterized by, The utility model relates to a kind of laser gain medium and heat sink structure, including: First structural member, internally set with through cavity; Second structural member, middle part is set with light transmission area, the second structural member is located in the cavity, the second structural member is provided with two; Gain medium, for generating laser under the action of pump source; Heat sink, surface with micro phase structure, the heat sink is respectively arranged in the two sides end surface of the gain medium; The gain medium and the heat sink connect to form laser gain core unit, the laser gain core unit is located in the cavity, the outside end surface of two heat sinks is connected with the inside end surface of two second structural members respectively and closes the light transmission area, the first structural member, the second structural member and the laser gain core unit except the part corresponding to the light transmission area form a closed cooling chamber, cooling medium flows in the cooling chamber; The micro phase structure of the first heat sink outer surface that incident light beam enters, according to actual incident light beam distribution and the light beam distribution expected to enter gain medium phase solution is obtained corresponding phase data, according to phase data, laser direct writing or photolithography is used to manufacture on heat sink;Desired light beam distribution into gain medium is flat top distribution or saddle-shaped distribution, to obtain higher energy extraction; The micro phase structure of the second heat sink outer surface that transmission light beam enters after gain medium, according to actual light beam distribution after gain medium and the light beam distribution expected to output of gain module phase solution is obtained corresponding phase data, according to phase data, laser direct writing or photolithography is used to manufacture on heat sink;Gain module expected output light beam distribution is base mode Gaussian distribution, to obtain better beam quality output.

2. The compact beam modulated laser gain module of claim 1, wherein, The gain medium and the heat sink are connected by one of bonding, optical cement or connector.

3. The compact beam modulated laser gain module of claim 1, wherein, The connection of the heat sink and the second structural member is provided with sealing ring, and the sealing ring is arranged around the outer boundary of the light transmission area.

4. The compact beam modulated laser gain module of claim 1, wherein, The shape of the heat sink and the gain medium is one of square, circle, triangle or polygon.

5. The compact beam modulated laser gain module of claim 1, wherein, The gain medium is laser crystal material.

6. The compact beam modulated laser gain module of claim 5, wherein, The material of the heat sink is light-transmitting material with high thermodynamic and optical properties.

7. The compact beam modulated laser gain module of claim 6, wherein, The material of the heat sink is one of sapphire, white gem, diamond or the base material of gain medium.

8. The compact beam modulated laser gain module of claim 1, wherein, The upper part of the first structural member is provided with cooling medium inlet communicated with the cooling chamber, and the lower part of the first structural member is provided with cooling medium outlet communicated with the cooling chamber.

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