Combined beam-modulated laser amplifier and system

Abstract

The application provides a combined light beam modulation laser amplifier and system, and belongs to the technical field of laser amplifiers. The laser amplifier comprises a first fixing member, an internal cavity is formed in the first fixing member; a plurality of laser amplification modules are arranged in the cavity, the laser amplification modules are arranged at intervals, each laser amplification module and the first fixing member form a closed cooling chamber; and a micro-optical element is arranged between two adjacent laser amplification modules, and the micro-optical element is connected with the first fixing member. Through the superposition of the plurality of laser amplification modules, a laser amplifier with more gain medium series effects is further obtained, and the micro-optical element is added between the two adjacent laser amplification modules to further modulate the transmission light beam, so that the purposes of high-power output and high-efficiency heat dissipation of the laser amplifier are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser amplifier, in particular to a combined beam modulation laser amplifier and system. BACKGROUND

[0002] High power all-solid-state laser pumped by laser diode (LD) is a hot spot in the international laser technology field, which has a wide range of applications in advanced manufacturing, precision detection, fusion research, military and other fields. However, the development of high power all-solid-state laser is always restricted by thermal effects, because a large amount of waste heat is generated in the gain medium while the laser is output in the process of high power pumping. The existence of these waste heat will lead to thermal lens, thermal stress, depolarization, birefringence and other adverse effects, thereby causing the laser beam quality to decline, the output power to be limited, and even causing the working medium to be damaged, which seriously limits the maximum output average power of the laser. In this case, a new type of thin sheet laser with smaller thermal effects emerges as the times require. Due to the advantages of LD pumped thin sheet laser, such as compact structure, light weight, small volume, high pump power allowed to be injected into the laser crystal, and the temperature in the crystal can be basically kept constant, it has become the research focus of research institutions at home and abroad.

[0003] Foreign research institutions have realized the leap from the concept of thin sheet laser to specific experiments, and have designed a scheme from single-pass to multi-pass pumped thin sheet, which has become the most widely used pumping method in thin sheet lasers. Many domestic institutions have also conducted research on multi-pass pumped thin sheet, but due to the limited gain medium volume of such thin sheet lasers, which restricts the energy storage of the laser, in order to achieve higher power laser output, research on multi-thin sheet laser has been carried out at home and abroad. This multi-thin sheet series scheme can make up for the disadvantages of insufficient energy storage of a single thin sheet laser, but the structure of the series scheme is generally complex and the volume is large.

[0004] In order to meet the requirements of higher power laser output and compact structure, especially under the pull of laser fusion demand, high power all-solid-state laser based on multi-sheet structure has attracted widespread attention. This structure uses multiple discrete gain media, which can provide higher gain, and can effectively remove the waste heat in the medium through high-speed air flow or direct liquid cooling to ensure the normal operation of the laser. Foreign and domestic high-speed gas-cooled laser amplifiers control the flow rate and temperature of the gas flow to match the thermal characteristics of the gain medium, achieving good heat dissipation effect. Liquid direct cooling of sheet solid laser medium is to directly put the gain medium into the cooling liquid, and the laser directly transmits through the cooling liquid and the gain medium. Selecting a cooling liquid with matched refractive index can greatly reduce the loss of laser passing through the cooling liquid and the gain medium, and a large number of sheet gain media can be connected in series, which is one of the technical routes for solid-state laser to achieve high power output of 100,000 watts.

[0005] At present, domestic and foreign scholars have been committed to the high-power laser output of the sheet laser. Since the single sheet gain of the sheet laser is limited, the energy storage is difficult to improve, the power scaling amplification is difficult, the inter-sheet optical system is complex, and the structure is not compact, the multi-sheet laser is an effective means to realize high-energy output and compact structure. When the gain medium develops from a single sheet to multiple sheets, the cooling method also develops from the initial end face direct connection of the heat dissipation device, which can be water cooling, air cooling, etc., to the direct cooling method of high-speed gas and liquid. However, for the design and research of multi-sheet laser, when high-speed gas cooling is used, the instability of the fluid will disturb the wavefront shape of the laser beam when the laser beam passes through the fluid channel, which will affect the output of the laser. Therefore, the control requirement for the uniformity of the cooling gas flow is extremely high, which undoubtedly increases the difficulty and complexity of the system; when liquid direct cooling is used, since the laser directly passes through the cooling liquid, the flow field characteristics, thermodynamic characteristics and various optical characteristics are coupled with each other, so that the action process is complex. Although the active optical control technology can correct some low-frequency aberrations, when high-frequency turbulence is generated in the laser light path, better control means is needed to improve the beam quality. SUMMARY

[0006] The application provides a combined beam modulation laser amplifier and system, which solves the problems of beam wavefront interference and beam quality degradation caused by high-speed gas flow or high-frequency turbulence heat dissipation in the prior art. At the same time, the beam modulation changes the light intensity distribution of the transmission beam to obtain higher energy extraction in the gain medium and better beam quality output. In addition, the superposition of multiple laser amplification modules is used to meet the needs of high-power output, effective heat dissipation and miniaturization of the laser.

[0007] The application provides a combined beam modulation laser amplifier, which comprises:

[0008] A first fixing member, which has a through cavity inside;

[0009] A plurality of laser amplification modules, which are arranged in the cavity at intervals, and each laser amplification module and the first fixing member form a closed cooling chamber;

[0010] A micro-optical element with a micro-phase structure, which is arranged between two adjacent laser amplification modules and connected with the first fixing member;

[0011] Each of the laser amplification modules comprises a gain medium, a heat sink with a micro phase structure on a surface, and a second fixing member, two second fixing members are provided, a light passing area is formed in a middle part of each of the second fixing members, two ends of the gain medium are connected with the heat sink, outer side end faces of the two heat sinks are connected with inner side end faces of the two second fixing members respectively and the light passing areas are closed, the second fixing members, parts of the gain medium corresponding to the light passing areas, parts of the heat sink corresponding to the light passing areas and the first fixing member enclose the cooling cavity, cooling medium flows in the cooling cavity, and the light passing areas on two adjacent laser amplification modules correspond to each other.

[0012] According to the application, a combined laser beam modulation amplifier is provided, the gain medium is used to generate laser under the action of a pump source, in the laser amplification module, a micro phase structure on an outer surface of a first heat sink where an incident light beam enters, corresponding phase data is obtained by phase solving according to actual incident light beam distribution and expected light beam distribution entering the gain medium, the heat sink is manufactured by laser direct writing or lithography according to the phase data, the expected light beam distribution entering the gain medium is flat top distribution or saddle-shaped distribution, and higher energy extraction is obtained.

[0013] According to the application, a combined laser beam modulation amplifier is provided, in the laser amplification module, a micro phase structure on an outer surface of a second heat sink where a transmission light beam enters after passing through the gain medium, corresponding phase data is obtained by phase solving according to actual light beam distribution after passing through the gain medium and light beam distribution expected to be output by the module, the heat sink is manufactured by laser direct writing or lithography according to the phase data, and the light beam distribution expected to be output by the module is fundamental mode Gaussian distribution, and better light beam quality output is obtained.

[0014] According to the application, a combined laser beam modulation amplifier is provided, the micro phase structure of the micro optical element, corresponding phase data is obtained by phase solving according to actual output light beam of a previous laser amplification module and actual incident light beam distribution at the initial time, and the micro optical element is manufactured according to the phase data, so that the incident light beam entering each laser amplification module has the same light intensity distribution characteristics.

[0015] According to the application, a combined laser beam modulation amplifier is provided, a sealing ring is arranged at a connection position of the heat sink and the second fixing member, and the sealing ring surrounds an outer boundary of the light passing area.

[0016] According to the application, a combined laser beam modulation amplifier is provided, the heat sink and the gain medium are in one of square, circular, triangular or polygonal shapes, and the gain medium and the heat sink are connected by one of bonding, optical cementing or a connecting member.

[0017] The combined light beam modulation laser amplifier provided by the application has a gain medium of laser crystal material; the material of the heat sink is a light-transmitting material with high thermodynamic and optical performance, and the material of the heat sink is one of sapphire, white sapphire, diamond or the base material of the gain medium.

[0018] The combined light beam modulation laser amplifier provided by the application has a micro-optical element of quartz or k9 glass.

[0019] The combined light beam modulation laser amplifier provided by the application has a first fixing member, and the upper part of the first fixing member is provided with a cooling medium inlet corresponding to each cooling chamber, and the lower part of the first fixing member is provided with a cooling medium outlet corresponding to each cooling chamber.

[0020] The application further provides a combined light beam modulation laser amplifier system, which comprises the combined light beam modulation laser amplifier, a pump source and a dichroic mirror.

[0021] The pump light emitted by the pump source pumps from one side or both sides of the laser amplifier, passes through the dichroic mirror, enters the combined light beam modulation laser amplifier from the light-transmitting area, and realizes energy amplification of the input laser.

[0022] The combined light beam modulation laser amplifier and system provided by the application have the following advantages: the first fixing member and each laser amplification module form a closed cooling chamber, the laser amplification module is composed of two second fixing members, two optical heat sinks with micro-phase structures and a gain medium, the gain medium is sandwiched between the two heat sinks, the micro-phase structure of the two heat sinks is used to modulate the light beam of the transmission laser, so that the transmission light beam entering the gain medium has a specific light intensity distribution, and the purpose of obtaining higher energy extraction is achieved.

[0023] The two light-transmitting end faces of the gain medium are conducted and cooled by the two heat sinks, the outer edge surface (other than the two light-transmitting surfaces) of the gain medium and the heat sink (other than the other areas within the sealing ring) have cooling medium flowing thereon, and the cooling medium is used to cool them; the cooling medium (gas, cooling liquid, etc.) directly acting on the light-transmitting range of the gain medium is avoided, and the influence on the output light beam is avoided.

[0024] Meanwhile, the application further obtains a laser amplifier with more gain media in series through the superposition of multiple laser amplification modules, and a micro-optical element is added between the adjacent two laser amplification modules to further modulate the transmission light beam, so that the purposes of high-power output and high-efficiency heat dissipation of the laser amplifier are achieved. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to make the technical solutions in the present application or prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are only some embodiments of the present application, and all other embodiments obtained by those of ordinary skill in the art without any creative work based on the accompanying drawings are within the protection scope of the present application.

[0026] Figure 1 is a front view of the combined beam modulation laser amplifier provided by the present application;

[0027] Figure 2 is a connection schematic diagram of the single laser amplification module and the first fixing member;

[0028] Figure 3 is a side view of the combined beam modulation laser amplifier provided by the present application;

[0029] Figure 4 is a side view of the first fixing member;

[0030] Figure 5 is a schematic diagram of the combined beam modulation laser amplification system provided by the present application.

[0031] Reference signs:

[0032] 100, first fixing member; 101, cooling chamber; 102, cooling medium inlet;

[0033] 103, cooling medium outlet; 200, laser amplification module;

[0034] 201, gain medium; 202, heat sink; 203, second fixing member;

[0035] 204, light transmission area; 205, sealing ring;

[0036] 300, micro-optical element. DETAILED DESCRIPTION

[0037] In order to make the technical solutions in the present application or prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are only some embodiments of the present application, and all other embodiments obtained by those of ordinary skill in the art without any creative work based on the accompanying drawings are within the protection scope of the present application.

[0038] The present application will be described below in combination with Figures 1-5 a combined beam modulation laser amplifier and system.

[0039] As Figures 1-4As shown, a combined light beam modulation laser amplifier comprises a first fixing member 100, a laser amplification module 200 and a micro-optical element 300.

[0040] The first fixing member 100 is internally provided with a through cavity;

[0041] The laser amplification module 200 is provided with a plurality of laser amplification modules 200 which are arranged in the cavity at intervals, and each laser amplification module 200 is surrounded by the first fixing member 100 to form a closed cooling chamber 101;

[0042] The micro-optical element 300 is provided with a micro-phase structure, and the micro-optical element 300 is arranged between two adjacent laser amplification modules 200, and the micro-optical element 300 is connected with the first fixing member 100;

[0043] Each laser amplification module 200 comprises a gain medium 201, a heat sink 202 provided with a micro-phase structure on the surface and a second fixing member 203, the second fixing member 203 is provided with two second fixing members 203, and the middle part of each second fixing member 203 is provided with a light transmission area 204, the two ends of the gain medium 201 are connected with the heat sink 202, the outer side end surfaces of the two heat sinks 202 are respectively connected with the inner side end surfaces of the two second fixing members 203 and the light transmission area 204 is closed, and the second fixing member 203, the part of the gain medium 201 corresponding to the light transmission area 204 and the part of the heat sink 202 corresponding to the light transmission area 204 are surrounded by the first fixing member 100 to form the cooling chamber 101, and the cooling medium flows in the cooling chamber 101, and the light transmission areas 204 on the two adjacent laser amplification modules 200 correspond to each other.

[0044] The gain medium 201 is used to generate laser under the action of a pump source; in each laser amplification module 200, the two heat sinks 202 are provided with a micro-phase structure only at the positions of the outer side end surfaces corresponding to the light transmission area 204, the micro-phase structure on the outer surface of the first heat sink 202 where the incident light beam enters is solved according to the actual incident light beam distribution and the light beam distribution expected to enter the gain medium 201 to obtain corresponding phase data, and the micro-phase structure is made on the heat sink 202 according to the phase data by laser direct writing or lithography; the light beam distribution expected to enter the gain medium 201 is flat-top distribution, saddle-shaped distribution or a certain specific light intensity distribution, so as to obtain higher energy extraction;

[0045] In the laser amplification module 200, the micro-phase structure on the outer surface of the second heat sink 202 where the transmitted light beam enters after passing through the gain medium 201 is solved according to the actual light beam distribution after passing through the gain medium 201 and the light beam distribution expected to be output by the module to obtain corresponding phase data, and the micro-phase structure is made on the heat sink 202 according to the phase data by laser direct writing or lithography; the light beam distribution expected to be output by the module is fundamental mode Gaussian distribution or specific light intensity distribution, so as to obtain better light beam quality output.

[0046] The micro phase structure of the micro optical element 300 is solved according to the actual output light beam of the last laser amplification module 200 and the initial actual incident light beam distribution to obtain corresponding phase data, and the phase data is made on the micro optical element 300 to ensure that the incident light beam entering each laser amplification module 200 has the same light intensity distribution characteristics.

[0047] In order to further improve the sealing effect, the connecting part of the heat sink 202 and the second fixing part 203 is provided with a sealing ring 205, which surrounds the outer boundary of the light transmission area 204. At the same time, the existence of the sealing ring 205 makes the gap between the heat sink 202 and the second fixing part 203, which increases the heat dissipation area.

[0048] The shape of the heat sink 202 and the gain medium 201 is not limited, which can be one of square, circular, triangular or polygonal; the gain medium 201 and the heat sink 202 are connected by one of bonding, optical cement or connecting part. Since the area of the incident light beam can cover the light transmission area 204, the area of the heat sink 202 and the gain medium 201 is larger than that of the light transmission area 204, which ensures that the incident light beam passing through the light transmission area 204 can completely pass through the heat sink 202 and the gain medium 201 during transmission.

[0049] The gain medium 201 is a laser crystal material; the selection of the material of the heat sink 202 is limited. Since the heat sink 202 is in the optical path, the existence of the heat sink 202 cannot affect the beam quality. The material of the heat sink 202 is a light transmission material with high thermodynamic and optical properties, which is one of sapphire, white sapphire, diamond or the base material of the gain medium 302 and the like, and the thickness of each heat sink 202 can be set according to actual needs.

[0050] The material of the micro optical element 300 is quartz or k9 glass.

[0051] The upper part of the first fixing part 100 is provided with a cooling medium inlet 102 at the position corresponding to each cooling chamber 101, and the lower part of the first fixing part 100 is provided with a cooling medium outlet 103 at the position corresponding to each cooling chamber 101. A plurality of cooling medium inlets 102 can be connected to the same cooling medium conveying main pipe, and a plurality of cooling medium outlets 103 can be connected to the same cooling medium discharge main pipe, which facilitates the input and discharge of the cooling medium.

[0052] Each laser amplification module 200 corresponds to a cooling chamber 101, and the cooling medium can be gas, liquid, etc. The cooling medium enters each cooling chamber 101 from the upper part of the first fixing part 100, flows through the outer edge surface of the gain medium 201 (other surfaces except the two light transmission surfaces), and other surfaces within the range of the heat sink 202 excluding the sealing ring 205, and then flows out from the lower part of the first fixing part 100, thereby conducting large-scale heat dissipation for the laser amplification module 200. At the same time, the two light transmission surfaces of the gain medium 201 can also conduct heat dissipation by using the two heat sinks 202. Since the light transmission range of the gain medium 201 does not have direct contact with the cooling medium, the influence of the cooling medium on the transmission light beam is avoided, thereby achieving the purposes of high-power output and high-efficiency heat dissipation of the laser amplifier.

[0053] As shown in Figure 5 , a combined beam modulation laser amplification system includes a combined beam modulation laser amplifier as described above, and further includes a pump source and a dichroic mirror.

[0054] The pump light emitted by the pump source pumps from one side or both sides of the laser amplifier, enters the combined beam modulation laser amplifier from the light transmission area 204 after passing through the dichroic mirror, and realizes energy amplification of the input laser.

[0055] The pump source emits pump light, which pumps from one side or both sides, and after passing through the dichroic mirror (DM, high transmission for pump light and high reflection for output light), enters each amplification module placed in series in the laser amplifier. After the transmission light beam in each module is subjected to the micro-phase modulation of the first heat sink 202, the transmission light beam with a specific light intensity distribution enters the gain medium 201, and can extract energy to the maximum extent. After the micro-phase modulation of the other heat sink 202, the output light beam satisfying the specific light intensity distribution can be output. At this time, part of the energy absorbed by the gain medium 201 is converted into heat. Part of the heat is conducted into the heat sink 202, and the other part of the heat enters the cooling medium through the outer edge surface. In addition, micro-optical elements 300 can also be placed between each amplification module to further modulate the transmission light beam. Thus, after passing through multiple amplification modules, the purposes of high-power output and high-efficiency heat dissipation are achieved.

[0056] Under the demand of high power laser output and compact structure, the gain medium of the current high-speed gas-cooled multi-piece laser amplifier needs to be gradually and interval doped or gradient doped, which increases the difficulty and complexity of the preparation of the gain medium; and the direct liquid-cooled multi-piece laser has problems such as complex action process, the need to control the aberration and beam quality, and a relatively complex system; compared with the current existing multi-piece laser amplifier, the combined beam modulation laser head provided in the application has the advantages of no special requirement for the doping of the gain medium, a relatively simple action process, compact structure, high energy output and effective heat dissipation, and provides a new idea and development direction for the high-power output of the multi-piece laser.

[0057] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A combined beam modulation laser amplifier, characterized in that, include: The first fastener has a through cavity inside; A laser amplification module is provided, and multiple laser amplification modules are arranged at intervals in the cavity. Each laser amplification module and the first fixing member form a closed cooling chamber. A micro-optical element, the micro-optical element having a micro-phase structure, the micro-optical element being disposed between two adjacent laser amplification modules, and the micro-optical element being connected to the first fixing member; Each laser amplification module includes a gain medium, a heat sink with a micro-phase structure on its surface, and a second fixing component. Two second fixing components are provided, and each second fixing component has a light-transmitting area in its middle. Both ends of the gain medium are connected to the heat sink. The outer end faces of the two heat sinks are respectively connected to the inner end faces of the two second fixing components, thus enclosing the light-transmitting area. The second fixing component, the portion of the gain medium excluding the portion corresponding to the light-transmitting area, the portion of the heat sink excluding the portion corresponding to the light-transmitting area, and the first fixing component form a cooling chamber. A cooling medium flows through the cooling chamber, and the light-transmitting areas on two adjacent laser amplification modules correspond to each other. The gain medium is used to generate laser light under the action of a pump source; in the laser amplification module, 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 desired beam distribution entering the gain medium, and the phase data is fabricated on the heat sink by laser direct writing or photolithography based on the phase data; the desired beam distribution entering the gain medium is a flat-top distribution or a saddle-shaped distribution to obtain higher energy extraction; In the laser amplification module, the micro-phase structure on the outer surface of the second heat sink after the transmitted 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 module. The phase data is then fabricated on the heat sink using laser direct writing or photolithography. The expected beam distribution of the module output is a Gaussian distribution of the fundamental mode to obtain better beam quality output. The micro-phase structure of the micro-optical element is obtained by solving the phase data based on the actual output beam of the previous laser amplification module and the initial actual incident beam distribution. The phase data is then fabricated on the micro-optical element to ensure that the incident beam entering each laser amplification module has the same light intensity distribution characteristics.

2. The combined beam modulation laser amplifier according to claim 1, characterized in that, A sealing ring is provided at the connection between the heat sink and the second fixing member, and the sealing ring is arranged around the outer boundary of the light-transmitting area.

3. The combined beam modulation laser amplifier according to claim 1, characterized in that, The heat sink and the gain medium are square, circular, triangular or polygonal in shape; the gain medium and the heat sink are connected by bonding, photoresist or connector.

4. The combined beam modulation laser amplifier according to claim 1, characterized in that, The gain medium is a laser crystal material; the heat sink material is a light-transmitting material with high thermodynamic and optical properties, and the heat sink material is one of sapphire, sapphire, diamond, or the substrate material of the gain medium.

5. The combined beam modulation laser amplifier according to claim 1, characterized in that, The material of the micro-optical element is quartz or K9 glass.

6. The combined beam modulation laser amplifier according to claim 1, characterized in that, The upper part of the first fixing member has a cooling medium inlet at the position corresponding to each of the cooling chambers, and the lower part of the first fixing member has a cooling medium outlet at the position corresponding to each of the cooling chambers.

7. A combined beam modulation laser amplification system, characterized in that, The combined beam modulation laser amplifier according to any one of claims 1-6 further includes a pump source and a dichroic mirror; The pump light emitted from the pump source pumps the laser amplifier from one or both sides, passes through the dichroic mirror, and enters the combined beam modulation laser amplifier from the light-transmitting region, thereby amplifying the energy of the input laser.

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