A laser multi-pass amplifier

Abstract

The present invention relates to a laser multi-pass amplifier, comprising a seed light source, a gain medium, and a reflector group consisting of a plurality of reflectors, wherein the reflector group is arranged on the optical path of the seed light generated by the seed light source, and is used to receive the seed light and reflect the optical path of the seed light on each reflector; the optical path of the seed light passes through the gain medium multiple times; the amplifier is characterized in that it also includes a pump source group, wherein the pump source group includes a plurality of pump sources uniformly arranged in space on both sides of the gain medium; the pump lasers generated by the respective pump sources form light spots on the gain medium that overlap with each other. The present invention can effectively solve the problems of poor quality, low energy, and poor stability of the amplified light spot existing in the existing traditional technology, and effectively suppress the TASE (transverse spontaneous emission) and parasitic amplification problems generated under high-energy pumping. The gain mode of the amplifier of the present invention meets the parameter requirements of large-system lasers.

Description

Technical Field

[0001] The invention relates to a laser multi-pass amplifier, belongs to the technical field of lasers, and in particular to an ultrafast and ultra-strong titanium sapphire laser multi-pass amplifier. Background Art

[0002] Ti:sapphire laser multi-pass amplifiers are the primary components of ultrafast, ultra-intense Ti:sapphire lasers. Their gain medium is titanium sapphire (Ti:sapphire). A typical 100TW multi-pass amplifier consists of an oscillator, a stretcher, an amplifier, and a compressor. The amplifier stages are further categorized as regenerative amplifiers and multi-stage multi-pass amplifiers. With the advancement of laser technology, demands for laser output energy and long-term stability are increasing. At the same time, laser devices are increasingly demanding compact structures and stable performance. Consequently, the conflict between gain requirements and parasitic amplification in Ti:sapphire multi-pass amplifiers remains an urgent issue.

[0003] A traditional Ti:sapphire multi-pass amplifier consists of a seed beam, a gain medium, and an excitation source. The excitation source, also known as a pump source, excites the gain medium. When the pump laser irradiates the Ti:sapphire crystal, a population inversion occurs within the crystal. When the seed beam passes through this Ti:sapphire crystal, the inverted population transitions to a lower energy level, resulting in stimulated emission and amplification of the seed beam energy. Multiple penetrations of the gain medium allow the seed beam to be amplified to a sufficient degree. Therefore, the pump source's excitation method significantly affects the output beam quality and energy.

[0004] In the existing technology, due to optical components such as lenses, the pump light has randomly distributed scattered light spots with uneven light intensity in the light spot on the gain medium, resulting in uneven gain on the gain medium. After the seed light is amplified under such conditions, bright spots with uneven light intensity are also generated in the seed laser, which ultimately leads to poor quality of the amplifier amplified light spot, strong areas, poor amplification energy and stability, as well as TASE (transverse spontaneous emission) and parasitic amplification generated under high-energy pumping. It may also damage the optical components in the laser cavity. Summary of the Invention

[0005] The purpose of the present invention is to provide a laser multi-pass amplifier to solve the problems of poor amplified spot quality, low energy, poor energy stability, TASE, parasitic amplification, etc.

[0006] To achieve the above object, the solution of the present invention includes:

[0007] A technical solution for a laser multi-pass amplifier of the present invention includes a seed light source, a gain medium, and a reflector group consisting of a plurality of reflectors. The reflector group is arranged on the optical path of seed light generated by the seed light source and is used to receive the seed light and reflect the optical path of the seed light on each reflector. The optical path of the seed light passes through the gain medium multiple times. The technical solution also includes a pump source group, which includes multiple pump sources uniformly arranged in space on both sides of the gain medium. The pump lasers generated by the respective pump sources form light spots on the gain medium that overlap with each other.

[0008] The present invention forms overlapping light spots on the gain medium through multiple pump sources evenly distributed in space. The randomly distributed light spots in each pump light complement each other, making the superimposed pump light spot on the final gain medium more uniform. This weakens or eliminates the strong area in the seed light caused by the scattered light spots in the pump light, improves the energy and stability of the amplified light spot, and enhances the quality of the amplified light spot.

[0009] Furthermore, the pump sources are an even number and are evenly distributed on both sides of the gain medium; two pump sources located on both sides of the gain medium constitute a group, and a group of pump sources is located on a straight line passing through the gain medium.

[0010] The pump sources are arranged in groups of two on both sides of the gain medium. A group of pump sources is arranged on the same straight line from both sides toward the gain medium, which can achieve a better superposition optimization effect on the gain medium.

[0011] Furthermore, the reflectors are distributed on both sides of the gain medium.

[0012] Furthermore, the reflector includes an input mirror and a reversing mirror, wherein the input mirror is used to reflect the seed light toward the gain medium on a corresponding side of the gain medium, and the reversing mirror is used to reflect the seed light passing through the gain medium toward the input mirror on the same side.

[0013] On one side of the gain medium, the seed light is reflected on the input mirror serving as the first reflector and then passes through the gain medium. After reflecting on the reversing mirror on the other side, it changes direction and reaches the incident mirror on the same side, and is reflected and passes through the gain medium again. After repeating this process multiple times, the seed light is reflected on the reversing mirror on one side serving as the output mirror and outputs the amplified light outward.

[0014] Furthermore, in the propagation direction of the seed light, the distance between a group of input mirrors and reversing mirrors that are adjacent to each other on the optical path on the same side of the gain medium gradually decreases.

[0015] Furthermore, in the propagation direction of the seed light, a group of input mirrors and reversing mirrors that are adjacent to each other on the optical path on the same side of the gain medium are increasingly farther away from the gain medium.

[0016] In the propagation direction of the seed light, the seed light continuously undergoes reversal and incidence on both sides of the gain medium and then enters the other side. The distance between a set of input mirrors and reversing mirrors upstream on the same side of the optical path is larger than that between a set of input mirrors and reversing mirrors downstream on the same side of the optical path, and the seed light is closer to the gain medium.

[0017] Furthermore, the direction of the connection line between a set of input mirrors and the reversing mirror is longitudinal; on either side of the gain medium, the distance in the longitudinal direction of the area where the pump source is distributed is smaller than the distance between a set of input mirrors and the reversing mirror with the smallest spacing on that side.

[0018] Furthermore, on any side of the gain medium, the distance from the region where the pump sources are distributed to the gain medium in the lateral direction is longer than the distance from any one of the reflectors on that side to the gain medium.

[0019] The multiple pump sources on both sides of the gain medium are staggeredly distributed in the outer space between the farthest set of input mirrors and the reversing mirrors on both sides, so as to achieve the effect of superposition optimization on the gain medium.

[0020] Furthermore, the pump source is a pulse pump source of a solid laser or a semiconductor laser.

[0021] Furthermore, the gain medium is titanium-doped sapphire crystal.

[0022] The solution of the present invention takes a titanium-sapphire-doped laser multi-pass amplifier as an example and proposes a new pumping method. In addition to titanium-sapphire crystal, the gain medium can also be, for example, ytterbium-doped potassium gadolinium tungstate crystal or ytterbium-doped potassium yttrium tungstate crystal, as well as other substances that can serve as gain media. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structural principle of the laser multi-pass amplifier of the present invention.

[0024] The figure includes: 10, optical path; 11, light source incident end; 12, amplified light output end; 20, gain medium; 31, input mirror; 32, reversing mirror; 40, pump source. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present invention and are not intended to limit the present invention. That is, the embodiments described herein are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein may be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0027] It should be noted that, in the specific embodiments of the present invention, terms such as "first" and "second" and other relational terms that may appear are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, terms such as "include", "comprise" or any other variants thereof that may appear are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the phrase "including a ..." or other defined elements that may appear does not exclude the presence of other identical elements in the process, method, article or device that includes the elements.

[0028] In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0029] In the description of the present invention, unless otherwise expressly specified or limited, the terms "provided with" and "provided with" should be understood broadly. For example, the object "provided with" may be a part of the main body, or may be arranged separately from the main body and connected to the main body. The connection may be detachable or non-detachable. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0030] The present invention will be further described in detail below with reference to the accompanying drawings.

[0031] like Figure 1 The laser multi-pass amplifier of the present invention shown includes seed light, a gain medium 20 , a reflector system composed of a plurality of reflectors, and a pump source group 40 .

[0032] The seed light comprises a light source incident port 11, an amplified light output port 12, and an optical path 10 between the two ports. A reflector system receives the seed light and, under the action of each reflector, directs the optical path 10 repeatedly through the gain medium 20. Pump source groups 40 are located on both sides of the gain medium 20, emitting pump light toward the gain medium 20, with the pump light spots on the gain medium overlapping.

[0033] In this embodiment, pump sources A1 and A2 are respectively positioned on either side of the gain medium 20, along the central axis passing through the gain medium 20. Four other groups of pump sources are provided: pump sources B1 and B4, pump sources B2 and B3, pump sources C1 and C4, and pump sources C2 and C3. The two pump sources in each group are positioned on either side of the gain medium and located along the same straight line passing through the gain medium 20. The pump lasers emitted by the two pump sources in a group are directed in opposite directions along the same straight line, toward opposite sides of the gain medium 20. The pump sources on both sides are located within a predetermined range around pump sources A1 and A2.

[0034] In this embodiment, five groups of pump sources are included. As other implementations, there may also be 1 to 4 groups of pump sources, or more than five groups of pump sources.

[0035] In this embodiment, the reflector system is specifically as follows: the reflector includes an input mirror 31 and a reversing mirror 32. Seed light from the light source incident end 11 is irradiated onto the first input mirror 31. After reflection from the input mirror 31, the seed light passes through the gain medium 20 and enters the other side of the gain medium 20, where it is irradiated onto the first reversing mirror 32. The first reversing mirror 32 reflects the seed light back onto the input mirror 31 on the same side. After reflection from the input mirror 31, the seed light passes through the gain medium 20 again and returns to the side of the gain medium 20 where the light source incident end 11 is located. After reflection from the first reversing mirror 32 and the second input mirror 31 on that side, the seed light passes through the gain medium 20 for the third time. This process is repeated several times. After the seed light is fully amplified, it is output through the last reversing mirror 32. On the same side of the gain medium 20, the adjacent input mirrors 31 and reversing mirrors 32 on the optical path 10 form a set of reflectors. After several reflections from the reflector group, the optical path 10 repeatedly passes through the gain medium 20, and the seed light energy is amplified before being output from the laser multi-pass amplifier of the present invention.

[0036] Furthermore, the input mirror 31 and the reversing mirror 32 of each set of reflectors and the gain medium 20 as the three vertices of the triangle form an isosceles triangle, and the angle where the gain medium 20 is the vertex is the angle between the two sides.

[0037] On both sides of the gain medium 20, the reflector group located upstream of the seed light propagation direction in optical path 10 is closer to the gain medium 20, while the spacing between the input mirror 31 and the reversing mirror 32 in the same group is larger. This results in the seed light's reflection angle on the reflector decreasing along the optical path 10, causing the angle between the seed light and the central axis of the gain medium 20 to become smaller and smaller as it passes through the gain medium 20.

[0038] The pump sources are distributed on both sides of the gain medium 20, outside the reflector group farthest from the gain medium 20. Their longitudinal range is smaller than the distance between the input mirror 31 and the deflection mirror 32 in the reflector group farthest from the gain medium 20, with the longitudinal direction being the line connecting the input mirror 31 and the deflection mirror 32 in the reflector group. That is, the distribution area of ​​pump sources A1, B1, B2, C1, and C2 is outside the outermost reflector group on the same side, and the longitudinal dimension of this area is smaller than the distance between the input mirror 31 and the deflection mirror 32 in the outermost reflector group. The distribution area of ​​pump sources A2, B3, B4, C3, and C4 is outside the outermost reflector group on the same side, and the longitudinal dimension of this area is smaller than the distance between the input mirror 31 and the deflection mirror 32 in the outermost reflector group.

[0039] Taking the straight line passing through the gain medium 20 as the symmetry axis, the pump sources on both sides of the gain medium 20 are distributed axially symmetrically. Specifically, the positions of the pump sources B2 and B4, C2 and C4, A1 and A2, C1 and C3, and B1 and B3 are axially symmetrical.

[0040] This invention improves the structure of a Ti:Sapphire multi-pass amplifier, enhancing the quality of the amplified beam spot and making it suitable for compact ultrafast and ultra-intense Ti:Sapphire lasers. It solves the problems of low laser energy and poor energy stability, and suppresses the parasitic amplification caused by high-energy output.

[0041] The newly designed excitation source and pumping method increase the number of pump sources by a factor of two. Spatially, the input mirrors are staggered to achieve an optimized spatial overlap on the gain medium. The pump sources are primarily pulsed, including but not limited to solid-state and semiconductor lasers.

[0042] The core of the present invention is to provide a method for exciting the gain medium, including the arrangement of a pump source, which can achieve more uniform amplified seed light. This embodiment uses titanium-doped sapphire (Ti:Sapphire) as an example to introduce the pumping method of the laser multi-pass amplifier of the present invention, but the present invention is not limited to this. The pumping method proposed by the present invention can also be used for laser multi-pass amplifiers using other gain media, such as laser multi-pass amplifiers using ytterbium-doped potassium gadolinium tungstate crystal (Yb:KGW), ytterbium-doped potassium yttrium tungstate crystal (Yb:KYW), or other gain media. In other words, the laser amplifier of the present invention using the new pumping method is not limited to the type of gain medium. This embodiment uses titanium-doped sapphire crystal as a typical example of the gain medium. As other embodiments, the gain medium can also be replaced with other crystals that can be used as gain media for laser amplifiers, such as ytterbium-doped potassium gadolinium tungstate and ytterbium-doped potassium yttrium tungstate.

[0043] The present invention can increase the amplification factor and energy of the seed light. Its spatially bilateral multi-source pumping design can improve problems such as poor amplified spot quality, strong areas, poor amplified energy, and stability caused by uneven gain, significantly reducing the risk of damage to optical components within the laser cavity. Furthermore, because the pump source used to excite the gain medium (Ti:Sapphire) in a 100TW laser requires a high energy pumping rate, parasitic amplification and TASE phenomena can occur, significantly affecting and limiting the output of ultrafast and ultra-intense Ti:Sapphire lasers (such as 100TW and PW laser systems). The use of this new pumping structure and method provides more operating space and corresponding matching solutions to suppress parasitic amplification and TASE issues. Ultimately, the result is an output with high-quality spot quality, high energy, and high energy stability, effectively resolving the problems caused by parasitic amplification and TASE.

[0044] While specific embodiments have been described above, the present invention is not limited to the described embodiments. The basic structure and functionality of the present invention reside in the aforementioned basic scheme. Those skilled in the art, based on the teachings of the present invention, may employ other modules, devices, structures, and installation methods without inventive effort. Changes, modifications, substitutions, and variations to the embodiments without departing from the principles and spirit of the present invention remain within the scope of protection of the present invention.

Claims

1. A laser multi-pass amplifier, comprising a seed light source, a gain medium, and a reflector group consisting of a plurality of reflectors, wherein the reflector group is arranged on the optical path of seed light generated by the seed light source and is used to receive the seed light and reflect the seed light on each reflector; the optical path of the seed light passes through the gain medium multiple times; characterized in that The invention also includes a pump source group, which includes a plurality of pump sources symmetrically distributed in space on both sides of the gain medium; the pump lasers generated by the respective pump sources form light spots on the gain medium that overlap with each other; the pump sources are an even number and are evenly distributed on both sides of the gain medium; two pump sources located on both sides of the gain medium constitute a group, and a group of pump sources is located on the same straight line passing through the gain medium; the pump lasers emitted by the two pump sources in a group are opposite in direction on the same straight line, respectively, toward two opposite surfaces of the gain medium; there are 3 to 5 groups of pump sources; and the pump sources on both sides of the gain medium are axially symmetrically distributed with the straight line passing through the gain medium as the axis of symmetry.

2. The laser multi-pass amplifier according to claim 1, characterized in that: The reflecting mirrors are distributed on both sides of the gain medium.

3. The laser multi-pass amplifier according to claim 2, characterized in that: The reflector includes an input mirror and a reversing mirror. The input mirror is used to reflect the seed light toward the gain medium at a corresponding side of the gain medium. The reversing mirror is used to reflect the seed light passing through the gain medium toward the input mirror on the same side.

4. The laser multi-pass amplifier according to claim 3, characterized in that: In the propagation direction of the seed light, the distance between a group of input mirrors and reversing mirrors adjacent to each other on the optical path on the same side of the gain medium gradually decreases.

5. The laser multi-pass amplifier according to claim 4, characterized in that: In the propagation direction of the seed light, a group of input mirrors and reversing mirrors adjacent to each other on the optical path on the same side of the gain medium are increasingly farther away from the gain medium.

6. The laser multi-pass amplifier according to claim 5, characterized in that: The direction of the connection line between a set of input mirrors and the reversing mirror is longitudinal; on either side of the gain medium, the distance of the area where the pump source is distributed in the longitudinal direction is smaller than the distance between the set of input mirrors and the reversing mirror with the smallest spacing on that side.

7. The laser multi-pass amplifier according to claim 6, characterized in that: On any side of the gain medium, the distance from the region where the pump sources are distributed to the gain medium in the lateral direction is longer than the distance from any one of the reflectors on that side to the gain medium.

8. The laser multi-pass amplifier according to claim 1, characterized in that: The pump source is a pulse pump source of a solid laser or a semiconductor laser.

9. The laser multi-pass amplifier according to claim 1, characterized in that: The gain medium is titanium-doped sapphire crystal.

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