CN100428586C - Laser Amplifier and Laser Resonator with Multi-reflection Folding Optical Path Structure - Google Patents

Abstract

The invention belongs to the technical field of laser amplifiers and laser resonators, and is characterized in that it includes: two curved reflectors, and a laser gain medium located between the two curved reflectors, and a resonator located outside the optical path structure can also be added. Cavity mirror, the two curved mirrors are placed obliquely to form a non-telescopic and non-confocal structure. The laser beam injected into the optical path structure is reflected multiple times by the two curved mirrors to form a folded optical path. Gain medium, the laser beam is normally incident on one of the two curved mirrors along its optical axis and is reflected, returns along the original optical path, passes back and forth in the gain medium, and can also be obliquely incident and reflected , a one-way pass through the gain medium. The invention has the advantages of few components, simple structure, easy assembly and adjustment, insensitive to errors and disturbances, easy to realize output with high efficiency and high beam quality, and the like.

Description

Laser Amplifier and Laser Resonator with Multi-reflection Folding Optical Path Structure

technical field

The invention belongs to the field of optics, in particular to a laser amplifier and laser resonance.

Background technique

Because the multi-reflection folded optical path structure has the advantages of reducing the optical length, increasing the path and coverage of the light beam passing through the medium, and being suitable for various materials, the folding method has been deeply studied and widely used. The optical path of multiple reflections was first used in the folded waveguide cavity of gas lasers in the laser field. Later, with the emergence of INNOSLAB's new solid-state lasers (see Optics Letters, Vol.23, No.18, 370-372), it also began to be used in solid-state lasers. At present, there are three main schemes for various folded optical paths in laser amplifiers and laser resonators:

Option 1, using a plane mirror structure, the reflection system is composed of two or more plane mirrors. The light beam is reflected multiple times between the mirrors to form a folded optical path (see US Patent Nos. 4703491, 6654163).

The second option is to use two or more optical lenses to form the structure of the telescopic system. US Patent No. 6256332 describes a telescopic system whose resonant cavity is composed of 4 optical mirrors, and the optical axis is outside the laser gain medium. U.S. Patent No. 6442186 describes a variety of telescopic systems that use 4 optical lenses to form an optical path structure, and one of the optical lenses is drilled or partially coated to achieve laser output; it also describes three types of confocal or near-confocal The telephoto system uses 3 optical lenses to form the optical path structure; there are also 4 optical lenses to form the optical path structure.

Option three, using two or more optical lenses to form a one-way reflection light path of other structures. US Patent No. 6,654,163 describes an optical path structure composed of two optical lenses, in which the laser beam is folded and reflected in a single pass through the laser gain medium. German Patent No. 10156081 describes an optical path structure composed of 4 optical lenses, in which the laser beam is folded and reflected in a single pass through the laser gain medium.

In addition, there is a multi-mirror folding optical path system using a combination of plane and curved mirrors, which can be considered as a combination of the above three solutions (see US Patent No. 20040076210).

For laser amplifiers and laser resonators, the above solutions have corresponding shortcomings:

In Solution 1, the flat mirror is sensitive to adjustment, alignment errors and external disturbances, and after each reflection, the reflection angle and width of the beam will expand by a certain factor, which is not conducive to multiple reflections and control of the quality of the output beam.

In the second scheme, the optical lenses that realize the optical path folding need to form a telescopic system (also called a confocal structure), and its adjustment needs to accurately ensure the distance, position, angle, etc. of each optical lens. Therefore, the installation of the laser amplifier and laser resonator The adjustment accuracy is very high, it is more sensitive to the adjustment error and external disturbance, and the working stability and reliability are relatively low. Among them, some optical path structures are composed of 3, 4 or more optical lenses, which are complex in structure and more difficult to install and adjust.

In the third scheme, the optical lens to realize the folding of the optical path also needs to form a telescopic system (also known as a confocal structure). Due to the limitation of the structure, the laser can only be folded and reflected in the cavity one way, and the laser gain medium can pass through the laser gain medium one way, and the absorption is not sufficient. , the working efficiency of the laser amplifier and the laser resonator is low. Similarly, some optical path structures are composed of 3, 4 or more optical lenses, which are complex in structure and more difficult to install and adjust.

Contents of the invention

The object of the present invention is to provide a laser amplifier and a laser resonant cavity with a multi-reflection folded optical path structure. The novel optical path structure overcomes the disadvantages of the prior art, and can be generally applied to laser amplifiers, laser resonant cavities or other optical systems. The laser amplifier in the prior art adopts a telescopic structure or a confocal structure, which is complex in structure, difficult to install and adjust, cannot form a round-trip two-way reflection, and the laser amplification is not sufficient; the laser resonator in the prior art adopts a telescopic structure or a confocal structure. Structure, complex structure, difficult installation and adjustment, sensitive to installation and adjustment errors and external disturbances, low working stability and reliability, unable to form round-trip two-way reflection, and low laser oscillation efficiency. In the laser amplifier and resonant cavity proposed by the present invention, the expansion or shrinkage of the laser beam is not serious with the increase of the number of reflections; the laser beam passes back and forth in the gain medium, with sufficient absorption and high efficiency; the number of optical lenses is small, the structure is simple, and the installation Easy to adjust, insensitive to errors and disturbances generated during the installation and use process, the laser amplifier and resonator work stably and have high reliability.

The laser amplifier proposed by the present invention has a multi-reflection folded optical path structure, and the optical path structure includes two curved reflectors and a laser gain medium between the two curved reflectors; the two curved reflectors are placed obliquely to form an The telephoto non-confocal structure; the laser beam injected into the multi-reflection folded optical path structure is reflected multiple times by two curved mirrors to form a folded optical path and passes through the gain medium multiple times.

In the above-mentioned laser amplifier, the placement of two curved mirrors in the optical path structure makes the laser beam incident on one of the two curved mirrors along its optical axis and is reflected, and returns along the original optical path, so that the laser beam is on the curved surface The number of reflections on the mirror is doubled, making a double pass back and forth in the gain medium.

In the above-mentioned laser amplifier, the placement of the two curved mirrors in the optical path structure makes the laser beam obliquely incident on the two curved mirrors along the optical axis and reflected, and the laser beam passes through the gain medium one way.

The laser resonant cavity proposed by the present invention has a multi-reflection folded optical path structure, and the optical path structure includes two curved mirrors, a laser gain medium located between the two curved mirrors, and a resonant cavity mirror located outside the optical path structure ; Two curved mirrors are placed obliquely to form a non-telescopic and non-confocal structure; the laser beam injected into the multi-reflection folded optical path structure is reflected multiple times by the two curved mirrors to form a folded optical path and passes through the gain medium multiple times.

In the above-mentioned laser resonant cavity, the placement of two curved mirrors in the optical path structure makes the laser beam incident on one of the two curved mirrors along its optical axis and is reflected, and returns along the original optical path, so that the laser beam is in the Twice the number of reflections on the curved mirror, double the number of folds in the round-trip pass in the gain medium.

In the above-mentioned laser resonator, the placement of the two curved mirrors in the optical path structure makes the laser beam obliquely incident and reflected along the optical axis of the two curved mirrors, and the laser beam passes through the gain medium one way.

In the above-mentioned laser resonator, the cavity mirror is a convex lens or a concave lens.

In the above-mentioned laser resonator, a frequency doubling device, a Q-switching device, and a mode-locking device are also arranged between the multi-reflection folded optical path structure and the resonator cavity mirror to form a corresponding laser optical path.

Compared with the prior art, the present invention has the following advantages: the optical path structure in the laser amplifier and the laser resonator of the present invention adopts curved surface reflectors to be placed obliquely to form a folded optical path with a non-telescopic and non-confocal structure, and the structure is simple and easy to use. There are few optical components, the requirements for the position, distance and angle of the two curved mirrors are not strict, the installation and adjustment are easy, insensitive to errors and disturbances, and the practical operability is strong; the laser beam can be controlled within a small volume of the laser gain medium Realize round-trip multiple reflections, pass through the gain medium multiple times, and the beam width does not change much after multiple reflections, and it is easier to achieve high-power and high-beam quality output; it can be applied to both laser amplifiers and laser resonators.

Description of drawings

FIG. 1 is a schematic diagram of a first embodiment of a laser resonator provided by the present invention.

FIG. 2 is a schematic diagram of a second embodiment of the laser resonator provided by the present invention.

FIG. 3 is a schematic diagram of a third embodiment of the laser resonator provided by the present invention.

FIG. 4 is a schematic diagram of a fourth embodiment of the laser resonator provided by the present invention.

FIG. 5 is a schematic diagram of a fifth embodiment of the laser resonator provided by the present invention.

FIG. 6 is a schematic diagram of a sixth embodiment of the laser resonator provided by the present invention.

FIG. 7 is a schematic diagram of a seventh embodiment of the laser resonator provided by the present invention.

FIG. 8 is a schematic diagram of an eighth embodiment of the laser resonator provided by the present invention.

FIG. 9 is a schematic diagram of the first embodiment of the laser amplifier proposed by the present invention.

FIG. 10 is a schematic diagram of a second embodiment of the laser amplifier proposed by the present invention.

Detailed ways

The laser resonant cavity with multi-reflection folded optical path structure proposed by the present invention is shown in Figure 1, including a reflector 1, a normal optical axis 2 of the reflector 1, a cavity mirror 6, a laser gain medium 7, a reflector 8, a reflector The normal optical axis 3 of the mirror 8, wherein 5 and 10 indicate the laser beam, and 4, 9 and 11 indicate the pumping direction of the pumping light. Wherein, the normal optical axis 3 of the convex reflector 8 is placed horizontally, and the normal optical axis 2 of the concave reflector 1 is placed obliquely, forming a non-telescopic and non-confocal optical path structure. In addition to the non-telescopic and non-confocal multiple folded optical path structure formed by the convex reflector 8 and the concave reflector 1, a cavity mirror 6 is placed perpendicular to the light beam 5 to form a laser resonant cavity. Between the cavity mirror 6 and the optical path structure, other devices, such as frequency doubling devices, Q-switching devices, and mode-locking devices, can also be placed.

The normal optical axes 2 and 3 intersect at the center of the concave mirror 1, and the intersection angle is α. Assuming that the optical axis 3 is in the horizontal direction, and the laser beam 5 forms an angle θ with the optical axis 3, the two should satisfy the following formula relation. Let the radius R1 of the reflector 1, the radius R2 of the reflector 8, the distance L between the centers of the reflector 1 and the reflector 8, and the distance h between the intersection point of the light beam 5 and the reflector 8 and the optical axis 3 pass through N round trips (one round trip is defined as: Firstly, it is reflected by the mirror 8, travels L distance to the mirror 1, and then is reflected by the mirror 1, and travels L distance to the mirror 8 again). The light beam 5 is finally incident on the mirror 8, propagates along the optical axis 3 and is reflected, and propagates along the optical axis 3 in the opposite direction, and finally folds and propagates along the original optical path in the opposite direction, forming a double folded optical path back and forth. Using the matrix optical transmission theory, the transmission matrix M1 of mirror 1, the transmission matrix M2 of free space transmission L, and the transmission matrix M3 of mirror 8 are respectively:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="m"\; filenames="C20071000100900091.png,C20071000100900092.png"\; state="\{\{state\}\}">m</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\left(\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="C20071000100900091.png,C20071000100900092.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right)<span\; class="notranslate">\; ,</span>$ ${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="m"\; filenames="C20071000100900091.png,C20071000100900092.png"\; state="\{\{state\}\}">m</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\left(\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; L</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right)<span\; class="notranslate">\; ,</span>$ ${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="m"\; filenames="C20071000100900091.png,C20071000100900092.png"\; state="\{\{state\}\}">m</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>\left(\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C20071000100900091.png,C20071000100900092.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right)<span\; class="notranslate">\; .</span>$

When coaxial, a round-trip transmission matrix M satisfies:

M＝M ₃ M ₂ M ₁ M ₂

The beam matrix in front of the convex mirror after N reflections satisfies:

$\left(\begin{array}{c}{\mathrm{<span\; class="notranslate">\; h</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\end{array}\right)<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; N</span>}}\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; h</span>}\\ \mathrm{<span\; class="notranslate">\; \&theta;</span>}\end{array}\right)$

，经过N次反射后，在反射镜8中心前的高度失调量Δh和角度失调量Δθ为：The augmented matrix method is used to represent the influence of the tilt of the mirror 1, since the initial misalignment of the mirror 1 is

, after N times of reflection, the height misalignment Δh and angle misalignment Δθ in front of the center of mirror 8 are:

$\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; \&Delta;h</span>}\\ \mathrm{<span\; class="notranslate">\; \&Delta;\&theta;</span>}\end{array}\right)<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; k</span>}}\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; \&alpha;</span>}\end{array}\right)$

After adding tilt, it should satisfy:

$\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right)<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; N</span>}}\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; h</span>}\\ \mathrm{<span\; class="notranslate">\; \&theta;</span>}\end{array}\right)<span\; class="notranslate">\; +</span>\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; \&Delta;h</span>}\\ \mathrm{<span\; class="notranslate">\; \&Delta;\&theta;</span>}\end{array}\right)$

After calculation, when L=25mm, R1=625mm, R2=516mm, and h=9mm, adjusting θ and α can make the laser beam reflect 6 times on the mirror 1, that is, the direction of the laser beam 10 propagates to the direction of the laser beam 5. Pass through the gain medium 14 times, and the upper part of the gain medium is relatively dense. Taking the slab-shaped solid gain medium as an example, the pump light can be injected from the upper part of the gain medium along the pumping direction 11 to achieve higher system efficiency. Pump light can also be injected into the gain medium from the horizontal pump direction 4,9.

Fig. 2 is the second embodiment of the laser cavity with multi-reflection folded optical path structure proposed by the present invention, including reflector 1, normal optical axis 2 of reflector 1, cavity mirror 6, laser gain medium 7, reflector 8. The normal optical axis 3 of the reflector 8, wherein 5 and 10 indicate the laser beam, and 4, 9 and 11 indicate the pumping direction of the pumping light. Wherein, the normal optical axis 3 of the convex reflector 8 is placed horizontally, and the normal optical axis 2 of the concave reflector 1 is placed obliquely, forming a non-telescopic and non-confocal optical path structure. In addition to the non-telescopic non-confocal multi-pass folded optical path structure formed by the convex reflector 8 and the concave reflector 1, the cavity mirror 6 is placed perpendicular to the laser beam 5 to form a laser resonant cavity. Other devices, such as frequency doubling devices, Q-switching devices, and mode-locking devices, can also be placed between the cavity mirror 6 and the optical path structure to realize laser output.

Among them, h, θ and α should satisfy:

$\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right)<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; h</span>}\\ \mathrm{<span\; class="notranslate">\; \&theta;</span>}\end{array}\right)<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; k</span>}}\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; \&alpha;</span>}\end{array}\right)$

Similarly, under the conditions of L=25mm, R1=625mm, R2=516mm, and h=9mm, adjusting θ and α can make the laser beam reflect 7 times on the concave mirror, that is, the direction of the laser beam 11 propagates to the direction of the laser beam 5. The gain medium passes through the gain medium 16 times, and the upper part of the gain medium is relatively dense. Taking the slab-shaped solid gain medium as an example, the pump light can be injected from the upper part of the gain medium along the pumping direction 11 to achieve higher system efficiency. In addition, the pump light Light can also be injected into the gain medium from the horizontal pump direction 4,9.

For above-mentioned 2 embodiments, the relative position of reflecting mirror 1 and reflecting mirror 8, the change of the outgoing direction of laser beam 5 etc., the light path structure of laser resonator correspondingly has other multiple combinations (Fig. 3～Fig. 8), similarly Similar analyzes and calculations can be performed using the matrix optics theory. The specific descriptions of FIGS. 3 to 8 are similar to those of FIGS. 1 to 2 . Wherein, the normal optical axis of the convex reflector 8 and the concave reflector 1 is placed obliquely relative to each other, forming a non-telescopic and non-confocal optical path structure. In addition to the non-telescopic non-confocal multi-pass folded optical path structure formed by the convex reflector 8 and the concave reflector 1, the cavity mirror 6 is placed perpendicular to the laser beam 5 to form a laser resonant cavity. Other devices, such as frequency doubling devices, Q-switching devices, and mode-locking devices, can also be placed between the cavity mirror 6 and the optical path structure to realize laser output. In Fig. 3, the normal optical axis of the concave reflector 1 is placed obliquely, the laser beam 5 emerges from the left side of the optical path structure, the laser beam after multiple reflections is incident on the concave reflector 1, and returns along the original optical path after reflection; Fig. 4 Among them, the normal optical axis of the convex mirror 8 is placed obliquely, and the laser beam 5 emerges from the left side of the optical path structure. After multiple reflections, the laser beam is incident on the convex mirror 8, and returns along the original optical path after reflection; in Fig. 5, the concave The normal optical axis of the reflector 1 is placed obliquely, and the laser beam 5 exits from the right side of the optical path structure. After multiple reflections, the laser beam is incident on the concave reflector 1, and returns along the original optical path after reflection; in Fig. 6, the convex reflector 8 The normal optical axis of is placed obliquely, and the laser beam 5 emerges from the right side of the optical path structure. After multiple reflections, the laser beam is incident on the concave reflector 1, and returns along the original optical path after reflection; in Fig. 7, the normal of the concave reflector 1 The optical axis is placed obliquely, and the laser beam 5 emerges from the right side of the optical path structure. After multiple reflections, the laser beam is incident on the convex reflector 8, and returns along the original optical path after reflection; in Figure 8, the normal optical axis of the convex reflector 8 is inclined Placed, the laser beam 5 emerges from the right side of the optical path structure, and after multiple reflections, the laser beam is incident on the convex mirror 8, and returns along the original optical path after reflection. Other specific details will not be repeated here.

In the above eight embodiments, the described multi-reflection folded optical path structure of the laser resonator is also applicable to the laser amplifier, and can constitute a corresponding laser amplifier. Taking the first embodiment of the present invention shown in FIG. 1 as an example, FIG. 9 shows a first embodiment of a laser amplifier corresponding to this embodiment.

In FIG. 9 , the normal optical axis 3 of the convex reflector 8 is placed horizontally, and the normal optical axis 2 of the concave reflector 1 is placed obliquely, forming a non-telescopic and non-confocal optical path structure. Outside the non-telescopic non-confocal multi-pass folded optical path structure formed by the convex reflector 8 and the concave reflector 1, the laser beam 12 of the main oscillator to be amplified passes through the polarizing reflector 13 and the λ/2 wave plate 15, The Faraday rotator 16 is injected into the laser amplifier of the folded optical path structure of multiple reflections, and the specific parameters of the folded optical path structure are consistent with those shown in Figure 1, so the reflection output by the polarizing reflector is shown in the laser beam 14. Similarly, the pump The light can be injected along the direction 4, the laser beam is amplified and then along the original path of the laser beam 12, and then injected through the Faraday rotator 16, the λ/2 wave plate 15, 9 or the direction 11.

Similarly, for the other seven embodiments of the present invention, they respectively correspond to embodiments of laser amplifiers, and will not be repeated here.

Fig. 10 is the second embodiment of the laser amplifier with multi-reflection folded optical path structure proposed by the present invention, including a mirror 1, a normal optical axis 2 of the mirror 1, a laser gain medium 7, a mirror 8, and a mirror 8 The normal optical axis 3 of , where 5 and 10 indicate the laser beam, and 6 and 9 indicate the pumping direction of the pumping light. Wherein, the normal optical axis 2 of the concave reflector 1 is placed horizontally, and the normal optical axis 3 of the convex reflector 8 is placed obliquely, forming a non-telescopic and non-confocal optical path structure. The laser beam 5 of the main oscillator to be amplified is injected into the laser amplifier with a multi-reflection folded optical path structure. After multiple reflections, the laser beam passes through the laser gain medium 7 one way and is output along the laser beam 10 .

Claims (4)

1. A laser amplifier, characterized in that: the laser amplifier has multiple reflection folded optical path structures, the optical path structure comprises a concave reflector, a convex reflector and a laser gain medium, and the laser gain medium is positioned at the concave surface between the reflector and the convex reflector; the concave reflector and the convex reflector are relatively inclined to form a non-telescopic and non-confocal structure; the normal optical axis of the concave reflector and the convex reflector The normal optical axis of the mirror intersects the center of the concave reflector or the convex reflector, and the laser beam injected into the optical path structure is reflected multiple times between the concave reflector and the convex reflector so that After passing through the laser gain medium for a second time, it is normally incident on the concave reflector or the convex reflector, returns along the original optical path after reflection, and exits the optical path structure. 2. A laser resonant cavity, characterized in that: the laser resonant cavity includes a multi-reflection folded optical path structure and a resonant cavity cavity mirror positioned outside the optical path structure, and the optical path structure includes a concave reflector, a convex reflector A mirror and a laser gain medium, the laser gain medium is located between the concave reflector and the convex reflector; the concave reflector and the convex reflector are relatively inclined to form a non-telescopic and non-confocal structure; The normal optical axis of the concave reflector and the normal optical axis of the convex reflector intersect at the center of the concave reflector or the convex reflector, and the laser beam entering the optical path structure is on the concave surface Multiple reflections between the reflector and the convex reflector, thereby passing through the laser gain medium multiple times, and then being normal incident on the concave reflector or the convex reflector, returning along the original optical path after reflection, from the resonance Laparoscopic exit. 3. The laser resonator according to claim 2, wherein the cavity mirror is a convex lens or a concave lens. 4. The laser resonator according to claim 2, wherein the laser resonator further comprises a frequency doubling device, a Q-switching device or a mode-locking device arranged between the optical path structure and the resonator cavity mirror device.

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