阅读说明：本技术 一种端泵板条固体激光器的波前改善方法和系统 (Wavefront improvement method and system for end-pump slab solid-state laser ) 是由 王钢 梁兴波 唐晓军 王文涛 于 2019-08-16 设计创作，主要内容包括：本发明提出了一种适用于端泵板条固体激光器的波前改善方法和系统,针对激光在通过板条后激光光束质量退化,减小因激光器散热不均匀导致的热致波前畸变,提高激光光束质量。所述端泵板条固体激光器的波前改善方法,包括：测量通过板条后的激光波前并输出测量结果,所述测量结果中包括泵浦光调节参考信息,所述泵浦光用于调制所述激光光束的波前形状；根据所述泵浦光调节参考信息,确定所述泵浦光的调节信息；根据所述调节信息对注入板条中的泵浦光进行调节。(The invention provides a wavefront improvement method and a wavefront improvement system suitable for an end pump slab solid laser, aiming at the degradation of laser beam quality after laser passes through a slab, the thermotropic wavefront distortion caused by uneven heat dissipation of the laser is reduced, and the laser beam quality is improved. The wavefront improvement method of the end-pumped slab solid-state laser comprises the following steps: measuring the laser wavefront passing through the slab and outputting a measurement result, wherein the measurement result comprises pump light adjusting reference information, and the pump light is used for modulating the wavefront shape of the laser beam; determining the adjustment information of the pump light according to the pump light adjustment reference information; and adjusting the pump light injected into the slab according to the adjustment information.)

1. A method of wavefront modification of an end-pumped slab solid state laser, comprising:

measuring the laser wavefront passing through the slab and outputting a measurement result, wherein the measurement result comprises pump light adjusting reference information, and the pump light is used for modulating the wavefront shape of the laser beam;

determining the adjustment information of the pump light according to the pump light adjustment reference information;

and adjusting the pump light injected into the slab according to the adjustment information.

2. The method of claim 1, wherein the pump light adjustment reference information includes peak/valley position information of a laser wavefront and a wavefront distortion index PV value;

determining the adjustment information of the pump light according to the pump light adjustment reference information, specifically comprising:

determining the adjustment direction of the pump light according to the position information of the wave crest/wave trough of the laser wavefront;

and determining the adjustment quantity of the pump light according to the wave front distortion index PV value.

3. The method of claim 1, further comprising:

the conditioned pump light is injected into the slab through the pump light coupling conduit.

4. The method of claim 3, wherein the pump light coupling conduit comprises a shaping mirror, a mirror, and a light pipe, wherein:

the shaping mirror is used for adjusting the size of the pump light according to the size of the end face of the slab;

the reflector is used for adjusting the pump light according to the adjusting direction and the adjusting amount;

the light guide pipe is used for avoiding stray light in the pumping light from escaping.

5. The method of any of claims 1-4, wherein the slab laser employs a plurality of gain modules in series;

determining the adjustment information of the pump light according to the pump light adjustment reference information, specifically comprising:

and determining the adjustment information of the pump light injected into each stage of gain module according to the pumping adjustment reference information, so that the wave front shapes of the laser beams in each gain module are complementary.

6. A wavefront modification system for an end-pumped slab solid state laser, comprising:

the measuring device is used for measuring the laser wave front passing through the slab and outputting a measuring result, wherein the measuring result comprises pump light adjusting reference information, and the pump light is used for modulating the wave front shape of the laser beam;

the pump light adjusting device is used for determining the adjusting information of the pump light according to the pump light adjusting reference information; and adjusting the pump light injected into the slab according to the adjustment information.

7. The system of claim 6, wherein the pump light adjustment reference information comprises peak/valley position information of a laser wavefront and a wavefront distortion index (PV) value;

the pumping light adjusting device is specifically used for determining the adjusting direction of the pumping light according to the position information of the wave crest/wave trough of the laser wave front; and determining the adjustment quantity of the pump light according to the wave front distortion index PV value.

8. The apparatus of claim 6, wherein the pump light modulation device is a pump light coupling conduit;

the pump light coupling guide is used for injecting the adjusted pump light into the batten.

9. The apparatus of claim 8, wherein the pump light coupling conduit comprises a shaping mirror, a mirror, and a light pipe, wherein:

the shaping mirror is used for adjusting the size of the pump light according to the size of the end face of the slab;

the reflector is used for adjusting the pump light according to the adjusting direction and the adjusting amount;

the light guide pipe is used for avoiding stray light in the pumping light from escaping.

10. The system of any of claims 6-9, wherein the slab laser employs a plurality of gain modules in series;

the pump light adjusting device is specifically configured to determine adjustment information of the pump light injected into each level of gain module according to the pump adjustment reference information, where the pump light injected into each gain module is used to control the wave front shape complementation of the laser beam in each gain module.

Technical Field

The invention relates to the technical field of laser beam purification, in particular to a wavefront improvement method and a wavefront improvement system of a pump slab solid laser.

Background

In the development of a high-power slab solid-state laser, in addition to the technical scheme of power/energy increase, the problems of beam control and beam quality improvement must be studied, and the laser with high power and high beam quality can meet the requirements of practical application. In actual operation, the laser output from the high-power laser system has amplitude modulation and phase distortion, and the phase distortion is the main influence factor for far-field beam quality. After a laser beam passes through a laser gain medium with a certain temperature distribution or a non-ideal optical system, the wavefront of the laser beam is distorted, and the wavefront distortion generally becomes more serious as the output power of the laser increases.

The distortion of the laser wavefront of the high-power slab solid laser generally comprises low-order distortion caused by factors such as thermal lens effect and the like and high-order distortion caused by factors such as temperature uneven distribution, diffraction and the like, the low-order distortion can be corrected or compensated by optical elements such as a cylindrical mirror and the like, the high-order distortion is purified by an adaptive optical system mainly composed of deformable mirrors at present, the technology is generally used for purifying phase difference caused by atmospheric disturbance, and the technology is successfully used in a high-power solid laser system. However, with the development of high-power solid laser technology, the output power of the laser is higher and higher, the affected wavefront distortion is larger and larger, the deformable mirror system encounters some obstacles difficult to overcome, firstly, the resolution is not enough, and limited by the technical level, the distance between deformable mirror actuators for high-power laser wavefront purification is larger, the minimum distance between the deformable mirror actuators for high-power laser wavefront purification in China at present is 8mm, the change of high-order aberration is very complex, and generally exceeds the purification capacity range of the deformable mirror, and the purification effect under the condition is poorer. Secondly, the stroke amount is small, the shape of the deformable mirror cannot be changed in a large range due to the limitation of the material of the deformable mirror, the normal maximum stroke is about 10 μm, and if the laser beam in the high-power solid laser system needs to pass through a longer gain medium to increase the laser output power, a large wavefront distortion is correspondingly generated, which often exceeds the stroke range of the deformable mirror, thereby further increasing the laser power is limited in turn.

Disclosure of Invention

The invention aims to solve the technical problem that the quality of laser beams is degraded after laser passes through a lath, reduce the thermally-induced wavefront distortion caused by uneven heat dissipation of a laser and improve the quality of the laser beams.

The invention adopts the technical scheme that a wave front improvement method suitable for an end pump slab solid laser is provided, and comprises the following steps:

measuring the laser wavefront passing through the slab and outputting a measurement result, wherein the measurement result comprises pump light adjusting reference information, and the pump light is used for modulating the wavefront shape of the laser beam;

determining the adjustment information of the pump light according to the pump light adjustment reference information;

and adjusting the pump light injected into the slab according to the adjustment information.

In a possible embodiment, the pump light adjustment reference information includes peak/valley position information of laser wavefront and a wavefront distortion index PV value;

determining the adjustment information of the pump light according to the pump light adjustment reference information, specifically comprising:

determining the adjustment direction of the pump light according to the position information of the wave crest/wave trough of the laser wavefront;

and determining the adjustment quantity of the pump light according to the wave front distortion index PV value.

In a possible implementation manner, an embodiment of the present invention provides a method for improving a wavefront of an end-pumped slab solid-state laser, further including:

the conditioned pump light is injected into the slab through the pump light coupling conduit.

In one possible embodiment, the pump light coupling conduit comprises a shaping mirror, a reflecting mirror and a light guide, wherein:

the shaping mirror is used for adjusting the size of the pump light according to the size of the end face of the slab;

the reflector is used for adjusting the pump light according to the adjusting direction and the adjusting amount;

the light guide pipe is used for avoiding stray light in the pumping light from escaping.

In one possible embodiment, the slab laser employs a plurality of gain modules in series;

determining the adjustment information of the pump light according to the pump light adjustment reference information, specifically comprising:

and determining the adjustment information of the pump light injected into each stage of gain module according to the pumping adjustment reference information, so that the wave front shapes of the laser beams in each gain module are complementary.

The invention also provides a wavefront improving system of an end-pump slab solid-state laser, comprising:

the measuring device is used for measuring the laser wave front passing through the slab and outputting a measuring result, wherein the measuring result comprises pump light adjusting reference information, and the pump light is used for modulating the wave front shape of the laser beam;

the pump light adjusting device is used for determining the adjusting information of the pump light according to the pump light adjusting reference information; and adjusting the pump light injected into the slab according to the adjustment information.

In a possible embodiment, the pump light adjustment reference information includes peak/valley position information of laser wavefront and a wavefront distortion index PV value;

the pumping light adjusting device is specifically used for determining the adjusting direction of the pumping light according to the position information of the wave crest/wave trough of the laser wave front; and determining the adjustment quantity of the pump light according to the wave front distortion index PV value.

In one possible embodiment, the pump light adjusting means is a pump light coupling conduit;

the pump light coupling guide is used for injecting the adjusted pump light into the batten.

In one possible embodiment, the pump light coupling conduit comprises a shaping mirror, a reflecting mirror and a light guide, wherein:

the shaping mirror is used for adjusting the size of the pump light according to the size of the end face of the slab;

the reflector is used for adjusting the pump light according to the adjusting direction and the adjusting amount;

the light guide pipe is used for avoiding stray light in the pumping light from escaping.

In one possible embodiment, the slab laser employs a plurality of gain modules in series;

the pump light adjusting device is specifically configured to determine adjustment information of the pump light injected into each level of gain module according to the pump adjustment reference information, where the pump light injected into each gain module is used to control the wave front shape complementation of the laser beam in each gain module.

By adopting the technical scheme, the invention at least has the following advantages:

the invention relates to a method and a system for improving the wave front of an end pump slab solid laser, which are used for measuring laser passing through a slab, determining the adjustment information of pump light injected into the slab according to the measurement result, adjusting the pump light accordingly, and changing the position of the area with the strongest pump light irradiated on the slab through the adjustment so as to change the temperature field distribution in the slab.

Drawings

FIG. 1a is a diagram of the initial far field intensity distribution of an end-pumped slab solid state laser in the prior art;

FIG. 1b is a diagram illustrating a far field intensity distribution corrected by adaptive optics in the prior art;

FIG. 2a is a diagram illustrating the intensity distribution of pump light at the upper portion of a slab in the prior art;

FIG. 2b is a diagram illustrating the intensity distribution of pump light at the lower portion of a slab in the prior art;

FIG. 2c is a diagram illustrating the intensity distribution of pump light in the middle of a slab in the prior art;

FIG. 2d is a diagram illustrating the intensity distribution of pump light at two ends of a slab in the prior art;

FIG. 3a is a diagram of the wave front distribution of pump light on the upper portion of a slab in the prior art;

FIG. 3b is a diagram of the wave front distribution of pump light at the lower part of a slab in the prior art;

FIG. 3c is a diagram of a wavefront profile of a pump light in the middle of a slab according to the prior art;

FIG. 3d is a diagram of the wavefront profile of pump light at two ends of a slab in the prior art;

FIG. 4a is a flow chart of a method for improving the wavefront of an end-pumped slab solid state laser according to an embodiment of the present invention;

FIG. 4b is a schematic structural diagram of a pump light coupling tube according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of an end-pumped slab solid state laser according to an embodiment of the present invention;

fig. 6a is a schematic view of the wavefront distribution of the wanwa laser link amplification module in the working stage 1 according to the embodiment of the present invention;

fig. 6b is a schematic diagram of a wavefront distribution of a wanwa laser link amplification module according to an embodiment of the present invention when operating at level 2;

fig. 6c is a schematic diagram of the wavefront distribution of the wanwa laser link amplifying module in the simultaneous working of the 1 st and 2 nd stages according to the embodiment of the present invention;

fig. 7a is a schematic view of a wavefront distribution of a wanwa laser link amplification module adjusted during level 1 operation according to an embodiment of the present invention;

fig. 7b is a schematic view of a wavefront distribution of the wanwa laser link amplification module adjusted during the level 2 operation according to the embodiment of the present invention;

fig. 7c is a schematic diagram of the adjusted wavefront distribution when the 1 st and 2 nd stages of the wanwa laser link amplification module of the embodiment of the present invention operate simultaneously;

FIG. 8a is a schematic diagram illustrating the calibration effect of the pump light adjusting pre-adaptive optics system according to the embodiment of the present invention;

FIG. 8b is a schematic diagram illustrating the calibration effect of the adaptive optics system after adjusting the pump light according to the embodiment of the present invention;

fig. 9 is a schematic diagram of a wavefront modification system of an end-pumped slab solid state laser according to an embodiment of the present invention.

Detailed Description

To further explain the technical means and effects of the present invention adopted to achieve the intended purpose, the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

Due to the uneven heat dissipation and uneven pumping of the end-pumped slab laser in the longitudinal axis direction, there will be a large number of initial aberrations that are varied more than the correction capability of the anamorphic mirror, as shown in fig. 1a and 1b, respectively. In fig. 1a, the initial far field intensity distribution of the end-pumped slab solid-state laser, and in fig. 1b, the far field intensity distribution of the end-pumped slab solid-state laser after being corrected by using the adaptive optics system, it can be seen that the corrected beam quality is not ideal because the initial aberration exceeds the correction capability of the deformable mirror. In view of this, the embodiment of the present invention provides a method for improving a wavefront of an end-pumped slab solid-state laser, which adjusts pumping of the slab laser before calibration, and optimizes wavefront distribution.

The intensity distribution of the pump light corresponds to the wavefront distribution of the slab laser, as shown in fig. 2a, fig. 2b, fig. 2c, and fig. 2d, which are schematic diagrams of the intensity distribution of the pump light at the upper portion, the lower portion, the middle portion, and the two ends of the slab, respectively, and the corresponding wavefront distributions of these four cases are shown in fig. 3a, fig. 3b, fig. 3c, and fig. 3d, respectively.

Fig. 3a, 3b, 3c and 3d are wavefront profiles of pump light corresponding to different intensities, respectively, measured by a four-wave lateral shearing interferometer (SID4), where the upper diagram in each figure represents the wavefront distribution in the "y" direction of the slab and the lower diagram represents the wavefront distribution in the "x" direction. The main effect of the pump light distribution is the wavefront distribution in the slab "y" direction, which has no effect in the "x" direction due to the compensation of the "zig-zag" optical path in the "x" direction. As can be seen from the figure, the wavefront distributions have a common point in the case of four different pump light distributions: the wave front distribution corresponding to the position with stronger pump light has a wave trough, which indicates that the phase propagation speed at the position with stronger pump light distribution is slow, so that the wave front distribution has a wave trough at this position. The reason why the wave front has the wave front trough is that the temperature is higher at the position because the intensity of the pump light at the position is large, and according to the corresponding formula (optical path-refractive index), the optical path of the light beam is lengthened after passing through the region with high temperature, the path is longer in the same time, and therefore the wave front passing through the position lags behind the other regions relatively, so that the wave front trough is formed. According to the above principle, by adjusting the directivity of the pump light, the wavefront distribution can be changed, i.e., wavefront compensation is realized, and a more "flat" wavefront distribution can be obtained, and the optimal state of the wavefront is to adjust it to a plane wave.

As shown in fig. 4a, it is a schematic flow chart of an implementation of a wavefront modification method for an end-pumped slab solid-state laser according to an embodiment of the present invention, including the following steps:

and S41, measuring the laser wave front passing through the lath and outputting the measurement result.