A thermal lens adaptive dual-resonance pulsed solid-state laser

Abstract

The invention discloses a thermal lens adaptive dual-resonance cavity pulse solid-state laser, comprising a total reflection mirror, an LD side pump gain module, a polarizer, a Q switch, a corner cube prism, a first wedge mirror group, a half-wave voltage switch, a first PBS prism, a first output mirror, a first reflection prism, a second wedge mirror group, a second output mirror, a second reflection prism, a third wedge mirror group and a second PBS prism, the Q switch comprises a λ / 4 wave plate and a Q-switched crystal sequentially arranged on the output light path of the polarizer, the dual-resonance cavity comprises a short cavity resonant cavity and a long cavity resonant cavity, the short cavity resonant cavity is composed of the first output mirror and the total reflection mirror, and the long cavity resonant cavity is composed of the second output mirror and the total reflection mirror. The invention ensures stable laser oscillation through the dual-resonance cavity adaptive thermal lens change design, so that the laser energy, pulse width and optical axis stability of the laser can all maintain high consistency within the full pump power range, and at the same time realizes that the laser pulse width is greater than 10ns when the single oscillation level laser has a large energy output.

Description

Technical Field

[0001] The invention relates to the technical field of laser diode pumped all-solid-state lasers, in particular to a thermal lens adaptive double-resonance cavity pulsed solid-state laser. Background Art

[0002] In the laser guidance system, the laser light finder is the core component of the semi-active homing laser guidance, and its performance is directly related to the accuracy and reliability of the guidance. The key component in the laser light finder, the laser, especially the LD (laser diode) pumped all-solid-state pulsed laser, plays a vital role in laser ranging and target indication. However, the pulsed solid-state laser in the existing technology faces many technical challenges while achieving high energy output.

[0003] At present, pulsed solid-state lasers are mainly classified according to the pumping method and whether the amplification stage scheme is adopted. Among them, LD side pump and end pump Nd:YAG crystal rod or slab crystal are the mainstream technical routes. However, when these lasers increase the pump power to increase the laser energy output, they will encounter the problem of reduced laser pulse width. Laser pulse width is one of the important factors that determine the accuracy of laser guidance. Too small pulse width may cause the seeker to lose frame tracking, thus affecting the guidance effect.

[0004] Specifically, the laser pulse width is mainly affected by the transit time of the oscillating photons in the cavity, and the transit time depends on the physical cavity length of the resonant cavity. Under limited mechanical length, in order to extend the physical cavity length of the cavity resonant cavity, the method of multiple folding of the optical path is usually adopted. However, this method not only increases the number of devices in the cavity and increases the difficulty of debugging the laser, but is also easily affected by the deformation or stress of the entire machine housing. On the other hand, if multiple optical path foldings are not performed, due to the strict requirements of the airborne laser light finder on volume and weight, the laser can only adopt the traditional U-shaped folding structure once, and its cavity length is severely limited. In order to increase the laser energy, the pump power can only be increased, but this will lead to an increase in the thermal lens effect of the crystal and a decrease in the equivalent thermal lens focal length. Since the fixed resonant cavity mirror parameters cannot match different thermal lenses, this will cause the laser energy fluctuation to increase, the beam quality to deteriorate, and the laser optical axis stability to deteriorate.

[0005] In addition, for some laser light finders with strict weight and volume requirements, the length of the whole machine is strictly limited, making the pulse width design more difficult. In the technical solution of a single oscillator without amplification, when the laser output energy exceeds 80mJ, due to the limited cavity length, increasing the pump power will cause the laser pulse width to further decrease. At present, the pulse width of domestic lasers that directly output energy above 110mJ is generally small, only 5 to 7ns, which is difficult to meet the use requirements of laser light finders.

[0006] In summary, when increasing the pump power to improve the laser energy output, the pulsed solid laser in the prior art has problems such as small laser pulse width, poor optical axis stability and beam quality, and difficulty in adapting to the changes in the intracavity spot pattern caused by the change in the focal length of different thermal lenses. These problems seriously restrict the performance and development of laser guidance systems. Therefore, a new technical solution is urgently needed to solve these problems in order to meet the needs of laser guidance systems for high-energy, stable pulse width laser output. Summary of the invention

[0007] In view of this, the present invention aims to address the deficiencies in the prior art, and its main purpose is to provide a thermal lens adaptive dual-resonance cavity pulsed solid-state laser, which solves the technical problems of reduced laser pulse width, deterioration of optical axis stability and beam quality when increasing the pump power to improve laser energy output, and difficulty in adapting to changes in the intracavity spot pattern caused by changes in the focal length of different thermal lenses.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A thermal lens adaptive dual-resonance cavity pulsed solid-state laser of the present invention comprises:

[0010] A total reflective mirror, used as a shared reflective mirror of a dual resonant cavity, wherein the dual resonant cavity includes a short cavity resonant cavity and a long cavity resonant cavity;

[0011] An LD side pump gain module is arranged at the optical path reflection end of the total reflector and is used to provide pump energy;

[0012] A polarizer, arranged on the output optical path of the LD side pump gain module, for generating polarized light;

[0013] A Q switch comprises a λ / 4 wave plate and a Q-switched crystal which are sequentially arranged on the output light path of the polarizer, wherein the λ / 4 wave plate is used to adjust the polarized light, the Q-switched crystal is used to receive the polarized light adjusted by the λ / 4 wave plate, and load a λ / 4 wave voltage to output pulse light, and the Q switch is used to control the output of the pulse light;

[0014] A corner cube prism is arranged on the output optical path of the Q-switched crystal and is used to fold the optical path of the pulsed light;

[0015] A first wedge lens group is arranged on the output light path of the corner cube prism and is used for fine-tuning the light path of the pulse light folded by the corner cube prism;

[0016] A half-wave voltage switch, arranged on the output optical path of the first wedge mirror group, for changing the polarization direction of the pulse light according to a control signal;

[0017] A first PBS prism is arranged on the output optical path of the half-wave voltage switch, and is used to split the pulse light according to the polarization direction of the pulse light, and divide the pulse light into reflected s light and transmitted p light, and output them;

[0018] A first output mirror is arranged on the optical path of the reflected s light and forms the short cavity resonant cavity with the total reflection mirror, and the first output mirror is used to match the spot mode under medium and low pump power and output the first laser;

[0019] A first reflecting prism is arranged on the optical path of the transmitted p light and is used to change the optical path direction of the transmitted p light;

[0020] A second wedge lens group is arranged on the output light path of the first reflecting prism, and is used for fine-tuning the light path of the transmitted p light whose light path direction is changed after passing through the first reflecting prism;

[0021] A second output mirror is arranged on the output optical path of the second wedge mirror group, and forms the long cavity resonant cavity with the total reflection mirror, and is used to match the spot mode under high pump power and output a second laser;

[0022] A second reflecting prism is arranged on the output light path of the second output mirror, and is used to change the light path direction of the second laser;

[0023] A third wedge lens group is arranged on the output light path of the second reflecting prism and is used for fine-tuning the light path direction of the second laser;

[0024] The second PBS prism is arranged at the intersection of the output light paths of the first output mirror and the third wedge lens group, and is used to make the light paths of the first laser and the second laser overlap.

[0025] As a preferred solution, the LD side pump gain module is composed of two symmetrically pumped LD bar arrays and two Nd:YAG crystals.

[0026] As a preferred solution, the half-wave voltage switch is a lithium niobate electro-optical crystal, which is used to rotate the polarization direction of the pulse light by 90°.

[0027] As a preferred solution, the first output mirror and the second output mirror are both concave-convex mirrors, the curvature radius and coating parameters of the first output mirror are used to match medium and low pump powers, and the curvature radius and coating parameters of the second output mirror are used to match high pump powers.

[0028] As a preferred solution, the LD side pump gain module has a medium-low power state and a high power state;

[0029] When in the medium-low power state, the half-wave voltage switch is loaded with a half-wave high voltage, the optical path in the solid laser cavity oscillates in the short cavity resonant cavity, and passes through the first PBS prism and is output through the first output mirror;

[0030] When in the high power state, the half-wave voltage switch is powered off, the light path in the solid laser cavity oscillates in the long cavity resonant cavity, is reflected by the first reflecting prism, reaches the second output mirror and is output.

[0031] As a preferred solution, the first reflecting prism is used to reflect the light path of the transmitted p light in the long cavity resonant cavity at 45°.

[0032] As a preferred solution, the second reflecting prism is used to reflect the optical path of the second laser in the long cavity resonant cavity at 45°.

[0033] As a preferred solution, it also includes a main control circuit board, which is electrically connected to the LD side pump gain module through an LD driving circuit, the main control circuit is electrically connected to the Q-switched crystal through a λ / 4 Q-switched high-voltage circuit, and the main control circuit is electrically connected to the half-wave voltage switch through a λ / 2 Q-switched high-voltage circuit.

[0034] As a preferred solution, the LD driving circuit is used to power the LD side pump gain module, the LD side pump gain module has a pumping cycle, and the solid-state laser has a short cavity resonance state and a long cavity resonance state;

[0035] After the LD driving circuit outputs a pulse current to maintain a single pumping cycle, the main control circuit board triggers the λ / 4 Q-switched high-voltage circuit and the λ / 2 Q-switched high-voltage circuit respectively through the synchronous trigger signal 1 and the synchronous trigger signal 2 at the end of the single pumping cycle, and the λ / 4 Q-switched high-voltage circuit and the λ / 2 Q-switched high-voltage circuit are used to load the λ / 4 high voltage and the λ / 2 high voltage to the Q-switched crystal and the half-wave voltage switch respectively, and the optical path in the solid-state laser cavity oscillates in the short cavity resonant cavity, and the solid-state laser is in the short cavity resonant state;

[0036] After the LD driving circuit outputs a pulse current to maintain a single pumping cycle, the main control circuit board triggers the λ / 4 Q-switched high-voltage circuit only through the synchronization trigger signal 1 at the end of the single pumping cycle. The λ / 4 Q-switched high-voltage circuit is used to load λ / 4 high voltage to the Q-switched crystal. The optical path in the solid-state laser cavity oscillates in the long cavity resonant cavity, and the solid-state laser is in the long cavity resonant state.

[0037] As a preferred solution, a single pumping period is 230 μs.

[0038] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, it can be seen from the above technical solution that it mainly has the following advantages:

[0039] 1. The dual-resonance cavity adapts to the change of thermal lens to ensure stable laser oscillation: By designing two resonant cavities with different cavity mirror parameters, the problem that the spot pattern in the cavity is prone to change when the focal length of the thermal lens changes under different pump powers in a single resonant cavity is solved. The introduction of the half-wave voltage switch can flexibly change the polarization direction of the polarized light in the cavity, thereby realizing the optical path switching of the resonant cavity under different pump powers. This mechanism ensures that the laser energy, pulse width and optical axis stability can remain highly consistent within the full pump power range, significantly improving the adaptability and stability of the laser;

[0040] 2. Single-oscillation laser outputs large energy while maintaining a laser pulse width greater than 10ns: When the pump power increases, resulting in an increase in the intracavity gain, the laser pulse width is effectively increased through the dual-resonance cavity design, especially by switching the intracavity optical path to increase the physical cavity length under high-power pumping. This allows the single-oscillation laser to output large energy, i.e. greater than 120mJ, while maintaining a laser pulse width greater than 10ns without any amplification scheme, fully meeting the strict requirements of high-precision applications such as laser guidance on laser pulse width and energy. This not only simplifies the structure of the laser system and reduces costs, but also improves the reliability and stability of the laser system to meet the requirements of laser guidance.

[0041] In order to more clearly illustrate the structural features and effects of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of the structure of a thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to an embodiment of the present application;

[0043] Figure 2 This is a schematic diagram of the principle of a thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to an embodiment of the present application;

[0044] Figure 3 This is a schematic diagram of the optical path of the low-power pump, long thermal lens focal length, short cavity polarization characteristics of the embodiment of the present application;

[0045] Figure 4 This is a schematic diagram of the optical path of the high-power pump short thermal lens focal length long cavity polarization characteristics of the embodiment of the present application;

[0046] Figure 5 This is a schematic diagram of the principle of optical path switching controlled by the hardware circuit of the thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to an embodiment of the present application.

[0047] Description of reference numerals:

[0048] 1. Total reflection mirror; 2. LD side pump gain module; 3. Polarizer; 4. λ / 4 wave plate; 5. Q-switched crystal; 6. Corner cone prism; 7. First wedge mirror group; 8. Half-wave voltage switch; 9. First PBS prism; 10. First output mirror; 11. First reflecting prism; 12. Second wedge mirror group; 13. Second output mirror; 14. Second reflecting prism; 15. Third wedge mirror group; 16. Second PBS prism; 17. Q switch. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0050] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0051] As the core component of the semi-active homing laser guidance system, the realization of the core functions of the laser light finder depends on high-performance lasers, especially LD (laser diode) pumped all-solid-state pulsed lasers. According to the different pumping methods, this type of laser is mainly divided into two categories: LD side pump and LD end pump, and each category can be subdivided into technical routes using Nd:YAG crystal rods or Nd:YAG slab crystals. In addition, according to whether the amplifier stage is introduced, these technical routes can be further divided into two types: single oscillator and MOPA (master oscillator power amplifier).

[0052] In laser guidance applications, pulsed solid-state lasers generally use electro-optical Q-switching technology to control the laser pulse width. The primary determinant of laser pulse width is the transit time of the oscillating photons in the cavity, which directly depends on the physical cavity length of the resonant cavity. In order to increase the cavity length within a limited mechanical length, the method of folding the optical path multiple times is usually used, but this will increase the number of devices in the cavity, increase the difficulty of debugging, and be easily affected by the deformation or stress of the entire machine housing. However, for airborne laser light finders, due to strict restrictions on volume and weight, only the traditional U-shaped folding structure can be used, resulting in limited cavity length. In order to increase the laser energy, the pump power must be increased. Although this can quickly increase the intracavity gain, the pulse width is reduced, and the thermal lens effect of the crystal is also aggravated, resulting in a smaller equivalent thermal lens focal length, increased laser energy fluctuations, deteriorated beam quality, and decreased laser optical axis stability. Specifically, for traditional single-resonance cavity lasers, the reason for the decrease in pulse width is that the cavity length is limited, and the reason for the deterioration of beam quality is that as the pump power increases, the thermal effect of the crystal in the cavity becomes more serious, and the parameters of the single resonant cavity mirror do not meet the conditions for stable oscillation in the cavity. Especially for unstable cavities, the focal length of the crystal equivalent thermal lens changes, and the ABCD matrix in the cavity changes. g 1 g When the 2 parameter is less than 1, it is no longer in the unstable cavity category, and the laser spot pattern will be redistributed, causing the beam quality to deteriorate seriously.

[0053] Theoretically, the above-mentioned different technical routes can all achieve laser output with different single pulse energies, but in laser guidance, the laser pulse width is required to be designed to be above 10ns to 20ns. For some application scenarios with strict weight and volume requirements and strict restrictions on the length of the whole machine, in order to achieve a pulse width greater than 10ns, the use of the MOPA solution has become the most reasonable and feasible technical choice. For laser light meters with energies of 80mJ and below, the technical solution of a single oscillator without amplification is applicable. However, when it is necessary to output more energy, the limited cavity length means that the energy can only be enhanced by increasing the pump power, but this will lead to an increase in the intracavity gain and a decrease in the laser pulse width. The current domestic LD side-pump or end-pump single Nd:YAG crystal rod or single slab crystal technical solution, when directly outputting energy above 110mJ, its pulse width is generally small, only 5 to 7ns, which is difficult to meet the use requirements of laser light meters. Because the rise time of the four-quadrant detector in the seeker laser spot tracker is usually around 10ns, even if some high-performance detectors have a faster response time, when the laser pulse width is significantly shorter than the detector rise time, laser pulse code loss may still occur, causing the seeker to lose tracking frames, thereby affecting the laser guidance accuracy and even causing the target to miss.

[0054] To solve the above technical problems, please refer to Figures 1 to 5The embodiment of the present invention provides a thermal lens adaptive dual-resonance cavity pulsed solid-state laser, comprising:

[0055] The total reflection mirror 1 adopts a plano-concave mirror to effectively reflect and focus the laser. It is used as a common reflection mirror of the dual-resonance cavity to ensure the stable transmission of the laser in the dual-resonance cavity. The dual-resonance cavity includes a short-cavity resonant cavity and a long-cavity resonant cavity. The dual-resonance cavity design can adaptively match the spot mode under different pump powers according to the thermal lens effect, ensuring that the output optical axis is stable and the beam quality is consistent under different pump powers.

[0056] The LD side pump gain module 2 is arranged at the optical path reflection end of the total reflective mirror 1 and is used to provide pump energy.

[0057] The polarizer 3 is arranged on the output light path of the LD side pump gain module 2 and is used to generate polarized light.

[0058] The Q switch 17 includes a λ / 4 wave plate 4 and a Q-switched crystal 5 which are sequentially arranged on the output light path of the polarizer 3. The λ / 4 wave plate 4 is used to adjust the phase of the polarized light to achieve the conversion of the polarization direction and enhance the modulation effect of the laser pulse. The Q-switched crystal 5 is used to receive the polarized light adjusted by the λ / 4 wave plate 4 and load the λ / 4 wave voltage to output pulse light. The Q switch 17 is used to control the output timing and energy of the pulse light.

[0059] Corner cube prism 6 is arranged on the output optical path of Q-switched crystal 5 and is used to fold the optical path of pulsed light and is beneficial to improve the anti-detuning of the laser optical axis. The design of corner cube prism 6 further shortens the physical length of the laser while maintaining a longer resonant cavity length.

[0060] The first wedge lens group 7 is arranged on the output light path of the corner cube prism 6 and is used to fine-tune the light path of the pulse light folded by the corner cube prism 6 to ensure stable transmission of the light path.

[0061] The half-wave voltage switch 8 is arranged on the output optical path of the first wedge mirror group 7, and is used to change the polarization direction of the pulse light according to the control signal, so as to realize the fast switching between the short cavity resonant cavity and the long cavity resonant cavity to adapt to the thermal lens effect under different pump powers.

[0062] The first PBS prism 9 is arranged on the output optical path of the half-wave voltage switch 8, and is used to split the pulse light according to its polarization direction, and divide the pulse light into reflected s light and transmitted p light, and output them to achieve the effect of independent output of dual resonant cavities.

[0063] The first output mirror 10 is arranged on the optical path of the reflected s light and forms a short cavity resonant cavity with the total reflection mirror 1. The first output mirror 10 is used to match the spot mode under medium and low pump power and ensure stable output of the first laser to meet the demand of low energy laser output.

[0064] The first reflecting prism 11 is arranged on the optical path of the transmitted p light and is used to change the optical path direction of the transmitted p light.

[0065] The second wedge lens group 12 is disposed on the output light path of the first reflecting prism 11 and is used for fine-tuning the light path of the transmitted p light whose light path direction is changed after passing through the first reflecting prism 11 .

[0066] The second output mirror 13 is arranged on the output optical path of the second wedge mirror group 12 and forms a long cavity resonant cavity with the total reflection mirror 1 to match the spot mode under high pump power and ensure stable output of high-energy second laser.

[0067] The second reflecting prism 14 is disposed on the output light path of the second output mirror 13 and is used to change the light path direction of the second laser to ensure that the second laser can be output smoothly.

[0068] The third wedge lens group 15 is disposed on the output light path of the second reflecting prism 14 and is used to fine-tune the light path direction of the second laser to ensure the accuracy of the output direction of the second laser.

[0069] The second PBS prism 16 is disposed at the intersection of the output light paths of the first output mirror 10 and the third wedge lens group 15 to make the light paths of the first laser and the second laser overlap.

[0070] In this embodiment, the LD side pump gain module 2 is composed of two symmetrically pumped LD bar arrays and two Nd:YAG crystals, which improves the pumping efficiency and ensures the stable output of laser energy.

[0071] The half-wave voltage switch 8 is a lithium niobate electro-optical crystal, which has fast response and high stability, and can ensure the precise switching of the laser polarization direction. When it is loaded with a half-wave voltage, the half-wave voltage switch 8 functions as a λ / 2 wave plate, which is used to rotate the polarization direction of the pulsed light by 90°.

[0072] The first output mirror 10 and the second output mirror 13 are both concave-convex mirrors. The curvature radius and coating parameters of the first output mirror 10 are used to match medium and low pump powers, and the curvature radius and coating parameters of the second output mirror 13 are used to match high pump powers to ensure stable output of laser under different pump powers.

[0073] The first reflecting prism 11 is used to reflect the light path of the transmitted p light in the long cavity resonant cavity at 45 degrees.

[0074] The second reflecting prism 14 is used to reflect the optical path of the second laser in the long cavity resonant cavity at 45 degrees.

[0075] This design effectively shortens the physical length of the laser while maintaining the stability of laser transmission.

[0076] Furthermore, the LD side pump gain module 2 has a medium-low power state and a high power state, and these two states ensure the efficient and stable operation of the laser under different pump powers.

[0077] When in the medium and low power state, the half-wave voltage switch 8 is loaded with half-wave high voltage, the focal length of the crystal equivalent thermal lens is large, and a short cavity resonant cavity composed of a total reflection mirror 1 and a first output mirror 10 is adopted. The short cavity resonant cavity adopts an unstable cavity technology, and the cavity mirror parameters of the first output mirror 10 match the cavity ABCD parameters corresponding to the medium and low power, so that it can be maintained within this power range. g 1 g 2 parameter is greater than 1. At this time, the light path in the solid laser cavity oscillates in the short cavity resonant cavity, passes through the first PBS prism 9, and is output through the first output mirror 10.

[0078] When in high power state, the half-wave voltage switch 8 is powered off, and a long cavity resonant cavity composed of the full reflection mirror 1 and the second output mirror 13 is used. The long cavity resonant cavity also adopts the unstable cavity technology. At this time, the focal length of the crystal equivalent thermal lens becomes smaller, and the output mirror parameters need to be re-matched to make the cavity g 1 g 2 parameter is still maintained in a range greater than 1 to maintain stable oscillation. At this time, the light path in the solid laser cavity oscillates in the long cavity resonator, is reflected by the first reflection prism 11, reaches the second output mirror 13 and is output.

[0079] In the above two resonant cavity optical paths, the polarization direction of the laser in the cavity is changed by introducing a half-wave voltage switch 8 to achieve the switching of the oscillation optical path under different pump powers. This design not only improves the adaptability of the laser, but also ensures the stability and efficiency of the laser output under different pump powers.

[0080] It should also be noted that when the pump power increases, a long cavity resonator is used to increase the physical cavity length, thereby increasing the pulse width. By rationally laying out the optical path and optimizing the design, the pulse width can be maintained at more than 10ns at maximum energy, thus meeting the needs of high-energy, long-pulse laser output. On the other hand, the two sets of resonator mirror parameters match the ABCD matrix at different thermal lens focal lengths in the cavity, thereby maintaining the stability of the laser energy optical axis and ensuring that the beam quality is basically consistent with the short cavity, further improving the laser performance.

[0081] Specifically, when the pump power of the LD side pump gain module 2 is at a medium or low power, the thermal lens effect of the crystal in the laser cavity is relatively small, and its equivalent thermal lens focal length is relatively large. The intracavity optical path oscillates in the short cavity resonant cavity composed of the total reflection mirror 1 and the first output mirror 10. The polarization direction of the polarized light in the laser cavity changes as follows: the fluorescence generated by the LD side pump gain module 2 is an arbitrarily polarized light. After passing through the polarizer 3, the p-polarized light oscillates, and then passes through the λ / 4 wave plate 4 and the Q-switched crystal 5 in sequence to become s-polarized light. At this time, it is switched by a half-wave voltage loaded with a half-wave high voltage, and the vibration direction rotates 90°, and becomes p-polarized light again. Then, the p-polarized light can pass through the first PBS prism 9 to reach the first output mirror 10, so that the first laser oscillates and outputs inside the short cavity resonant cavity. Please refer to Figure 3 The light path 1 is shown in Figure 1. The p direction is defined as the horizontal direction, that is, the vibration direction of the light is parallel to the paper surface. The s direction is defined as the vertical direction, that is, the vibration direction of the light is perpendicular to the paper surface.

[0082] When the pump power of the LD side pump gain module 2 is at high power, the thermal lens effect of the crystal in the laser cavity becomes serious, and its equivalent thermal lens focal length becomes smaller. The optical path in the cavity oscillates in the long cavity resonant cavity composed of the total reflection mirror 1 and the second output mirror 13. The polarization direction of the polarized light in the laser cavity changes as follows: the fluorescence generated by the LD side pump gain module 2 is an arbitrarily polarized light, which is p-polarized light after passing through the polarizer 3, and then becomes s-polarized light after passing through the λ / 4 wave plate 4 and the Q-switched crystal 5 in sequence. At this time, the half-wave voltage switch 8 is not energized, and it is still s-polarized light after passing through. The s-polarized light passes through the first PBS prism 9, is reflected at 90° into the first reflection prism 11, and then reflects to the second output mirror 13, so that the laser vibrates and outputs in the long cavity resonant cavity. Please refer to Figure 4 The light path 2 is shown.

[0083] For further information, see Figure 5 The thermal lens adaptive dual-resonant cavity pulsed solid-state laser also includes a main control circuit board, which is electrically connected to the LD side pump gain module 2 through the LD driving circuit. The main control circuit is not only electrically connected to the Q-switched crystal 5 through the λ / 4 Q-switched high-voltage circuit to achieve precise control of the Q-switching process, but the main control circuit is also electrically connected to the half-wave voltage switch 8 through the λ / 2 Q-switched high-voltage circuit, thereby being able to flexibly switch the resonant cavity state of the laser.

[0084] Among them, the LD driving circuit serves as the power source of the laser and is used to provide stable and reliable electric energy for the LD side pump gain module 2. It is worth noting that the LD side pump gain module 2 has a pumping cycle, and the solid laser has a short cavity resonance state and a long cavity resonance state.

[0085] Specifically, a single pumping cycle is taken as an example for description.

[0086] When the LD driving circuit outputs a pulse current to maintain a single pumping cycle, the main control circuit board triggers the λ / 4 Q-switched high-voltage circuit and the λ / 2 Q-switched high-voltage circuit respectively through the synchronous trigger signal 1 and the synchronous trigger signal 2 at the end of the single pumping cycle. The λ / 4 Q-switched high-voltage circuit and the λ / 2 Q-switched high-voltage circuit are used to load the λ / 4 high voltage and the λ / 2 high voltage to the Q-switched crystal 5 and the half-wave voltage switch 8 respectively. The optical path in the solid-state laser cavity oscillates in the short cavity resonant cavity, and the solid-state laser is in a short cavity resonance state.

[0087] When the LD driving circuit outputs a pulse current to maintain a single pumping cycle, the main control circuit board triggers the λ / 4 Q-switched high-voltage circuit only through the synchronous trigger signal 1 at the end of the single pumping cycle. The λ / 4 Q-switched high-voltage circuit is used to load the Q-switched crystal 5 with a λ / 4 high voltage. The optical path in the solid-state laser cavity oscillates in the long cavity resonant cavity, and the solid-state laser is in a long cavity resonance state.

[0088] It should be noted that a single pump cycle is 230μs, which ensures that the laser can complete stable pumping, Q-switching and output processes in each cycle. Through the precise control of the main control circuit board and the synergy of various circuits, the thermal lens adaptive dual-resonance cavity pulsed solid-state laser can achieve efficient and stable laser output at different pump powers.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A thermal lens adaptive dual-resonance cavity pulsed solid-state laser, characterized in that: include: A total reflection mirror (1) is used as a common reflection mirror of a dual resonant cavity, wherein the dual resonant cavity comprises a short cavity resonant cavity and a long cavity resonant cavity; An LD side pump gain module (2) is arranged at the optical path reflection end of the total reflection mirror (1) and is used to provide pump energy; A polarizer (3), arranged on the output light path of the LD side pump gain module (2), and used for generating polarized light; A Q switch (17) comprises a λ / 4 wave plate (4) and a Q-switching crystal (5) which are sequentially arranged on the output light path of the polarizing plate (3), wherein the λ / 4 wave plate (4) is used to adjust the polarized light, and the Q-switching crystal (5) is used to receive the polarized light adjusted by the λ / 4 wave plate (4), and load a λ / 4 wave voltage to output pulsed light, and the Q switch (17) is used to control the output of the pulsed light; A corner cube prism (6) is arranged on the output optical path of the Q-switched crystal (5) and is used to fold the optical path of the pulsed light; A first wedge lens group (7) is arranged on the output light path of the corner cube prism (6) and is used to fine-tune the light path of the pulse light folded by the corner cube prism (6); A half-wave voltage switch (8) is arranged on the output light path of the first wedge mirror group (7) and is used to change the polarization direction of the pulse light according to a control signal; A first PBS prism (9) is arranged on the output optical path of the half-wave voltage switch (8) and is used to split the pulse light according to the polarization direction of the pulse light, and divide the pulse light into reflected s light and transmitted p light, and output the light; A first output mirror (10) is arranged on the optical path of the reflected S light and forms the short cavity resonant cavity with the total reflection mirror (1), the first output mirror (10) being used to match the light spot mode under medium and low pump power and output the first laser; A first reflecting prism (11), arranged on the optical path of the transmitted p light, and used for changing the optical path direction of the transmitted p light; A second wedge lens group (12) is arranged on the output light path of the first reflecting prism (11) and is used to fine-tune the light path of the transmitted p light whose light path direction is changed after passing through the first reflecting prism (11); A second output mirror (13) is arranged on the output light path of the second wedge mirror group (12) and forms the long cavity resonant cavity with the total reflection mirror (1) to match the light spot mode under high pump power and output a second laser; A second reflecting prism (14) is arranged on the output light path of the second output mirror (13) and is used to change the light path direction of the second laser; A third wedge lens group (15) is arranged on the output light path of the second reflecting prism (14) and is used to fine-tune the light path direction of the second laser; The second PBS prism (16) is arranged at the intersection of the output light paths of the first output mirror (10) and the third wedge mirror group (15), and is used to make the light paths of the first laser and the second laser overlap.

2. The thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to claim 1, characterized in that: The LD side pump gain module (2) is composed of two symmetrically pumped LD bar arrays and two Nd:YAG crystals.

3. The thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to claim 1, characterized in that: The half-wave voltage switch (8) is a lithium niobate electro-optical crystal, which is used to rotate the polarization direction of the pulse light by 90°.

4. The thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to claim 1, characterized in that: The first output mirror (10) and the second output mirror (13) are both concave-convex mirrors; the curvature radius and coating parameters of the first output mirror (10) are used to match medium and low pump powers, and the curvature radius and coating parameters of the second output mirror (13) are used to match high pump powers.

5. The thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to claim 1, characterized in that: The LD side pump gain module (2) has a medium-low power state and a high power state; When in the medium-low power state, the half-wave voltage switch (8) is loaded with a half-wave high voltage, the optical path in the solid laser cavity oscillates in the short cavity resonant cavity, and passes through the first PBS prism (9) and is output through the first output mirror (10); When in the high power state, the half-wave voltage switch (8) is powered off, the light path in the solid laser cavity oscillates in the long cavity resonant cavity, is reflected by the first reflecting prism (11), reaches the second output mirror (13), and is output.

6. The thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to claim 1, characterized in that: The first reflecting prism (11) is used to reflect the light path of the transmitted p light in the long cavity resonant cavity at 45 degrees.

7. The thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to claim 1, characterized in that: The second reflecting prism (14) is used to reflect the optical path of the second laser in the long cavity resonant cavity at 45 degrees.

8. The thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to claim 1, characterized in that: It also includes a main control circuit board, the main control circuit board is electrically connected to the LD side pump gain module (2) through an LD drive circuit, the main control circuit is electrically connected to the Q-switched crystal (5) through a λ / 4 Q-switched high-voltage circuit, and the main control circuit is electrically connected to the half-wave voltage switch (8) through a λ / 2 Q-switched high-voltage circuit.

9. The thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to claim 8, characterized in that: The LD driving circuit is used to supply power to the LD side pump gain module (2), the LD side pump gain module (2) has a pumping cycle, and the solid-state laser has a short cavity resonance state and a long cavity resonance state; After the LD driving circuit outputs a pulse current to maintain a single pumping cycle, the main control circuit board triggers the λ / 4 Q-switched high-voltage circuit and the λ / 2 Q-switched high-voltage circuit respectively through the synchronous trigger signal 1 and the synchronous trigger signal 2 at the end of the single pumping cycle, and the λ / 4 Q-switched high-voltage circuit and the λ / 2 Q-switched high-voltage circuit are used to load the λ / 4 high voltage and the λ / 2 high voltage to the Q-switched crystal (5) and the half-wave voltage switch (8), respectively, and the optical path in the solid-state laser cavity oscillates in the short cavity resonant cavity, and the solid-state laser is in the short cavity resonant state; After the LD driving circuit outputs a pulse current to maintain a single pumping cycle, the main control circuit board triggers the λ / 4 Q-switched high-voltage circuit only through the synchronous trigger signal 1 at the end of the single pumping cycle. The λ / 4 Q-switched high-voltage circuit is used to load a λ / 4 high voltage to the Q-switched crystal (5). The optical path in the solid-state laser cavity oscillates in the long cavity resonant cavity, and the solid-state laser is in the long cavity resonant state.

10. The thermal lens adaptive dual-resonance cavity pulsed solid-state laser according to claim 9, characterized in that: The single pumping period is 230 μs.

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