Picosecond laser system and control method thereof

Abstract

The embodiment of the invention provides a picosecond laser system and a control method thereof, and relates to the technical field of ultrafast laser, and the method comprises the following steps: receiving first power outputted by a first power detection assembly; judging whether the first power is in a first preset power interval or not; if the first power is within the first preset power interval, a first amplification module is started to perform first-stage amplification on the seed laser to form first laser; receiving second power output by the second power detection assembly; judging whether the second power is in a second preset power interval or not; if the second power is in a second preset power interval, starting a second amplification module; the crystal temperature, output by the temperature control assembly, of the bicrystal tandem connection assembly is received; judging whether the crystal temperature is within a preset temperature interval or not; and if the crystal temperature is within the preset temperature interval, the crystal temperature is adjusted to the optimal temperature control interval, so that the first laser is amplified to form second laser, and the second laser is modulated by the output module to output target laser.

Description

Technical Field

[0001] The present application relates to the field of ultrafast laser technology, and in particular to a picosecond laser system and a control method thereof. Background Art

[0002] In the field of ultrafast laser technology, high-power picosecond lasers are widely used in aerospace, biomedicine, transportation equipment, 3C components and other fields due to their narrow pulse width, high peak power, and small heat-affected zone on materials. Compared with traditional continuous lasers and nanosecond lasers, picosecond laser processing has significant advantages such as high processing accuracy, small heat-affected zone, and wide material applicability, showing broad application prospects.

[0003] In the related art, high-power picosecond lasers are usually obtained by a picosecond laser system using a master oscillator power amplification method. The output power of the seed source of a high-power picosecond laser is low, so a high-gain amplifier is required to achieve power boost. Common solid-state laser amplifiers include regenerative amplifiers and traveling wave amplifiers. The advantage of a regenerative amplifier is that it has high gain and can obtain large energy pulse output, but its system structure is complex and the cost is too high. The traveling wave amplifier has the advantages of simple structure and low manufacturing cost, and can provide high power and high single pulse energy output, but the gain of a single-stage amplification is small, and it is usually necessary to increase the number of amplification stages to obtain higher power. However, the setting of a solid-state laser amplifier will not only increase the size of the picosecond laser system, but also introduce more optical elements due to multi-stage amplification, increasing the complexity and cost of the system. Taking a bulk crystal traveling wave amplifier as an example, if you want to reduce the number of amplification stages to reduce the system size or increase the power, you need to increase the pump power of each stage.

[0004] However, increasing the pump power at each stage will significantly increase the heat power consumption and heat deposition inside the laser gain medium, which will in turn lead to thermal effects such as birefringence and thermal lensing. These effects will not only reduce the overall efficiency of the laser, but also degrade the beam quality and affect the performance and stability of the laser system. Summary of the invention

[0005] The embodiments of the present application provide a picosecond laser system and a control method thereof to solve the problem in the related art that increasing the pump power at each stage will cause a significant increase in the thermal power consumption and heat deposition inside the laser gain medium, which will in turn cause thermal effects such as birefringence and thermal lensing. These effects will not only reduce the overall efficiency of the laser, but also degrade the beam quality, affecting the performance and stability of the laser system.

[0006] In a first aspect, an embodiment of the present application provides a control method for a picosecond laser system, comprising the following steps: Receiving a first power output by a first power detection component; wherein the first power detection component is used to detect a first power of a seed laser; Determining whether the first power is within a first preset power range; If the first power is within a first preset power interval, the first amplification module is turned on to amplify the seed laser to form a first laser, and in the first amplification module, the incident path of the seed laser and the first laser exit path are off-axis arranged; Receiving a second power output by a second power detection component; wherein the second power detection component is used to detect the second power of the first laser; Determining whether the second power is within a second preset power range; If the second power is within a second preset power range, the second amplification module is turned on to amplify the first laser to form a second laser; wherein the second amplification module includes a temperature control component and a dual crystal series connection component; receiving a third power and a beam quality parameter, and acquiring an optimal temperature value of the dual-crystal series-connected component according to the third power and the beam quality parameter; wherein the third power detection component is used to detect the third power of the second laser, and the beam quality detection component is used to detect the beam quality of the second laser; Receive the crystal temperature of the dual crystal series assembly output by the temperature control assembly; Determine whether the crystal temperature is within the preset temperature range; If the crystal temperature is within the preset temperature range, the PID control algorithm is started to adjust the crystal temperature to the optimal temperature value, so as to amplify the first laser to form a second laser at the optimal temperature value of the dual crystal series assembly, and output the target laser after modulation by the output module.

[0007] In a feasible implementation, determining whether the crystal temperature is within a preset temperature range; If the crystal temperature is within the preset temperature range, the PID control algorithm is started to adjust the crystal temperature to the optimal temperature value, so that the first laser is amplified at the optimal temperature value in the second amplification module to form a second laser, and the target laser is output after being modulated by the output module; specifically, the following steps are included: receiving the crystal temperature of the second laser crystal output by the first temperature control component; Determining whether the temperature of the second laser crystal is within a first preset temperature range; If the temperature of the second laser crystal is within the first preset temperature range, the PID control algorithm is started, and the temperature of the second laser crystal is adjusted to the first optimal temperature using the first temperature control component; receiving the crystal temperature of the third laser crystal output by the second temperature control component; Determining whether the temperature of the third laser crystal is within a second preset temperature range; If the temperature of the third laser crystal is within the first preset temperature range, the PID control algorithm is started, and the temperature of the third laser crystal is adjusted to the second optimal temperature using the second temperature control component, so as to amplify the first laser within the optimal temperature range in the second amplification module to form a second laser, and output the target laser after modulation by the output module.

[0008] In a feasible implementation, the steps of receiving the third power and beam quality parameters and obtaining the optimal temperature value of the dual crystal series connection assembly according to the third power and beam quality parameters specifically include: The temperature of the third laser crystal is adjusted to a first temperature setting value by using a second temperature control component; The temperature of the third laser crystal is fixed to a first temperature setting value, and the temperature of the second laser crystal is adjusted step by step within the first temperature range according to a first preset step length using a first temperature control component; receiving a first beam quality parameter of the second laser crystal at each temperature value, and obtaining a first optimal temperature according to the first beam quality parameter; The temperature of the second laser crystal is fixed to the first optimal temperature, and the temperature of the third laser crystal is adjusted step by step within the second temperature range according to the second preset step length using the second temperature control component; A second beam quality parameter and a third power of the third laser crystal at each temperature value are received, and a second optimal temperature is obtained according to the second beam quality parameter and the third power.

[0009] In a feasible implementation, the control method further includes: receiving a fourth power output by a fourth power detection component; wherein the fourth power detection component is used to detect a fourth power of S-polarized light; determining whether the fourth power is within a fourth power range; If the fourth power is not within the fourth power interval, outputting an adjustment signal to the motor to adjust the polarization angle of the second half-wave plate; receiving a fifth power output by a fifth power detection component; wherein the fifth power detection component is used to detect the fifth power of the P-polarized light; determining whether the fifth power is within a fifth power range; If the fifth power is not within the fifth power interval, an adjustment signal is output to the motor to adjust the polarization angle of the second half-wave plate.

[0010] In a feasible implementation, the control method further includes: receiving a first power output by a first power detection component; Calculate the number of seed laser pulses according to the first power and the comparison relationship between the preset power and the number of pulses; Determine whether the number of seed laser pulses is within a preset number range; If the number of seed laser pulses is not within the preset number range, the picosecond laser system is turned off.

[0011] In a second aspect, an embodiment of the present application further provides a picosecond laser system, which adopts the control method of the picosecond laser system in any technical solution of the first aspect, and the picosecond laser system includes: a control module, a seed source module, a first amplification module, a second amplification module and an output module; The control module includes an electric control component, a power detection component for detecting laser power, and a beam quality detection component for detecting beam quality; the electric control component is signal-connected to the power detection component and the beam quality detection component, respectively, and the electric control component is used to provide power for the laser system; wherein the power detection component includes a first power detection component, a second power detection component, and a third power detection component; The seed source module is used to generate a seed laser; the first amplification module and the first power detection assembly are both arranged downstream of the optical path of the seed source module, and the first power detection group is used to detect the first power of the seed laser; The first amplification module is configured to amplify the seed laser to form a first laser; wherein, in the first amplification module, the incident path of the seed laser and the first laser output path are arranged off-axis, and the incident direction of the seed laser and the direction in which the first pump light is emitted by the first amplification module are arranged relative to each other; The second power detection component and the second amplification module are both arranged downstream of the optical path of the first amplification module, and the second power detection module is used to detect the second power of the first laser; The second amplification module includes a dual crystal structure, the dual crystal structure includes a dual crystal series assembly and a temperature control assembly for adjusting the temperature of the dual crystal series assembly, and the electric control assembly and the temperature control assembly are signal-connected; the second amplification module is configured to amplify the first laser in the dual crystal series assembly to form a second laser; wherein the incident direction of the first laser input to the dual crystal series assembly and the direction of the second pump light emitted by the second amplification module are arranged relative to each other; The third power detection component, the beam quality detection component and the output module are all arranged downstream of the optical path of the second amplifying module, the third power detection component is used to detect the third power of the second laser, and the beam quality detection component is used to detect the beam quality of the second laser, so that the electric control component obtains the optimal temperature value of the dual-crystal series component according to the third power and the beam quality parameter, and enables the dual-crystal series component to amplify the first laser to form the second laser at the optimal temperature value; The output module is configured to modulate the second laser and then output the target laser.

[0012] In a feasible implementation, the dual-crystal series connection component includes a second laser crystal and a third laser crystal, and the temperature control component includes a first temperature control component and a second temperature control component; The first temperature control component is configured to adjust the temperature of the second laser crystal, and the second temperature control component is configured to adjust the temperature of the third laser crystal.

[0013] In a feasible implementation, the first temperature control component includes a first heat sink, a first thermoelectric cooler, and a first temperature sensor; The second laser crystal is arranged between two first heat sinks, the two first heat sinks are used to support the second laser crystal, the first thermoelectric cooler is arranged on the surface of one of the first heat sinks, and the first thermoelectric cooler is configured to adjust the temperature of the first laser crystal by adjusting the temperature of the first heat sink through electric current; the first temperature sensor is arranged on the first heat sink, and the first thermoelectric cooler and the first temperature sensor are respectively connected to the electric control component signal; The second temperature control assembly includes a second heat sink, a second thermoelectric cooler and a second temperature sensor; The third laser crystal is arranged between two second heat sinks, the two second heat sinks are used to support the third laser crystal, the second thermoelectric cooler is arranged on the surface of one of the second heat sinks, and the second thermoelectric cooler is configured to adjust the temperature of the second heat sink by current to adjust the temperature of the third laser crystal; the second temperature sensor is arranged on the second heat sink, and the second thermoelectric cooler and the second temperature sensor are respectively connected to the signal of the electronic control component.

[0014] In a feasible implementation, the dual crystal structure further includes a liquid cooling heat sink; The first thermoelectric cooler and the second thermoelectric cooler are arranged in parallel, and the liquid cooling radiator is arranged on the same side of the first thermoelectric cooler and the second thermoelectric cooler. The liquid cooling radiator is configured to dissipate heat for the first thermoelectric cooler and the second thermoelectric cooler, and the liquid cooling radiator is signal-connected to the electronic control component.

[0015] In a feasible implementation, the first amplification module includes a first focusing lens, a first laser crystal, a first dichroic mirror, a second focusing lens, a first collimating lens and a first pump which are coaxially arranged along the transmission path of the seed laser; The picosecond laser system comprises a first beam splitter, and a first power detection component is arranged on the transmission side of the first beam splitter; The first focusing lens is arranged on the reflection side of the first beam splitter, and the first focusing lens is configured to input the seed laser into the first laser crystal through the first path, and receive the first laser output by the first laser crystal through the second path, wherein the first path and the second path are respectively arranged on both sides of the first focusing lens; The first dichroic mirror is configured to transmit the first pump light generated by the first pump to the first laser crystal, and reflect the first laser output in the first laser crystal along the second path to the first focusing lens; wherein the first pump light and the seed laser are pumped in the first laser crystal to form the first laser; The second focusing lens and the first collimating lens are configured to shape the first pump light and then inject it into the first laser crystal through the first dichroic mirror.

[0016] In a feasible implementation, the second amplification module further includes a second dichroic mirror, a third focusing lens, a second collimating lens, and a second pump; The picosecond laser system further includes a first light splitting component, and a second power detection component is arranged on the transmission side of the first light splitting component; The double crystal structure is arranged on the reflection side of the first light splitting component; the double crystal structure, the second dichroic mirror, the third focusing lens, the second collimating lens and the second pump are coaxially arranged along the transmission path of the first laser; The second dichroic mirror is configured to transmit the second pump light generated by the second pump to the dual crystal structure, and reflect the second laser light outputted from the dual crystal structure to the output module; The third focusing lens and the second collimating lens are configured to shape the second pump light and then inject it into the double crystal structure through the second dichroic mirror.

[0017] In a feasible implementation, the output module includes an adjustable half-wave plate component, a polarization beam splitter, a first window mirror, and a second window mirror; The laser system further includes a fifth beam splitter and a sixth beam splitter; the third power detection component is arranged on the transmission side of the fifth beam splitter, the sixth beam splitter is arranged on the reflection side of the fifth beam splitter, and the beam quality detection component is arranged on the reflection side of the sixth beam splitter; The adjustable half-wave plate component is arranged on the transmission side of the sixth light splitting component, and the adjustable half-wave plate component includes a motor and a second half-wave plate arranged at the rotating end of the motor. The motor is connected to the electric control component by signal, and the electric control component is configured to modulate the linear polarization angle of the second laser to form a third laser by controlling the rotation angle of the motor; The polarization beam splitter is disposed at the output side of the third laser, and the polarization beam splitter is configured to split the beam of the third laser into P polarized light and S polarized light; The first window mirror is arranged at the S light path output end of the polarization beam splitter to output S polarized light; The second window mirror is arranged at the P light path output end of the polarization beam splitter to output P polarized light.

[0018] In a feasible implementation, the output module further includes a seventh beam splitter, an eighth beam splitter, a ninth beam splitter, a fourth power detection component and a fifth power detection component; The seventh beam splitter is arranged at the S optical path output end of the polarization beam splitter, the fourth power detection component is arranged at the reflection side of the seventh beam splitter to detect the laser power of the S polarized light, and the first window mirror is arranged at the transmission side of the seventh beam splitter; The eighth beam splitter is arranged at the P optical path output end of the polarization beam splitter, the ninth beam splitter is arranged at the reflection side of the eighth beam splitter, the fifth power detection component is arranged at the reflection side of the ninth beam splitter to detect the laser power of the P polarized light, and the second window mirror is arranged at the transmission side of the ninth beam splitter; The fourth power detection component and the fifth power detection component are respectively connected to the electric control component signal.

[0019] On the one hand, a control method of a picosecond laser system provided in an embodiment of the present application is provided. In the embodiment of the present application, a power detection component is provided and a feedback link is formed with an electronic control component to realize dynamic power calibration of the whole process of seed source injection, first-stage amplification, and second-stage amplification, so as to ensure that the seed laser injection of the laser system, the amplification of the seed laser, and the amplification of the first laser until the output of the target laser can be carried out under the preset state of the laser system, and a multi-level protection mechanism is constructed, thereby achieving high stability and high reliability of the laser system. In the first amplification module, by setting the incident path of the seed laser input to the first laser crystal and the exit path of the first laser output to the first laser crystal off-axis, that is, the laser amplification circuit and the central optical axis of the gain medium are arranged off-axis, the spontaneous radiation, parasitic oscillation, and unintentional resonant cavity problems existing in the traditional coaxial structure are effectively suppressed, and the beam spatial mode and overall amplification efficiency are further improved. Furthermore, a dual crystal structure is used in the second amplification module, and the optimal temperature value of the dual crystal series assembly is obtained by monitoring the third power and beam quality parameters, that is, the second laser can have a higher beam quality under the premise of ensuring that the third power is high. After determining the optimal temperature value, the temperature of the laser crystal is closed-loop controlled by the temperature control component, and the refractive index change caused by the thermal lens effect is compensated in real time, so that the dual crystal series assembly amplifies the first laser at the optimal temperature value to obtain a second laser with higher laser power and better beam quality, so that the laser system maintains a stable gain output during continuous operation. In other words, through the configuration of the embodiment of the present application, a control method for a picosecond laser system with a compact structure, high stability, high output power, and good beam quality is provided.

[0020] On the second aspect, the embodiments of the present application provide a picosecond laser system, which effectively suppresses the spontaneous radiation, parasitic oscillation and unintentional formation of the resonant cavity problems existing in the traditional coaxial structure by arranging the incident path of the seed laser input to the first laser crystal and the exit path of the first laser output to the first laser crystal off-axis, that is, arranging the laser amplification circuit and the central optical axis of the gain medium off-axis, and combining the reverse transmission configuration of the first pump light and the seed laser, so that the laser signal obtains a higher gain density at the amplification end, thereby effectively improving the spatial mode of the light beam and the overall amplification efficiency. Further, a dual crystal structure is adopted in the second amplification module. Through the setting of the third power detection component and the beam quality detection component, the optimal temperature value of the dual crystal series component can be obtained by monitoring the third power and beam quality parameters, that is, the second laser can have a higher beam quality under the premise of ensuring that the third power is high. After determining the optimal temperature, the temperature of the laser crystal is closed-loop controlled by the temperature control component, and the refractive index change caused by the thermal lens effect is compensated in real time, so that the dual crystal series component amplifies the first laser at the optimal temperature value to obtain a second laser with higher laser power and better beam quality, ensuring the consistency of the dual crystal gain distribution. Combined with the design of reverse pumping, the temperature gradient inside the laser crystal is further balanced, so that the laser system maintains a stable gain output during continuous operation. In the embodiment of the present application, the power detection component is set and a feedback link is formed with the electronic control component to realize dynamic power calibration of the whole process of seed source injection, first-stage amplification, and second-stage amplification, so as to ensure that the seed laser injection of the laser system, the amplification of the seed laser, and the amplification of the first laser until the output of the target laser can be carried out under the preset state of the laser system, and a multi-level protection mechanism is constructed, so as to achieve high stability and high reliability of the laser system. In addition, the laser amplification circuit is arranged off-axis from the central optical axis of the gain medium, the pump light and the signal light are arranged in reverse, and the double crystal is connected in series, so that the compactness of the laser system is improved. In other words, through the arrangement of the embodiment of the present application, a picosecond laser system with compact structure, high stability, high output power and good beam quality is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present application and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is a structural schematic diagram of a picosecond laser system provided in one embodiment of the present application; Figure 2 for Figure 1 Schematic diagram of the structure of the double crystal structure; Figure 3A method flow of a control method of a picosecond laser system provided in an embodiment of the present application Figure 1 ; Figure 4 for Figure 3 The specific steps of S16 in the figure; Figure 5 for Figure 3 Specific step diagram of S17, S18, and S19; Figure 6 A method flow of a control method of a picosecond laser system provided in an embodiment of the present application Figure 2 ; Figure 7 A method flow of a control method of a picosecond laser system provided in an embodiment of the present application Figure 3 ; Figure 8 It is the fitting curve diagram of output power and pulse number; Fig. 9 is the seed laser output wavelength data diagram; Fig.10 This is the data diagram of seed laser output power and stability; Fig.11 This is the data diagram of seed laser output pulse width; Fig.12 is a beam quality data diagram of the second laser in the x direction; Fig.13 is a beam quality data diagram of the second laser in the y direction; Fig.14 This is the data diagram of 5 pulses of the target laser; Fig.15 This is a graph of 10 pulses of target laser data.

[0022] Description of reference numerals: 200-seed source module; 300-first spectroscope; 400-first amplification module; 500-first spectroscopic component; 600-second amplification module; 800-output module; 900-cooling module; 110-electric control component; 120-first power detection component; 121-second spectroscope; 122-oscilloscope; 123-first photodetector; 130-second power detection component; 140-third power detection component; 150-fourth power detection component; 160-fifth power detection component; 170-beam quality detection component; 210- picosecond seed source; 220- optical fiber collimator; 230- first half-wave plate; 240- first photoelectric isolator; 410 - first focusing lens; 420 - first laser crystal; 430 - first dichroic mirror; 440 - second focusing lens; 450 - first collimating lens; 460 - first pump; 510 - third beam splitter; 520 - second photoelectric isolator; 530 - fourth focusing lens; 540 - fourth beam splitter; 610-dual crystal structure; 611-second laser crystal; 612-first heat sink; 613-first temperature sensor; 614-first thermoelectric cooler; 615-third laser crystal; 616-second heat sink; 617-second temperature sensor; 618-second thermoelectric cooler; 619-liquid cooling radiator; 619a-liquid inlet; 619b-liquid outlet; 620-second dichroic mirror; 630-third focusing lens; 640-a second collimating lens; 650-a second pump; 701-fifth beam splitter; 702-sixth beam splitter; 810 - adjustable half-wave plate assembly; 820 - polarization beam splitter; 830 - first window mirror; 840 - second window mirror; 850 - seventh beam splitter; 860 - eighth beam splitter; 870 - ninth beam splitter. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0024] Figure 1 It is a structural schematic diagram of a picosecond laser system provided in one embodiment of the present application.

[0025] Reference Figure 1 , the embodiment of the present application provides a picosecond laser system, the picosecond laser system includes: a control module, a seed source module 200, a first amplification module 400, a second amplification module 600 and an output module 800; The control module includes an electric control component 110 and a power detection component for detecting laser power; the electric control component 110 is connected to the power detection component by signal, and the electric control component 110 is used to provide power for the laser system; wherein the power detection component includes a first power detection component 120 and a second power detection component 130; The seed source module 200 is used to generate a seed laser; the first amplification module 400 and the first power detection assembly 120 are both arranged downstream of the optical path of the seed source module 200, and the first power detection group is used to detect the first power of the seed laser; The first amplifying module 400 is configured to amplify the seed laser to form a first laser; wherein, in the first amplifying module 400, the incident path of the seed laser and the first laser emission path are arranged off-axis, and the incident direction of the seed laser and the direction in which the first pump light is emitted by the first amplifying module 400 are arranged relative to each other; The second power detection component 130 and the second amplification module 600 are both arranged downstream of the optical path of the first amplification module 400, and the second power detection module is used to detect the second power of the first laser; The second amplifying module 600 includes a dual crystal structure 610, and the dual crystal structure 610 includes a dual crystal series component and a temperature control component for adjusting the temperature of the dual crystal series component, and the electric control component 110 is signal-connected to the temperature control component; the second amplifying module 600 is configured to amplify the first laser in the dual crystal series component to form a second laser; wherein the incident direction of the first laser input to the dual crystal series component and the direction of the second pump light emitted by the second amplifying module 600 are arranged relative to each other; The output module 800 is disposed downstream of the optical path of the second amplifying module 600 , and the output module 800 is configured to modulate the second laser and then output the target laser.

[0026] In some examples, the seed source module 200 includes a picosecond seed source 210, a fiber collimator 220, a first half-wave plate 230, and a first photoelectric isolator 240, which are sequentially arranged along the seed laser transmission path. The first seed laser output by the picosecond seed source 210 is collimated by the fiber collimator 220 to obtain a seed laser, and the laser spot diameter of the collimated seed laser is 100μm~400μm, and the collimated laser spot diameter is set to D1. The second seed laser is adjusted to horizontal polarized light by the first half-wave plate 230 and then forms a seed laser by the first photoelectric isolator 240. The first photoelectric isolator 240 is used to isolate the laser returned by the output side device to avoid damage to the device on the input side of the first photoelectric isolator 240.

[0027] For example, the picosecond seed source 210 can be set to have a central wavelength of 1064 nm, a pulse width of 10.2 ps, and a beam quality factor M 2 <1.1, laser with adjustable repetition frequency in the range of 500Hz~15MHz.

[0028] From the above description, it can be seen that this solution achieves the following technical effects: In the embodiment of the present application, the incident path of the seed laser input to the first laser crystal 420 and the exit path of the first laser output to the first laser crystal 420 are set off-axis, that is, the laser amplification circuit and the central optical axis of the gain medium are arranged off-axis, thereby effectively suppressing the spontaneous radiation, parasitic oscillation and unintentional formation of the resonant cavity problems existing in the traditional coaxial structure. Combined with the reverse transmission configuration of the first pump light and the seed laser, the laser signal obtains a higher gain density at the amplification end, thereby effectively improving the spatial mode of the light beam and the overall amplification efficiency. Furthermore, a dual crystal structure 610 is adopted in the second amplification module 600. Through the setting of the third power detection component 140 and the beam quality detection component 170, the optimal temperature value of the dual crystal series component can be obtained by monitoring the third power and beam quality parameters, that is, the second laser can have a higher beam quality under the premise of ensuring that the third power is high. After determining the optimal temperature, the temperature of the laser crystal is closed-loop controlled by the temperature control component, and the refractive index change caused by the thermal lens effect is compensated in real time, so that the dual crystal series component amplifies the first laser at the optimal temperature value to obtain a second laser with higher laser power and better beam quality, thereby ensuring the consistency of the dual crystal gain distribution. Combined with the design of reverse pumping, the temperature gradient inside the laser crystal is further balanced, so that the laser system maintains a stable gain output during continuous operation. In the embodiment of the present application, by setting the power detection component and forming a feedback link with the electronic control component, dynamic power calibration of the whole process of seed source injection, first-stage amplification, and second-stage amplification is realized to ensure that the seed laser injection of the laser system, the amplification of the seed laser, and the amplification of the first laser until the output of the target laser can be carried out under the preset state of the laser system, and a multi-level protection mechanism is constructed, thereby achieving high stability and high reliability of the laser system. In addition, by arranging the laser amplifier circuit and the central optical axis of the gain medium off-axis, and the reverse arrangement of the pump light and the signal light, and the series connection structure of the double crystal, the structural compactness of the laser system is improved. In other words, through the setting of the embodiment of the present application, a picosecond laser system with compact structure, high stability, high output power and good beam quality is provided.

[0029] Figure 2 for Figure 1 Schematic diagram of the structure of the twin crystal structure.

[0030] In some examples, reference Figure 2 The dual-crystal series component includes a second laser crystal 611 and a third laser crystal 615, and the temperature control component includes a first temperature control component and a second temperature control component; the first temperature control component is configured to regulate the temperature of the second laser crystal 611, and the second temperature control component is configured to regulate the temperature of the third laser crystal 615.

[0031] For example, the second laser crystal 611 and the third laser crystal 615 can both be made of Nd:YVO4 (neodymium-doped yttrium vanadate crystal). 3+ The doping concentration is 0.1%-0.5%, in a bonded or non-bonded form. Among them, the bonding form includes a single-end bonded crystal (Nd:YVO4-YVO4) or a double-end bonded crystal (YVO4-Nd:YVO4-YVO4). The undoped YVO4 crystal acts as a heat sink, which is beneficial for better heat dissipation of the crystal and reduces the thermal effect of the crystal. The geometric size of the first laser crystal 420 can be designed according to the actual amplification power requirements.

[0032] In the embodiment of the present application, the temperature of the second laser crystal 611 is controlled by the first temperature control component, and the temperature of the third laser crystal 615 is controlled by the second temperature control component, so that the second laser crystal 611 and the third laser crystal 615 can be independently temperature-controlled, respectively, so as to accurately control each crystal, thereby significantly reducing problems such as gain efficiency loss and beam quality degradation caused by uneven temperature, thereby improving the stability and reliability of the overall system.

[0033] In some examples, the picosecond laser system further includes a third power detection component 140 and a beam quality detection component 170; The third power detection component 140 and the beam quality detection component 170 are both arranged downstream of the optical path of the second amplification module 600, the third power detection component 140 is configured to detect the third power of the second laser, and the beam quality detection component 170 is configured to detect the beam quality of the second laser; The temperature control component is configured to receive the third power output by the third power detection component 140 and the beam quality parameters output by the beam quality detection component 170, and determine the optimal temperature control range of the dual crystal series connection component according to the third power and the beam quality parameters.

[0034] Exemplarily, the first temperature control component includes a first heat sink 612, a first thermoelectric cooler 614, and a first temperature sensor 613; The second laser crystal 611 is disposed between the two first heat sinks 612, the two first heat sinks 612 are used to support the second laser crystal 611, the first thermoelectric cooler 614 is disposed on the surface of one of the first heat sinks 612, and the first thermoelectric cooler 614 is configured to adjust the temperature of the first heat sink 612 through electric current to adjust the temperature of the first laser crystal 420; the first temperature sensor 613 is disposed on the first heat sink 612, and the first temperature sensor 613 is connected to the electric control component 110 by signal; The second temperature control assembly includes a second heat sink 616, a second thermoelectric cooler 618 and a second temperature sensor 617; The third laser crystal 615 is arranged between two second heat sinks 616, and the two second heat sinks 616 are used to support the third laser crystal 615. The second thermoelectric cooler 618 is arranged on the surface of one of the second heat sinks 616, and the second thermoelectric cooler 618 is configured to adjust the temperature of the second heat sink 616 through electric current to adjust the temperature of the third laser crystal 615; the second temperature sensor 617 is arranged on the second heat sink 616, and the second temperature sensor 617 is connected to the electronic control component 110 by signal.

[0035] For example, the second laser crystal 611 and the third laser crystal 615 are both wrapped with indium foil.

[0036] For another example, the first heat sink 612 and the second heat sink 616 are both configured as copper heat sinks.

[0037] In the embodiment of the present application, the first heat sink 612 and the second heat sink 616 are provided, on the one hand, to support the second laser crystal 611 and the third laser crystal 615, and on the other hand, to conduct cooling quickly. In the embodiment of the present application, the first temperature sensor 613 and the second temperature sensor 617 are provided, so that the real-time temperature of the second laser crystal 611 and the third laser crystal 615 can be monitored in real time by the electric control component 110, and according to the monitored real-time temperature, the first thermoelectric cooler 614 and the second thermoelectric cooler 618 can be used to control the temperature of the second laser crystal 611 and the third laser crystal 615, respectively, so as to achieve accurate temperature control of the second laser crystal 611 and the third laser crystal 615.

[0038] Exemplarily, the dual crystal structure 610 further includes a liquid cooling heat sink; The first thermoelectric cooler 614 and the second thermoelectric cooler 618 are arranged in parallel, and the liquid cooling radiator is arranged on the same side of the first thermoelectric cooler 614 and the second thermoelectric cooler 618. The liquid cooling radiator is configured to dissipate heat for the first thermoelectric cooler 614 and the second thermoelectric cooler 618, and the thermoelectric cooler and the electronic control component 110 are signal-connected.

[0039] In a specific implementation, the laser system also includes a cooling module 900, and the liquid-cooled radiator 619 includes a liquid inlet 619a and a liquid outlet 619b, and the liquid inlet 619a and the liquid outlet 619b are respectively connected to the cooling module 900, so that the liquid-cooled radiator 619 takes away the heat on the surfaces of the first thermoelectric cooler 614 and the second thermoelectric cooler 618 through the flow of cooling liquid, so as to reduce the influence of temperature on the second laser crystal 611 and the third laser crystal 615. While the cooling liquid in the liquid-cooled radiator 619 takes away the surface temperature of the first thermoelectric cooler 614 and the second thermoelectric cooler 618, the temperature of the cooling liquid increases. The cooling liquid with increased temperature enters the cooling module 900 for cooling, and then enters the liquid-cooled radiator 619 through the liquid inlet 619a.

[0040] Furthermore, the embodiment of the present application can dissipate heat for the first thermoelectric cooler 614 and the second thermoelectric cooler 618 by setting a water-cooled radiator, so as to avoid the first thermoelectric cooler 614 and the second thermoelectric cooler 618 interfering with the temperature of the second laser crystal 611 and the third laser crystal 615, and ensure the stable operation of the first thermoelectric cooler 614 and the second thermoelectric cooler 618.

[0041] In some other examples, the first amplification module 400 includes a first focusing lens 410, a first laser crystal 420, a first dichroic mirror 430, a second focusing lens 440, a first collimating lens 450, and a first pump 460, which are coaxially arranged along the transmission path of the seed laser; The picosecond laser system includes a first beam splitter 300 , and a first power detection component 120 is disposed on the transmission side of the first beam splitter 300 ; The first focusing lens 410 is disposed on the reflection side of the first beam splitter 300, and the first focusing lens 410 is configured to input the seed laser into the first laser crystal 420 through the first path, and receive the first laser output by the first laser crystal 420 through the second path, wherein the first path and the second path are respectively disposed on both sides of the first focusing lens 410; The first dichroic mirror 430 is configured to transmit the first pump light generated by the first pump 460 to the first laser crystal 420, and the first laser outputted from the first laser crystal 420 is reflected along the second path to the first focusing lens 410; wherein the first pump light and the seed laser are pumped in the first laser crystal 420 to form the first laser; The second focusing lens 440 and the first collimating lens 450 are configured to shape the first pump light and then inject it into the first laser crystal 420 through the first dichroic mirror 430 .

[0042] In a specific implementation, the first path and the second path are respectively arranged on both sides of the first focusing lens 410, and the angle formed by the first path and the second path is the off-axis angle of the incident path of the seed laser and the output path of the first laser, wherein too large or too small an off-axis angle will affect the beam quality of the output target laser.

[0043] For example, the off-axis angle can be continuously changed by moving the position where the seed laser is incident on the first focusing lens 410 and fine-tuning the left and right deflection of the first dichroic mirror 430, and the beam quality detection component is used to detect the beam quality. Since the off-axis amplification operation occurs in the horizontal direction, the output beam quality in the horizontal direction is greatly affected by the off-axis angle, while the beam quality in the vertical direction remains basically unchanged.

[0044] After testing, it was found that when the off-axis angle range is [47mrad, 57mrad], a higher output power and better beam quality can be achieved. When the off-axis angle is less than 47mrad, the laser signal is affected by the thermal lens of the first laser crystal 420 due to the smaller off-axis angle, which makes the spot size larger, so that the spot is closer to the edge of the third beam splitter 510, and then diffraction occurs, so that a small part of the output power cannot be reflected by the third beam splitter 510, and the beam quality is also affected. Further, when the off-axis angle is greater than 57mrad, the too small off-axis angle will cause a part of the seed laser to appear outside the first pump light and cannot be effectively amplified, thereby reducing the output power and beam quality.

[0045] It should be noted that the first laser crystal 420 is configured to provide a gain medium for laser power amplification of the seed laser, and the first pump 460 is used to generate a semiconductor laser to provide pump energy for laser power amplification of the seed laser.

[0046] It should be noted that the first pump 460 can use multiple wavelengths such as 808nm, 878nm, etc. Among them, the maximum output power of the first pump 460 is set to 60W, and the fiber core diameter is set to 100μm; in the first pump 460, the 808nm wavelength pump has a lower quantum loss than the 678nm wavelength pump, which can significantly reduce the thermal effect of the laser crystal.

[0047] For example, the first dichroic mirror 430 is coated with a film that is highly transparent to the first pump light and a film that is highly reflective to the 1064nm laser. In a specific implementation, the transmittance of the first pump light is greater than 98.5%, and the reflectance to the seed laser (1064nm laser) is greater than 99%.

[0048] For another example, the second focusing lens 440 and the first collimating lens 450 form a 4F optical system, wherein the 4F optical system is an optical information processing system based on the Fourier transform principle, and its core function is to realize the spectrum analysis and spatial modulation of the light field by physical means. In a specific implementation, the first collimating lens 450 is used to collimate the first pump light, and the second focusing lens 440 is used to focus the collimated first pump light into the first laser crystal 420, and match it with the seed laser transmitted by the first focusing lens 410, thereby forming a reverse single-ended pump power amplification form.

[0049] For another example, the second focusing lens 440 is used to focus the first pump light collimated by the first collimating lens 450. The diameter of the focused spot is related to the focal length of the second focusing lens 440 and the first collimating lens 450, and the diameter of the focused spot is set to D2. The ratio of D1 to D2 is the filling factor, that is, the ratio of the spot diameter D1 of the collimated seed laser to the spot diameter D2 of the collimated first pump light. The filling factor largely determines the coupling matching degree between the laser beam and the pumping area. Whether it is large or small, it will aggravate the thermal effect inside the laser crystal. In order to improve the laser amplification efficiency of the picosecond laser system and ensure good beam quality, the filling factor can be designed to be 0.7~0.8.

[0050] In some other examples, the seed laser is incident on the first beam splitter 300 after passing through the first photoelectric isolator 240. For example, the first beam splitter 300 is set as a first 45° beam splitter, wherein the first 45° beam splitter is configured to split the seed laser. In a specific implementation, the first 45° beam splitter can be set as a beam splitter with a splitting ratio of 99:1, that is, it has a transmittance of 99% and a reflectivity of 1% for the 1064nm seed laser.

[0051] Furthermore, the first beam splitter 300 transmits a portion of the seed laser to the first power detection component 120 , and reflects another portion of the seed laser to the first amplification module 400 .

[0052] For example, the first power detection component 120 includes a second beam splitter 121, an oscilloscope 122 and a first photodetector 123. The second beam splitter 121 is arranged on the transmission side of the first beam splitter 300, the first photodetector 123 is arranged on the transmission side of the second beam splitter 121, and the oscilloscope 122 is arranged on the reflection side of the second beam splitter 121. The second beam splitter 121 is arranged as a second 45° beam splitter, and the splitting ratio of the second beam splitter 121 is set to 1:1, that is, it has a transmittance of 50% and a reflectivity of 50% for the seed laser. The first photodetector 123 is connected to the electronic control component 110 by signal, and the first photodetector 123 is used to convert the optical signal of the seed laser into an electrical signal and then output it to the electronic control component 110, so that the electronic control component 110 can monitor the laser power of the seed laser through the electrical signal. The oscilloscope 122 is used to monitor the output waveform of the seed laser.

[0053] In the embodiment of the present application, the seed laser is focused into the first laser crystal 420 through the first focusing lens 410, the first pump light is collimated by the first collimating lens 450, and then focused into the first laser crystal 420 by the first focusing lens 410, the seed laser is power-amplified inside the first laser crystal 420 to form the first laser, the first laser is reflected by the first dichroic mirror 430, passes through the first laser crystal 420 again, and then is coupled to the first beam splitter 500 from the edge of the first focusing lens 410, thereby realizing the off-axis double-pass setting of the seed laser and the first laser, which not only improves the compactness of the structure, but also significantly reduces the common spontaneous radiation, parasitic oscillation and unintentional resonant cavity oscillation in the coaxial configuration, and effectively improves the spatial mode and overall amplification efficiency of the light beam. Further, in the embodiment of the present application, the first pump light and the seed laser are transmitted in the opposite direction, which not only further improves the compactness of the structure, but also ensures that the seed laser amplification end can still obtain sufficient gain.

[0054] In some other examples, the second amplification module 600 further includes a second dichroic mirror 620 , a third focusing lens 630 , a second collimating lens 640 , and a second pump 650 ; The picosecond laser system further includes a first light splitting component 500, and a second power detection component 130 is disposed on the transmission side of the first light splitting component 500; The double crystal structure 610 is disposed on the reflection side of the first light splitting component 500; the double crystal structure 610, the second dichroic mirror 620, the third focusing lens 630, the second collimating lens 640 and the second pump 650 are coaxially disposed along the transmission path of the first laser; The second dichroic mirror 620 is configured to transmit the second pump light generated by the second pump 650 to the dual crystal structure 610 and reflect the second laser light outputted from the dual crystal structure 610 to the output module 800; The third focusing lens 630 and the second collimating lens 640 are configured to shape the second pump light and then inject it into the dual crystal structure 610 through the second dichroic mirror 620 .

[0055] For example, the second collimating lens 640 and the third focusing lens 630 constitute a 4F optical system.

[0056] For another example, the second dichroic mirror 620 is coated with a film that is highly transparent to the second pump light and a film that is highly reflective to the second laser (1064nm laser). The transmittance of the second dichroic mirror 620 to the second pump light is greater than 98.5%, and the reflectivity to the second laser is greater than 99%.

[0057] For another example, the second pump light is collimated by the second collimating lens 640 , and then focused to the third laser crystal 615 by the third focusing lens 630 , and then matched with the first laser emitted by the first beam splitting component 500 through the second laser crystal 611 .

[0058] Exemplarily, the third focusing lens 630 is used to focus the second pump light collimated by the second collimating lens 640. The diameter of the focused spot is related to the focal length of the third focusing lens 630 and the second collimating lens 640. The spot diameter of the focused spot is set to D4. The focusing spot diameter of the first laser is set to D3. The ratio of the focusing spot D4 of the collimated second pump 650 is also the filling factor. In order to improve the laser amplification efficiency and ensure good beam quality, the filling factor can be set to 0.85~0.95.

[0059] Exemplarily, the dual crystal structure 610 is used to provide a gain medium for laser power amplification of the first laser, and the second pump 650 is used to generate a semiconductor laser to provide pump energy for laser power amplification of the first laser.

[0060] It should be noted that the second pump 650 can use multiple wavelengths such as 808nm, 878nm, etc. Among them, the maximum output power of the second pump 650 is set to 110W, and the fiber core diameter is set to 400μm. In the second pump 650, the 808nm wavelength pump has a lower quantum loss than the 678nm wavelength pump, which can significantly reduce the thermal effect of the laser crystal.

[0061] For example, the first laser crystal 420 may be made of Nd:YVO4 (neodymium-doped yttrium vanadate crystal). 3+The doping concentration is 0.1%-0.5%, in a bonded or non-bonded form. The bonding form includes a single-end bonded crystal (Nd:YVO4-YVO4) or a double-end bonded crystal (YVO4-Nd:YVO4-YVO4). The undoped YVO4 crystal acts as a heat sink, which is beneficial for better heat dissipation of the crystal and reduces the thermal effect of the crystal. The geometric dimensions of the second laser crystal 611 and the third laser crystal 615 can be designed according to the actual amplification power requirements.

[0062] Exemplarily, the first beam splitter component 500 includes a third beam splitter 510, a second photoelectric isolator 520, a fourth focusing lens 530 and a fourth beam splitter 540. The seed laser is amplified by the first amplification module 400 to form a first laser, the first laser is reflected to the second photoelectric isolator 520 through the third 45° beam splitter, the second laser through the second photoelectric isolator 520 is focused by the fourth focusing lens 530, and then reflected by the fourth beam splitter 540 to the second amplification module 600.

[0063] Exemplarily, the focus spot diameter of the fourth focusing lens 530 for the first laser is set to D3, wherein the selection of D3 needs to be comprehensively considered and designed based on the structure of the first amplifying module 400 and the structure of the second amplifying module 600.

[0064] It should be noted that the third beam splitter 510 is set as a third 45° beam splitter, and the third beam splitter 510 is coated with a 1064nm anti-reflection film, and the reflectivity of the first laser is greater than 99%. The second photoelectric isolator 520 is used to isolate the first amplifier module 400 and the second amplifier module 600 to prevent the laser return on the output side of the second photoelectric isolator 520 from damaging the components on the input side of the second photoelectric isolator 520. The fourth beam splitter 540 is set as a fourth 45° beam splitter, and its splitting ratio is set to 1:99, with a transmittance of 1% and a reflectivity of 99% for the 1064nm laser. That is, the fourth beam splitter 540 transmits 1% of the first laser to the second power detection component 130, and reflects 99% of the first laser to the second amplifier module 600.

[0065] Exemplarily, the second power detection component 130 is configured as a second photodetector, and the second photodetector is signal-connected to the electric control component 110 .

[0066] In the embodiment of the present application, the first laser is input to the dual crystal structure 610 via the first beam splitter component 500, the second pump light generated by the second pump 650 is collimated by the second collimating lens 640 and then focused to the dual crystal structure 610 via the third focusing lens 630, the first laser and the second pump light are matched and amplified in the dual crystal structure 610 to form a second laser, and the second laser is then reflected to the fifth beam splitter 701 via the second dichroic mirror 620 to form a reverse pumping structure, which not only improves the structural compactness of the picosecond laser system, but also further improves the amplification efficiency of the laser power.

[0067] In another implementation, the output module 800 includes an adjustable half-wave plate assembly 810, a polarization beam splitter 820, a first window mirror 830, and a second window mirror 840; The laser system further includes a fifth beam splitter 701 and a sixth beam splitter 702; the third power detection component 140 is arranged on the transmission side of the fifth beam splitter 701, the sixth beam splitter 702 is arranged on the reflection side of the fifth beam splitter 701, and the beam quality detection component 170 is arranged on the reflection side of the sixth beam splitter 702; The adjustable half-wave plate assembly 810 is arranged on the transmission side of the sixth light splitting assembly, and the adjustable half-wave plate assembly 810 includes a motor and a second half-wave plate arranged at the rotating end of the motor, and the motor is connected to the electric control assembly 110 by signal, and the electric control assembly 110 is configured to modulate the linear polarization angle of the second laser to form a third laser by controlling the rotation angle of the motor; The polarization beam splitter 820 is disposed at the output side of the third laser, and the polarization beam splitter 820 is configured to split the beam of the third laser into P polarized light and S polarized light; The first window mirror 830 is disposed at the S light path output end of the polarization beam splitter 820 to output S polarized light; The second window mirror 840 is disposed at the P light path output end of the polarization beam splitter 820 to output P polarized light.

[0068] Exemplarily, the output module 800 further includes a seventh beam splitter 850, an eighth beam splitter 860, a ninth beam splitter 870, a fourth power detection component 150, and a fifth power detection component 160; The seventh beam splitter 850 is disposed at the S optical path output end of the polarization beam splitter 820, the fourth power detection component 150 is disposed at the reflection side of the seventh beam splitter 850 to detect the laser power of the S polarized light, and the first window mirror 830 is disposed at the transmission side of the seventh beam splitter 850; The eighth beam splitter 860 is disposed at the P optical path output end of the polarization beam splitter 820, the ninth beam splitter 870 is disposed at the reflection side of the eighth beam splitter 860, the fifth power detection component 160 is disposed at the reflection side of the ninth beam splitter 870 to detect the laser power of the P polarized light, and the second window mirror 840 is disposed at the transmission side of the ninth beam splitter 870; The fourth power detection component 150 and the fifth power detection component 160 are respectively connected to the electric control component 110 for signals.

[0069] It should be noted that the fifth beam splitter 701 and the sixth beam splitter 702 are respectively set as the fifth 45° beam splitter and the sixth 45° beam splitter, and the fifth 45° beam splitter and the sixth 45° beam splitter are both set as beam splitters with a splitting ratio of 99:1. That is, the fifth beam splitter 701 reflects 99% of the second laser to the sixth beam splitter 702, and the fifth beam splitter 701 transmits 1% of the second laser to the third power detection component 140, wherein the third power detection component 140 is set as a third photodetector. The sixth beam splitter 702 reflects 99% of the second laser input by the fifth beam splitter 701 to the output module 800, and outputs 1% of the second laser input by the fifth beam splitter 701 to the beam quality detection component 170.

[0070] It should be further explained that the seventh beam splitter 850 and the ninth beam splitter 870 are both configured as beam splitters with a splitting ratio of 99:1, that is, a transmittance of 99% and a reflectivity of 1%, and the eighth beam splitter 860 is coated with a film that is highly reflective to the third laser (1064nm) laser, and has a reflectivity greater than 99%.

[0071] Exemplarily, the first window mirror 830 and the second window mirror 840 are used to block the influence of the external environment (such as air humidity, dust, etc.) on the laser cavity and precision circuits. The surfaces of the first window mirror 830 and the second window mirror 840 are coated with a high-transmittance film for 1064nm laser, and the transmittance is greater than 99%.

[0072] In a specific implementation, the electric control component 110 receives the output power of the S-polarized light detected by the fourth power detection component 150, and determines whether the output power of the S-polarized light is within a preset range of the S-polarized light power. If the output power of the S-polarized light is not within the preset range of the S-polarized light power, the electric control component 110 controls the motor to rotate and adjust the second half-wave plate.

[0073] Similarly, the electrical control component 110 receives the output power of the P polarized light detected by the fifth power detection component 160, and determines whether the output power of the S polarized light is within the preset range of the P polarized light power. If the output power of the P polarized light is not within the preset range of the P polarized light power, the electrical control component 110 will control the motor to rotate and adjust the second half-wave plate.

[0074] The fourth power detection component 150 and the fifth power detection component 160 are respectively configured as a fourth photodetector and a fifth photodetector.

[0075] In an embodiment of the present application, the second laser is separated into P polarized light and S polarized light by a polarization beam splitter 820, and two polarization components can be obtained at the output end of the laser system at the same time. Furthermore, the embodiment of the present application can achieve an adjustable ratio of the output power of P polarized light and S polarized light by setting the adjustable half-wave plate component 810. That is, through the setting of the present application, P polarized light and S polarized light can be used in parallel to improve the flexibility and efficiency of the system, and by connecting the electric control component 110 to the fifth power detection component 160, the sixth power detection component and the motor for signal connection, it is possible to achieve real-time regulation of the power of P polarized light and S polarized light, realize real-time adjustment of polarized light, and improve the flexibility and stability of the system.

[0076] Figure 3 A method flow of a control method of a picosecond laser system provided in an embodiment of the present application Figure 1 .

[0077] Reference Figure 3 Based on a picosecond laser system, the present application embodiment further provides a control method for the picosecond laser system, the method comprising the following steps: S11: receiving the first power output by the first power detection component 120 .

[0078] The first power detection component 120 is used to detect the first power of the seed laser.

[0079] The electric control component 110 receives the current signal of the seed laser output by the first photodetector 123 , and obtains the output power of the seed laser after amplifying the current signal, that is, the first output power.

[0080] S12: Determine whether the first power is within a first preset power range.

[0081] The electric control component 110 determines whether the first power is within a first preset power range. In specific implementation, the fluctuation setting range of the output power is usually within ±1% of the first preset power value.

[0082] S13: If the first power is within the first preset power range, the first amplification module 400 is turned on to perform a first-stage amplification of the seed laser to form a first laser.

[0083] In a specific implementation, since the electric control component 110 is electrically connected to the picosecond laser system, that is, the electric control component 110 provides power for the operation of the picosecond laser system, that is, the electric control component 110 provides power for the first amplification module 400. When the electric control component 110 determines that the first power is within the first preset power range, the first amplification module 400 will be turned on.

[0084] It should be noted that when the first power is not within the first preset power range, the electric control component 110 directly cuts off the power supply of the picosecond laser system.

[0085] S14: receiving the second power output by the second power detection component 130 .

[0086] The second power detection component 130 is used to detect the second power of the first laser; The electric control component 110 receives the current signal of the first laser output by the second photodetector, and obtains the output power of the first laser after amplifying the current signal, that is, the second power.

[0087] S15: Determine whether the second power is within a second preset power range.

[0088] The electric control component 110 determines whether the second power is within a second preset power range. In specific implementation, the fluctuation setting range of the output power is usually within ±5% of the second preset power.

[0089] S16: Receive a third power and a beam quality parameter, and acquire an optimal temperature value of the dual-crystal series connection assembly according to the third power and the beam quality parameter.

[0090] The third power detection component 140 is used to detect the third power of the second laser, and the beam quality detection component 170 is used to detect the beam quality of the second laser; Wherein, S16 specifically includes the following steps: S16-1: The temperature of the third laser crystal 615 is adjusted to a first temperature setting value using a second temperature control component.

[0091] The electronic control component 110 controls the temperature of the third laser crystal 615 by adjusting the second thermoelectric cooler 618, and adjusts the temperature of the third laser crystal 615 to the first temperature setting value, so that the third laser crystal 615 is in a stable gain state to prevent gain fluctuations from affecting subsequent steps.

[0092] S16-2: Fix the temperature of the third laser crystal 615 to a first temperature setting value, and use a first temperature control component to gradually adjust the temperature of the second laser crystal 611 within the first temperature range according to a first preset step size.

[0093] For example, within the temperature range of 18° C. to 25° C., the first thermoelectric cooler 614 is used to gradually adjust the temperature of the second laser crystal 611 with a step length of 0.01° C.

[0094] S16-3: Receive the first beam quality parameter of the second laser crystal 611 at each temperature value, and obtain the first optimal temperature according to the first beam quality parameter.

[0095] The electric control component 110 receives the first beam quality parameter of the second laser crystal 611 at each temperature value output by the beam quality detection component 170 .

[0096] A plurality of first beam quality parameters are compared to obtain a first optimal temperature corresponding to an optimal first beam quality parameter.

[0097] The temperature control component records the first beam quality parameter of the second laser crystal 611 at each temperature level, each first beam quality parameter corresponds to a first beam quality factor, and each first beam quality factor corresponds to a temperature value. After comparing the values ​​of the first beam quality factors, the temperature control component obtains the minimum value of the first beam quality factor. The temperature value corresponding to the minimum value of the first beam quality factor is the first optimal temperature of the second laser crystal 611. Then, the floating range is set around the first optimal temperature to obtain the first optimal temperature.

[0098] For example, the first optimal temperature is 25° C., and the floating range is set to ±0.03%.

[0099] It should be noted that the higher the beam quality, the smaller the corresponding beam quality factor.

[0100] S16-4: Fix the temperature of the second laser crystal 611 to the first optimal temperature, and use the second temperature control component to gradually adjust the temperature of the third laser crystal 615 within the second temperature range according to the second preset step size.

[0101] On the premise that the temperature of the second laser crystal 611 is locked, the temperature of the third laser crystal 615 is optimized.

[0102] For example, within the temperature range of 18° C. to 25° C., the second thermoelectric cooler 618 is used to gradually adjust the temperature of the third laser crystal 615 with a step size of 0.01° C.

[0103] S16-5: receiving the second beam quality parameter and the third power of the third laser crystal 615 at each temperature level, and obtaining the second optimal temperature according to the second beam quality parameter and the third power.

[0104] The electronic control component 110 records the second beam quality parameter and the third power of the third laser crystal 615 at each temperature level, selects the parameters corresponding to the second beam quality parameters whose second beam quality factor is less than 1.3, and compares the third powers corresponding to the selected second beam quality parameters to obtain the largest third power. The temperature value corresponding to the second beam quality factor less than 1.3 and the largest third power is the second optimal temperature of the third laser crystal 615.

[0105] For example, the second best temperature is 20°C and the floating range is set to ±0.03%.

[0106] The third beam quality factor is data output by the beam quality detection component 170 , and the third power is data output by the third power detection component 140 .

[0107] S17: If the second power is within the second preset power range, turning on the second amplification module 600; Furthermore, if the second power is within the second preset power range, it means that the first amplification module 400 can operate normally. At this time, the electronic control component 110 adjusts the working current of the first pump 460 through the PID control algorithm. For example, the working current of the first pump 460 is adjusted in steps of 0.1A to increase or decrease the output power of the first pump 460 within a smaller range to ensure that the fluctuation range of the second power does not exceed ±2% of the second preset power.

[0108] The second amplifying module 600 includes a temperature control component and a dual crystal series connection component.

[0109] It should be noted that if the second power is not within the second preset power range, the electric control component 110 will cut off the power supply of the laser system.

[0110] Figure 4 for Figure 3 Specific step diagram of S16.

[0111] It should be further explained that, referring to Figure 4 , S16 specifically includes the following steps: S18: Receive the crystal temperature of the dual crystal series assembly output by the temperature control assembly.

[0112] The electric control component 110 receives the crystal temperature of the dual crystal series assembly output by the temperature control component. Since the dual crystal series assembly includes the second laser crystal 611 and the third laser crystal 615, the electric control component 110 receives the crystal temperature of the second laser crystal 611 and the crystal temperature of the third laser crystal 615 respectively.

[0113] S19: Determine whether the crystal temperature is within a preset temperature range.

[0114] S20: If the crystal temperature is within the preset temperature range, the PID control algorithm is started to adjust the crystal temperature to the optimal temperature control range, so as to amplify the first laser within the optimal temperature control range of the dual crystal series component in the second amplification module 600 to form a second laser, and output the target laser after modulation by the output module 800.

[0115] Figure 5 for Figure 3 Specific step diagram of S17, S18 and S19.

[0116] Reference Figure 5 It should be noted that S17, S18, and S19 specifically include the following steps: S18-1: receiving the crystal temperature of the second laser crystal 611 output by the first temperature control component; S19-1: Determine whether the temperature of the second laser crystal 611 is within a first preset temperature range; S20-1: If the temperature of the second laser crystal 611 is within the first preset temperature range, start the PID control algorithm and use the first temperature control component to adjust the temperature of the second laser crystal 611 to a first optimal temperature; S18-2: receiving the crystal temperature of the third laser crystal 615 output by the second temperature control component; S19-2: Determine whether the temperature of the third laser crystal 615 is within a second preset temperature range; S20-2: If the temperature of the third laser crystal 615 is within the first preset temperature range, the PID control algorithm is started, and the temperature of the third laser crystal 615 is adjusted to the second optimal temperature using the second temperature control component, so as to amplify the first laser within the optimal temperature range in the second amplification module 600 to form a second laser, and output the target laser after modulation by the output module 800.

[0117] Taking S20 - 1 as an example, a PID control algorithm is adopted and a first temperature control component is used to adjust the temperature of the second laser crystal 611 to the first optimal temperature. The specific method is explained below.

[0118] The electronic control component 110 at each discrete moment The current temperature of the second laser crystal 611 is collected. .

[0119] Set the target temperature to The temperature error for:

[0120] A positive error indicates that the current temperature is lower than the target value and needs to be heated; a negative error indicates that the temperature is higher than the target value and needs to be cooled.

[0121] In order to avoid excessive integral accumulation (integral saturation) in the traditional position PID and system jitter caused by frequent switching of the current across the first thermoelectric cooler 614, an incremental PID method is used to calculate the change in the control signal. The calculation formula is as follows:

[0122] in, is the proportional gain, responsible for responding to error changes; is the integral gain, which is related to the current cycle error and sampling interval The product of helps eliminate steady-state errors; is the differential gain, which predicts the error change by the second-order difference of the current and previous two sampling errors; is the sampling time interval; and are the temperature errors at the previous moment and the moment before that respectively.

[0123] This calculation method is based only on the current sampled data and the most recent error change, thus naturally avoiding the saturation problem caused by excessive accumulation of the integral term, and making the control output update amplitude smaller when the temperature change is small, which helps to reduce system jitter.

[0124] The control output is calculated by incremental updating:

[0125] in For the The value of the control signal of the cycle corresponds to the reference value for adjusting the driving current of the second thermoelectric cooler 618. In practical applications, the output signal can be further converted to limit the adjustment step size each time (for example, the corresponding temperature change does not exceed 0.01°C) to ensure a smooth and stable temperature control process.

[0126] In a specific implementation, the target temperature of the second laser crystal 611 is The current temperature of the second laser crystal 611 measured by the second temperature control component ; Second; ; PID parameters: , , ; .

[0127] The error is calculated as follows:

[0128] The proportional part is calculated as follows:

[0129] The integral part is calculated as follows:

[0130] The differential part is calculated as follows:

[0131] Calculate the numerator: ,and then:

[0132] The total increment and control signal update are calculated as follows:

[0133]

[0134] That is to say, the electric control component 110 only needs to drive the driving current of the first thermoelectric cooler 614 to increase by 0.1805° C., which provides a basis for adjusting the driving current of the first thermoelectric cooler 614 so that the temperature gradually approaches the target temperature.

[0135] In addition, it should be noted that in S19-2, the third laser crystal 615 is adjusted to the second optimal temperature by the second temperature control component through the PID control algorithm. Please refer to the above method and it will not be repeated here.

[0136] In S17 , the electronic control component 110 adjusts the working current of the first pump 460 through the PID control algorithm, which is also referred to the above method and will not be described in detail here.

[0137] Furthermore, in a specific implementation, the second thermoelectric cooler 618 is provided with an H-bridge circuit, which is composed of four switch components and can realize the forward and reverse switching of the second thermoelectric cooler 618. When is positive, the H-bridge circuit allows current to flow through the second thermoelectric cooler 618 in one direction, thereby achieving cooling; When it is negative, the current flows in the reverse direction to achieve heating. The incremental PID control algorithm outputs a slight current adjustment.

[0138] Of course, in S20 - 2 , the first thermoelectric cooler 614 may also be configured as an H-bridge circuit, and the specific control method is similar to that in S17 , which will not be described in detail herein.

[0139] A control method for a picosecond laser system provided in an embodiment of the present application realizes dynamic power calibration of the whole process of seed source injection, first-stage amplification, and second-stage amplification by setting a power detection component and forming a feedback link with an electric control component, so as to ensure that the seed laser injection of the laser system, the amplification of the seed laser, and the amplification of the first laser until the output of the target laser can be carried out under the preset state of the laser system, and a multi-level protection mechanism is constructed, thereby achieving high stability and high reliability of the laser system. In the first amplification module, by setting the incident path of the seed laser input to the first laser crystal and the exit path of the first laser output to the first laser crystal off-axis, that is, the laser amplification circuit and the central optical axis of the gain medium are arranged off-axis, the spontaneous radiation, parasitic oscillation, and unintentional resonant cavity problems existing in the traditional coaxial structure are effectively suppressed, and the beam spatial mode and overall amplification efficiency are further improved. Furthermore, a dual crystal structure is used in the second amplification module, and the optimal temperature value of the dual crystal series assembly is obtained by monitoring the third power and beam quality parameters, that is, the second laser can have a higher beam quality under the premise of ensuring that the third power is high. After determining the optimal temperature value, the temperature of the laser crystal is closed-loop controlled by the temperature control component, and the refractive index change caused by the thermal lens effect is compensated in real time, so that the dual crystal series assembly amplifies the first laser at the optimal temperature value to obtain a second laser with higher laser power and better beam quality, so that the laser system maintains a stable gain output during continuous operation. In other words, through the configuration of the embodiment of the present application, a control method for a picosecond laser system with a compact structure, high stability, high output power, and good beam quality is provided.

[0140] Figure 6 A method flow of a control method of a picosecond laser system provided in an embodiment of the present application Figure 2 .

[0141] In some other examples, refer to Figure 6 The present application also provides a control method for a picosecond laser system, wherein the control method comprises the following steps: S21: receiving the fourth power output by the fourth power detection component 150.

[0142] The fourth power detection component 150 is used to detect the fourth power of the S-polarized light.

[0143] The temperature control component receives the fourth power of the S polarized light output by the fourth power detection component 150, S22: Determine whether the fourth power is within a fourth power range; S23: if the fourth power is not within the fourth power interval, outputting an adjustment signal to the motor to adjust the polarization angle of the second half-wave plate; S24: receiving the fifth power output by the fifth power detection component 160; wherein the fifth power detection component 160 is used to detect the fifth power of the P polarized light; S25: Determine whether the fifth power is within the fifth power range; S26: If the fifth power is not within the fifth power interval, outputting an adjustment signal to the motor to adjust the polarization angle of the second half-wave plate.

[0144] Figure 7 A method flow of a control method of a picosecond laser system provided in an embodiment of the present application Figure 3 .

[0145] In another implementation, referring to Figure 7 The present application also provides a control method for a picosecond laser system, wherein the control method comprises the following steps: S31: receiving the first power output by the first power detection component 120; S32: Calculating the number of seed laser pulses according to the first power and the comparison relationship between the preset power and the number of pulses; It should be noted that the preset power and pulse number comparison relationship is established based on existing experimental data. For example, in a specific experiment, the experimental device includes a picosecond seed source 210 and a photodetector. Different numbers of pulses are output by adjusting the acousto-optic modulator of the picosecond seed source 210, and the power corresponding to different numbers of pulses is recorded by the photodetector. The corresponding relationship between the number of pulses and the output power is shown in Table 1.

[0146] Table 1 Correspondence between pulse number and output power

[0147] Figure 8 It is the fitting curve diagram of output power and pulse number.

[0148] According to the data measured in Table 1, linear regression fitting is performed, where the fitting curve is shown in Figure 8 .

[0149] Through linear regression fitting, the mathematical relationship between output power and pulse number is as follows:

[0150] Among them, P represents the output power and N represents the number of pulses.

[0151] Reference Figure 8 , Figure 8The data point a1 marked in the figure is the data point with an output power of 10 when the number of pulses is 1; the data point a2 is the data point with an output power of 17.6 when the number of pulses is 2; the data point a3 is the data point with an output power of 23.9 when the number of pulses is 3; the data point a4 is the data point with an output power of 28.9 when the number of pulses is 4; the data point a5 is the data point with an output power of 33.4 when the number of pulses is 5; the data point a2 is the data point with an output power of 33.4 when the number of pulses is 6. The data point a7 is the data point with the corresponding output power of 37.8 when the number of pulses is 7; the data point a8 is the data point with the corresponding output power of 45.2 when the number of pulses is 8; the data point a9 is the data point with the corresponding output power of 49.6 when the number of pulses is 8; the data point a10 is the data point with the corresponding output power of 53.5 when the number of pulses is 10; the data point a15 is the data point with the corresponding output power of 70.1 when the number of pulses is 15.

[0152] Curve A is a curve fitted according to data points a1 to a15, that is, a curve showing the change of output power with the number of pulses.

[0153] S33: If the number of seed laser pulses is not within a preset number range, the picosecond laser system is turned off.

[0154] It should be noted that, in specific implementation, the number of seed laser pulses obtained by calculation may be a decimal. In this case, the number of seed laser pulses needs to be corrected by rounding. If the corrected number of seed laser pulses is not within the preset number range, the picosecond laser system is shut down.

[0155] Of course, if the corrected number of seed laser pulses is within the preset number range, the picosecond laser system can continue to operate.

[0156] In order to verify the actual application effect of a picosecond laser system, a picosecond laser system was built for testing.

[0157] The picosecond seed source 210 uses a picosecond pulse laser with SESAM (Semiconductor Saturable Absorber Mirror) mode-locking technology. The central wavelength of the output pulse is 1064nm, the single pulse energy is 60nJ, and the repetition frequency is 1 MHz.

[0158] The first laser crystal 420 uses a rod-shaped YVO4 / Nd:YVO4 (yttrium vanadate) composite crystal. The size of the first laser crystal 420 is set to 3×3×(1.5+19.5) mm³, where Nd 3+The doping concentration is 0.15%. The first laser crystal 420 is coated with 878 nm and 1064 nm anti-reflection films at both ends, and the transmittance is greater than 99%.

[0159] In a specific implementation, the first laser crystal 420 is wrapped in a 0.15 mm thick indium foil. The first laser crystal 420 is disposed between two third copper heat sinks, and a third thermoelectric cooler is disposed on one side of one of the third copper heat sinks. The temperature of the third copper heat sink is controlled at 18°C ​​by the third thermoelectric cooler. The first laser crystal 420 is pumped by a first pump 460 having a wavelength of 878 nm, a core diameter of 200 μm, and an output power of 60 W. The first pump light of 878 nm is sequentially adjusted through the first collimating lens 450 and the first focusing lens 410 to ensure that when incident on the end face of the first laser crystal, the spot diameter is 200 μm and the filling factor reaches 0.75.

[0160] The second laser crystal 611 and the third laser crystal 615 are both made of rod-shaped YVO4 / Nd:YVO4 (yttrium vanadate) composite crystals, with a doping concentration of 0.15at% and a size of 3×3×(1.5+19.5) mm³. The second laser crystal 611 and the third laser crystal 615 are both wrapped with indium foil and supported by the first copper heat sink and the second copper heat sink, respectively, and the temperature is controlled by the first thermoelectric cooler 614 and the second thermoelectric cooler 618, respectively. Both ends of the second laser crystal 611 and the third laser crystal 615 are coated with 878 nm and 1064 nm anti-reflection films, and the transmittance is greater than 99%.

[0161] In order to obtain a higher power laser output, the output power of the second pump 650 is set to 110 W, the core diameter is 400 μm, and the pump wavelength of the second pump 650 is 878 nm. The 878 nm second pump light is adjusted to a spot size through the second collimating lens 640 and the third focusing lens 630 to ensure a filling factor of 0.85.

[0162] By adjusting the first half-wave plate 230 and the polarization beam splitter 820 , the laser polarization state is adjusted to P polarized light to ensure that only P polarized picosecond laser is output. The 1064 nm laser is totally reflected by the seventh beam splitter and output through the second window mirror 840 .

[0163] Fig. 9 This is the data diagram of seed laser output wavelength.

[0164] The central wavelength of the laser is 1064.17 nm as tested by spectrum analyzer. Fig. 9 , Fig. 9 Curve B is the normalized intensity versus wavelength curve. Fig. 9 It can be seen that the central wavelength of the test laser is 1064.17nm. It should be noted that Fig. 9 The unit au of normalized intensity is an arbitrary unit without standardization.

[0165] Fig.10 This is a graph showing the seed laser output power and stability data.

[0166] The average power at 1064 nm was 42.01 W when tested with a laser power meter. The power stability was 1.25% rms when the power was continuously recorded for 4 hours at a step of 0.3 s / single. Fig.10 Curve C is a graph showing the variation of output power over time, and the power stability calculated by the laser power energy meter is less than 1.25% rms.

[0167] Fig.11 This is the data diagram of seed laser output pulse width.

[0168] The picosecond pulse width was 10.4 ps using an autocorrelator test. Fig.11 ,exist Fig.11 In the figure, curve D is the fitting curve of the normalized intensity over time, and curve E is the normalized intensity measured by the autocorrelation instrument over time. Fig.11 It can be seen that the width of the picosecond pulse is 10.4ps. It should be noted that Fig.11 The unit au of normalized intensity is an arbitrary unit without standardization.

[0169] Fig.12 is a beam quality data diagram of the second laser in the x direction; Fig.13 This is a graph showing the beam quality data of the second laser in the y direction.

[0170] The beam quality of the 1064 nm laser is measured by a beam quality analyzer. x 2 =1.112,M y 2 =1.223. Reference Fig.12 and Fig.13 , Curve M refers to the curve of the change of the spot radius of the second laser with the spot position in the x direction. Curve N refers to the curve of the change of the spot radius of the second laser with the spot position in the y direction. Among them, the x direction and the y direction represent the measurement results of the two orthogonal directions of the light beam, Z represents the spatial position along the propagation direction of the second laser, and R represents the spot radius measured at the corresponding Z position.

[0171] Further, in Fig.12 and Fig.13 in Fig.12 In the figure, M² is 1.112, which means that in the x direction, the beam quality factor of the second laser is 1.112, which is M x 2 =1.112.

[0172] exist Fig.13 In the figure, M² is 1.223, which means that in the y direction, the beam quality factor of the second laser is 1.223, which is M y 2 =1.223.

[0173] Fig.14 This is the data diagram of 5 pulses of the target laser; Fig.15 This is a graph of 10 pulses of target laser data.

[0174] Use a digital storage oscilloscope to test the laser sequence in burst mode. Fig.14 In the figure, curve P is a graph showing the change of the output voltage of the target laser over time. From curve P, it can be seen that the target laser outputs 5 pulses. Fig.15 This is a curve diagram of the change of the output voltage of the target laser over time. It can be seen from the curve Q that the target laser outputs 10 pulses.

[0175] It is easy to understand that those skilled in the art can combine, split, reorganize, etc. the embodiments of the present application to obtain other embodiments based on the several embodiments provided in the present application, and these embodiments do not exceed the protection scope of the present application.

[0176] The above specific implementation methods further explain in detail the purpose, technical solutions and beneficial effects of the embodiments of the present application. It should be understood that the above are only specific implementation methods of the embodiments of the present application and are not used to limit the protection scope of the embodiments of the present application. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solutions of the embodiments of the present application should be included in the protection scope of the embodiments of the present application.

Claims

1. A control method for a picosecond laser system, characterized in that: The following steps are involved: Receiving a first power output by a first power detection component; wherein the first power detection component is used to detect the first power of the seed laser; Determining whether the first power is within a first preset power range; If the first power is within the first preset power range, the first amplification module is turned on to amplify the seed laser to form a first laser, and in the first amplification module, the incident path of the seed laser and the first laser output path are off-axis; Receiving a second power output by a second power detection component; wherein the second power detection component is used to detect the second power of the first laser; Determining whether the second power is within a second preset power range; If the second power is within the second preset power range, the second amplification module is turned on to amplify the first laser to form a second laser; wherein the second amplification module includes a temperature control component and a dual crystal series connection component; receiving a third power and a beam quality parameter, and acquiring an optimal temperature value of the dual-crystal series-connected component according to the third power and the beam quality parameter; wherein the third power detection component is used to detect the third power of the second laser, and the beam quality detection component is used to detect the beam quality of the second laser; Receiving the crystal temperature of the dual crystal series connection component output by the temperature control component; Determining whether the crystal temperature is within a preset temperature range; If the crystal temperature is within the preset temperature range, the PID control algorithm is started to adjust the crystal temperature to the optimal temperature value, so as to amplify the first laser to form a second laser at the optimal temperature value of the dual crystal series component, and output the target laser after modulation by the output module.

2. The control method of a picosecond laser system according to claim 1, characterized in that: Determining whether the crystal temperature is within a preset temperature range; If the crystal temperature is within the preset temperature range, the PID control algorithm is started to adjust the crystal temperature to an optimal temperature value, so that the first laser is amplified at the optimal temperature value in the second amplification module to form a second laser, and the target laser is output after being modulated by the output module; specifically, the following steps are included: receiving the crystal temperature of the second laser crystal output by the first temperature control component; Determining whether the temperature of the second laser crystal is within a first preset temperature range; If the temperature of the second laser crystal is within the first preset temperature range, the PID control algorithm is started, and the temperature of the second laser crystal is adjusted to a first optimal temperature using the first temperature control component; receiving the crystal temperature of the third laser crystal output by the second temperature control component; Determining whether the temperature of the third laser crystal is within a second preset temperature range; If the temperature of the third laser crystal is within the first preset temperature range, the PID control algorithm is started, and the temperature of the third laser crystal is adjusted to a second optimal temperature using a second temperature control component, so as to amplify the first laser within the optimal temperature range of the second amplification module to form a second laser, and output the target laser after modulation by the output module.

3. The control method of a picosecond laser system according to claim 2, characterized in that: The step of receiving the third power and the beam quality parameter, and obtaining the optimal temperature value of the dual crystal series connection component according to the third power and the beam quality parameter specifically includes: The temperature of the third laser crystal is adjusted to a first temperature setting value by using a second temperature control component; The temperature of the third laser crystal is fixed to a first temperature setting value, and the temperature of the second laser crystal is adjusted step by step within the first temperature range according to a first preset step length using a first temperature control component; receiving a first beam quality parameter of the second laser crystal at each temperature value, and acquiring a first optimal temperature according to the first beam quality parameter; The temperature of the second laser crystal is fixed to a first optimal temperature, and the temperature of the third laser crystal is adjusted step by step within a second temperature range according to a second preset step length using a second temperature control component; A second beam quality parameter and a third power of the third laser crystal at each temperature value are received, and a second optimal temperature is obtained according to the second beam quality parameter and the third power.

4. A control method for a picosecond laser system according to any one of claims 1 to 3, characterized in that: The control method further comprises: Receiving a fourth power output by a fourth power detection component; wherein the fourth power detection component is used to detect a fourth power of S-polarized light; Determining whether the fourth power is within a fourth power interval; If the fourth power is not within the fourth power interval, outputting an adjustment signal to the motor to adjust the polarization angle of the second half-wave plate; receiving a fifth power output by a fifth power detection component; wherein the fifth power detection component is used to detect the fifth power of the P-polarized light; determining whether the fifth power is within a fifth power interval; If the fifth power is not within the fifth power interval, an adjustment signal is output to the motor to adjust the polarization angle of the second half-wave plate.

5. A control method for a picosecond laser system according to any one of claims 1 to 3, characterized in that: The control method further comprises: Receiving a first power output by the first power detection component; Calculating the number of seed laser pulses using the first power according to a comparison relationship between a preset power and the number of pulses; Determine whether the number of seed laser pulses is within a preset number range; If the number of seed laser pulses is not within a preset number range, the picosecond laser system is turned off.

6. A picosecond laser system, characterized in that: The picosecond laser system adopts the control method of the picosecond laser system according to any one of claims 1 to 5, and the picosecond laser system comprises: a control module, a seed source module, a first amplification module, a second amplification module and an output module; The control module includes an electric control component, a power detection component for detecting laser power, and a beam quality detection component for detecting beam quality; the electric control component is signal-connected with the power detection component and the beam quality detection component, respectively, and the electric control component is used to provide power for the laser system; wherein the power detection component includes a first power detection component, a second power detection component, and a third power detection component; The seed source module is used to generate a seed laser; the first amplification module and the first power detection component are both arranged downstream of the optical path of the seed source module, and the first power detection component is used to detect the first power of the seed laser; The first amplifying module is configured to amplify the seed laser to form a first laser; wherein, in the first amplifying module, the incident path of the seed laser and the first laser emission path are arranged off-axis, and the incident direction of the seed laser and the direction in which the first pump light is emitted by the first amplifying module are arranged relative to each other; The second power detection component and the second amplification module are both arranged downstream of the optical path of the first amplification module, and the second power detection module is used to detect the second power of the first laser; The second amplification module includes a dual crystal structure, the dual crystal structure includes a dual crystal series component and a temperature control component for adjusting the temperature of the dual crystal series component, and the electric control component and the temperature control component are signal-connected; the second amplification module is configured to amplify the first laser in the dual crystal series component to form the second laser; wherein the incident direction of the first laser input to the dual crystal series component and the direction of the second pump light emitted by the second amplification module are arranged relative to each other; The third power detection component, the beam quality detection component and the output module are all arranged downstream of the optical path of the second amplifying module, the third power detection component is used to detect the third power of the second laser, and the beam quality detection component is used to detect the beam quality of the second laser, so that the electric control component obtains the optimal temperature value of the dual-crystal series component according to the third power and the beam quality parameter, and enables the dual-crystal series component to amplify the first laser to form the second laser at the optimal temperature value; The output module is configured to modulate the second laser and then output a target laser.

7. A picosecond laser system according to claim 6, characterized in that: The double-crystal series connection component includes a second laser crystal and a third laser crystal, and the temperature control component includes a first temperature control component and a second temperature control component; The first temperature control component is configured to adjust the temperature of the second laser crystal, and the second temperature control component is configured to adjust the temperature of the third laser crystal.

8. A picosecond laser system according to claim 7, characterized in that: The first temperature control component includes a first heat sink, a first thermoelectric cooler, and a first temperature sensor; The second laser crystal is arranged between two of the first heat sinks, the two first heat sinks are used to support the second laser crystal, the first thermoelectric cooler is arranged on a surface of one of the first heat sinks, the first thermoelectric cooler is configured to adjust the temperature of the first heat sink by current to adjust the temperature of the first laser crystal; the first temperature sensor is arranged on the first heat sink, the first thermoelectric cooler and the first temperature sensor are respectively connected to the electronic control component by signal; The second temperature control assembly includes a second heat sink, a second thermoelectric cooler and a second temperature sensor; The third laser crystal is arranged between two of the second heat sinks, and the two second heat sinks are used to support the third laser crystal. The second thermoelectric cooler is arranged on the surface of one of the second heat sinks, and the second thermoelectric cooler is configured to adjust the temperature of the second heat sink by current to adjust the temperature of the third laser crystal; the second temperature sensor is arranged on the second heat sink, and the second thermoelectric cooler and the second temperature sensor are respectively connected to the electronic control component signal.

9. A picosecond laser system according to claim 8, characterized in that: The dual crystal structure also includes a liquid cooling radiator; The first thermoelectric cooler and the second thermoelectric cooler are arranged in parallel, and the liquid-cooled radiator is arranged on the same side of the first thermoelectric cooler and the second thermoelectric cooler. The liquid-cooled radiator is configured to dissipate heat for the first thermoelectric cooler and the second thermoelectric cooler, and the liquid-cooled radiator is signal-connected to the electronic control component.

10. A picosecond laser system according to any one of claims 6 to 9, characterized in that: The first amplification module includes a first focusing lens, a first laser crystal, a first dichroic mirror, a second focusing lens, a first collimating lens and a first pump which are coaxially arranged along the transmission path of the seed laser; The picosecond laser system comprises a first beam splitter, and the first power detection component is arranged on the transmission side of the first beam splitter; The first focusing lens is arranged on the reflection side of the first beam splitter, and the first focusing lens is configured to input the seed laser into the first laser crystal through a first path, and receive the first laser output by the first laser crystal through a second path, wherein the first path and the second path are respectively arranged on both sides of the first focusing lens; The first dichroic mirror is configured to transmit the first pump light generated by the first pump to the first laser crystal, and reflect the first laser outputted from the first laser crystal along the second path to the first focusing lens; wherein the first pump light and the seed laser are pumped in the first laser crystal to form the first laser; The second focusing lens and the first collimating lens are configured to shape the first pump light and then inject it into the first laser crystal through the first dichroic mirror.

11. The picosecond laser system according to claim 6, characterized in that: The second amplification module also includes a second dichroic mirror, a third focusing lens, a second collimating lens, and a second pump; The picosecond laser system further comprises a first light splitting component, and the second power detection component is arranged on the transmission side of the first light splitting component; The double crystal structure is arranged on the reflection side of the first light splitting component; the double crystal structure, the second dichroic mirror, the third focusing lens, the second collimating lens and the second pump are coaxially arranged along the transmission path of the first laser; The second dichroic mirror is configured to transmit the second pump light generated by the second pump to the dual crystal structure, and reflect the second laser light output from the dual crystal structure to the output module; The third focusing lens and the second collimating lens are configured to shape the second pump light and then inject it into the double crystal structure through the second dichroic mirror.

12. A picosecond laser system according to any one of claims 6 to 9, characterized in that: The output module includes an adjustable half-wave plate component, a polarization beam splitter, a first window mirror, and a second window mirror; The laser system further comprises a fifth beam splitter and a sixth beam splitter; a third power detection component is arranged on the transmission side of the fifth beam splitter, the sixth beam splitter is arranged on the reflection side of the fifth beam splitter, and a beam quality detection component is arranged on the reflection side of the sixth beam splitter; The adjustable half-wave plate component is arranged on the transmission side of the sixth light splitting component, the adjustable half-wave plate component comprises a motor and a second half-wave plate arranged at the rotating end of the motor, the motor is signal-connected to the electric control component, and the electric control component is configured to modulate the linear polarization angle of the second laser to form a third laser by controlling the rotation angle of the motor; The polarization beam splitter is disposed at the output side of the third laser, and the polarization beam splitter is configured to split the beam of the third laser into P polarized light and S polarized light; The first window mirror is arranged at the S light path output end of the polarization beam splitter to output S polarized light; The second window mirror is arranged at the P light path output end of the polarization beam splitter to output P polarized light.

13. A picosecond laser system according to claim 12, characterized in that: The output module also includes a seventh beam splitter, an eighth beam splitter, a ninth beam splitter, a fourth power detection component and a fifth power detection component; The seventh beam splitter is arranged at the S optical path output end of the polarization beam splitter, the fourth power detection component is arranged at the reflection side of the seventh beam splitter to detect the laser power of the S polarized light, and the first window mirror is arranged at the transmission side of the seventh beam splitter; The eighth beam splitter is arranged at the P optical path output end of the polarization beam splitter, the ninth beam splitter is arranged at the reflection side of the eighth beam splitter, the fifth power detection component is arranged at the reflection side of the ninth beam splitter to detect the laser power of the P polarized light, and the second window mirror is arranged at the transmission side of the ninth beam splitter; The fourth power detection component and the fifth power detection component are respectively connected to the electric control component by signal.

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