Wide-tuning large-energy high-beam-quality optical parametric oscillation amplifier

Abstract

The invention discloses an optical parametric oscillation amplifier with wide tuning, large energy and high light beam quality. The optical parametric oscillation amplifier comprises a 1064nm pumping source, a light beam regulating and shaping module, an optical parametric oscillator and an optical parametric amplifier. The regulation and shaping module realizes independent and accurate regulation of total energy of pump light and splitting ratios of two paths leading to an oscillator and an amplifier through combination of at least two sets of half-wave plates and a polarization beam splitter; the optical parametric oscillator comprises two nonlinear crystals which are placed in a plane-plane resonant cavity in a walk-off compensation mode and are used for generating tunable seed light; and the optical parameter amplifier receives the seed light and the other path of pump light, and amplifies the seed light by using two amplification crystals placed in a walk-off compensation mode. Through the specific structure, the problem that wide tuning, large energy and high beam quality are difficult to consider at the same time is solved, high-precision continuous tuning can be achieved in the human eye safe wave band of 1535-1578 nm, large-energy and high-beam-quality laser output is obtained, and the laser is suitable for the fields of laser remote sensing, laser radar and the like.

Description

Technical Field

[0001] This invention relates to the field of optical parametric oscillator amplifier technology, and in particular to an optical parametric oscillator amplifier with wide tuning range, high energy, and high beam quality. Background Technology

[0002] An optical parametric oscillator (OPO) is a laser device based on nonlinear optical effects. It utilizes frequency conversion in a nonlinear crystal to convert the input pump light into two different wavelengths—a signal light and an idler light. Compared to conventional lasers, OPOs can also achieve wavelength tuning by adjusting the nonlinear matching conditions of the crystal, rather than outputting only a single wavelength of laser light. Currently, lasers based on optical parametric oscillators are widely used in spectroscopy, military countermeasures, laser remote sensing, and lidar. Balancing wide tuning range, high energy, and high beam quality in the design of optical parametric oscillators has always been a challenge.

[0003] Patent document 1 (publication number: CN 110556699 B) discloses a high-energy, high-beam-quality tunable optical parametric oscillator pumped by a nanosecond laser. This device is a three-mirror ring OPO pumped by a 1064nm laser, utilizing the nonlinear conversion of a KTP crystal to achieve a high beam-quality output of 10.6mJ of mid-infrared light at 2.6µm. The crystal rotation is controlled by a stepper motor, and a pentagonal prism is used to propagate the generated signal light and idler light along fixed optical paths. However, it does not specify the achievable tuning range or wavelength tuning accuracy, and the stepper motor-controlled rotation exhibits poor stability. Under high beam-quality requirements, the signal light pulse energy generated by the OPO alone is relatively low.

[0004] Reference 2 (Nanosecond high-pulse energy 1.57 μm KTA optical parametric amplifier with time delay. Chinese Optics Letters, 2015, 13(11): 111402) reports a nanosecond high-pulse energy 1.57µm KTA optical parametric amplifier. This device employs an OPO + two-stage optical parametric amplifier (OPA) amplification configuration. By introducing an additional time delay between the pump pulse and the signal pulse, it ultimately achieves a laser output of 98mJ at a wavelength of 1572nm, with a beam quality M... 2 The value is 5.6. However, the wavelength tuning process is not involved; optimization is only performed for a single wavelength.

[0005] Reference 3 (High energy mid-infrared laser pulse output from a BaGa4Se7 crystal-based optical parametric oscillator. Optics Letters, 2020, 45(16):4595-4598) reports a high-energy mid-infrared laser pulse output based on a BGSe crystal. The device is a 1064nm-pumped BGSe crystal-based OPO mounted on a servo-controlled oven mounted on a high-precision rotating stage. Wavelength output of 1439nm-1576nm was achieved by tuning the angle from 53.9° to 57.1°, but the tuning rotation precision was not specified. Wavelength output of 1511nm-1476nm was achieved by tuning the temperature from 26℃ to 100℃, but the angle tuning precision was not specified. Although the temperature can be relatively stable and respond quickly through servo control, the 26℃-100℃ condition is quite demanding. Ultimately, a maximum energy output of 21.5 mJ was achieved at a wavelength of 3816 nm, but the beam quality was very poor. 2 ≈68.

[0006] Based on the above analysis, we can see that there are few reports on laser generation schemes with wide tuning range, high energy and high beam quality. Schemes that can achieve wide tuning range rarely mention tuning accuracy. Using rotary tables and stepper motors will have disadvantages such as poor stability and slow response speed. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of existing technologies in simultaneously achieving wide tuning range, large output energy, and high beam quality. It provides a compact, precisely adjustable, and stable wide-tunable high-energy, high-beam-quality optical parametric oscillator amplifier. It utilizes the minute displacement generated by the piezoelectric ceramic during operation to precisely adjust the crystal rotation angle. By adopting an OPO-OPA structure, it can maintain good beam quality at high energies and achieve wavelength tuning over a wide range.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A wide-tunability, high-energy, high-beam-quality optical parametric oscillator amplifier (OPA) comprises four parts: a 1064nm pump source, a beam modulation and shaping module, an OPA, and an OPA amplifier. The pump source provides pump light for the entire system. The modulation and shaping module is used for energy distribution, shaping, and polarization control of the pump light. A portion of the distributed pump light is used to pump the OPA to generate a tunable seed signal light. The remaining pump light is provided to the OPA amplifier, which receives the seed signal light and uses the remaining pump light to amplify its power. The 1064nm pump source includes a 1064nm seed source, an optical fiber amplification module, and a solid-state amplification module arranged in sequence. The laser output from the seed source is amplified by the optical fiber amplification module and the solid-state amplification module in sequence, and finally outputs a near-square pump spot with a single pulse energy of hundreds of millijoules at a repetition frequency of 100 Hz.

[0009] The beam control and shaping module includes a first half-wave plate, a first polarizing beam splitter, a second half-wave plate, a first beam shrinker, a second polarizing beam splitter, a third half-wave plate, and a first 45° reflector arranged sequentially. This module is used to comprehensively process the pump light from the 1064nm pump source: First, the total input energy is controlled by the first half-wave plate and the first polarizing beam splitter; then, the pump light is split and its ratio is adjusted by the second half-wave plate and the second polarizing beam splitter, thereby distributing the pump light into two beams with independently controllable energy ratios; one beam leading to the optical parametric oscillator is sequentially shaped by the first beam shrinker, its polarization state is adjusted by the third half-wave plate, and finally it is turned and output by the first 45° reflector.

[0010] The optical parametric oscillator includes a first cavity mirror, a first oscillating crystal, a second oscillating crystal, a second cavity mirror, a first multi-wavelength reflecting dichroic mirror, and a second multi-wavelength reflecting dichroic mirror arranged sequentially. The first and second cavity mirrors form a flat resonant cavity. The first and second oscillating crystals are placed within the resonant cavity with walk-off compensation. This module utilizes the received pump light to generate a tunable seed signal light within the resonant cavity through nonlinear frequency conversion of the crystals. The signal light is then separated and output through the first and second multi-wavelength reflecting dichroic mirrors.

[0011] The optical parametric amplifier includes a first delay plate, a second delay plate, a 0° reflector, a second beam shrinker, a second 45° reflector, a beam combiner, a first amplifying crystal, a second amplifying crystal, and a multi-wavelength dichroic mirror arranged sequentially. This module is used to amplify the power of the seed signal light from the optical parametric oscillator: the pump light it receives passes through the first delay plate, the second delay plate, the 0° reflector, the second beam shrinker, and the second 45° reflector in sequence for optical path delay, reversal, and spot matching, and then reaches the beam combiner to spatially combine with the seed signal light; the beam-combined light is injected into the first and second amplifying crystals, which are placed in a walk-off compensation manner to achieve nonlinear amplification, and the amplified laser is finally separated and output by the multi-wavelength dichroic mirror.

[0012] Furthermore, to ensure beam matching and prevent optical damage, both the first and second beam-shrinking mirrors are Galilean telescope structures, with the first beam-shrinking mirror positioned after the second half-wave plate and before the second polarizing beam splitter. This arrangement ensures that the high-energy pump light undergoes polarization modulation before the beam is shrunken to form a high-power-density beam, thereby preventing the high-power-density beam from damaging the second half-wave plate.

[0013] Furthermore, in order to reduce the absorption of idler light during nonlinear frequency conversion, thereby suppressing the thermal lensing effect and improving beam quality, the first and second oscillating crystals in the optical parametric oscillator, as well as the first and second amplifying crystals in the optical parametric amplifier, are all KTA (KTiOAsO4) crystals, rather than the commonly used KTP crystals.

[0014] Furthermore, in order to achieve wide-range wavelength tuning with a small amount of mechanical adjustment, the first and second oscillating crystals used in the optical parametric oscillator are selected with their cutting angles in the fast tuning region with a large slope in the KTA crystal tuning curve under 1064nm pump.

[0015] Furthermore, to construct a resonant cavity with a high damage threshold and functional separation, the first cavity mirror in the flat resonant cavity of the optical parametric oscillator is made of JGS3 material, which is highly reflective of the signal light and highly transparent of the pump light and idler light; the second cavity mirror is made of CaF2 material, serving as a partially transmitted output coupling mirror. This design gives the first cavity mirror, which bears the main pump power, higher damage resistance, thereby ensuring the stable operation of the resonant cavity under high power.

[0016] Furthermore, to improve the long-term operational stability of the system under high power, damage-resistant optimization designs were implemented for key optical components. Specifically, considering the relatively low energy of the signal light output from the optical parametric oscillator, the first and second multi-wavelength reflection dichroic mirrors were made of CaF2 material. Their film system was designed to provide high transmission for 1064nm pump light and 3270-3504nm idler light, and high reflection for 1528-1577nm signal light, which already meets the usage requirements. In the optical parametric amplifier, since it needs to process amplified high-energy laser light, the multi-wavelength reflection dichroic mirrors were preferably made of JGS3 material with a higher laser damage threshold and coated with corresponding functional films. This material ensures efficient processing of 3μm idler light while significantly improving the long-term operational stability of the device under high power.

[0017] Furthermore, to achieve precise and adjustable optical path delay, the first delay plate and the second delay plate in the optical parametric amplifier are placed parallel to each other, and the pump beam undergoes multiple round-trip reflections between them. The delay amount is continuously adjusted by adjusting the distance between the two plates or the number of round-trips of the beam.

[0018] Furthermore, this invention achieves coordinated wavelength tuning of the optical parametric oscillator and the optical parametric amplifier through a wavelength tuning synchronization control system. The system includes a central controller and multiple piezoelectric ceramic angle adjustment execution units. Each execution unit is mechanically connected to the first oscillating crystal, the second oscillating crystal, the first amplifying crystal, and the second amplifying crystal, and includes a flexible guiding mechanism that converts the linear displacement of the piezoelectric ceramic into crystal rotation angle. This flexible guiding mechanism is used to isolate thermal deformation stress from the crystal heat sink. The central controller is communicatively connected to all execution units and can synchronously generate drive commands based on a single target wavelength input, causing the crystals in the optical parametric oscillator and the optical parametric amplifier to deflect collaboratively. This automatically maintains phase matching between the output signal light of the optical parametric amplifier and the output signal light of the optical parametric oscillator while changing the output wavelength.

[0019] By cascading the aforementioned optical parametric oscillator (OPO) and optical parametric amplifier (OPA), and integrating the wide tuning, precise ratio, high stability, and high precision design, this invention successfully achieves a unified output laser that is tunable over a wide range (1535 nm-1578 nm), has high single-pulse energy (>34 mJ), and high beam quality (M²<2.5).

[0020] Compared to existing technologies, the wide-tuning, high-energy, and high-beam-quality optical parametric oscillator provided by this invention achieves the following outstanding beneficial effects through the synergistic effect of the above-mentioned technical solutions and improved design: This invention realizes a wide-tunable, high-energy, and high-beam-quality optical parametric oscillator amplifier, which balances wide tuning range, high energy, and high beam quality. Specifically, the output laser can be continuously tuned within the eye-safe wavelength range of 1535 nm to 1578 nm. Through a wavelength tuning synchronization control system, the tuning accuracy reaches 0.4 nm, and one-button operation is available for convenient operation. A pulse energy output of greater than 34 mJ is achieved at a wavelength of 1556 nm, while maintaining excellent beam quality with an M² greater than 2.5. The system exhibits high overall stability, and all key adjustments (energy ratio and wavelength) can be achieved electronically, making operation extremely simple.

[0021] The beam quality assurance of this invention stems from a two-stage collaborative mechanism: First, through the aforementioned precise energy matching system, the pump energy of the optical parametric oscillator (OPO) is optimized to a low level, thereby preferentially generating high-quality seed light with a pure mode; second, all nonlinear crystals in the OPO and optical parametric amplifier are strictly placed with walk-off compensation, fundamentally suppressing beam walk-off and wavefront distortion during the nonlinear conversion process. The synergy of these two mechanisms ensures the perfect preservation of beam characteristics during energy amplification.

[0022] To address the core challenges of high-power lasers, multiple damage-resistant designs were implemented: the first cavity mirror, which bears the main pump power, and the multi-wavelength reflection dichroic mirrors in critical positions are both made of JGS3 material with a high damage threshold; simultaneously, an optimized layout, placing the first beam-shrinking mirror behind the second half-wave plate, prevents damage to sensitive components from the high-power-density light spot. Furthermore, the actuator of the wavelength tuning synchronization control system employs a thermal stress isolation design, further ensuring the reliability of the precision tuning components under long-term high-power operation. These designs significantly improve the system's reliability and lifespan.

[0023] The laser generated by this invention is located in the 1.5 μm band (1535-1578 nm), which is within the eye-safe band. Through the above-mentioned system-level innovation, it is the first time that wide tuning, high energy, high beam quality and high stability are organically unified in a single device, which has important application value in the fields of laser remote sensing, lidar and military. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall optical path of a wide-tuning, high-energy, high-beam-quality optical parametric oscillator amplifier. Figure 2 This is a characterization diagram of the output beam quality at a wavelength of 1.55µm according to an embodiment of the present invention.

[0025] Figure reference numerals: 1-1064nm pump source, 101-1064nm seed source, 102-fiber amplification module, 103-solid-state amplification module, 2-beam control and shaping module, 201-first half-wave plate, 202-first polarization beam splitter, 203-second half-wave plate, 204-first beam shrinker, 205-second polarization beam splitter, 206-third half-wave plate, 207-first 45° reflector, 3-optical parametric oscillator, 301-first cavity mirror, 30 2-First oscillating crystal, 303-Second oscillating crystal, 304-Second cavity mirror, 305-First multi-wavelength dichroic mirror, 306-Second multi-wavelength dichroic mirror, 4-Optical parametric amplifier, 401-First delay plate, 402-Second delay plate, 403-0° reflector, 404-Second beam shrinker, 405-Second 45° reflector, 406-Beam combiner, 407-First magnifying crystal, 408-Second magnifying crystal, 409-Multi-wavelength dichroic mirror Detailed Implementation The present invention will now be described more precisely, more in detail, and more completely with reference to the accompanying drawings of the embodiments of the present invention. All other embodiments made by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0026] The following is in conjunction with the appendix Figure 1 The present invention will be described in detail below: The 1064nm pump source 1 amplifies the energy output from the 1064nm seed source 101 through the fiber amplification module 102 and the solid-state amplification module 103 in sequence to obtain pump light with a single pulse energy of 240mJ at a repetition frequency of 100 Hz, and the light spot is a near square of about 3.1 mm × 3.0 mm.

[0027] The pump light enters the beam control and shaping module 2. First, it is incident on the subsequent optical path by the first half-wave plate 201 and the first polarization beam splitter (PBS) 202, so as to achieve precise control of the pump energy. Then, the pump light is split and matched by the second half-wave plate 203 and the second polarization beam splitter (PBS) 205. Through the combination of these two sets of half-wave plates and polarization beam splitters, the pump energy entering the optical parametric oscillator 3 and the optical parametric amplifier 4 can be independently and precisely adjusted. One of the pump beams leading to the optical parametric oscillator 3 requires further processing: the beam is shaped by a first beam-shrinking mirror 204, which is a Galilean telescope with a magnification of 1.45X, reducing the beam size from approximately 3.1 mm × 3.0 mm to a near-square size of approximately 2.5 mm × 2.4 mm to match the input requirements of the optical parametric oscillator 3. Here, it is placed after the second half-wave plate 203 to avoid damage to the optical components caused by the high-energy-density beam after beam shrinkage; its polarization state is adjusted back to s-light by a third half-wave plate 206 to meet the phase-matching conditions of the KTA crystal; finally, it is turned by a first 45° reflector 207, which has a reflectivity of over 99% for 1064nm laser (HR > 99% @ 1064nm) to efficiently inject the pump beam into the optical parametric oscillator 3.

[0028] After the pump light enters the optical parametric oscillator (OPO) 3, it undergoes nonlinear frequency conversion sequentially through the first cavity mirror 301, the first KTA crystal 302, and the second oscillating crystal 303. The pump energy pumped into this part is approximately 90 mJ, and the spot size is approximately 2.5 mm × 2.4 mm. The first KTA crystal 302 and the second oscillating crystal 303 are placed in a walk-off compensation manner and are temperature-controlled at 28°C by a thermoelectric cooler (TEC). They form a flat resonant cavity with the first cavity mirror 301 and the second cavity mirror 304. The first cavity mirror 301 is made of JGS3 material, and its film system is specially designed for high-power operation, exhibiting high reflectivity (HR>99.5%) for 1528-1577 nm signal light, high transmittance (HT>95%) for 1064 nm pump light, and high transmittance (HT>95%) for 3270-3504 nm signal light. High transmittance of idler light (HT>80%), this material and film system combination has a high damage threshold to withstand the main pump energy; the second cavity mirror 304 is made of CaF2 material, the film system is highly transmittance of 1064 nm and 3270-3504 nm, and partially transmittance of 1528-1577 nm signal light (T≈50%), used for output coupling. Although its damage threshold is slightly lower than JGS3, the second cavity mirror 304 can still work stably because the first cavity mirror 301 bears most of the pump light intensity; the first oscillating crystal 302 and the second oscillating crystal 303 are both 8 mm × 8 mm × 20 mm KTA crystals, placed in a walk-off compensation manner, and the crystal temperature is stabilized at 28℃ by TEC; the laser generated by oscillation is separated by the first multi-wavelength reflection dichroic mirror 305 and the second multi-wavelength reflection dichroic mirror 306. The first and second multi-wavelength reflection dichroic mirrors (305, 306) are made of CaF2 material, placed at 45°, and their film system is designed to be highly transmittance of 1064 nm and 3270-3504 nm signal light. The 3270-3504 nm pump light and the 3270-3504 nm idler light have high transmittance (HT), while the 1528-1577 nm signal light has high reflectivity (HR), thus efficiently separating the signal light generated by the oscillation from the resonant cavity and guiding it to the optical parametric amplifier (OPA)4.

[0029] The pump light reflected from the second polarization beam splitter 205 is used to pump the light parametric amplifier 4. To compensate for the pulse setup time of the OPO, the pump light used to pump the OPO needs to be precisely delayed optically. Measurements show that this time difference is approximately 6.5 ns, corresponding to an optical path of approximately 2 m. To achieve this delay, the pump light path is extended via a folded optical path formed by the first delay plate 401 and the second delay plate 402. In the specific optical layout of this embodiment, to achieve precise optical path compensation of approximately 2 m, the round-trip number is set to 6. By precisely adjusting the parallel spacing between the first delay plate 401 and the second delay plate 402, continuous fine-tuning of the optical path can be achieved, thereby achieving precise time matching with the signal light pulse from the OPO. The delayed pump light is guided sequentially by the 0° reflector 403, the second beam shrinker 404, and the second 45° reflector 405 to reach the beam combiner 406. The second beam shrinker 404 is a 1.9x Galilean telescope used to compensate for beam divergence caused by optical path lengthening. It reshapes the pump beam from approximately 6.4 mm × 3.3 mm to approximately 3.3 mm × 1.8 mm, thereby achieving optimized spatial pattern matching with the signal light from the OPO at the beam combiner 406. The signal light and the delayed and shaped pump light are spatially combined at the beam combiner 406. The combined light is injected into the first amplifying crystal 407 and the second amplifying crystal 408. Both crystals are 8 mm × 8 mm × 20 mm KTA crystals, placed with walk-off compensation and temperature-controlled at 28°C by TEC. After this stage of nonlinear amplification, the generated laser is wavelength-separated by a multi-wavelength reflection dichroic mirror 409 to output the final signal light. This multi-wavelength reflection dichroic mirror 409 is made of JGS3 material, placed at 45°, and its film system is designed to support the 1064 nm pump light and the 3270-3504 nm light. The device exhibits high reflectivity (HR) for 1528-1577 nm idler light and high transmittance (HT) for 1528-1577 nm signal light. When this film system is coated with JGS3 material, it has a higher laser damage threshold than CaF2, ensuring the stability of the device during long-term high-power operation.

[0030] In a preferred embodiment of the present invention, a wavelength tuning synchronization control system is employed to achieve wide-range, high-precision wavelength tuning. This system includes: a central controller; and four piezoelectric ceramic angle adjustment actuators, which are mechanically connected to the first oscillating crystal 302 and the second oscillating crystal 303 in the optical parametric oscillator 3, and the first amplifying crystal 407 and the second amplifying crystal 408 in the optical parametric amplifier 4, respectively.

[0031] At the core of each piezoelectric ceramic angle adjustment actuator is a high-precision flexible guide mechanism. This mechanism is integrally machined from a single metal blank (such as titanium alloy or precipitation-hardening stainless steel) via wire cutting, and its main body is a thin-walled structure employing a double parallelogram flexible hinge principle. This design ensures that the linear micro-displacement of the piezoelectric ceramic stack is converted into a micro-radius precision angle of the end crystal mounting stage without friction or hysteresis. To achieve long-term stable operation of the device under high power and high repetition rate, the flexible guide mechanism incorporates a specialized thermal management design to isolate thermal deformation stress from the crystal heat sink. Specifically, the flexible guide mechanism is connected to the metal heat sink of the underlying thermoelectric cooler (TEC) via a thermally insulating pad made of a low thermal conductivity material (such as zirconia ceramic or polyimide). This connection method significantly reduces the axial heat conduction path while ensuring mechanical support rigidity. More importantly, the thin wall of the double parallelogram flexible hinge has high stiffness in the driving direction (perpendicular to the crystal's light-transmitting surface) to ensure the bandwidth and accuracy of angle control, while in the direction parallel to the heat sink plane, the orientation and size of the thin wall are optimized to give it relatively low stiffness. This characteristic allows the stress generated when the TEC heat sink undergoes in-plane thermal expansion or contraction due to active temperature control or ambient temperature fluctuations to be absorbed by the elastic deformation of the flexible thin wall, without being transmitted to the crystal mounting stage above. This effectively isolates the interference of thermal deformation on the absolute angle and relative parallelism of the crystal, ensuring the long-term repeatability and stability of wavelength tuning.

[0032] The wavelength tuning synchronization control system operates as follows: The central controller (e.g., an industrial computer or embedded control board) pre-stores optimal matching angle combination data for each KTA crystal in the optical parametric oscillator and optical parametric amplifier corresponding to different target wavelengths. When the output wavelength needs to be changed via human-machine interface or remote command, the operator only needs to input a single target wavelength value (e.g., 1550 nm) to the central controller. Upon receiving the command, the controller immediately calls up the corresponding angle combination data, synchronously generates the corresponding drive voltage signal through a multi-channel digital-to-analog converter, and sends it to the four piezoelectric ceramic angle adjustment execution units via cables. The piezoelectric ceramic stacks in each execution unit generate corresponding micro-displacements according to the received voltage signals, thereby driving the connected crystals to precisely deflect to the target angle through their flexible guiding mechanisms. Since all drive commands are synchronously issued by the same controller based on the same wavelength model, the two crystals in the optical parametric oscillator and the two crystals in the optical parametric amplifier can achieve coordinated and matched angle changes. This process ensures that: 1) the optical parametric oscillator outputs signal light of the required wavelength; 2) the phase matching angle of the optical parametric amplifier crystal is automatically adjusted to maintain efficient amplification of the signal light throughout the entire tuning range, i.e., the phase matching condition of the optical parametric amplifier relative to the output signal light of the optical parametric oscillator is automatically maintained.

[0033] Through the above-mentioned wavelength tuning synchronization control system, the present invention realizes one-click, high-precision wavelength tuning in the range of 1535nm to 1578nm, and ensures high energy and high beam quality of output laser in a wide tuning range.

[0034] In a preferred embodiment of the present invention, the cut angle between the first oscillating crystal 302 and the second oscillating crystal 303 in the optical parametric oscillator 3 is selected as θ = 41.6° and φ = 0°. This angle is located in the fast tuning region with a large slope in the KTA crystal tuning curve under 1064nm pump. According to calculations by the nonlinear optical simulation software SNLO, at this cut angle, the crystal only needs to rotate about ±0.22° to achieve a signal light wavelength tuning range of about 60nm (e.g., 1535nm-1595nm). To ensure that the optical parametric amplifier 4 can operate efficiently throughout the entire tuning range, the first amplifying crystal 407 and the second amplifying crystal 408 preferably adopt the same cut angle as the oscillating crystal, and synchronous rotation with the oscillating crystal is achieved through the piezoelectric ceramic-based angle adjustment closed-loop control system to maintain phase matching. This together embodies the advantages of the present invention in achieving wide tuning and efficient amplification with minute mechanical adjustments.

[0035] In this embodiment, approximately 90 mJ of pump light is injected into the OPO to generate approximately 10 mJ of signal light with good beam quality; approximately 150 mJ of pump light is used to pump the OPA. Ultimately, a signal light output of greater than 34 mJ is obtained at a wavelength of 1556 nm, and the beam quality factor M is [missing value]. 2 Less than 2.5.

[0036] The above energy ratio is based on the following considerations: Since the OPO uses a flat-cavity design, its ability to suppress higher-order modes is limited. If the pump energy is too high, the beam quality will deteriorate rapidly. Therefore, the pump energy of the OPO is limited to a low level (approximately 90 mJ) to prioritize the generation of high-quality seed light; the OPA stage is then responsible for the main energy amplification. This design achieves a balance between high energy output and high beam quality. The beam quality of the output laser at a wavelength of 1.55 µm in this embodiment of the invention was measured, and the results are as follows: Figure 2 As shown. Figure 2 The x-axis represents the beam propagation distance (Z Locations), and the y-axis represents the beam width (Beam Widths) measured using the D4σ method. The two curves in the figure represent the changes in beam width with propagation distance in the mutually orthogonal X and Y directions, respectively. Both curves exhibit good linear propagation characteristics and small divergence angles. Based on the measurement data, the beam quality factors in both the X and Y directions are calculated to be better than 2.5, with a combined beam quality factor M... 2 Better than 2.5. This result fully demonstrates that the device of the present invention can ensure excellent beam quality in both main directions while achieving high energy output.

[0037] The above provides a detailed description of the wide-tuning, high-energy, high-beam-quality optical parametric oscillator and amplifier provided by the present invention. Specific examples have been used to illustrate the principle and implementation of the present invention, but these should not be construed as limiting the scope of protection of the present invention.

Claims

1. A wide-tuning, high-energy, high-beam-quality optical parametric oscillator amplifier, characterized in that, It includes four parts: a 1064nm pump source (1), a beam modulation and shaping module (2), an optical parametric oscillator (3), and an optical parametric amplifier (4). The 1064nm pump source (1) includes a 1064nm seed source (101), an optical fiber amplification module (102), and a solid-state amplification module (103) connected in sequence. The beam control and shaping module (2) is connected to the output end of the pump source (1) and includes a first half-wave plate (201), a first polarizing beam splitter (202), a second half-wave plate (203), a first beam shrinking mirror (204), a second polarizing beam splitter (205), a third half-wave plate (206), and a first 45° reflector (207) arranged sequentially along the optical path. The pump light is first passed through the first half-wave plate (201) and the first polarization beam splitter (202) for energy modulation, and then its transmitted light passes through the second half-wave plate (203) and the first beam shrinking mirror (204) to reach the second polarization beam splitter (205). The second polarization beam splitter (205) splits the light into two paths: its transmitted light passes through the third half-wave plate (206) and the first 45° reflector (207) and is output as the first pump light; its reflected light is output as the second pump light. The optical parametric oscillator (3) receives the first pump light and includes a first cavity mirror (301) arranged sequentially along the first pump light path, a first crystal (302) and a second crystal (303) placed in a walk-off compensation manner, a second cavity mirror (304), a first multi-wavelength reflection dichroic mirror (305), and a second multi-wavelength reflection dichroic mirror (306); the first cavity mirror (301), the first crystal (302), the second crystal (303), and the second cavity mirror (304) together constitute a flat resonant cavity; The optical parametric amplifier (4) receives signal light from the optical parametric oscillator (3) and the second pump light from the beam modulation and shaping module (2), and includes: Pump light processing branch: a first delay board (401), a second delay board (402), a 0° reflector (403), a second beam shrinker (404), and a second 45° reflector (405) are arranged in sequence. Signal light amplification branch: beam combiner (406), first amplifying crystal (407) and second amplifying crystal (408) placed in a walk-off compensation manner, and multi-wavelength reflection dichroic mirror (409); The second pump light, after passing through the pump light processing branch, is guided by the second 45° reflector (405) to the beam combiner (406); the signal light from the optical parametric oscillator (3) is introduced into the beam combiner (406), and after being spatially combined with the second pump light, it is amplified sequentially by the first amplifying crystal (407) and the second amplifying crystal (408), and finally output by the multi-wavelength reflection dichroic mirror (409).

2. The optical parametric oscillator amplifier according to claim 1, characterized in that, The first crystal (302), the second crystal (303), the first amplifying crystal (407), and the second amplifying crystal (408) are all KTA crystals.

3. The optical parametric oscillator amplifier according to claim 2, characterized in that, The cutting angle between the first KTA crystal (302) and the second KTA crystal (303) is located in the fast tuning region of the KTA crystal tuning curve under 1064nm pump with a slope greater than a preset threshold.

4. The optical parametric oscillator amplifier according to claim 1, characterized in that, The first cavity mirror (301) is made of JGS3, which has a reflectivity of more than 99.5% for light in the 1528-1577nm band and a transmittance of more than 95% and 80% for light in the 1064nm and 3270-3504nm bands, respectively; the second cavity mirror (304) is made of CaF2, which has a transmittance of about 50% for light in the 1528-1577nm band; the first multi-wavelength reflection dichroic mirror (305) and the second multi-wavelength reflection dichroic mirror (306) are made of CaF2, which have high transmittance for 1064nm pump light and 3270-3504nm idler light, and high reflectivity for 1528-1577nm signal light.

5. The optical parametric oscillator amplifier according to claim 1, characterized in that, The multi-wavelength reflective dichroic mirror (409) in the optical parametric amplifier (4) is made of JGS3, which has high reflectivity for light in the 1064nm and 3270-3504nm bands and high transmittance for light in the 1528-1577nm band.

6. The optical parametric oscillator amplifier according to claim 1, characterized in that, The wavelength tuning of the optical parametric oscillator (3) and the optical parametric amplifier (4) is performed by a wavelength tuning synchronization control system; The wavelength tuning synchronization control system includes: a central controller; multiple piezoelectric ceramic angle adjustment execution units, which are mechanically connected to the first crystal (302), the second crystal (303), the first amplifying crystal (407), and the second amplifying crystal (408), respectively; the piezoelectric ceramic angle adjustment execution unit includes a flexible guiding mechanism that converts the linear displacement of the piezoelectric ceramic into the crystal rotation angle, and the flexible guiding mechanism is used to isolate the thermal deformation stress from the crystal heat sink; The central controller is communicatively connected to all the piezoelectric ceramic angle adjustment execution units. Based on a single target wavelength input, it synchronously generates and sends drive commands to each execution unit, causing the crystal in the optical parametric oscillator and the crystal in the optical parametric amplifier to deflect in tandem, so as to automatically maintain the phase matching of the optical parametric amplifier with respect to the output signal light of the optical parametric oscillator while changing the output wavelength.

7. The optical parametric oscillator amplifier according to claim 1, characterized in that, The first beam reducer (204) is a Galilean telescope with a magnification of 1.45X, and the second beam reducer (404) is a Galilean telescope with a magnification of 1.9X.

8. The optical parametric oscillator amplifier according to claim 1, characterized in that, In the beam control and shaping module (2), the first half-wave plate (201) and the first polarization beam splitter (202) constitute a first control unit for controlling the total input energy, and the second half-wave plate (203) and the second polarization beam splitter (205) constitute a second control unit for independently adjusting the energy ratio of the first and second pump light paths.

9. The optical parametric oscillator amplifier according to claim 1, characterized in that, The first crystal (302) and the second crystal (303) in the flat resonant cavity are temperature-controlled at 28°C by a thermoelectric cooler (TEC), and the first amplifying crystal (407) and the second amplifying crystal (408) in the optical parametric amplifier (4) are temperature-controlled at 28°C by a thermoelectric cooler (TEC).

10. The optical parametric oscillator amplifier according to claim 1, characterized in that, The first and second delay plates in the optical parametric amplifier are placed parallel to each other, and the pump beam undergoes multiple round-trip reflections between them. The delay amount can be continuously adjusted by adjusting the distance between the two plates or the number of round-trips of the beam.

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