A high peak power dual wavelength laser

Abstract

A kind of high peak value dual-wavelength laser, including full mirror, electro-optic Q-switching crystal KD*P, polarizer, 1 / 4 wave plate, gain medium Nd:YAG crystal, output mirror, frequency doubling crystal KTP and dichroic mirror connected in sequence;LD array is arranged on the side of the gain medium Nd:YAG;Reflecting mirror is further arranged above dichroic mirror;Above-mentioned element optical elements are all fixed on the same optical platform, and full mirror and output mirror are strictly parallel, and optical path is high collimation, coaxial and stable.The utility model discloses specific pumping structure, cavity type and output mirror transmittance, Q-switching mode, the matching angle and installation mode of frequency doubling crystal and global precision temperature control etc., successfully solved the high peak value power and high pulse energy electro-optic Q-switching laser in pursuit of high efficiency, high stability and dual-wavelength output when facing the key technical bottleneck of heat management, pulse control and frequency doubling conversion, provides the comprehensive solution of excellent performance, reliable and easy to realize.

Description

Technical Field

[0001] This utility model relates to the field of laser technology, and in particular to a high peak dual-wavelength laser. Background Technology

[0002] Laser diode (LD)-pumped solid-state lasers (DPSSLs) have become a hot topic in modern laser technology research due to their high efficiency, long lifespan, and compact structure. Q-switching is a key technique in achieving high peak power pulse output. Compared to acousto-optic Q-switching, electro-optic Q-switching has a near 100% loss modulation depth, which helps to obtain higher peak power and narrower pulse widths. Nd:YAG crystals, as commonly used laser gain media, not only have a high gain cross-section in the 1064nm band but also excellent thermomechanical properties, thus being widely used in the design of high peak power lasers. Green lasers (532nm) have shown significant application value in laser medicine, underwater communication, spectral analysis, and precision machining due to their short wavelength, high photon energy, long underwater transmission distance, and sensitivity to the human eye. Through nonlinear frequency conversion technology, especially second harmonic generation (SHG), near-infrared 1064nm laser light can be efficiently converted into 532nm visible green light. Among the many nonlinear crystals that generate second harmonics, KTP (KTiOPO4) crystal has become one of the preferred materials for frequency doubling of 1064nm lasers due to its advantages such as high nonlinear coefficient, wide light transmission range and high damage threshold.

[0003] Currently, LD-pumped electro-optically Q-switched green lasers have been studied. However, research on systems combining LD side-pumping with KD*P electro-optical Q-switching and KTP external frequency doubling is still relatively insufficient, especially in terms of high peak power output, which is a weakness. That is, existing technologies still have varying degrees of problems in terms of the stability of dual-wavelength output, system compactness, and overall performance at high peak power. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a high-peak dual-wavelength laser with an ingenious structure, efficient thermal management, and the ability to output high beam quality laser light stably for a long time.

[0005] The equipment includes a total reflection mirror, an electro-optic Q-switching crystal KD*P, a polarizer, a quarter-wave plate, a gain medium Nd:YAG crystal, an output mirror, a frequency doubling crystal KTP, and a dichroic mirror connected in sequence. An LD array is disposed on the side of the gain medium Nd:YAG; a reflector is also disposed above the dichroic mirror; All the aforementioned optical components are fixed on the same optical platform, and the total reflection mirror and output mirror are strictly parallel, ensuring that the optical path is highly collimated, coaxial, and stable.

[0006] The beneficial effects of this utility model are: 1. Compact and modular structure: The design of the three major modules makes the system structure clear, which facilitates independent debugging, maintenance and performance optimization. It has strong overall robustness and high practical value.

[0007] 2. High peak power, high pulse energy, and stability: The fundamental frequency optical peak power reaches 537kW, and the pulse energy reaches 9.13mJ. A specially designed high-voltage pulse power supply is used to drive the KD*P crystal, with a repetition frequency adjustable from 1-50Hz. An independent temperature control system is used to control the temperature of the KD*P crystal, combined with the fast response characteristics of electro-optic Q-switching, ensuring stable operation.

[0008] 3. High-efficiency dual-wavelength output: Extracavity frequency doubling using a type II critical phase-matched KTP crystal achieved a 532nm green light output with a single-pulse energy of 4.68mJ, with a frequency doubling efficiency as high as 51.3%, placing it at the forefront of similar extracavity frequency doubling systems. This fully demonstrates the comprehensive advantages of this patent in crystal cutting, phase matching (θ=90°, φ=23.5°), and cavity mirror design (including cavity mirror parameters and coating). Through an optimized dual-color mirror separation system, high-purity, low-loss, and spatially separated output of two laser beams, 1064nm and 532nm, was achieved.

[0009] 4. Achieving a narrower pulse width: Using the KD*P electro-optic Q-switching switch, a faster switching speed and a higher extinction ratio were achieved, resulting in a pulse width of 17ns. This demonstrates the success of the Q-switching module and its matching design with the resonant cavity.

[0010] 5. Excellent pulse and energy stability: A precise temperature control system is used to control the temperature of the Nd:YAG laser crystal, effectively suppressing the thermal lensing effect of the Nd:YAG crystal. An air-cooling system is used for effective thermal management of the KTP crystal, eliminating thermally induced phase mismatch and other unstable factors at the source, resulting in laser output energy fluctuations of less than ±1%. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of a high-peak dual-wavelength laser according to the present invention; Figure 2 This is a pulse sequence diagram of a high-peak dual-wavelength Nd:YAG electro-optic Q-switched laser according to the present invention; Figure 3 This is the output spectrum of a high-peak dual-wavelength Nd:YAG electro-optic Q-switched laser described in this utility model; Figure label: 1-Total Reflection Mirror 2-Electro-optic Q-switching Crystal KD*P 3-Polarizer 4-1 / 4 Wave Plate 5-Gain Medium Nd:YAG Crystal 6-LD Array 7-Output Mirror 8-Frequency Doubling Crystal KTP 9-Dichroic Mirror 10-Reflecting Mirror The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0012] Reference Figure 1 , Figure 2 The present invention discloses a high peak value dual-wavelength laser, comprising a total reflection mirror 1, an electro-optic Q-switching crystal KD*P2, a polarizer 3, a quarter-wave plate 4, a gain medium Nd:YAG crystal 5, an output mirror 7, a frequency doubling crystal KTP8, and a dichroic mirror 9 connected in sequence. An LD array 6 is disposed on the side of the gain medium Nd:YAG; a reflector 10 is also disposed above the dichroic mirror 9; All the aforementioned optical components are fixed on the same optical platform, with the total reflection mirror 1 and the output mirror 7 strictly parallel, and the optical path is highly collimated, coaxial, and stable.

[0013] Preferably, the optical elements are fixed on the same optical platform by precision mechanical clamps and adjusted by laser collimation using a helium-neon laser.

[0014] In Example 1, the LD array 6 is an LD array with a peak power of 30W. The emission center wavelength of the LD array 6 is 808nm, and the wavelength of the LD array matches the absorption peak of the gain medium Nd:YAG crystal 5.

[0015] Furthermore, the LD array 6 employs both a TEC electric cooling system and a wind-cooling system for simultaneous cooling, and its operating temperature is stabilized at a set value, preferably 25°C, with a control accuracy of ±0.1°C, through a temperature controller. This ensures the stability of the output wavelength and avoids drift in the pump light wavelength.

[0016] In Example 2, the gain medium Nd:YAG crystal 5 uses an Nd:YAG crystal with a doping concentration of 1.0 at.% as the gain medium. The crystal is cylindrical with dimensions of Φ6 mm × 60 mm.

[0017] In Example 3, the two end faces of the gain medium Nd:YAG crystal 5 are provided with optical coatings. The two end faces of the crystal are coated with 1064nm anti-reflection coatings to reduce the round-trip loss of the oscillating laser in the cavity; the side face of the crystal is coated with 808nm anti-reflection coatings to improve the pumping efficiency. The Nd:YAG crystal 5, the gain medium, is tightly encapsulated in a copper heat sink. Copper has extremely high thermal conductivity, enabling rapid heat dissipation from the crystal. Furthermore, the heat sink has a sealed coolant channel, forming a water-cooling system. An external constant-temperature circulating water chiller forces the coolant to circulate within the channel. This precisely maintains the laser crystal's operating temperature within the range of 20±0.3°C. This precise temperature control is crucial for suppressing the thermal lensing effect and ensuring the long-term stable operation of the laser.

[0018] Example 4: The total reflection mirror 1 is an optical plane mirror coated with a high-reflectivity film for 1064nm laser light, with a reflectivity R > 99.9%. The output mirror 7 is a concave mirror with a radius of curvature of 1000 mm. It is coated with a partial reflective film for 1064 nm lasers and has a transmittance of 80%.

[0019] This high transmittance design facilitates the rapid extraction of intracavity energy under high repetition frequency Q-switching conditions, forming pulses with high peak power.

[0020] In Example 5, the electro-optic Q-switching crystal KD*P2 uses a potassium dideuterium phosphate crystal as the Q-switch, with dimensions of 6×6×20mm. Both light-transmitting surfaces at both ends of the KD*P crystal are coated with anti-reflection films for 1064nm and 532nm, and the residual reflectivity on one side is less than 0.2% to minimize insertion loss. The crystal is mounted in a metal base with electrodes.

[0021] In the high-voltage drive aspect of the electro-optic Q-switched crystal KD*P2, a 3000V quarter-wave voltage is applied to the electrodes of the KD*P crystal via wires. This high-voltage pulse is generated by a specially designed high-voltage pulse generator with an adjustable repetition frequency of 1-50Hz, featuring a narrow pulse width and fast rise time. By applying and removing voltage to the KD*P crystal, the KD*P crystal, along with the subsequent polarizer 3 and quarter-wave plate 4, coordinates to adjust the Q value of the resonant cavity.

[0022] Polarizer 3 is a thin-film polarizer whose optical axis direction is precisely adjusted. It is used to polarize the laser in the cavity into linearly polarized light, which is the basis for electro-optic Q-switching.

[0023] The fast and slow axes of the quarter-wave plate 4 are at a 45° angle to the transmission axis of the polarizer 3. Together with the KDP crystal, they modulate the polarization state of the laser and achieve precise Q-switching.

[0024] Example 6 describes the KTP8 frequency doubling crystal as a nonlinear frequency doubling medium that achieves Type II critical phase matching. The crystal dimensions are 3×3×15 mm. Its light transmission direction is cut according to the phase matching angle, with a cutting angle of θ=90° and φ=23.5°. This cutting angle is the optimal phase matching direction for generating 532nm laser from 1064nm laser frequency doubling.

[0025] The two light-transmitting end faces of the frequency doubling crystal KTP8 are coated with dual-wavelength anti-reflection films for 1064nm and 532nm, and the residual reflectivity of each side is less than 0.2%, thereby significantly reducing transmission loss during the frequency doubling process.

[0026] The frequency doubling crystal KTP8 is fixed on a precision three-dimensional adjustment frame. This frame has pitch, yaw, and translational adjustment functions along the optical axis, with an adjustment accuracy down to the micrometer level. By precisely adjusting the spatial position and angle of the KTP crystal, it can be ensured that the 1064nm laser beam passes through the crystal with the optimal phase matching angle, thereby achieving the highest frequency doubling conversion efficiency.

[0027] Example 7: The dichroic mirror 9, after coating design, exhibits high transmittance for light with a wavelength of 1064nm and high reflectivity for light with a wavelength of 532nm. Wherein: 1064nm laser output path: The remaining 1064nm fundamental frequency light after frequency doubling or the 1064nm fundamental frequency light directly output without frequency doubling crystal passes through the dichroic mirror 9 and is directly output to form an infrared laser beam.

[0028] 532nm Laser Output Path: The 532nm frequency-doubled light generated by the KTP crystal is incident on the dichroic mirror 9 and reflected at a 90° angle. To obtain a 532nm laser parallel to the 1064nm output light path, a plane mirror 10 is placed on the reflected light path of the frequency-doubled light. This mirror 10 is coated with a high-reflectivity film for 532nm. After being reflected again by this mirror 10, the 532nm laser finally outputs a beam of green light parallel to the 1064nm light path.

[0029] This invention constructs an LD-side-pumped Nd:YAG electro-optic Q-switched laser system and systematically evaluates its external frequency doubling performance. Under pump power of 6.7W and repetition frequency of 50Hz, the system achieves a 1064nm fundamental frequency output with a pulse width of 17ns and a single-pulse energy of 9.13mJ, with a peak power as high as 537kW. Further external frequency doubling using a KTP crystal yields a 532nm green light output with a single-pulse energy of 4.68mJ, achieving a frequency doubling efficiency of 51.3%. Experiments show that the LD side-pumping combined with electro-optic Q-switching can effectively generate high peak power pulsed laser output with good pulse stability and energy fluctuations of less than ±1%. The KD*P crystal, as an electro-optic Q-switching switch, exhibits good control precision and can achieve narrow pulse width laser output; the KTP crystal performs excellently in the frequency doubling of 1064nm lasers, possessing high conversion efficiency at moderate power densities. Thermal management is a key factor in ensuring the long-term stable operation of lasers. This study significantly improved the thermal stability of the system by implementing effective temperature control on Nd:YAG crystals, KD*P Q-switched crystals, and KTP frequency-doubling crystals. This laser system possesses advantages such as compact structure, high stability, and high peak power, and has broad application potential in laser processing, medical treatment, spectral analysis, and scientific research. Future research will focus on further optimizing the system structure to improve overall conversion efficiency, exploring its operating characteristics under higher repetition rates, and extending its frequency conversion capabilities to other wavelengths.

[0030] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. It will be apparent to those skilled in the art that this utility model is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this utility model is defined by the appended claims rather than the foregoing description, and thus all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this utility model. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0031] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-peak dual-wavelength laser, characterized in that, The high peak dual-wavelength laser comprises a total reflection mirror, an electro-optic Q-switching crystal KD*P, a polarizer, a quarter-wave plate, a gain medium Nd:YAG crystal, an output mirror, a frequency doubling crystal KTP, and a dichroic mirror connected in sequence. An LD array is disposed on the side of the gain medium Nd:YAG; a reflector is also disposed above the dichroic mirror; All the aforementioned optical components are fixed on the same optical platform, and the total reflection mirror and output mirror are strictly parallel, ensuring that the optical path is highly collimated, coaxial, and stable.

2. A high-peak dual-wavelength laser according to claim 1, characterized in that, The LD array is a 30W peak power LD array with an emission center wavelength of 808nm. The wavelength of the LD array matches the absorption peak of the Nd:YAG crystal, which is the gain medium.

3. A high-peak dual-wavelength laser according to claim 2, characterized in that, The LD array uses both a TEC electric cooling system and an air cooling system for cooling, and its operating temperature is stabilized at a set value by a temperature controller.

4. A high-peak dual-wavelength laser according to claim 1, characterized in that, The gain medium Nd:YAG crystal used is an Nd:YAG crystal with a doping concentration of 1.0 at.% as the gain medium. The crystal is cylindrical with dimensions of Φ6mm×60mm.

5. A high-peak dual-wavelength laser according to claim 1, characterized in that, The gain medium Nd:YAG crystal has optical coatings on both end faces, with 1064nm anti-reflection coatings on both end faces and 808nm anti-reflection coatings on the side face. The gain medium Nd:YAG crystal is tightly encapsulated in a copper heat sink; and the heat sink has a sealed coolant channel inside, forming a water cooling system.

6. A high-peak dual-wavelength laser according to claim 1, characterized in that, The total reflection mirror is an optical plane mirror coated with a high-reflectivity film for 1064nm laser light, with a reflectivity R > 99.9%. The output mirror is a concave mirror with a radius of curvature of 1000 mm. It is coated with a partial reflective film for 1064 nm lasers and has a transmittance of 80%.

7. A high-peak dual-wavelength laser according to claim 1, characterized in that, The electro-optic Q-switched crystal KD*P uses potassium dideuterium phosphate crystal as the Q switch, and its size is 6×6×20mm; both ends of the KD*P crystal are coated with anti-reflection coatings for 1064nm and 532nm, and the residual reflectivity on one side is less than 0.2%; The polarizer is a thin-film polarizer; The fast and slow axes of the quarter-wave plate are at a 45° angle to the transmission axis of the polarizer.

8. A high-peak dual-wavelength laser according to claim 1, characterized in that, The frequency doubling crystal KTP is a nonlinear frequency doubling medium that implements Type II critical phase matching; the crystal size is 3×3×15 mm, and its light transmission direction is cut according to the phase matching angle, with a cutting angle of θ=90° and φ=23.5°; Both light-transmitting end faces of the frequency doubling crystal KTP are coated with dual-wavelength anti-reflection films for 1064nm and 532nm, and the residual reflectivity of each side is less than 0.2%. The frequency doubling crystal KTP is fixed on a precision three-dimensional adjustment frame.

9. A high-peak dual-wavelength laser according to claim 1, characterized in that, The aforementioned dichroic mirror is designed with a coating, which has high transmittance for light with a wavelength of 1064nm and high reflectivity for light with a wavelength of 532nm.

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