磷锗锌光学参量振荡器技术研究

报道了一台高重复频率2 mm光学参量振荡器泵浦的磷锗锌光学参量振荡器。磷锗锌晶体(ZnGeP2,简称ZGP)采用Ⅰ类相位匹配方式,切割角度q为55°,f为0°,尺寸5.5 mm×6 mm×18 mm,在4.0 kHz重复频率下,当注入5.2 W的2 mm圆偏振光时,获得310 mW中红外输出,p偏振态2 mm到3～5 mm光-光转换效率12%。通过调节晶体的角度,实验获得ZGP光学参量振荡器的波长调谐曲线,在误差范围内与理论变化规律相符。     

磷锗锌光学参量振荡器技术研究

 报道了一台高重复频率2 mm光学参量振荡器泵浦的磷锗锌光学参量振荡器。磷锗锌晶体(ZnGeP₂,简称ZGP)采用Ⅰ类相位匹配方式,切割角度q为55°,f为0°,尺寸5.5 mm×6 mm×18 mm,在4.0 kHz重复频率下,当注入5.2 W的2 mm圆偏振光时,获得310 mW中红外输出,p偏振态2 mm到3～5 mm光-光转换效率12%。通过调节晶体的角度,实验获得ZGP光学参量振荡器的波长调谐曲线,在误差范围内与理论变化规律相符。     

Mid-infrared tunable dual-wavelength generation based on a quasi-phase-matched optical parametric oscillator

We report an efficient optical parametric oscillator (OPO) of dual idler wave output based on periodically poled MgO:LiNbO₃ with a periodically-phase-reversed grating structure, which is pumped by a Q-switched 1.064 μm laser with a repetition rate of 50 kHz. 0.98 W of dual idler-waves at 3.824 μm and 3.731 μm is achieved at room temperature, leading to a 12.9% conversion efficiency. The crystal temperature tuning provides output tunability of the dual idler wavelengths. In addition, the sum frequency generation of the dual signal waves is simultaneously observed in the OPO cavity.     

Singly-resonant optical parametric oscillator based on KTA crystal

Tunable mid-infra-red radiation by singly resonant optical parametric oscillation based on KTA crystal pumped by multi-axial Gaussian shape beam from Q-switched Nd:YAG laser has been demonstrated. Threshold energy of oscillation at different idler wavelengths for different cavity length has been demonstrated. Single pass conversion efficiency of incident pump energy to infra-red wavelength has also been measured.     

Synchronously pumped photonic crystal fiber-based optical parametric oscillator

We report the development of a compact, tunable synchronously pumped photonic crystal fiber (PCF)-based optical parametric oscillator (FOPO). The oscillator is pumped using a gain-switched laser diode producing 220?ps pulses around 1062?nm, amplified in a ytterbium doped amplifier to peak powers of 3.5?kW. The FOPO produces anti-Stokes pulses at wavelengths between 757 and 773?nm, with durations of 150?ps at average output powers exceeding 290?mW. The output slope efficiency of the device varies with output wavelength from 1.9 to 6.0%.     

Mid-infrared high-resolution absorption spectroscopy by use of a semimonolithic entangled-cavity optical parametric oscillator

By recording low-pressure absorption lines of N2O around 3.9 microm, we fully qualify a pulsed entangled-cavity doubly resonant optical parametric oscillator as a power tool for high-resolution spectroscopy. This compact source runs at a high repetition rate (>10 kHz) with a low threshold of oscillation (<8 microJ), is mode-hop-free tunable over 5 cm(-1), and displays single-frequency Fourier-transformed-limited operation (linewidth <0.005 cm(-1)). A high potential for nonlinear spectroscopy is also expected given the high peak power (70 W) and the good quality (M2 < 2) of the output beam.     

高功率KTP晶体光参量振荡器热效应

采用有限元分析方法对KTP晶体内部3维温度分布情况进行了精确计算。根据参量过程满足的能量守恒条件和动量守恒条件,利用KTP晶体的热光色散方程计算了参量过程中温度对相位匹配角、光波走离角、允许角及晶体的有效非线性系数的影响。结果表明:晶体内温度分布不均匀;在沿着通光方向上晶体截面温度分布不同;加强晶体表面冷却效果,可有效降低温度对相位匹配角、光波走离角、允许角及晶体的有效非线性系数的影响。     

高功率KTP晶体光参量振荡器热效应

采用有限元分析方法对KTP晶体内部3维温度分布情况进行了精确计算。根据参量过程满足的能量守恒条件和动量守恒条件,利用KTP晶体的热光色散方程计算了参量过程中温度对相位匹配角、光波走离角、允许角及晶体的有效非线性系数的影响。结果表明：晶体内温度分布不均匀;在沿着通光方向上晶体截面温度分布不同;加强晶体表面冷却效果,可有效降低温度对相位匹配角、光波走离角、允许角及晶体的有效非线性系数的影响。     

Widely tunable photonic crystal fiber Fabry-Perot optical parametric oscillator

We present a widely tunable low-threshold chi(3) optical parametric oscillator. The oscillator cavity is formed by butt coupling dichroic mirrors to either end of a highly nonlinear index-guiding photonic crystal fiber. This yields a singly resonant Fabry-Perot oscillator with a high feedback fraction for the resonant parametric sideband. The tuning range of the output parametric sideband stretches from 23 to 164 THz above the pump frequency. The threshold power of the oscillator is only 15 W.     

Mid-infrared generation based on a periodically poled LiNbO3 optical parametric oscillator

We report a nanosecond Nd:YVO_4-pumped optical parametric oscillator (OPO) based on periodically poled LiNbO_3 (PPLN). Tuning is achieved in this experiment by varying the temperature and period of the PPLN. The design of double-pass singly resonant oscillator (DSRO) and confocal cavity enables the OPO threshold to be lowered considerably, resulting in a simple, compact, all-solid-state configuration with the mid-infrared idler powers of up to 466mW at 3.41μm.     

宽调谐高效率的BBO光参量振荡器

本文报道用354.7nm泵浦的单共振BBO脉冲光参量振荡器在413～661nm和2513～765nm波段内获得了可调谐的振荡输出,最高总能量转换效率达52％;文中还讨论了输出特性。     

Wavelength tunability of tandem optical parametric oscillator based on single PPMgOLN crystal

The theoretical analysis and experimental results of the wavelength tunability of a tandem optical parametric oscillator (TOPO) based on a single nonlinear crystal are presented.TOPO is a configuration wherein the signal laser is used as a pump laser to generate secondary optical parametric oscillator (OPO).The cascaded parametric interactions are achieved synchronously in a single-grating-period MgO doped periodically poled lithium niobate (PPMgOLN).Tunable multiple-wavelength mid-infrared (mid-IR) lasers are obtained by changing the temperature of the crystal.When the PPMgOLN crystal with a grating period of 31.2 μm is operated at 148 ℃,the dual OPOs generate an identical mid-IR laser of 2.83 μm.The secondary OPO transforms into an optical parametric amplifier,in which different frequency mixing from the signal laser results in the amplification of the idler laser in the first OPO.TOPO is a useful configuration for multiple laser output,broad tuning range,and high-efficiency mid-IR lasers.     

Tunable mid-infrared optical parametric oscillator with intracavity parametric amplification based on a dual-grating PPLN crystal

Intracavity amplification of the idler radiation of a nanosecond optical parametric oscillator (OPO) is achieved within a single dual-grating PPLN crystal composed of a uniform-grating section followed by a fan-out grating section. While all the OPO wavelength-tuning capabilities are preserved, this configuration leads to a 60?% increase of the 4-??m idler power and a significant beam quality improvement when compared to a conventional singly resonant OPO.     

Single-longitudinal-mode optical parametric oscillator for spectroscopic applications

We have developed a tunable, narrow-bandwidth nanosecond optical parametric oscillator system and applied it to spectroscopic studies. The system consists of a narrow-bandwidth grazing-incidence oscillator and a seeded power oscillator, generating Fourier-transform-limited 1.5-ns pulses (bandwidth <500 MHz) in the wavelength range 435 to 2000 nm with energy of 3.5 mJ at a pump energy of 22 mJ. Continuous scanning over 30 to 100 GHz (depending on wavelength) is demonstrated by recording of the resonance line of the Hg atom at 253.7 nm and a vibrational transition of the CO (2) molecule at 1528 nm.     

Demonstration of improved beam quality in an image-rotating optical parametric oscillator

We performed laboratory and numerical modeling studies of an optical parametric oscillator with 90 degrees intracavity image rotation. We found that the signal beam was more symmetric than that from comparable cavities without image rotation, and it had low values of the beam quality factor, M(2) . Oscillator performance agreed well with our numerical model.     

光纤激光泵浦MgO:PPLN高功率中波红外光参量振荡器

为实现高效率、高功率中波红外激光输出,研制基于MgO:PPLN晶体的中波红外光参量振荡器（OPO）,泵浦源为基于主振荡功率放大（MOPA）结构的线偏振掺Yb光纤激光器（YDFL）。实验结果表明:YDFL可实现最高79.1 W的1064.1 nm脉冲线偏振激光输出;在YDFL泵浦下,通过优化输出镜曲率半径和泵浦光束腰直径,该OPO实现最高9.15 W的3.754 μm脉冲激光输出,光光转换效率为11.57%,重复频率为300 kHz,脉冲宽度约为110 ns。     

中红外光学参量振荡器技术进展

3~5μm中红外激光器在环境污染检测、医疗、工业等领域具有重要的应用价值。本文总结了基于ZnGeP_2、MgO∶PPLN晶体的光参量振荡器(OPO)的国内外发展现状,分析了其各自不同结构系统设计的优势和发展前景。指出高功率、小体积、轻重量的光学参量振荡器是未来重要发展方向,发展的技术核心是生长更大尺寸的中红外激光晶体以及研制更高性能指标的OPO泵浦源,并对中红外激光器的发展趋势进行了展望。     

光参量振荡器的模型仿真

在傍轴近似条件下建立了OPO的数学模型,通过引入三波混频中时间与空间关系,采用分步傅里叶算法模拟了纳秒级脉冲和连续光波在谐振腔内的三波混频过程。理论模型中考虑了不同频率光波之间的色散关系,可以在高转换效率情况下分析不同泵浦脉冲功率、脉冲时长、腔镜透反射比以及不同种子光输入等情况下的输出波形、功率以及OPO阈值等特性。实验中采用掺杂MgO的周期性极化铌酸锂晶体（MgO∶PPLN）为非线性介质,在输入1.06 m泵浦激光脉冲能量为0.4 mJ时,产生3.8 m闲频光超过0.07 mJ输出,与数值模拟结果0.08 mJ较为符合。     

Wavelength-swept optical parametric oscillator for broadband mid-infrared spectroscopy

In this work we describe a wavelength-swept continuous-wave optical parametric oscillator (OPO) for the rapid acquisition of mid-infrared spectra spanning over hundreds of wavenumbers. Rapid tuning of a ytterbium-doped fibre pump laser resulted in the OPO idler tuning over 900 cm^?1 in 3.36 ms at a resolution of 4.5 cm^?1, within a total accessible range of 2.67 to 4.34 μm (2304–3752 cm^?1). Predictable tuning characteristics allowed simple online calibration of recorded spectra for absolute mid-infrared frequency. The system thus offers a viable approach to broadband spectral acquisition in applications requiring high-radiance illumination.     

Analysis of time domain characteristics of high energy nano-second optical parametric oscillator

The time domain characteristics of high energy nano-second optical parametric oscillator are analysed with discrete-approximation method, and the procedure of signal wave is modeled. Different pulse widths result in varied build-up times and optimum crystal lengths, which dominate the efficiency of pulse pump. When the pump energy remains fixed, there is an optimum pulse width for the pump wave, with which the highest efficiency could be expected. In addition, for the first time, the analytic solutions for both small and large signal gain conditions are supplied with the discrete-approximation method. We also give the equations for the build-up time, the optimum crystal length and the efficiency, both in accurate form and simple form for estimation, and finally apply the results to the experiments.