A pulsed optical parametric oscillator, based on periodically poled lithium niobate (PPLN), for high-resolution spectroscopy

-1 ), approaching the limit imposed by the Fourier transform of the pulse duration. Received: 31 August 1998     

Angle-tuned signal-resonated optical parametric oscillator based on periodically poled lithium niobate

We demonstrate an angle-tuned signal-resonated optical parametric oscillator (OPO) with periodically poled lithium niobate (PPLN) pumped by a diode-pumped Nd:YVO4 laser. 1499.8 - 1506.6 nm of signal wavelength is achieved at 140℃ by rotating a 29-μm period PPLN from 0° - 10.22° in the x-y plane while keeping the pump wave vertical to the resonator mirrors. Two pairs of the signal and idler waves of the same wavelengths can be achieved symmetrically for each pair of angles of rotation with same absolute value and opposite sign. Theoretical analyses on angle-tuned PPLN-OPO with pump wave vertical to the resonator mirrors are presented and in good agreement with our experimental results. It is also found that all interacting waves in the cavity (not inside the crystal) are always collineax for PPLN-OPO with the pump wave vertical to the resonator mirrors while phase-matching is noncollinear within the crystal.     

High-power picosecond optical parametric oscillator based on periodically poled lithium niobate

A high-power picosecond optical parametric oscillator (OPO) based on a 47-mm periodically poled lithium niobate crystal is described. More than 12 W of total average power-almost 8 W of signal power at 1.85 microm and more than 4 W of idler radiation at 2.5 microm -is simultaneously extracted from less than 18 W of average pump power. The OPO is synchronously pumped by 80-ps (FWHM) cw mode-locked pulses at 1.064 microm , and its output is tunable from 1.7 to 2.84microm . Nearly transform-limited signal pulses are obtained following the introduction of two intracavity etalons.     

Frequency-agile kilohertz repetition-rate optical parametric oscillator based on periodically poled lithium niobate

We report kilohertz repetition-rate pulse-to-pulse wavelength tuning from 3.22 to 3.7 mum in a periodically poled lithium niobate (PPLN) optical parametric oscillator (OPO). Rapid tuning over 400 cm(-1) with random wavelength accessibility is achieved by rotation of the pump beam angle by no more than 24 mrad in the PPLN crystal by use of an acousto-optic beam deflector. Over the entire tuning range, a near-transform-limited OPO bandwidth can be obtained by means of injection seeding with a single-frequency 1.5-mum laser diode. The frequency agility, high repetition rate, and narrow bandwidth of this mid-IR PPLN OPO make it well suited as a lidar transmitter source.     

Continuous-wave 532-nm-pumped singly resonant optical parametric oscillator based on periodically poled lithium niobate

We report a continuous-wave (cw) 532-nm-pumped singly resonant optical parametric oscillator (SRO) based on periodically poled lithium niobate. The pump source is a commercial 5-W cw diode-pumped, multilongitudinal-mode, intracavity-doubled Nd:YVO(4) laser. Using a four-mirror ring SRO cavity and single-pass pumping, we achieved subwatt internal oscillation threshold, 56% quantum efficiency, and output tuning from 917 to 1266 nm.     

Continuous-wave mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

This paper reports a continuous-wave （CW） mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate （PPLN） pumped by a diode-end-pumped CW Nd：YVO4 laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN＇s grating period of 28.5 μm and the temperature of 140℃, the maximum idler output power of 155 mW at 3.86 μm has been achieved when the 808 nm pump power is 8.5 W, leading to an optical-to-optical conversion efficiency of 1.82%.     

Continuous-wave mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

This paper reports a continuous-wave (CW) mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate (PPLN) pumped by a diode-end-pumped CW Nd:YVO$_{4}$ laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN's grating period of 28.5\,$\mu$m and the temperature of 140\du, the maximum idler output power of 155\,mW at 3.86\,$\mu$m has been achieved when the 808\,nm pump power is 8.5\,W, leading to an optical-to-optical conversion efficiency of 1.82{\%}.     

Low-threshold singly-resonant continuous-wave optical parametric oscillator based on MgO-doped PPLN

We present a 532 nm-pumped singly-resonant cw optical parametric oscillator based on MgO-doped PPLN with a minimum threshold pump power of 0.3 W. The OPO with a two-mirror standing-wave cavity is optimized by using a tunable diode laser on the path of the resonant signal beam. The maximum output power is 200 mW at an idler wavelength near 1330 nm at a pump power of 2 W. We report the degradation of the output power and beam characteristics at high pump power indicating a strong thermal lensing in the crystal. The continuous tuning range of the OPO is measured to be 800 MHz which is close to 90% of the free spectral range of the OPO cavity.     

High-efficiency,high-repetition-rate,temperature-tuning optical parametric oscillator based on periodically poled MgO-doped lithium niobate

We report a compact and viable source of high-efficiency, high-repetition-rate, temperature-tuning, mid-IR optical parametric oscillator (OPO) based on periodically poled MgO-doped lithium niobate (PPMgOLN) pumped by a homemade high power AOM Q-switched Nd:YVO₄ laser centered at 1.064 μm. With an optimal plane-concave resonator configuration, average output power of 5.7 W at 2.73 μm was obtained when the pump power was 25 W at the repetition rate of 80 kHz. The conversion efficiency from the 1.064 μm laser to the 2.73 μm laser was 22.8%. Temperature tuning of the OPO yielded a signal wavelength range from 1.67 to 1.75 μm and an idler wavelength in the range of 2.72 to 2.92 μm.     

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。     

周期性极化铌酸锂晶体光参量振荡调谐与容差特性分析

研究了周期性极化铌酸锂晶体光参量振荡的工作机理,并讨论了其波长调谐特性与极化反转光栅周期、抽运光波长与晶体温度的关系.在此基础上,通过对相位失配因子求微分的方案,分析了光参量振荡的增益与光栅周期、抽运光波长与晶体温度的关系,以及光栅周期、抽运光波长与晶体温度容差的关系 关键词： 准相位匹配 周期性极化铌酸锂 光参量振荡     

Continuous wave monolithic quasi-phase-matched optical parametric oscillator in periodically poled lithium niobate

We demonstrate a monolithic and quasi-phasematched singly resonant cw optical parametric oscillator in periodically poled lithium niobate. The threshold is 1.0 W and the OPO delivers up to 0.98 W signal power tunable between 1750 and 1950 nm (2710 and 2340 nm idler, respectively). We identify cascaded parasitic oscillation effects and analyze their behavior theoretically, showing good agreement with our experiment. The analysis of parasitic effects points the way to improved device designs that should enable stable, compact, and frequency-tunable sources.     

Five-optical-cycle pulse generation in the mid infrared from an optical parametric oscillator based on aperiodically poled lithium niobate

We describe an optical parametric oscillator based on aperiodically poled lithium niobate that generates nearly transform-limited 53-fs duration pulses at a center wavelength of 3mum, corresponding to only 5 optical cycles. Results are presented illustrating the effect of pump- and grating-period chirp on the idler pulses, and a configuration capable of producing idler bandwidths in excess of 700 nm is discussed.     

Optimization of the idler wavelength tunable cascaded optical parametric oscillator based on chirp-assisted aperiodically poled lithium niobate crystal

We present the numerical results for the optimization of the pump-to-idler conversion efficiencies of nanosecond idler wavelength tunable cascaded optical parametric oscillators(OPO) in different wavelength tuning ranges, where the primary signals from the OPO process are recycled to enhance the pump-to-idler conversion efficiencies via the simultaneous difference frequency generation(DFG) process by monolithic aperiodically poled, magnesium oxide doped lithium niobate(APMg LN) crystals. The APMg LN crystals are designed with different chirp parameters for the DFG process to broaden their thermal acceptance bandwidths to different extents. The idler wavelength tuning of the cascaded OPO is realized by changing the temperature of the designed APMg LN crystal and the cascaded oscillation is achieved in a single pump pass singly resonant linear cavity. The pump-to-idler conversion efficiencies with respect to the pump pulse duration and ratio of OPO coefficient to DFG coefficient are calculated by numerically solving the coupled wave equations. The optimal working conditions of the tunable cascaded OPOs pumped by pulses with energies of 350 μJ and 700 μJ are compared to obtain the general rules of optimization. It is concluded that the optimization becomes the interplay between the ratio of OPO coefficient to DFG coefficient and the pump pulse duration when the idler wavelength tuning range and the pump pulse energy are fixed. Besides, higher pump pulse energy is beneficial for reaching higher optimal pump-to-idler conversion efficiency as long as the APMg LN crystal is optimized according to this pump condition. To the best of our knowledge,this is the first numerical analysis of idler wavelength tunable cascaded OPOs based on chirp-assisted APMg LN crystals.     

Broadly tunable mid-infrared femtosecond optical parametric oscillator using all-solid-state-pumped periodically poled lithium niobate

We describe a high-repetition-rate femtosecond optical parametric oscillator (OPO) that was broadly tunable in the mid infrared. The all-solid-state-pumped OPO was based on quasi-phase matching in periodically poled lithium niobate. The idler was tunable from approximately 1.7 mum to beyond 5.4 mum, with maximum average power levels greater than 200 mW and more than 20 mW of average power at 5.4 mum. We used interferometric autocorrelation to characterize the mid-infrared idler pulses, which typically had durations of 125 fs. This OPO had a pumping threshold as low as 65 mW of average pump power, a maximum conversion efficiency of >35% into the near-infrared signal, a slope efficiency for the signal of approximately 60%, and a maximum pump depletion of more than 85%.     

Aging effect in proton-exchanged optical waveguides based on lithium niobate crystals

The optical characteristics of planar waveguides produced by proton exchange in lithium niobate crystals in different acids (with and without additives) are unstable with time (“aging” effect). The aging effects in LiNbO₃ optical waveguides are investigated at room and elevated (50, 60, or 70°C) temperatures. In all cases, variations in the refractive index of the waveguide layer with time, i.e., for two or three years at room temperature and for several weeks at elevated temperatures, are determined for waveguides prepared in different media. The dependences of the optical characteristics of waveguides on the nature of proton sources and the aging conditions are obtained experimentally.     

Self-guided operation of singly resonant continuous-wave optical parametric oscillator based on bulk MgO-doped PPLN

We report on a self-guided operation of a green-pumped singly resonant continuous-wave optical parametric oscillator with a bulk MgO-doped PPLN crystal. It is achieved by increasing the OPO cavity length beyond the stability boundary so that the OPO can only oscillate with formation of a thermally induced waveguide inside the crystal. The effects of the thermal waveguide on the OPO performance are studied by measuring output power characteristics at different cavity lengths. Improvement of spatial mode quality and stability of output power by self-guiding is demonstrated. Measurement of temporal characteristics proves that formation of the waveguide originates from the photo-thermal effect in the nonlinear crystal by absorption of pump power.     

可调谐PPLN中红外光参量振荡器失调特性

 通过对晶体进行周期调谐,实现了中红外参量光输出,在此基础上研究了晶体移动、腔镜偏转等对失调特性的影响。结果表明：由于PPLN通道的小尺寸波导特性和参量振荡特性,其失调特性不同于常规激光器。PPLN晶体沿不同轴移动的功率变化曲线有不同的特点,沿x轴移动的失调容限大于沿y轴移动的失调容限;腔镜的失调容限与腔镜偏转方向有关,腔镜横向偏转的失调容限大于纵向偏转的失调容限;PPLN晶体温度和通道对失调容限几乎没有影响。     

High efficiency continuous-wave tunable signal output of an intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

In this paper we report on a continuous-wave (CW) intracavity singly resonant optical parametric oscillator (ICSRO) based on periodically poled LiNbO₃ (PPLN) pumped by a diode-end-pumped CW Nd:YVO₄ laser. Considering the thermal lens effects and diffraction loss, an optical ballast lens and a near-concentric cavity are adopted for better operation. Through varying the grating period and the temperature, the tunable signal output from 1406~nm to 1513~nm is obtained. At a PPLN grating period of 29~μ m and a temperature of 413~K, a maximum signal output power of 820~mW at 1500~nm is achieved when the 808~nm pump power is 10.9~W, leading to an optical-to-optical conversion efficiency of 7.51%.