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%.

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 pm 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%.

Low noise,continuous-wave single-frequency 1.5-μm laser generated by a singly resonant optical parametric oscillator

We report a low noise continuous-wave （CW） single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator （SRO） based on periodically poled lithium niobate （PPLN）. The SRO was pumped by a CW single-frequency Nd：YVO4 laser at 1.06μm. The 1.02 W of CW single-frequency signal laser at 1.5 μm was obtained at pump power of 6 W. At the output power of around 0.75 W, the power stability was better than ±l.5% and no mode-hopping was observed in 30 min and frequency stability was better than 8.5 MHz in 1 min. The signal wavelength could be tuned from 1.57 to 1.59 μm by varying the PPLN temperature. The 1.5-μm laser exhibits low noise characteristics, the intensity noise of the laser reaches the shot noise limit （SNL） at an analysis frequency of 4 MHz and the phase noise is less than 1 dB above the SNL at analysis frequencies above 10 MHz.

High-Efficiency Mid-Infrared Picosecond MgO:PPLN Single Resonant Optical Parametric Oscillator

We demonstrate a high-emciency mid-infrared picosecond optical parametric oscillator （OPO） based on MgO doped periodically poled lithium niobate （MgO：PPLN） with a laser diode array （LDA） pumped Innoslab amplifier as the pumping source. Under a 16 W synchronously pumping power, 4.5 W of idler light at 2896nm is obtained. A tuning range of idler light from 2688nm to 3016nm is achieved, within which the highest optical-optical conversion ettlciency from pump power to OPO output is 35.1%. Moreover, a signal light of -500mW from 1644 to 1700nm with a repetition rate of 233.8 MHz is generated.

Efficient continuous-wave eye-safe region signal output from intra-cavity singly resonant optical parametric oscillator

We report an efficient continuous-wave （CW） tunable intra-cavity singly resonant optical parametric oscillator based on the multi-period periodically poled lithium niobate and using a laser diode （LD） end-pumped CW 1064 nm Nd：YVO4 laser as the pump source. A highly efficiency CW operation is realized through a careful cavity design for mode matching and thermal stability. The signal tuning range is 1401 1500 nm obtained by varying the domain period. The maximum output power of 2.2 W at 1500 nm is obtained with a 17.1 W 808 nm LD power and the corresponding conversion efficiency is 12.9%.

Tunable femtosecond laser in the visible range with an intracavity frequency-doubled optical parametric oscillator

We demonstrated experimentally a synchronously pumped intracavity frequency-doubled femtosecond optical para- metric oscillator （OPO） using a periodically-poled lithium niobate （PPLN） as the nonlinear material in combination with a lithium triborate （LBO） as the doubling crystal. A Kerr-lens-mode-locked （KLM） Ti：sapphire oscillator at the wavelength of 790 nm was used as the pump source, which was capable of generating pulses with a duration as short as 117 fs. A tunable femtosecond laser covering the 624-672 nm range was realized by conveniently adjusting the OPO cavity length. A maximum average output power of 260 mW in the visible range was obtained at the pump power of 2.2 W, with a typical pulse duration of 205 fs assuming a sech2 pulse profile.

Tunable femtosecond near-infrared source based on a Yb:LYSO-laser-pumped optical parametric oscillator

We demonstrate a widely tunable near-infrared source from 767 nm to 874 nm generated by the intracavity second harmonic generation （SHG） in an optical parametric oscillator pumped by a Yb：LYSO solid-state laser. The home-made Yb：LYSO oscillator centered at 1035 nm delivers an average power of 2 W and a pulse duration as short as 351 fs. TWo MgO doped periodically poled lithium niobates （MgO：PPLN） with grating periods of 28.5-31.5 μm in steps of 0.5 μm and 19.5-21.3μm in steps of 0.2 μm are used for the OPO and intracavity SHG, respectively. The maximum average output power of 180 mW at 798 nm was obtained and the output pulses have pulse duration of 313 fs at 792 nm if a sech2-pulse shape was assumed. In addition, tunable signal femtosecond pulses from 1428 nm to 1763 nm are also realized with the maximum average power of 355 mW at 1628 nm.

High-average-power, high-repetition-rate tunable terahertz difference frequency generation with GaSe crystal pumped by 2 μm dual-wavelength intracavity KTP optical parametric oscillator

We have demonstrated a high-average-power,high-repetition-rate optical terahertz(THz)source based on difference frequency generation(DFG)in the GaSe crystal by using a near-degenerate 2μm intracavity KTP optical parametric oscillator as the pump source.The power of the 2μm dual-wavelength laser was up to 12.33 W with continuous tuning ranges of 1988.0–2196.2 nm/2278.4–2065.6 nm for two waves.Different GaSe cystal lengths have been experimentally investigated for the DFG THz source in order to optimize the THz output power,which was in good agreement with the theoretical analysis.Based on an 8 mm long GaSe crystal,the THz wave was continuously tuned from 0.21 to 3 THz.The maximum THz average power of 1.66μW was obtained at repetition rate of 10 kHz under 1.48 THz.The single pulse energy amounted to 166 pJ and the conversion efficiency from 2 μm laser to THz output was 1.68×10^(-6).The signal-to-noise ratio of the detected THz voltage was 23 dB.The acceptance angle of DFG in the GaSe crystal was measured to be 0.16°.

High efficiency,low threshold,high repetition rate H-βFraunhofer line light at 486.1 nm generation by an intracavity frequency-doubled optical parametric oscillator

A high efficiency,low threshold,high repetition rate H-βFraunhofer line light at 486.1 nm was demonstrated.A high-efficiency KTP optical parametric oscillator was achieved by double-pass pumping with a high-maturity 5 kHz 532 nm laser.Thanks to the efficient intracavity frequency doubling of the circulating signal wave by a BIBO crystal,the threshold pump power of the 486.1 nm output was 0.9 W,and the maximum output power of 1.6 W was achieved under the pump power of7.5 W.The optical–optical conversion efficiency was 21.3%,with the pulse duration of 45.2 ns,linewidth of~0.12 nm,and beam quality factor M~2 of 2.83.

Subnanosecond KTiOPO4 optical parametric oscillator intracavity pumped by a Kerr-lens, mode-locked YVO4/Nd:YVO4 laser coupled with an acousto-optic modulator

A Kerr-lens, mode-locked YVO4∕Nd:YVO4laser coupled with an acousto-optic modulator（AOM） Q-switching near1064 nm was employed to pump an intracavity KTi OPO4（KTP） optical parametric oscillator. A subnanosecond signal wave near 1572 nm with low repetition rate was realized. At an AOM repetition rate of 8 kHz, the maximum output power was 165 mW. The highest average pulse energy, the shortest duration, and the highest peak power of a mode-locking signal pulse were estimated to be ～10.3 μJ, ～120 ps, and ～82 kW, respectively.

Investigations on beam quality improvement of an NCPM-KTA-based high energy optical parametric oscillator using an unstable resonator with a Gaussian reflectivity mirror

Beam quality improvements by a large margin for signal and idler beams of a high energy 100 Hz KTiOAsO_(4)(KTA)non-critical phase matching(NCPM)optical parametric oscillator(OPO)were demonstrated using an unstable resonator configuration instead of a plane-parallel one.Theoretically,influences of cavity lengths and transmission of an output coupler on the OPO conversion efficiency for both were numerically simulated.For OPO based on an unstable resonator with a Gaussian reflectivity mirror,the maximum pulse energies at the signal(1.53μm)and idler(3.47μm)were about 75 mJ and 26 mJ,respectively.The corresponding beam quality factors of the signal were M_(x)^(2)=9.8 and M_(y)^(2)=9.9,and M_(x)^(2)=11.2 and M_(y)^(2)=11.5 for the idler.As a comparison,128 mJ of signal and 48 mJ of idler were obtained with the plane-parallel resonator,and the M~2 factors of the signal were M_(x)^(2)=39.8 and M_(y)^(2)=38.4,and M_(x)^(2)=32.1 and M_(y)^(2)=31.4 for the idler.Compared with a plane-parallel cavity,over eight times and three times brightness improvements were realized for the signal and idler light,respectively.

Widely tunable optical parametric oscillator in periodically poled congruently grown lithium tantalite whispering gallery mode resonators

We demonstrate a tunable optical parametric oscillator in a periodically poled congruently grown lithium tantalite whispering gallery mode resonator. The resonator is mechanically polished to millimeter size, and the quality factor is approximately 107 at 1064 nm. Our experiments show that this kind of resonator is capable of reaching a very low threshold and having a wide tuning range. Combined with its narrow resonant linewidth,it is potentially used as a compact, widely tunable, and narrow-linewidth infrared to mid-infrared laser source.

基于掺镁周期极化铌酸锂晶体的内腔单共振连续可调谐光参量振荡器

为了用简单、紧凑的谐振腔获得稳定的激光输出,大的调谐范围和转换效率,设计了信号光单共振V型光学参量振荡(OPO)腔,采用内腔式抽运周期极化掺镁铌酸锂晶体(PPMgLN)的光学参量振荡技术获得了连续中红外宽波段调谐激光的输出。用808nm半导体激光抽运Nd∶YVO4晶体产生的1 064nm激光作为光参量振荡的基频光,通过V型腔灵活控制激光光斑并改变PPMgLN的极化周期和控制温度实现了2 249～3 706nm中红外的连续宽波段调谐激光输出。在半导体激光抽运功率为10.5W,极化周期为29.98μm,控制温度为411K的情况下获得了最高650mW的中红外激光输出,对应的中心波长为3 466nm,线宽为2.6nm,具有较好的单色性。在7.5W的入射功率下,最高808nm抽运光到闲频光的转化效率达7.73%,对应输出功率为580mW。

1.57μm内腔光学参量振荡器研究

对内腔光学参量振荡器的工作机理进行了简要分析 ,报道了一种高效、紧凑的 1.5 7μm人眼安全内腔光学参量振荡器的实验结果。它的泵浦源为水冷闪光灯泵浦KD P电光调Q (Ce ,Nd) :YAG激光器 ,采用KTPⅡ类非临界相位匹配 ,输出信号光脉冲能量最高达 87.7mJ ,脉宽约7ns ,重复频率为 10Hz ,总电光效率最高达 5 .8‰ ,器件外形尺寸为 4 10mm× 130mm× 80mm。

大尺寸ZnGeP_2晶体生长与中红外光参量振荡

采用垂直布里奇曼方法生长了ZnGeP2单晶体,晶体毛坯尺寸达30 mm×120 mm。晶体在2.05μm吸收系数0.05cm-1,3-8μm吸收系数0.01 cm^-1,光损伤阈值2.0±0.3 J/cm2。利用2.05μmTm,Ho∶CdVO4激光器为泵浦源,脉冲重复频率10 kHz。当泵浦功率16.3 W时,3-5μm光参量振荡输出8.7 W,光-光转换效率为53%,斜率效率为64%。

2．6～2．8μm KTP OPO实验研究

为了得到2.7μm波段可调谐激光辐射,设计了信号光单谐振荡KTP光参量振荡器(OPO),给出了KTP OPOⅡ(B)类相位匹配方式下的角度调谐曲线、有效非线性系数.KTP晶体切割角为θ=62°,ψ=0°,有效非线性系数为-2.97 pm/V.利用该KTP OPO实现了2.6～2.8μm波段范围可调谐激光输出,用脉宽为16ns的基模高斯光束1.064μm激光泵浦得到了最大能量578μJ,能量转换效率达1.7%.

KTA和KTP晶体参量激光特性研究

讨论了激光二极管阵列(LDA)侧面泵浦声光调QNd∶YAG内腔式光学参量振荡器(OPO)的阈值特性;在相同的实验条件下,对比分析了KTA和KTP晶体参量激光输出特性。当声光重复频率为4kHz,输出镜透过率为30%,泵浦电流为14.5A时,波长为1.57μm,KTA晶体参量激光平均输出功率最大为613.4mW,脉冲宽度约2.5ns,峰值功率超过61kW。

高亮度人眼安全KTP OPO激光器

采用多模Nd:YAG激光器泵浦非临界相位匹配的KTP OPO,获得了光束角2.3 mrad、输出能量400 mJ、平均功率12 W、光光转换效率40%的1 572 nm激光。泵浦源的参数为:能量1 J、重复频率30 Hz。分析认为:采用KTP OPO将Nd:YAG激光器的1μm激光转换到人眼安全波段的方法是获得1.5μm激光的最有效的手段之一;非临界相位匹配的KTP OPO的主要优点是大的接受角和无走离,因此即使多纵模激光泵浦情况下也可以获得很高的转换效率。

加固型人眼安全OPO激光器的设计

考虑到军用激光器对可靠性的特殊要求 ,设计了一种加固型的内腔式人眼安全OPO激光器。采用双定向棱镜折叠谐振腔、Cr4+ ∶YAG被动调Q晶体、Ce Nd∶YAG激光棒、非临界相位匹配KTP光参量振荡晶体 ,获得5 .3mJ/pulse 1 .5 7μmOPO激光输出 ,脉冲宽度约为 6ns,发散角约为 5mrad ,重复频率为 3Hz ,连续工作时间为1min ,且输出能量和光轴指向稳定的结果。该激光器具有结构紧凑、可靠性高的特点。

被动调Q腔内单共振光参变振荡器和Cr^(4+):YAG激光器

分析了以Cr4+∶YAG作为饱和吸收体和激光增益介质的被动Q开关Cr4+∶YAG激光器腔内抽运的Cr4+∶YAG激光器和单共振光学参变振荡器(SRO)的特性。建立了描述这类激光器和单共振光学参变振荡器的动力学特性的速率方程。结果表明,适当条件下作为激光增益介质的Cr4+∶YAG同时具有对二阶非线性作用过程产生的处于Cr4+∶YAG激光增益谱范围内的SRO信号波的放大作用。分析中考虑了Cr4+∶YAG较高激发态和激光上能级之间的弛豫时间约为100ns的中间能级对Cr4+∶YAG饱和吸收体和激光器以及ICSRO的影响。