Compact, 1.5 mJ, 450 MHz, CdSiP2 picosecond optical parametric oscillator near 6.3 μm

We report a compact, efficient, high-energy, and high-repetition-rate mid-IR picosecond optical parametric oscillator (OPO) based on the new nonlinear material CdSiP(2) (CSP). The OPO is synchronously pumped by a master oscillator power amplifier system at 1064.1 nm, providing 1 μs long macropulses constituting 8.6 ps micropulses at 450 MHz, and it can be tuned over 486 nm across 6091-6577 nm, covering the technologically important wavelength range for surgical applications. Using a compact (～30 cm) cavity and improved, high-quality nonlinear crystal, idler macropulse energy as high as 1.5 mJ has been obtained at 6275 nm at a photon conversion efficiency of 29.5%, with >1.2 mJ over more than 68% of the tuning range, for an input macropulse energy of 30 mJ. Both the signal and idler beams are recorded to have good beam quality with a Gaussian spatial profile, and the extracted signal pulses are measured to have durations of 10.6 ps. Further, from the experimentally measured transmission data at 1064 nm, we have estimated the two-photon absorption coefficient of CSP to be β=2.4 cm/GW, with a corresponding energy bandgap, E(g)=2.08 eV.     

High-energy, narrow-bandwidth periodically poled Mg-doped LiNbO3 optical parametric oscillator with a volume Bragg grating

We have demonstrated a simple, high-energy, narrow spectral bandwidth optical parametric oscillator (OPO) by use of a large aperture periodically poled Mg-doped LiNbO(3) device with a volume Bragg grating (VBG). A free-running degenerate OPO pumped by a Q-switched 1.064 microm Nd:YAG laser exhibits maximum output pulse energy of 110 mJ with high slope efficiency of 75% around room temperature. Broad spectral bandwidth (Dlambda~100 nm) around the degeneracy wavelength was suppressed by using a VBG as an output coupler. Up to 61 mJ of the output pulse energy with narrowed spectral bandwidth of less than 1.4 nm was obtained at the degeneracy wavelength of 2.128 microm.     

6.1 MW, 10 kHz Side-Pumped Burst-Mode Nd:YAG Laser

We present a compact high-peak-power, high-repetition-rate burst-mode laser from a master-oscillator power amplifier (MOPA) at 1064 nm for laser-based measurement applications. The oscillator is an 808 nm pulsed laser diode side-pumped acousto-optical (A-O) Q-switched Nd:YAG laser at repetition rates ranging from 10–100 kHz, producing a pulse train with a pulse number of 2–25. The maximum output energy of the oscillator is 15.6 mJ at 10 kHz, whereas it is 1.7 mJ at 100 kHz. After twostage amplifiers, a single-pulse energy of 85.2 mJ with a pulse-width of 14.5 ns is achieved at 10 kHz, which produces a peak power of 6.1 MW. At 100 kHz, the total burst energy reaches 220 mJ with a single-pulse energy of 8.8 mJ in the pulse burst laser system.     

Injection-Seeded 500 Hz Repetition Rate High Peak Power Single-Frequency Nd:YAG Laser for Mid-Infrared Generation

We develop an injection-seeded single-frequency neodymium-doped yttrium aluminum garnet (Nd:YAG) laser with 500 Hz repetition rate and high peak power. The laser construction is designed as seed injection and master oscillator power amplifier (MOPA) including single-frequency master oscillator, extra-cavity frequency doubling crystal, and round-trip power amplifier. The master oscillator can emit 1,064 nm laser of 8.4 mJ with 6.8 ns pulse width at the pump energy equal to 23 mJ. A green laser energy of 1.1 mJ is obtained by setting the proper temperature of the LBO crystal. The pulse energy of 1,064 nm laser decreases to 6.5 mJ after passing through the LBO crystal and rises to 25.3 mJ after a round-trip power amplifier corresponding to the extraction efficiency of 29%. The final output pulse width is 6.5 ns, representing a peak power of 3.9 MW. The 1,064 nm laser beam quality factor M² of the master oscillator and the amplified one are 1.3 and 1.5, respectively. The laser will be used to generate mid-infrared where the 532 nm laser with narrow pulse width is to pump sheet optical parametric oscillator (OPO) and the 1,064 nm laser with high peak power to pump the OPO.     

Narrowband and tunable ring optical parametric oscillator with a volume Bragg grating

We demonstrate a tunable nanosecond optical parametric oscillator with a narrowed signal spectrum. This was done by use of a volume Bragg grating based retroreflector, which makes the tuning simple and yields a compact design. Using periodically poled KTiOPO4 as the nonlinear medium, we generated 0.42 mJ of signal energy at 760 nm with a tuning range of 5 nm(2.6 THz) and a bandwidth of 0.25 nm(130 GHz) when the oscillator was pumped at 532 nm with 1.3 mJ of energy.     

High-energy PPMgLN optical parametric oscillator pumped by a 1.064 μm E-O Q-Switched Nd:YAG laser

A high-energy PPMgLN optical parametric oscillator (OPO) pumped by a E-O Q-switched Nd:YAG laser working at 1.064 μm was successfully illustrated. A maximum output pulse energy of 3.4 mJ was obtained with a pump threshold of 1.5 mJ and a slope efficiency of 30% around room temperature. The OPO output signal and idler wavelength were 1552 and 3384 nm, respectively. The damage to the input surface of PPMgLN crystal was carefully observed with a damage threshold of 4.6 J/cm².     

可调谐钛宝石激光抽运的KTP单谐振光学参量振荡器的研究

介绍了 70 0nm～ 980nm的脉冲可调谐钛宝石激光抽运的KTP单谐振光学参量振荡器。通过改变抽运光波长作为光学参量振荡器输出参量光的调谐方式 ,确定了KTP晶体最佳切割角度 (θ=6 2 .5°,φ =0°) ,实验上获得了 12 5 1nm～ 2 5 32nm的连续参量光输出 ,最大输出能量约为 2 7 2mJ,最大转换效率为 35 7% (1311nm处 )。     

Multi-millijoule, nonlinear preamplifier for high intensity femtosecond Yb:YAG chirped-pulse amplification lasers at 1030 nm

We report the highest energy broadband laser pulses at a center wavelength of 1030 nm based on optical parametric chirped-pulse amplification (OPCPA). We have demonstrated amplification of 1030 nm femtosecond laser pulses from a broadband Yb oscillator to over 6.5 mJ with a total gain of greater than 10⁷ achieved in a single pass through only 56 mm of gain material at a 10 Hz repetition rate. The amplified spectral bandwidth of 10.8 nm affords recompression to a 230 fs pulse duration following amplification. As an alternative to the regenerative amplifier (RA) this system is one of the more promising candidates for realizing compact, high intensity, direct diode-pumped, high repetition rate femtosecond Yb:YAG chirped-pulse amplification (CPA) in laser systems.     

Q-switched Er:YAG lasers resonantly pumped by Erbium fiber laser

The study describes efficient, acousto-optic Q-switching of Er:YAG laser at the 1645 nm eye-safe wavelength. For longitudinal pumping at wavelength 1532 nm, linear-polarized 10 W Erbium fiber laser radiation was used. The investigated Er:YAG crystals were 25 and 40 mm long and their Erbium concentration was 0.20 and 0.25%, respectively. For giant pulse generation, a fused silica acousto-optic modulator was inserted inside the Er:YAG laser oscillator. For a maximum incident pump power of 7.95 W, pulse energy up to 4.1 mJ was generated with pulse duration 34 ns at 500-Hz repetition rate; the corresponding peak power was 119 kW.     

BiB3O6纳秒光参变振荡器

采用电光调Q脉冲Nd:YAG固体激光器的532 nm绿光作为抽运光源(10～13 ns,0～20 mJ),以Ⅱ类相位匹配(θ=57.5°Φ=0°)、尺寸为4 mmX 4 mm×12 mm的三硼酸铋晶体(BiB3O6)与一对1215 nm单谐振波长的平镜组成腔长为40 mm的谐振腔,构建了光参变振荡器的整个实验系统.系统将入射抽运光振荡产生1215 nm的信号光及946 nm的闲频光,结果显示,抽运阈值为9 mJ,最高耦合输出为2.57 mJ,抽运脉冲能量与信号脉冲能量的最高转换效率为14.59%.     

环形腔2.05μm单谐振KTP晶体光参量振荡器研究

针对大气CO_2浓度探测差分吸收激光雷达的应用需求,采用稳定环形腔和模式匹配设计,搭建了一套单纵模1 064nm激光泵浦的单谐振KTP晶体光参量振荡器,获得高斜率转换效率、基横模的2.05μm波长纳秒激光脉冲输出.在8字形环形行波稳定腔中,将2块II类相位匹配KTP晶体以走离补偿方式放置,在20Hz重复频率下,当泵浦单脉冲能量达到11mJ时,获得了单脉冲能量为2.4mJ的2.05μm信号光输出,脉宽约24ns,斜率效率达到53%.2.05μm信号光光束质量因子在x、y方向分别为1.3和1.2.     

Ultrahigh-frame-rate nitric oxide planar laser-induced fluorescence imaging

We demonstrate the ability to generate ultrahigh frequency burst sequences of deep UV at 226 nm by mixing the optical parametric oscillator signal output at 622 nm with third harmonic at 355 nm from a pulse burst laser system. We obtained 226 nm burst sequences with uniform burst envelopes, and the average pulse energy is approximately 0.5 mJ. Nitric oxide planar laser-induced fluorescence image sequences at ultrahigh (100 kHz) frame rates have been obtained.     

Diode-side-pumped AO Q-switched Tm,Ho:LuLF laser

A diode-side-pumped Tm,Ho:LuLiF laser at 2-m wavelength obtained in a ring resonator and its amplification experiment are reported. At the maximum pump energy of 4.7 J available for the oscillator,the output energy per pulse for the oscillator decreases from 904 to 483 mJ in free running mode,and decreases from 106 to 68 mJ in Q-switched mode,with an increase of pump pulse repetition rate from 1 to 5 Hz. When considering the amplifier,99-mJ Q-switched output energy is achieved at 5-Hz repetition rate.     

High-energy, broadly tunable, narrow-bandwidth mid-infrared optical parametric system pumped by quasi-phase-matched devices

We have developed a tunable, narrow-bandwidth (<2 cm(-1)) mid-infrared (MIR) optical parametric system with a large-aperture periodically poled Mg-doped LiNbO(3) (LA-PPMgLN)-based high-energy pump source. The system has a continuously tunable tuning range from 4.6 to 11.2 mum and produces a maximum output energy of 2.0 mJ at 5.1 mum. Practical use of the MIR source is demonstrated by MIR-UV double-resonance spectroscopy of jet-cooled acetanilide.     

宽波段温度调谐MgO∶LiNbO3光学参量振荡器

采用电光调Q脉冲Nd∶YAG激光的二次谐波 (5 32nm)抽运温度调谐的MgO∶LiNbO3晶体光学参量振荡器 ,调谐范围达 80 0nm～ 175 0nm。在单谐振运转条件下 ,抽运阈值为 2 1.5mJ/ pulse ,最大抽运能量为 5 8mJ时输出为 6 .45mJ ,在大信号情况下的能量转换效率达 11% ,输出线宽 1nm左右。     

输出能量4mJ的1kHz飞秒掺钛蓝宝石激光再生放大研究

针对高能量千赫兹重复频率飞秒激光的应用需求,设计了一套采用线性再生腔结构的高效率飞秒钛宝石激光啁啾脉冲放大系统.通过优化腔型设计,在重复频率为1 kHz、单脉冲能量为20 mJ的527 nm激光抽运下,将展宽后的800 nm啁啾脉冲激光的能量放大到5.8 mJ,对应斜效率达到30.7%.进一步通过色散补偿压缩脉冲宽度,获得了单脉冲能量为4 mJ、脉冲宽度为45.7 fs的输出,稳定性测量表明激光的能量抖动仅为0.18%(均方根值).     

高强度泵浦碱金属蒸气激光器的光参量振荡器

以电光调Q的Nd:YAG激光器为泵浦源,以磷酸氧钛钾（KTP）为非线性晶体,搭建了调谐范围为750~800 nm的光参量振荡器。信号光在中心波长780.2 nm处获得单脉冲能量113 mJ、脉宽15.43 ns、光斑直径5.5 mm的输出。用光栅单色仪测量信号光光谱宽度（FWHM）为0.38 nm。信号光通过120 ℃的铷蒸气池,观察到清晰的荧光轨迹。证明信号光能有效泵浦铷蒸气,可为铷激光器提供峰值功率7 MW的高强度脉冲泵浦源,进而研究铷激光器在高强度泵浦条件下的动力学过程和基础物理机制。     

52 mJ narrow-bandwidth degenerated optical parametric system with a large-aperture periodically poled MgO:LiNbO3 device

We have demonstrated efficient, high-energy, narrow-spectral-bandwidth 2.128 microm pulse generation by use of periodically poled MgO:LiNbO3 devices with a 36 mm length and a 5 mm x 5 mm large aperture. A free-running degenerated optical parametric oscillator (OPO) pumped with a Q-switched 1.064 microm Nd:YAG laser exhibits a high slope efficiency of 75% and an optical-to-optical conversion efficiency of 70% with a broad spectral bandwidth (>100 nm). In a configuration with a spectrally narrowed master oscillator followed by a power amplifier, we have achieved an output pulse energy of 52 mJ with a spectral bandwidth of less than 2 nm at the degeneracy point. The total optical-to-optical conversion efficiency of the system reached 50%.     

用于等离子体诊断的ps激光探针

 ps激光探针作为激光等离子体诊断的探针光源，它是通过两次倍频和两次受激喇曼散射，将波长为1 054nm、脉宽约为1ns激光转换成波长为308nm、脉宽小于30ps的紫外光。研究结果表明：探针光系统输出能量大于1mJ，脉宽小于30ps，均匀性较好，运行成功率大于90%，满足了激光等离子体诊断的要求。     

Improved efficiency of a pulsed optical parametric oscillator by delayed double-pass pump

By delaying the second pass of the pump of a singly resonant optical parametric oscillator, the conversion efficiency can be improved. We show the experimental results of an intracavity-doubled singly resonant parametric oscillator pumped by a Q-switched laser. Using 0.49 mJ of pump energy at 532 nm from a diode-pumped Nd:YAG laser, 0.085 mJ of 488 nm was obtained with the optimum delay for the second pass of the pump, giving a conversion efficiency of 17%. The improvement over the case of a single-pass pump was 85%, and the improvement over the double-pass pump with a small delay was 40%.