Idler-resonant optical parametric oscillator based on KTiOAsO4

An idler-resonant KTiOAsO₄ (KTA) optical parametric oscillator is demonstrated within a diode-end-pumped acousto-optically Q-switched Nd:YAG laser. With an X-cut KTA crystal, idler wave at 3467 nm and signal wave at 1535 nm are generated. Under an incident diode pump power of 15.4 W, the idler output power of 105 mW and signal power of 720 mW are obtained at a pulse repetition rate of 40 kHz. The pulse widths of the idler and signal waves are 7.2 and 3.1 ns, respectively. The beam quality factors (M²) of the idler wave are within 1.2 in both horizontal and vertical directions.     

Continuous-tunable 4.144-4.851 μm twin-MgO:PPLN cascaded optical parametric generator pumped by a 1.342 μm Nd:GdVO4 laser

An all-solid-state mid-infrared optical parametric generator with wide tunability by using multi-grating periodically poled 5 mol.-% MgO-doped lithium niobate (MgO:PPLN) is reported. The pump source is a diode-pumped Q-switched Nd:GdVO₄ laser operated at 1.342 μm with pulse width of 150 ns and repetition rate of 50 kHz. To extend the interaction length, two identical multi-grating MgO:PPLN crystals have been cascaded in the OPG system. When the incident pump average power is 10 W, the obtained maximum idler output power is 340 mW at 4.144 μm. Compared with only using one multi-grating MgO:PPLN crystal, the obtained idler output power increases by 20.1%. 4.144-4.851 μm continuous-tunable idler output is obtained with six grating periods from 29 to 31.5 μm and temperature from 40 to 200 °C. To our knowledge, this is the first time to use 1.342 μm laser as the pump source of OPG.     

High-power, high-repetition-rate mid-infrared generation with PE-SRO based on a fan-out periodically poled MgO-doped lithium niobate

We present a high-average-power, pulsed mid-infrared pump-enhanced singly-resonant optical parametric oscillator (PE-SRO) using a fan-out periodically poled MgO-doped lithium niobate (MgO:PPLN). The pump laser is a Q-switched Nd:YAG laser with a repetition rate of 10 kHz. When the pump power was 22.0 W, a maximum idler output power of 3.4 W at 3781.4 nm was obtained. The thermal guiding effect caused by signal absorption was observed and the crystal heating power was measured with a new method.     

Low-threshold, high-efficiency, high-repetition-rate optical parametric generator based on periodically poled LiNbO3

We report a high-repetition-rate optical parametric generator (OPG) with a periodically poled lithium niobate (PPLN) crystal pumped by an acousto-optically Q-switched CW-diode-end-pumped Nd:YVO_4 laser. For the maximum 1064nm pump power of 970mW, the maximum conversion efficiency is 32.9% under the conditions of 250℃, 1064nm pulse repetition rate of 22.6kHz and pulse width of 12ns, and the PPLN OPG threshold in the collinear case is less than 23.7μJ. The output power increases with the increase of the crystal temperature. The 1485－1553nm signal wave and 3383－3754nm idler wave are obtained by changing the temperature and the angle of the PPLN crystal.     

High repetition rate mid-infrared generation with singly resonant optical parametric oscillator using multi-grating periodically poled MgO:LiNbO3

A high repetition rate mid-infrared singly resonant optical parametric oscillator (OPO) using MgO-doped multi-grating periodically poled LiNbO₃ (MgO:PPLN) is demonstrated. A 1064 nm Q-switched Nd:YVO₄ laser at 10 kHz repetition rate and pulse width of 17.8 ns was used to pump the OPO. The period of the quasi-phase matched (QPM) grating in the multi-grating MgO:PPLN chip varied from 25.5 to 31.5 μm in steps of 0.5 μm. This corresponds to the generation of a signal beam from 1.37 to 1.64 μm and an idler beam from 3.0 to 4.8 μm, respectively. A maximum signal power of 250 mW and idler power of 140 mW has been obtained with an input pump beam of power 1.92 W, for a grating period of 30.5 μm. A maximum optic-optic conversion efficiency of 20% and 7.4% in the idler has been observed. It has been observed that the output power increases as the period of the grating increases.     

Numerical solution and experiment of a self-Q-switched 946 nm Cr,Nd:YAG laser

A LD-pumped self-Q-switched 946 nm laser by using a co-doped Cr,Nd:YAG crystal as a gain medium as well as a saturable absorber is studied. The 946 nm self-Q-switched rate equations of co-doped crystal are solved numerically by Runge–Kutta method directly. The important parameters of lasers, such as average output power, threshold pump power, pulse width, pulses repetition rate, and optimal transmission of output coupler are obtained numerically. Experimentally, the maximum average output power up to 2.61 W, corresponding to a slope efficiency of 23.43%, was obtained in a simple and compact linear cavity. The optical-to-optical efficiency is 17.3% and the peak power is 7.57 kW with repetition rate of 23.78 kHz and pulse width of 14.5 ns. In the experiments, a high-quality fundamental transverse mode can be preserved in a large range of incident pump power. The numerical results of the 946 nm self-Q-switched Cr,Nd:YAG laser are in good agreement with the experimental results.     

1.8 μm optical parametric oscillator based on KTiOPO4

A 1.8 ??m optical parametric oscillator pumped by a diode end-pumped acousto-optically Q-switched Nd:YAG is demonstrated. A 30-mm-long KTiOPO₄ crystal cut with an angle of ?? = 59.4°, ?? = 0° is employed as the OPO crystal. 685 mW signal laser at 1.8 ??m is obtained at the diode pump power of 13 W and the pulse repetition rate of 25 kHz. Simultaneously, 265 mW idler emission at 2.6 ??m is obtained. The corresponded diode-to-OPO conversion efficiency is 7.3%. The pulse width of the signal and idler wave are measured to be 4.5 and 2.5 ns, respectively. This gives a peak power of 6.1 and 4.2 kW, respectively.     

High-Power,high-repetition-rate operation of a period-continuously-tunable optical parametric oscillator at 3.78–4.62 μm based on a fan-out periodically poled MgO-doped lithium niobate

We present a period-continuously-tunable optical parametric oscillator based on a fan-out MgO:PPLN with a grating period range from 26.9 to 29.5 μm. The OPO was pumped by a Q-switched Nd:YAG laser with a repetition of 10 kHz. With a grating period of 29.3 μm and 22.0 W pump power, the idler output power at 3.78 μm arrived at 3.40 W. With a period of 27.1 μm and 13.5 W pump, the idler output at 4.58 μm arrived at 0.36 W. This is, to our best knowledge, the highest average power for pulsed OPO operating near 4.5 μm based on PPLN or MgO:PPLN. By translating the fan-out MgO:PPLN, the idler wavelength was tuned continuously from 3.78 to 4.62 μm.     

Laser-diode-pumped Nd:YVO<Subscript>4</Subscript>/Nd:YAG MOPA burst-mode laser

We report a high-repetition-rate, high-peak-power laser diode (LD) pumped burst-mode 1064 nm laser from a Nd:YVO₄/Nd:YAG master oscillator power amplifier. 10–100 kHz pulse burst in a duration up to 2 ms is achieved in LD end-pumped Nd:YVO₄ acousto-optically Q-switched laser. After amplification with LD side-pumped Nd:YAG rod amplifiers, the single pulse energy reaches 73 mJ in 10 kHz pulse burst laser with a peak power of 7.8 MW.     

Low-threshold mid-IR MgO:PPLN optical parametric generation with high reflectivity mirror for signal wavelength

A low-threshold middle-infrared(mid-IR) MgO:PPLN optical parametric generation(OPG)pumped by a laser diode(LDl end-pumped Z-type Nd:YLF laser at 1047 nm is realized with high reflectivity(HR) mirror for signal.At repetition rate of 10 kHz,the OPG threshold of 50μJ has been achieved with HR mirror for signal.Compared with the threshold without mirror,the threshold decreases by 17%.Using HR mirror for pump at output side of crystal,the threshold of 40μJ is achieved.The 2.7-4.1μm continuous tunable output is produced with seven grating periods from 28.5 to 31.5μm and temperatures from 30 to 200℃.When the incident average pump power is 3 W.the OPG idler output power is 0.46 W at 3.26 μm,which corresponds to optical-to-optical conversion efficiency up to 15.3%.     

基于光学参量振荡器的可调谐红外激光的强度噪声特性

红外激光光源在微量气体、高分辨率光谱分析和量子光学研究等领域具有重要的应用.本文利用锁定单共振光学参量振荡器内腔标准具的方案获得了无跳模连续调谐的红外激光输出,理论和实验研究了红外激光的强度噪声特性,分析了影响强度噪声的因素.通过控制非线性晶体的温度和标准具调制信号实现了对红外激光强度噪声的抑制.当控制非线性晶体工作温度为60℃,内腔标准具调制信号为8 kHz时,单共振光学参量振荡器输出信号光和闲置光的强度噪声分别降低了11和8 dB.     

Electro-optic periodically poled lithium niobate Bragg modulator as a laser Q-switch

We report an electro-optic Bragg modulator using a periodically poled lithium niobate (PPLN) crystal. We measured a half-wave voltage of 160 V when transmitting a 1064 nm laser through a 14.2 mm long, 780 microm thick, 20.13 microm period PPLN crystal at the Bragg angle. We also demonstrated a Q-switched Nd:YVO(4) laser using such a PPLN Bragg modulator as its Q-switch, producing 7.8 ns, 201 microJ pulses at a 10 kHz repetition rate when pumped by a 19.35 W diode laser at 808 nm.     

Multi-wavelength diode-pumped Nd:LGGG picosecond laser

Laser operation near 1.06 μm by a diode-pumped Nd:(Lu _x Gd_1?x )₃Ga₅O₁₂ (Nd:LGGG) disordered crystal has been investigated. Cw oscillation, with a slope efficiency as high as 61% and 230 mW output power, was achieved with 400 mW absorbed power from a 1-W laser diode. Stable passive mode locking with single- or multi-banded spectrum was obtained with a semiconductor saturable absorber mirror (SAM) and a single-prism, dispersion-compensated cavity. Fourier limited pulses with duration ≈3–9 ps and output power ≈40 mW were generated at three well-defined laser transitions in the range 1062–1067 nm.     

Generation of monochromatic visible light in microstructured optical fiber by nondegenerate four-wave mixing

We exploit nondegenerate four-wave mixing to generate narrow-bandwidth visible light from blue to orange in microstructured optical fiber. The process is excited by nanosecond dual-wavelength pump pulses (532/1064 nm) produced by a frequency-doubled passively Q-switched Nd:YAG laser. A linearly polarized, fundamental mode signal wave is generated in the visible, accompanied by an idler wave in the near-infrared. The signal and idler wavelengths are adjustable by the design of the microstructure.     

Pump tuned wide tunable noncritically phase-matched ZnGeP2 narrow line width optical parametric oscillator

A line tunable singly resonant noncritically phase matched narrow band width ZnGeP₂ (ZGP) optical parametric oscillator pumped by the output idler radiation from a KTA OPO based on a 20 mm long KTA crystal pumped from a Q-switched Gaussian shaped Nd:YAG laser beam with a grating having grooves density 85 lines/mm has been demonstrated in the spectral ranges of 3–7 μm. The measured threshold of oscillation energy was 10 μJ. The conversion efficiency was 20.5% and slope efficiency of the ZGP OPO was 20% using a 23 mm long ZGP crystal at 26 mm cavity length. Line width of the generated infrared radiation from ZGP OPO was 37–60 nm.     

Narrow-bandwidth, mid-infrared, seeded optical parametric generation in 90° phase-matched CdSiP₂ crystal pumped by diffraction limited 500 ps pulses at 1064 nm

Low-threshold, efficient optical parametric generation at ～6100 nm is demonstrated using CdSiP₂ nonlinear crystal at 1 to 10?kHz repetition rates with relatively long 500?ps pump pulses at 1064?nm. Maximum single pulse energy of 8.7?μJ and average power of 79?mW are achieved for the idler. Seeding at the signal wavelength is employed using a distributed feedback laser diode, which enables approximately tenfold narrowing of the idler bandwidth down to less than 1?nm.     

Widely and continuously tunable optical parametric generator infrared laser

The experimental results of a high efficiency infrared laser are demonstrated on a quasi phase matched optical parametric generator in PPMgLN (5% MgO doping) pumped by a 1064 nm Nd:YAG laser. A broad continuous signal spectrum 1.56?C1.67 ??m are obtained by tuning the crystal temperature from 20°C to 200°C. When the average pump power is 1.82 W with about 70 ns pulse duration operating at a repetition rate of 10 kHz, the maximum total output power of the PPMgLN OPG is about 323.58 mW consisting of 210 mW of 1.639 ??m signal radiation and 113.58 mW of 3.02 ??m idler radiation.     

LD抽运被动调Q固体激光器的脉冲稳定性

报道了二极管激光抽运Cr,Nd∶YAG被动调Q Nd∶YVO₄ 1064nm激光输出.为了提高被动调Q激光的输出稳定性，谐振腔采用长腔，增益介质位于谐振腔中间位置.实验中获得了稳定的被动调Q激光输出.在最高入射抽运功率为17.5W时，脉冲重复频率达到71.3kHz，脉冲宽度为0.4μs.调Q脉冲幅度不稳定性低于±10%，脉冲时间波动性低于±3.5%.     

Broadband infrared generation with noncollinear optical parametric processes on periodically poled LiNbO(3)

Broadband signal and idler generation based on the spectral retracing behavior in noncollinear phase matching of optical parametric generation in periodically poled LiNbO(3) (PPLN) is reported. Using PPLN of 29.5-mum quasi-phase-matching period and a Q-switched Nd:YAG laser as a pump, we obtained a broad signal spectrum from 1.66 to 1.96 mum and corresponding idler wavelengths from 2.328 to 2.963 mum. The experimental results were consistent with theoretical predictions. Circular and elliptical pump beams were also compared.     

Narrow-linewidth, pump-enhanced singly-resonant parametric oscillator pumped at 532 nm

3 is demonstrated. The pump wave is provided by a frequency-doubled miniature Nd:YAG ring laser and is resonantly enhanced in the SRO cavity, resulting in an external threshold of 200 mW. Stable single-frequency emission in the 1000–1135 nm range has been obtained with 2 GHz continuous tunability and signal/idler linewidths <160 kHz. Received: 25 August 1997