Growth of excellent-quality Nd : LuVO4 single crystal and laser properties

High-quality Nd:LuVO4 single crystal was successfully grown by Czochralski method. The assessment of the crystalline quality by the chemical etching method and Conoscope image was reported. The absorption spectra from 300 to 1000 nm and emission spectra from 960 to 1450 nm of Nd: LuVO4 were measured. Laser performance was achieved with Nd:LUVO4 crystal for the transition of F-4(3/2) -> I-4(11/2) (corresponding wavelength 1065.8 nm) in an actively Q-switched operation, and the average output power reached 5.42 W at a pulse repetition frequency (PRF) of 40 kHz under pump power of 18 W, giving an optical conversion efficiency of 30.1%. The pulse energy and peak power reached 138 mu J and 16.2 kW at PRF of 25 kHz under pump power of 14.2 W, and the pulse duration was 8.5 ns. (c) 2005 Elsevier B.V. All rights reserved.

Characterization of diode-pumped laser operation of a novel Yb : GSO crystal

We report what is believed to be the first demonstration of the laser action of Yb3+ -doped Gd2SiO5 (Yb:GSO) crystal pumped by a 940-nm laser diode at room temperature. The threshold of laser generation is only 0.85 kW/cm(2), which is smaller than the theoretic threshold of Yb:YAG (1.54 kW/cm(2)). The laser wavelength is 1090 mn. With a 2.5% output coupler, the maximum output power is 415 mW under a pump power of 5 W. By using the SESAM, the Q-switched mode locking and CW mode-locked operations are demonstrated.

铬、钕双掺钆镓石榴石（Cr^4＋，Nd^3＋）：Gd3Ga5O12激光晶体光学性能的研究

用提拉法生长了掺铬、钕的钆镓石榴石(Cr^4+，Nd^3+：GGG)自调Q激光品体。报道了室温下的吸收光谱和荧光光谱特性。分析了Cr离子浓度对光谱性质的影响。比较了Cr^4+：GGG，Nd^3+：GGG和(Cr^4+，Nd^3+)：GGG晶体吸收光谱的关系。测量了(Cr^4+，Nd^3+)：GGG晶体和Nd^3+：GGG晶体的荧光寿命，它们分别是33μs和250μs。实验表明，(Cr^4+，Nd^3+)：GGG晶体是一种非常有潜力的自调Q激光晶体，可以实现大功率激光器的小型化和全固态化。

Room-temperature cw and pulsed operation of a diode-end-pumped Tm:YAP laser

We report the continuous-wave and acousto-optical Q-switched operation of a diode-end-pumped Tm:YAP laser. Continuous-wave output power of 3.5 W at 1.99 mu m was obtained under the absorbed pump power of 14 W. Under Q-switched laser operation, the average output power increased from 1.57 W to 2.0 W, with an absorbed pump power of 12.6 W, as the repetition rate increased from 1 kHz to 10 kHz. The maximum Q-switched pulse energy was 1.57 mJ with a repetition rate of 1 kHz. The minimum pulse width was measured to be about 80 ns, corresponding to a peak power of 19.6 kW.

高真空室中的水蒸气对HfO2薄膜性能的影响

本文研究了在镀膜过程中真空室内水蒸气的含量对HfO2薄膜物理性能的影响。用电子束蒸发和光电极值监控的方法在BK7基底上制备HfO2薄膜。利用残余气体分析仪在线监测了真空室内的残余气氛组成。分别用Lambda 900光谱仪、X射线衍射方法、表面热透镜技术和1064nm的激光器测试了薄膜的光学性能、微结构、吸收和激光损伤阈值。实验发现，附加冷阱装置有助于我们有效控制镀膜过程中的水汽含量，且在水蒸气含量较少的真空室内镀制的薄膜具有较高的折射率，较小的晶粒尺寸，较低的弱吸收值和较高的损伤阈值。

Diode-pumped passively mode-locked YVO4/Nd : YVO4 composite crystal laser with LT-In0.25Ga0.75As saturable absorber

A passively mode-locked all-solid-state YVO4/Nd:YVO4 composite crystal laser was realized with a low temperature (LT) In0.25Ga0.75As semiconductor saturable absorber mirror. The saturable absorber was used as nonlinear absorber and output coupler simultaneously. Both the Q-switch and continous-wave mode locking operation were experimentally realized. At a pump power of 4 W, the Q-switched mode locking changed to continuous wave mode locking. An average output power of 4.1 W with 5 ps pulse width was achieved at the pump power of 12 W, corresponding to an optical-optical conversion efficiency of 34.2%.

Passive stabilization of a passively mode-locked Nd : GdVO4 laser by inverse saturable absorption

A diode-pumped Nd:GdVO4 laser mode-locked by a semiconductor saturable absorber and output coupler (SESAOC) is passively stabilized to suppress Q-switched mode-locking. A phase mismatched 131130 second-harmonic generation (SHG) crystal is used for passive stabilization. The continuous wave mode-locking (CWML) threshold is reduced and the pulse width is compressed. The pulse width is 6.5 ps as measured at the repetition rate of 128 MHz. (c) 2007 Elsevier B.V. All rights reserved.

A Diode-Side-Pumped Dynamic Fundamental Mode Nd:YAG Laser

A fundamental mode Nd YAG laser is experimentally demonstrated with a stagger pumped laser module and a special resonator. The rod is pumped symmetrically by staggered bar modules. A dynamic fundamental mode is achieved with the special resonator under different pump levels. A maximal continuous wave output of 61 W (M-2 = 1.4) is achieved with a single rod. An average output of 47 W, pulse width of 54 ns, pulse energy of 4.7 mJ and peak power of 87 kW are obtained under the Q-switched operation of 10 kHz.

Thermal effects investigation and cavity design in passively mode-locked Nd:YVO4 laser with a SESAM

A diode-pumped passively mode-locked Nd YVO4 laser with a five-mirror folded cavity is presented by using a semiconductor saturable absorber mirror (SESAM). The temperature distribution and thermal lensing in laser medium are numerically analyzed to design a special cavity which can keep the power density on SESAM under its damage threshold. Both the Q-switched and continuous-wave mode-locked operation are experimentally realized. The maximum average output power of 8.94 W with a 9.3 ps pulse width at a repetition rate of 111 MHz is obtained under a pump power of 24 W, correspondingly the optical slope efficiency is 39.2%. (C) 2008 Elsevier B.V. All rights reserved.

1ps passively mode-locked laser operation of Na, Yb : CaF2 crystal

Diode-pumped passively mode-locked laser operation of Yb3+,Na+:CaF2 single crystal has been demonstrated for the first time. By using a SESAM ( semiconductor saturable mirror), simultaneous transform-limited 1-ps passively mode-locked pulses, with the repetition rate of 183MHz, were obtained under the self-Q-switched envelope induced by the laser medium. The average output power of 360mW was attained at 1047nm for 3.34W of absorbed power at 976nm, and the corresponding pulse peak power arrived at 27kW, indicating the promising application of Yb3+,Na+-codoped CaF2 crystals in achieving ultra-short pulses and high pulse peak power. (c) 2005 Optical Society of America.

Experimental investigation of intracavity absorber low temperature GaAs in diode-pumped Nd : GdVO4 laser

A passively Q-switched and mode-locked diode-pumped Nd:GdVO4 laser was demonstrated using a low-temperature-grown GaAs wafer (LT-GaAs) as an intracavity saturable absorber. The maximal Q-switched mode-locked average output power was 750 mW with the Q-switched envelop having a repetition rate of 167 kHz. The mode-locked pulse trains inside the Q-switched pulse envelope had a repetition rate of similar to 790 MHz.

Experimental study of a pulsed ytterbium-doped fibre laser with fast and slow saturable absorbers in a linear cavity

We present a linear-cavity stretched-pulse fibre laser with mode locking by a nonlinear polarization rotation and by semiconductor saturable-absorber mirrors. A Q-switched mode-locking cw train and a mode-locking pulse train are obtained in the experiment. We investigate the effects of the equivalent fast saturable absorber and the slow saturable absorbers in experiment. It is found that neither the nonlinear polarization evolution effect nor a semiconductor saturable absorber mirror is enough to produce the stable cw mode-locking pulses in this experiment. A nonlinear polarization evolution effect controls the cavity loss to literally carve the pulses; semiconductor saturable absorber mirrors provide the self-restarting and maintain the stability of the mode-locking operation.

Experimental and theoretical analysis of nondegenerate ultrabroadband chirped pulse optical parametric amplification

Experimental investigations of nondegenerate ultrabroadband chirped pulse optical parametric amplification have been carried out. The general mathematical expressions for evaluating parametric bandwidth, gain and gain bandwidth for arbitrary three-wave mixing parametric amplifiers are presented. In our experiments, a type-I noncollinear phase-matched optical parametric amplifier based on lithium triborate, which was pumped by a 5-ns second harmonic pulses from a Q-switched Nd:YAG operating at 10 Hz, seeded by a 14-fs Ti:sapphire laser at 800 nm, was presented. The 0.85 nJ energy of input chirped signal pulse with 57-FWHM has been amplified to 3.1 muJ at pump intensity 3 GW/cm(2), the corresponding parametric gain reached 3.6 x 10(3), the 53 nm-FWHM gain spectrum bandwidth of output signal has been obtained. The large gain and broad gain bandwidth, which have been confirmed experimentally, provide great potentials to amplify efficiently the broad bandwidth femtosecond light pulses to generate new extremes in power, intensity, and pulse duration using optical parametric chirped pulse amplifiers pumped by powerful nanosecond systems.

Stacking chirped pulse optical parametric amplification

Stacking chirped pulse optical parametric amplification based on a home-built Yb(3+)-doped mode-locked fiber laser and an all-fiber pulse stacker has been demonstrated. Energic 11 mJ shaped pulses with pulse duration of 2.3 ns and a net total gain of higher than 1.1 x 10(7) at fluctuation less than 2% rms are achieved by optical parametric amplification pumped by a Q-switched Nd:YAG frequency-doubled laser, which provides a simple and efficient amplification scheme for temporally shaped pulses by stacking chirped pulse. (C) 2009 Elsevier B.V. All rights reserved.