Actively Q-switched Nd:YVO4 laser using an electro-optic periodically poled lithium niobate crystal as a laser Q-switch

We demonstrate a low-voltage and fast laser Q-switching by using an electro-optic periodically poled lithium niobate (EO PPLN) crystal. The half-wave voltage measured from the EO PPLN crystal was 0.36 V x d (microm)/L (cm), where d is the electrode separation and L is the electrode length. When a 13-mm-long EO PPLN was used as a laser Q switch at 7-kHz switching rate, we measured an approximately 12-ns pulse width and approximately 0.74-kW laser pulses at 1064-nm wavelength from a diode-pumped Nd:YVO4 laser with continuous 1.2-W pump power at 809-nm wavelength.     

A type of electro-optic Q-switch designed by using optically active crystal

A type of electro-optic Q-switch is designed by using optically active crystal La₃Ga₅SiO₁₄ (abbreviated as LGS), in which the polarization plane gyration and electro-optic effect exist simultaneously. The configuration of the Q-switch is based on the consideration that the total rotation angle of the polarization plane of the polarized laser is zero, while the laser in the cavity propagates through the Pockels cell back and forth. The Q-switch placed in a Nd^{3 +}:YAG laser behaves normally, like those without optical activity. Compared with the DKDP Q-switch, the LGS Q-switch has more superiorities, which make it a suitable replacement for the DKDP Q-switch in lasers with medium-output energy.     

Tunable continuous-wave laser at quasi-three-level with a disordered Nd:LGS crystal

A diode-pumped tunable CW Nd(3+):LGS laser at quasi-three-level has been demonstrated. The output power up to 403 mW at the central wavelength of 904 nm was obtained, corresponding to a slope efficiency of 29.7%. Taking advantage of the broad emission spectrum of the disordered crystal Nd:LGS, we tuned the laser wavelength within the spectral range of 899.8 to 906.6 nm with an etalon inserted into the V-type cavity. To the best of our knowledge, it is the first time to obtain a tunable laser based on the (4)F(3/2)-(4)I(9/2) transition of Nd(3+)-doped crystals.     

Diode-pumped green Nd:YAG laser with Q-switch and mode locking

We propose a new method for achieving simultaneous operation of laser mode locking and the Q-switch technique using only a single acousto-optic modulator (AOM) with a traveling wave; this AOM was placed inside the cavity of a green-emission Nd:YAG laser. The further shortening of the lasing pulse duration from 40 ps to less than 3.25 ps was obtained by the formation of a Kerr lens in a doubling-frequency crystal. At average output power of 1.5 W and pulse repetition rate of the Q-switch equal to 2 kHz, the peak power in a steady-operating laser exceeded 50 MW.     

Diode-pumped Nd:LGS intracavity-doubled green laser at 532 nm

It is reported that efficient continuous-wave (CW) green laser generation at 532 nm in a KTP crystal at type-II phase matching direction performed with a diode-pumped Nd:LGS laser. With incident pump power of 18.2 W, output power of 2.68 W at 532 nm has been obtained using a 5 mm-long KTP crystal. The optical conversion efficiency was up to 14.7%. At the output power level of 2.68 W, the output stability is better than 3.5%. The beam quality M ² values were equal to 1.33 and 1.19 in X and Y directions, respectively.     

Performance of Nd:YLF laser by using crystal electrooptic Q-switch

The polarization rotating coefficient and the laser-damage threshold of La₃Ga₅SiO₁₄ crystal at 1064 nm are measured, which are 1.1 deg/mm and , respectively. The working principle and the design method of electrooptic Q-switch based on La₃Ga₅SiO₁₄ crystal, which has the optical activity, are reported. The performance of Nd:YLF laser with the electrooptic Q-switch of La₃Ga₅SiO₁₄ crystal was studied. The output pulses with an energy of 379 mJ, a duration of 8.7 ns and repetition of 10 Hz are achieved.     

Comparison of RTP electro-optic Q-switch and acousto-optic Q-switch in Tm,Ho:GdVO<Subscript>4</Subscript> laser

We demonstrate a tunable, narrow linewidth, linearly polarized and gain-switched Cr²⁺:ZnSe laser pumped by a Tm, Ho:YVO₄ laser at 10 kHz pulse repetition frequency. By setting a quartz birefringent filter with a Brewster angle in the cavity, the linearly polarized Cr²⁺:ZnSe laser can be continuously tuned from 2.45 to 2.50 μm, and the output power was almost not changed. In addition, the linewidth was compressed to about 5 nm. At the incident pump power to the crystal of 14 W, the maximum output power of 2.84 W was obtained, corresponding to a slope efficiency of 20.4%.     

Precise calculation of the KTP crystal used as both an intracavity electro-optic Q-switch and a second harmonic generator

A method of precisely calculating the external applied voltage and the optimum type-Ⅱ phase matching angles for KTP crystal, which is used as both an intracavity electro-optic (EO) Q-switch and a frequency doubler, is presented. The effective EO coefficient along the phase-matching direction is defined to calculate the half-wave voltage and the quarter-wave voltage, and the precise calculation for the phase matching angles in the condition of KTP crystal optimum second harmonic phase matching is theoretically realized.     

A ruby laser with passive Q-switch element

The generation of giant impulses was observed experimentally in a medium consisting of two elements — a ruby single crystal and a plane-parallel glass plate. The dependence of the switch element on the intensity of the light ray was investigated. A semi-transparent mirror was realized by plates made from quartz or heavy flint glass. The results are compared with dielectric mirrors.The authors would like to thank Ing. Nebenský for helpful discussion, workers of Dioptra Turnov, national enterprise, for making the filters and grinding the plates, and T. Daíek and A. Novotný for help in the measurements.     

高平均功率电光开关晶体热畸变分析

深入分析了方板构型的电光开关晶体在高功率载荷条件下的热畸变行为,讨论了光强分布对热效应的影响。以KDP晶体为例,分别计算了激光束光强为高斯分布和均匀分布时晶体的温升、相应的热应力分布、波前畸变以及热退偏。结果表明,光强的分布形式对波前畸变和热退偏的影响是不同的。相对于光强均匀分布的激光束,高斯光束减缓了光斑边沿处的温度梯度,产生的热应力较小,因此可以减弱热退偏效应;另一方面,在光束口径范围内,高斯光束产生了附加的温度分布非均匀性,因而波前畸变会大一些。     

高平均功率电光开关晶体热畸变分析

 深入分析了方板构型的电光开关晶体在高功率载荷条件下的热畸变行为,讨论了光强分布对热效应的影响。以KDP晶体为例,分别计算了激光束光强为高斯分布和均匀分布时晶体的温升、相应的热应力分布、波前畸变以及热退偏。结果表明,光强的分布形式对波前畸变和热退偏的影响是不同的。相对于光强均匀分布的激光束,高斯光束减缓了光斑边沿处的温度梯度,产生的热应力较小,因此可以减弱热退偏效应;另一方面,在光束口径范围内,高斯光束产生了附加的温度分布非均匀性,因而波前畸变会大一些。     

Light-controlled electro-optic power limiter with a Bi(12)SiO(20) crystal

An optical power limiter is a self-actuating nonlinear optical device that transmits low-intensity light and blocks high-intensity light. A light-controlled electro-optic power limiter that uses a Bi(12)SiO(20) crystal has been demonstrated. The threshold light intensity is determined by the control light and can be set to any desired level. The response time of the light-controlled electro-optic power limiter is of the order of 1 ms.     

重频应用下等离子体电光开关热退偏损耗分析

基于有限元数值方法,给出电光晶体KDP在高平均功率激光负载下温度场分布和应力场分布。在此基础上得到了折射率随温度变化、电光系数随温度变化、及应力双折射引入的退偏损耗。数值模拟显示：电光系数随温度变化和应力双折射是引起开关退偏损耗的主要因素。当入射激光平均功率为40 W、辐照时间为420 s时,KDP晶体最高温度为38.43 ℃,电光系数随温度变化及应力双折射引入的最大退偏损耗分别为2.38%和4.04%。实验测量了应力双折射导致的退偏损耗,实验结果和理论结果符合较好。     

Comparison of laser performance of electro-optic Q-switched Nd:YAG ceramic/single crystal laser

An electro-optic Q-switched Nd:YAG ceramic laser operating at kHz repetition rate was demonstrated.Thermal induced lens' focus of ceramic rod was measured and compensated by plano-convex cavity structure. Depolarization loss at different output powers was measured in Nd:YAG single crystal and ceramic lasers. High-energy high-beam-quality laser pulse output was obtained in both laser structures. Pulse energy of about 20 mJ and pulse width of less than 12 ns were achieved, and the average power reached 20 W. The divergence of output laser beam was less than 1.2 mrad, and the beam propagation factor M2was about 1.4.     

重频应用下等离子体电光开关热退偏损耗分析

 基于有限元数值方法,给出电光晶体KDP在高平均功率激光负载下温度场分布和应力场分布。在此基础上得到了折射率随温度变化、电光系数随温度变化、及应力双折射引入的退偏损耗。数值模拟显示：电光系数随温度变化和应力双折射是引起开关退偏损耗的主要因素。当入射激光平均功率为40 W、辐照时间为420 s时,KDP晶体最高温度为38.43 ℃,电光系数随温度变化及应力双折射引入的最大退偏损耗分别为2.38%和4.04%。实验测量了应力双折射导致的退偏损耗,实验结果和理论结果符合较好。     

Double Q-switched 946 nm laser with MgO:LN electro-optic crystal and MoSe_2 saturable absorber

We report a double Q-switched 946 nm laser with a magnesium-oxide-doped LiNbO_3(MgO:LN) electro-optic(EO) crystal and a monolayer molybdenum diselenide(MoSe_2) saturable absorber(SA). A pulsed laser diode side-pumped long neodymium-doped yttrium aluminum garnet rod(φ3 × 65 mm) is used as the gain medium.Large pulse energy up to 3.15 m J and peak power up to 346 kW are generated at the repetition rate of 550 Hz,corresponding to the beam quality factors of M_x~2=3.849, M_y~2=3.868. Monolayer MoSe_2 nanosheets applied in the experiment would be a promising SA for a passive Q-switching operation.     

基于内置电光晶体F P标准具的扫描滤波方法

基于内置电光晶体的F-P标准具,利用F-P多光束干涉原理和晶体的线性电光效应,提出了一种能有效提高啁啾脉冲信噪比的扫描滤波方法。给出了电光晶体加载电压的时变函数表达式,分析了影响信噪比提升效果的主要因素,并重点讨论了电光晶体的电压控制参数对信噪比提升效果和滤波器透过率的影响。研究结果表明,利用该扫描滤波方法可将啁啾脉冲激光信噪比提升约2个量级。