LD抽运角锥棱镜腔电光调Q固体激光器

利用角锥棱镜的退偏效应实现了电光调Q固体激光器的偏振耦合输出.器件采用热传导冷却半圆柱面LD阵列侧向泵浦Nd:YAG泵浦几何,获得在20 Hz运行条件下,脉冲能量163 mJ/pulse、脉冲宽度6.5 ns、发散角3.5 mrad、能量稳定性土2.8%、光光效率16.7%的理想性能.与传统平行平面腔相比,具有效率高、峰值功率大、输出能量和脉宽可调,且输出稳定等优点.     

Electro-optically Q-switched Nd:YVO4 slab laser with a high repetition rate and a short pulse width

We report on a compact and highly efficient diode-end-pumped TEM00 Nd:YVO4 slab laser with an output power of 103 W and beam quality M2 < or = 1.5. The optical-to-optical efficiency was 41.5%. In electro-optically Q-switched operation, 83 W of average power at a pulse-repetition rate of 50 kHz with a pulse length of 11.3 ns was obtained. At a pulse-repetition rate of 10 kHz, 5.6 mJ of pulse energy, and 870 kW of peak power were measured.     

Dynamic gain induced pulse shortening in Q-switched lasers

We describe a novel mechanism of pulse shortening in a Q-switched laser induced by the gain compression effect under strong pumping conditions. The pulse shortening requires a large variation of the gain excursion during the saturation process and benefits from the large volume of the gain medium. The effect has been experimentally demonstrated using a passive Q-switched Tm/Ho-doped fiber laser that shows gain-induced pulse compression from 800 ns down to 160 ns when the pump threshold is exceeded by 15 times.     

Optimization of the pulse energy of GaAs saturable absorber Q-switched lasers

By taking into account the single-photon absorption (SPA) and two-photon absorption (TPA) processes of GaAs, the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density, and the pumping and the spontaneous emission during the pulse formation, the new normalized rate equations of a GaAs saturable absorber Q-switched laser are solved. The key parameters of an optimally coupled GaAs saturable absorber Q-switched laser are determined, including the optimal normalized coupling parameter and the optimal normalized GaAs saturable absorber parameters, which can maximize the pulse energy, and a group of general curves are generated for the first time, which clearly show the dependence of the optimal key parameters on the parameters of the gain medium, the GaAs saturable absorber, and the resonator. In addition, the influence including the space variation, the pumping and the spontaneous emission is also shown. Sample calculations for a diode-pumped Nd³⁺:YVO₄ laser with a GaAs saturable absorber are presented to demonstrate the use of the curves and the relevant formulas.     

Optimization of pulse width of double passively Q-switched lasers with GaAs and Cr-doped saturable absorbers

Compared with a single passively Q-switched laser, a double passively Q-switched laser with a GaAs saturable absorber and a Cr⁴⁺-doped saturable absorber can produce more symmetric and shorter pulses with high pulse peak power. New normalized coupled rate equations for a double passively Q-switched laser with both a GaAs saturable absorber and a Cr⁴⁺-doped saturable absorber are solved numerically, where the single-photon absorption (SPA) and two-photon absorption (TPA) processes of GaAs are combined. The Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density are considered. The optimization of a double passively Q-switched laser to obtain the shortest pulse width is performed, and a group of general curves are generated for the first time. The curves clearly show the dependence of the optimal normalized parameters on the parameters of the gain medium, the GaAs saturable absorber, the Cr⁴⁺-doped saturable absorber and the spatial distributions of the intracavity photon density. Sample calculations for a diode-pumped Nd³⁺:YVO₄ laser with both a GaAs saturable absorber and a Cr⁴⁺:YAG saturable absorber are presented to demonstrate the use of the curves and the related formulas.     

Control of the pulse duration in one- and two-axis passively Q-switched solid-state lasers

We study theoretically and experimentally different methods to control the pulses emitted by solid-state lasers passively Q-switched by a saturable absorber. We explore one- and two-axis laser schemes allowing to control the pulse duration, which is ruled by the saturation powers of the transitions in the absorber and in the gain medium. In one-axis lasers, it is shown that the adjustment of the pump and laser beam sizes in the active medium and in the absorber provides an efficient means to control the pulse temporal shape and duration. Furthermore, a two-axis laser cavity supporting so-called forked-eigenstate operation permits to freely adjust the parts of the mode power which circulate in the gain medium and in the absorber. In this case, a lengthening of the pulse duration up to 500 ns is obtained with an increase of the average output power. The theoretical results obtained by using rate equations adapted to each cavity geometry are in close agreement with experiments performed on a diode-pumped Nd³⁺:YAG laser Q-switched by a Cr⁴⁺:YAG saturable absorber. The relevance of the different techniques to control the pulse durations in the framework of potential applications is discussed. Received 3 December 2001     

Passively Q-switched Nd:YAG ring lasers with high average output power in single-frequency operation

Applying Cr(4+):YAG saturable absorbers, we demonstrate efficient passively Q -switched operation of diode-pumped Nd:YAG lasers with a maximum average output power of more than 800 mW. Pulse durations below 3 ns, energies of 70 muJ, and peak powers of 30 kW are observed with kilohertz repetition rates. Single-frequency operation is accomplished for all output powers by a nonplanar ring geometry.     

Modeling the pulse shape of Q-switched lasers to account for terminal-level relaxation

To account for the effect of lower-level relaxation,we have derived a characteristic equation for describing the laser pulse from the modified rate equations for Q-switched lasers.The pulse temporal profile is related to the ratio of the lower-level lifetime to the cavity lifetime and the number of times the population inversion density is above the threshold.By solving the coupled rate equations numerically,the effect of terminal-level lifetime on pulse temporal behaviour is analysed.The mode is applied to the case of a diode-pumped Nd:YAG laser that is passively Q-switched by a Cr 4+:YAG absorber.Theoretical results show good agreement with the experiments.     

Far-field timing effects with passively Q-switched lasers

Pulse-timing effects in the far field of a passively Q -switched microchip laser that are caused by the changing cavity mode during pulse emission are described. Measurements are performed on a passively Q -switched Nd:YAG laser that produces 3-ns pulses, and delays in pulse arrival times of up to ~270 ps are observed between the center and the off-axis position. The measured data agree well with a simple analytical model. Pulse delays of this order are important, for instance, in high-precision range-finding applications.     

High-pulse-energy passively Q-switched quasi-monolithic microchip lasers operating in the sub-100-ps pulse regime

We present passively Q-switched microchip lasers with items bonded by spin-on-glass glue. Passive Q-switching is obtained by a semiconductor saturable absorber mirror. The laser medium is a Nd:YVO(4) crystal. These lasers generate pulse peak powers up to 20 kW at a pulse duration as short as 50 ps and pulse repetition rates of 166 kHz. At 1064 nm, a linear polarized transversal and longitudinal single-mode beam is emitted. To the best of our knowledge, these are the shortest pulses in the 1 microJ energy range ever obtained with passively Q-switched microchip lasers. The quasi-monolithic setup ensures stable and reliable performance.     

Experimental study of the pulse energy of pulsed LD-pumped acousto-optically Q-switched Tm:YAG lasers

We study a pulsed LD-pumped high-energy acousto-optically (AO) Q-switched Tm:YAG laser. The output pulse energy is mainly influenced by the output energy at free running and the energy-extraction efficiency under Q-switching operation. The output energy at free running can be improved by optimizing the parameters of the pump source, laser cavity, and laser medium. We show that, in order to avoid the insufficiency or waste of the population inversion and obtain higher energy-extraction efficiency, a proper pumping width and opening time of the Q switch can be found.     

Modeling of Q-switched lasers with top-hat pump beam distribution

For laser diode end-pumped solid-state lasers, the pump beam can be considered to be a Gaussian distribution or a top-hat distribution or between them. The rate equations for Q-switched lasers have been treated before, by considering the pump beam as a Gaussian distribution. This paper deals with the rate equations and the solutions for Q-switched lasers under a top-hat pump beam distribution. The normalized rate equation is obtained and solved numerically. A group of general curves are given and the comparison with the results under the Gaussian pump beam distribution and the plane-wave approximation is made. The results show that the solutions of the rate equations under a top-hat pump beam distribution are different from those under a Gaussian pump beam distribution, but the difference is very small. The solutions of the rate equations under both situations can give much more precise theoretical results than those under the plane-wave approximation. PACS 42.60.Gd; 42.55.Xi; 42.55.Ah     

Effect of turnoff time on characteristics of the output pulse in an AO Q-switched laser

A laser-end-diode-pumped actively Q-switched Nd:YVO₄ laser with acoustic-optic (AO) modulator is realized. By changing the position of AO in the cavity for changing the transit time of the acoustic-wave, the effect of the AO turnoff time on the characteristics of the output Q-switched pulse is obtained. The experimental results show that the longer transit time leads to the wider pulse duration. By considering the Gaussian spatial distribution of the intra-cavity photon density and the AO turnoff time including the electronic turnoff time and the transit time of the acoustic-wave, the numerical solutions of the coupled Q-switched rate equations are consistent with the experimental results.     

Modelling of passively Q-switched lasers with intracavity Raman conversion

We present a model of passively Q-switched Raman lasers by utilizing the rate equations. The intracavity fun-damental photon density, Raman photon density and the initial population-inversion density of the gain medium are assumed to be of Gaussian spatial distributions. These rate equations are normalized by introducing some synthetic parameters and solved numerically, and a group of general curves are generated. Prom these curves we can understand the dependence of the Raman laser pulse characteristics on the parameters about the pumping, the gain medium, the Raman medium and the resonator. An illustrative calculation for a passively Q-switched Nd^3＋：GdVO4 self-Raman laser is presented to demonstrate the usage of the curves and related formulas.[第一段]     

不同脉冲重复频率下抽运方式对全光纤声光调Q激光器性能的影响

在不同初始边界条件下数值求解描述全光纤声光调Q双包层光纤激光器的速率方程,得到前向抽运结构和后向抽运结构下激光器上能级粒子数在增益光纤中的分布,以及脉冲能量、平均功率、脉宽、光纤中储能与脉冲重复频率、抽运合束器对信号光透过率、抽运功率的相互关系.从谐振腔内放大自发辐射光的产生影响谐振腔损耗的角度分析仿真结果,并实验验证两种抽运方式对输出脉冲功率和脉冲宽度的影响.结果表明：不同脉冲重复频率下抽运方式会对全光纤声光调Q激光器性能产生显著影响,为获得较好的脉冲输出性能,在重复频率较低 关键词： 光纤激光器 Q')" href="#">声光调Q 抽运方式     

交叉型波荡器软X射线自由电子激光极化控制的影响因素

 交叉型波荡器是一种实现软X射线自由电子激光极化控制的有效方式。以自放大自发辐射自由光电子激光为例,采用统计的方法系统地分析了交叉型波荡器软X射线自由电子激光极化控制的影响因素。通过对光场相干长度、光脉冲两分量之间相对滑移长度和光场分量平均功率差异等的分析,给出了优化交叉型波荡器极化控制方案遵循的原则,即：辐射场相干时间尽可能长,光场分量相对滑移长度尽可能短,辐射场分量功率差异尽可能小等。该原则为交叉型波荡器软X射线自由电子激光极化控制方案的优化提供了依据。     

Cr4+：YAG被动调Q激光器中受激粒子上转换效应对脉冲的影响研究

分析和报道了受激粒子能量上转换(ETU)效应对Cr:YAG 被动调Q Nd:YAG/Nd:YVO₄激光器的输出脉冲影响研究.结合ETU理论分析和被动调Q速率方程组，得到了初始反转粒子密度，末态反转粒子密度和光强最大时反转粒子密度的比值变化对激光输出脉冲宽度和脉冲能量的影响，和实验结果相一致.同时讨论了降低ETU效应的方法，有助于这类被动调Q激光器的优化设计. 关键词： 受激粒子能量上转换 Cr:YAG饱和吸收体 被动调Q