Modeling of diode-pumped actively Q-switched lasers

The intracavity photon density and initial population inversion density in the diode-pumped actively Q-switched laser rate equations are assumed to be Gaussian distributions. These space-dependent rate equations are solved numerically and a group of general curves are generated. By using these curves and the related formulas, the pulse parameters of an arbitrary actively Q-switched laser can be easily estimated and an optimally coupled Q-switched laser can be designed. A sample calculation for a Q-switched Nd³⁺:YVO₄ laser is presented to demonstrate the use of the curves and the related formulas     

Reducing pulse durations in diode pumped Q-switched solid-state lasers

The authors describe a subminiature, laser-diode-pumped, acoustooptic Q-switched Nd:YLF laser. The laser utilizes a very short cavity and laser crystal cooling to increase gain and reduce pulse width. Exploiting this technology results in 1.321 mu m pulses with durations and peak powers of 4.7 ns and 1100 W at 2 kHz and 8.7 ns and 250 W at 10 kHz in Nd:YLF. Similarly, 10 kHz pulses at 1.047 mu m have 2.7 ns duration and 1500 W peak power, also in Nd:YLF.<>     

LD 脉冲泵浦被动调Q 窄脉冲大能量全固态激光器

利用Nd:YAG/Cr4+:YAG 键合微片激光晶体研制了被动调Q 大能量窄脉冲的全固态激光器,激光器采用脉冲激光二极管泵浦方式,设计了本振级和两级放大结构,分析了激光器系统的自激振荡和其抑制方法,在激光器本振级获得稳定脉冲激光输出的基础上,当两级放大器泵浦电流分别为83A 和85 A 时,获得了最大单脉冲输出能量为120 mJ,脉冲宽度为1.28 ns 的1 064 nm 激光输出,激光通过倍频后可得到65 mJ 的532 nm 绿光输出,其窄脉宽和高光束质量特性可为飞秒激光器啁啾放大提供良好的泵浦源。     

Passively Q-switched lasers

Passively Q-switched, diode pumped, all solid-state lasers are an elegant, yet simple, means to generate single-frequency laser pulses in the nanosecond and sub-nanosecond regions. The majority of the work on these systems has been in the 1-/spl mu/m region, but recent developments at eye-safe and mid-infrared wavelengths of both diode-pumped lasers and solid-state saturable absorbers will probably lead to practical, passively Q-switched lasers at longer wavelengths. However, longer wavelength material properties are expected to only allow the generation of longer duration pulses. In the 1-/spl mu/m region, near-term advances are anticipated in the development of higher average power systems operating at multikilohertz pulse rates, with pulse energies exceeding 1 mJ and corresponding improvements at second, third, fourth, and even fifth harmonic wavelengths.     

Q-switched semiconductor diode lasers

Diode lasers with an intracavity electroabsorption modulator have been operated with full on/off modulation at rates of 3 GHz. In addition, modulation of the lasers has been shown up to a detector-limited frequency of 6 GHz. A new model of these devices, which includes amplified spontaneous emission and high gain is developed in this paper. A quasi-static gain approximation is introduced and the dynamics of the electron and photon population are modeled by three coupled nonlinear difference equations which can be numerically solved with very little computation time. The model predicts the possibility of a new mode ofQ-switched operation with the capacity for repetition rates of tens of gigahertz and binary pulse position modulation at rates of the order of 10 Gbits/s.     

Q-switched unidirectional ring lasers

Traveling-wave operation of a ruby laser has been obtained by the use of a 5° Faraday rotator. Mode selection in a TW ruby laser with electroopticalQswitching is discussed.     

Injection-locked passively Q-switched lasers

The time-dependent behavior of an injection locked single-mode passivelyQ-switched laser may be described by three coupled first-order rate equations relating the laser gain, the absorber loss, and the optical power density. Injection locking results in a substantial increase in the mean output power and the output pulse energy and higher pulsation rate than when freely running. Stability analysis allows the determination of the maximum injected power that allows pulsations.     

Optimization of dye Q-switched lasers

Analytical expressions for all key parameters of the optimally coupled Q-switched laser are derived. These parameters include the optimal reflectivity of the output mirror, the optimal initial transmission of the dye, and the maximum attainable output energy and corresponding peak power and pulse width for a given pump level. Meanwhile, according to the optimization theory of dye Q-switched lasers, a NAB miniature dye Q-switched laser is studied experimentally and experiment shows a good agreement with the theory     

Q-switched operation of quasi-three-level lasers

A theoretical model for longitudinally pumped quasi-three-level lasers under Q-switched, repetitively Q-switched, and cw operating conditions is developed. The model is applied using 8% Ho:YAG as the gain medium, and it is found that for typical conditions the effective energy storage time can be much less than the upper state lifetime, in agreement with experiment but not predicted by earlier theories. This effect is attributed to details of laser design and pumping conditions, as opposed to being an intrinsic property of the gain material     

Coherent combining of Q-switched fibre lasers

The power rising of an actively Q-switched erbium-doped fibre laser by using two coupled cavities with amplifying fibres in an interferometer configuration is reported. This study shows that the pulse peak power obtained is 1.7 higher than in a case of a unique laser. This concept brings some novel perspectives for scaling the output peak power of singlemode Q-switched fibre lasers.     

Dynamics of passively Q-switched microchip lasers

Self-pulsing in passively Q-switched microchip lasers is investigated in detail. The typical range of values of the parameters motivates a new analysis of the laser rate equations. We determine basic properties of the laser intensity oscillations such as threshold conditions, repetition rate, pulsewidth, peak power, and pulse energy. We show that these oscillations appear through a quasi-vertical Hopf bifurcation located slightly above the lasing threshold. Our bifurcation results are verified numerically by modeling a microchip laser experiment with Nd:YAG as the gain medium and YAG:Cr as saturable absorber. Our results agree with the experiment to within 10%     

主动调Q全光纤激光器的发展评述

调Q全光纤激光器相比非全光纤激光器具有效率高、结构紧凑和携带方便等潜在优点,并且主动Q开关的重复频率稳定、易于控制,所以全光纤化和主动Q开关的完美结合将引发调Q光纤激光器质的飞跃。在调Q全光纤激光器的发展历程中,布喇格光栅的出现是调Q全光纤激光器发展的重要一步,Q开关的光纤化更是关键的环节。目前,已光纤化的主被动Q开关均很常见,但主动光纤型Q开关技术并不成熟,或许将传统工艺上比较成熟的声光或电光Q开关光纤化是解决该问题的可行途径。     

Pulse characteristics of Q-switched fiber lasers

A theoretical investigation of the anticipated properties of optically end-pumpedQ-switched fiber lasers is reported. This analysis stresses the effect of the transverse structure of the interacting pump and signal (guided) waves, in particular of the fiberVnumber, on the device performance. In Nd : YAG single crystal fibers thresholds as low as a fraction of a milliwatt may be achieved; pulses with peak powers of hundreds of watts and subnanosecond widths may be generated under laser diode pumping conditions.     

Multipulsing behavior of electrooptically Q-switched lasers

The influence of the piezooptical effect on postlasing in electroopticallyQ-switched Nd:YAG lasers is discussed and a simple method for its elimination is presented.     

Satellite pulse generation in diode-pumped passively Q-switched Nd:GdVO/sub 4/ lasers

We have both experimentally and numerically investigated the satellite pulse generation in diode-pumped passively Q-switched Nd:GdVO/sub 4/ lasers with Cr/sup 4+/:YAG saturable absorber. We show experimentally that satellite pulse generation is a general effect of the lasers under strong pumping, and its formation is always associated with the appearance of strong Q-switched pulses. Satellite pulse generation of the lasers is further numerically simulated based on a coupled rate-equation model. Our numerical simulations show that the phenomenon is caused by the finite lifetime of the lower laser energy level of the lasers.     

调Q和调Q锁模脉冲共存双波长光纤激光器

为了使光纤激光器同时运转在不同的工作状态,搭建了非线性偏振旋转（NPR）技术和碳纳米管可饱和吸收体（CNT-SA）混合的掺铒光纤激光器。其中,基于NPR效应的腔内双折射引入的梳状滤波器可以实现双波长输出,NPR和CNT-SA的可饱和吸收效应共同作用可以获得调Q或调Q锁模脉冲,因此在该激光器中通过调节参数可以使光纤激光器同时获得双波长调Q和调Q锁模脉冲输出。该双波长脉冲经滤波处理后,观察到1531.23 nm处的波长对应调Q脉冲,其重复率为45.62 kHz,1557.18 nm处的波长对应调Q锁模,调Q包络重复率也为45.62 kHz,包络内锁模脉冲的重复率为18.18 MHz,与激光器腔长相符。该实验结果增强了光纤激光器工作的灵活性,有望进一步拓展其在相关领域的应用。     

Optimization of quasi-three level end-pumped Q-switched lasers

Equations describing the pump excitation and Q-switched energy extraction of end-pumped, quasi-three level laser systems are collected. A transcendental expression relating the Q-switched laser output energy to the laser's initial gain and cavity transmission which is valid for arbitrary output coupling is derived. This expression simplifies sensitivity and optimization studies of such systems. A first order ordinary differential equation is derived which describes the rod-integrated excited state number density resulting from an arbitrary pump excitation pulse, The equation is valid for both single pass and double pass pump geometries. To illustrate the utility of the collected set of equations an end-pumped joule class, Q-switched Yb:YAG oscillator is optimized and studied     

被动调Q固体激光器参数计算及优化设计

在考虑可饱和吸收体受激态吸收的条件下,用拉格朗日乘数法求出了被动调Q激光器输出关键参数的解析解,给出了被动调Q激光器输出能量与输出耦合镜反射率的解析表达式,并通过数值解来优化选择被动调Q激光器可饱和吸收体的初始透过率、耦合输出镜反射率等关键性参数,计算和分析了红宝石被动调Q激光实验数据,计算结果十分接近实验的真实值,较好的说明了被动调Q激光器关键参数的优化效果.     

调Q系列脉冲激光器理论

本文从变率方程出发,分析了系列脉冲激光器在一个周期内的粒子数积累过程和振荡时的消耗过程,从而建立了系列脉冲激光器的粒子数方程.通过对这一方程的分析和计算,得到了以周期t_T和有效泵浦速率R为变数的输出能量、峰值功率、脉冲宽度和延迟时间的解析表达式.