用于锁模Nd：YAG激光器的单脉冲开关

 锁模Nd:YAG激光器选取单脉冲时，通常采用KD*P普克尔盒。 波长1.06μm的激光半波电压为6.6kV。应用冷阴极闸流管KN-22作为开关线路比较广泛，但近年来我们改用MOS场效应管线路代替KN-22，该线路性能稳定可靠，输出脉冲幅度为－6.6～－8kV，脉冲宽度5～10ns可调，触发晃动小于0.5ns，触发延时30～40ns，单脉冲选出率为100％。经长时间使用未发现异常，此线路也可在削波器及脉冲剪切等技术中应用。     

振幅和相位涨落对锁模脉冲列特性的影响

用傅里叶变换的方法分析了锁模激光器中模式间的相位和振幅涨落对锁模脉冲列特性的影响。将锁模激光器中各模式的相位和振幅涨落作傅里叶展开,再通过增益谱抽样的傅里叶变化得到其时域行为。分析结果表明振幅系统涨落及随机涨落均不引起脉宽的明显变化,只引起脉冲间背景的加大,但相位涨落随机会使脉冲列强度产生波动。所用物理图像简明,结果对获得稳定的锁模脉冲列的实验研究有参考意义。     

振幅和相位涨落对锁模脉冲列特性的影响

 用傅里叶变换的方法分析了锁模激光器中模式间的相位和振幅涨落对锁模脉冲列特性的影响。将锁模激光器中各模式的相位和振幅涨落作傅里叶展开，再通过增益谱抽样的傅里叶变化得到其时域行为。分析结果表明振幅系统涨落及随机涨落均不引起脉宽的明显变化，只引起脉冲间背景的加大，但相位涨落随机会使脉冲列强度产生波动。所用物理图像简明，结果对获得稳定的锁模脉冲列的实验研究有参考意义。     

Regimes of operation states in passively mode-locked fiber soliton ring laser

The principal of passively mode-locked fiber soliton ring lasers is summarized, including its three output operation states: normal soliton, bound–solitons and noise-like pulse. The experimental results of the passively mode-locked fiber soliton ring lasers developed by us are given. Bound–solitons with different discrete separations and three-bound–solitons state have been observed in our fiber laser for the first time. The relationship among three operation states in fiber soliton laser is analyzed.     

Interaction of parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser

We numerically investigate the formation and interaction of parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser. Based on a lumped model, the parabolic-shaped pulse pair is obtained by controlling the inter-cavity average dispersion and gain saturation energy, Moreover, pulse repulsive and attractive motion are also achieved with different pulse separations. Simulation results show that the phase shift plays an important role in pulse interaction, and the interaction is determined by the inter-cavity average dispersion and gain saturation energy, i.e., the strength of the interaction is proportional to the gain saturation energy, the stronger gain saturation energy will result in higher interaction intensity. On the contrary, the increase of the inter-cavity dispersion will counterbalance some interaction force. The results also show that the interaction of a parabolic-shaped pulse pair has a larger interaction distance compare to the conventional solitons.     

Interaction of a parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser

We numerically investigate the formation and interaction of a parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser. Based on a lumped model, the parabolic-shaped pulse pair is obtained by controlling the intercavity average dispersion and gain saturation energy, Moreover, pulse repulsive and attractive motion are also achieved with different pulse separations. Simulation results show that the phase shift plays an important role in pulse interaction, and the interaction is determined by the inter-cavity average dispersion and gain saturation energy, i.e., the strength of the interaction is proportional to the gain saturation energy, a stronger gain saturation energy will result in a higher interaction intensity. On the contrary, the increase of the inter-cavity dispersion will counterbalance some interaction force. The results also show that the interaction of a parabolic-shaped pulse pair has a larger interaction distance compared to conventional solitons.     

用倍频晶体KTP实现Nd：YAG激光锁模的研究

报道用倍频晶体KTP实现Nd:YAG激光锁模的系统研究,给出了该锁模激光器输出脉宽的表达式,并和实验测量值相比较,计算值跟实验结果符合较好.文中还分析了各种参数对该锁模激光输出性能的影响.     

Simulation of the passively mode-locked laser with a SESAM

By solving the Haus master equation through split step Fourier transform method, several programs which can simulate the soliton mode-locked dynamic processes of the passively mode-locked solid laser with a semiconductor saturable absorber mirror (SESAM) are established, based on a MATLAB environment. The pulse evolution equations are solved numerically. Sample calculations for a diode-pumped Nd³⁺:YVO₄ (0.5% doped) laser with a SESAM are presented to demonstrate the use of the simulation programs and the related formulas. Several theoretical results such as the pulse width, the peak power and the average output power are obtained with a given cavity structure, which are in good agreement with the reported experimental results.     

Theoretical and experimental investigations of a passively mode-locked Nd: Glass laser

The presented theoretical model for a mode-locked Nd-glass laser simultaneously takes into account dynamics of the mode-locking dye, amplification saturation and radiation background. A systematic variation of laser parameters gives insight into the pulse formation process and allows to improve the laser design. The calculations show that it should be possible to decrease considerably the duration of light pulses of a mode-locked Nd-glass laser. Using a new mode-locking dye with a switching time of τ=2.7×10⁻¹² s we obtained stable laser operation and a pulse duration of 1.7×10⁻¹²s.     

Pump pulse characteristics of quasi-continuous-wave diode-side-pumped Nd:YAG laser

The influence of pumping laser pulse on the property of quasi-continuous-wave (QCW) diode-side-pumped Nd:YAG laser is investigated theoretically and experimentally. Under remaining a fixed duty cycle, the average output power increases, and the corresponding thermal focal length shorten with the increase of the pump pulse duration, which attributes to the decrease of the ratio of pulse buildup time to the pulse duration. At a pump power of 146 W, the laser output power changes from 65.1 W to 81.2 W when the pulse duration is adjusted from 150 μ s to 1000 μ s, confirming a significant enhancement of 24.7%. A laser rate equation model incorporating the amplified spontaneous emission is also utilized and numerically solved, and the simulated results agree well with the experimental data.     

Ti:sapphire laser pumped by a long train of pulses from mode-locked Nd:YAG laser with negative feedback

Investigation of the buildup dynamics of a Ti:sapphire laser pumped by a 500 ns long second harmonic pulse train from a mode-locked Nd:YAG laser with a passive negative feedback using GaAs is reported. The 400 ns long output pulse has a buildup time of 70 ns for a pump energy of 1.25 mJ. A slope efficiency of 15.1% was achieved with a 94% reflective output coupler.     

Optimization of passively Q-switched and mode-locked laser with Cr:YAG saturable absorber

By considering the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density, the coupled rate equations for a diode-pumped passively Q-switched and mode-locked (QML) laser with Cr⁴⁺:YAG saturable absorber are given. These coupled rate equations are solved numerically and the key parameters of an optimally coupled passively QML laser are determined for the first time. These key parameters include the parameters of the gain medium, the saturable absorber and the resonator, which can maximize the pulse energy of singly Q-switched envelope. The optimal calculations for a diode-pumped passively QML Nd:GdVO₄ laser with Cr⁴⁺:YAG saturable absorber are presented to demonstrate the numerical simulation applicable.     

Mathematical modelling of an Nd: YAG laser: peak power and pulse width

In a previous paper, the author presented an empirically derived mathematical model of a pulse pumped laser which allowed calculation of the output energy from the laser—from the mirrors-only resonator to the fully assembled Q-switched state. In this paper the model is developed further by deriving an expression for the peak output power. New coupling and loss time constant are stated. The validity of the model is demonstrated by the ability of calculate the laser parameters from a measured pulse shape, knowing the rod dimensions and the pump energy at which the pulse was measured.     

Ouput characteristics of a passively mode-locked ruby laser

Characteristics of the pulse train from a ruby laser have been studied at different output intensity levels. At a low output level, broadening of the spectrum of the pulses is followed by a gradual increase of temporal width in the train. At a high output level, rapid deformation arises closer to the peak of the train, resulting in splitting of the pulses into several fragments. The width of a transform-limited pulse obtained at the beginning of the train was 28±2 picoseconds.     

超短光脉冲在分段中空光波导中的光谱展宽和脉冲压缩

运用分步傅里叶法解非线性薛定谔方程来对超短脉冲在充满惰性气体的中空光波导中的展宽 与压缩进行数值模拟计算.模拟证明，分段光纤展宽光谱具有损耗小，可能压缩脉冲窄等潜 在优点，对在实验中进一步压缩脉冲到周期量级有指导意义. 关键词： 超短脉冲 中空光波导 广义非线性薛定谔方程 脉冲压缩     

The pulse shape of a passively Q-switched microchip laser

The shape of the intensity pulse of a passively Q-switched microchip laser is investigated numerically and analytically. Our analysis is motivated by independent microchip laser experiments exhibiting nearly symmetric pulses in the case of a semiconductor saturable absorber and asymmetric pulses in the case of a solid state saturable absorber. Asymptotic methods are used to determine limiting behaviors of the pulse shape for both symmetric and asymmetric pulses. In the first case, we determine a sech² solution parametrized by one parameter which can be determined by solving two coupled nonlinear algebraic equations. In the second case, the pulse solution is decomposed into two distinct approximations exhibiting different amplitude and time scales properties. We review earlier approximations of the repetition rate and the pulse width. Received 2 August 1999     

5.1-ps passively mode-locked Nd:Gd0.42Y0.58VO4 laser with a LT-GaAs absorber

We propose a diode end-pumped passively mode-locked Nd: Gd0.42 Y0.58 VO4 (Nd: GdYVO4) laser at 1064nm using a GaAs absorber grown at low temperature as the output coupler.Stable continuous-wave (CW) mode locking with a 5.1-ps pulse duration at a repetition rate of 113MHz is obtained.The maximum average output power is 2.29W at the incident pump power of 12W with the slope efficiency of about 24.8%.     

Nd∶YAG激光诱导等离子体冲击波实验及对晶状体破坏的研究

测试了利用调Q的Nd∶YAG脉冲激光在水中诱导金属钛产生等离子体冲击波的声压和速度。并利用自行研制的激光乳化系统,对离体猪眼晶状体经硬化处理摹拟白内障进行乳化试验。实验结果表明Nd∶YAG激光等离子体冲击波能对一定硬度的晶状体进行乳化,有可能成为白内障乳化的一种能量源。     

4-W and 23-ps pulses from a lamp-pumped Nd:YAG laser passively mode-locked by polarization switching in a KTP crystal

Passive mode-locking of a cw lamp-pumped Nd:YAG laser using nonlinear polarization switching in a type-II SHG crystal is reported. Light pulses with more than 5 W of average power and pulse duration shorter than 25 ps have been obtained at 1064 nm. Received: 29 January 1999 / Revised version: 24 March 1999 / Published online: 1 July 1999