泵浦光聚焦特性对高重频1064 nm被动调Q激光器的影响

研究了泵浦光聚焦特性对被动调Q激光器输出激光特性的影响。使用10 W激光二极管(LD)和焦距为4 mm的耦合聚焦镜,在不改变LD和谐振腔结构与间距(15 mm)的情况下,选取5个耦合聚焦镜位置,研究对应泵浦光聚焦特性对输出激光特性的影响,特别是对输出脉冲稳定性的影响。泵浦功率为3.550 W时,相较于其他耦合聚焦镜位置,在耦合聚焦镜距离LD 7.50 mm处,被动调Q激光器实现了更高重复频率(160 kHz)、更高平均输出功率(360 mW)、更高单脉冲能量(2.250 μJ)、更低时域抖动(120 ns)的稳定脉冲输出。实验数据说明,耦合聚焦镜距离LD 7.50 mm处,泵浦光聚焦光斑与谐振腔基模光斑的匹配程度较好。理论计算得出,耦合聚焦镜距离LD 7.50 mm时,谐振腔基模光斑尺寸与泵浦光聚焦光斑束腰尺寸的比值为0.854,该比值对今后开展高重频被动调Q激光器相关研究具有一定的借鉴意义。     

基于全固态调Q激光器的激光实验设计

利用简化的Ga As被动调Q激光器设计激光器教学实验,研究了激光谐振腔腔镜参数变化以及可饱和吸收体小信号透过率改变对激光输出特性(脉冲输出功率、脉冲宽度和重复频率)的影响,然后给出描述Ga As被动调Q激光器的速率方程组,并利用该方程组完成对Ga As被动调Q激光器输出特性的数值模拟.将该实验应用于本科教学,加深学生对激光原理的理解,锻炼学生的动手能力和创新意识.     

声光Q开关在稳定YAG激光器输出功率中的应用

利用声光调Q YAG激光器中激光输出功率与声光调Q频率和声光驱动功率之间的关系,提出了一种声光调Q YAG激光器输出功率的新稳定方法,即简单又实用,激光输出功率稳定度可达±1.2％。     

LD端面抽运1KHz电光调Q Nd:YVO4激光器输出功率特性研究

报道了全固态激光器连续抽运高重复率电光调Q Nd:YVO4激光器的实验和理论分析结果,用BBO晶体作电光调Q元件,在激光二极管(LD)端面抽运Nd:YVO4激光器中实现了较高重复率的电光调Q输出.实验中在1 kHz重复率下,抽运功率为10 W时,平均功率超过170 mW.对输出功率曲线中的凹陷现象进行了分析,指出了制约激光器的内在诸因素,并用传播圆-变换圆图解分析方法给出了合理的解释.     

LD端面抽运1KHz电光调Q Nd∶YVO4激光器输出功率特性研究

报道了全固态激光器连续抽运高重复率电光调Q Nd∶YVO4激光器的实验和理论分析结果,用BBO晶体作电光调Q元件,在激光二极管（LD）端面抽运Nd∶YVO4激光器中实现了较高重复率的电光调Q输出.实验中在1 kHz重复率下,抽运功率为10 W时,平均功率超过170 mW.对输出功率曲线中的凹陷现象进行了分析,指出了制约激光器的内在诸因素,并用传播圆－变换圆图解分析方法给出了合理的解释.     

被动调Q自拉曼Nd:GdVO4激光器

对激光二极管(LD)抽运的自拉曼Nd:GdVO4被动调Q激光器进行了详细的理论和实验研究.实验中采用Nd:GdVO4晶体同时作为激光介质和拉曼晶体,分别用了两块不同初始透射率的Cr4 :YAG晶体,得到并比较了采用不同初始透射率的Cr4 :YAG晶体时被动调Q自拉曼激光器的性能.测量了平均输出功率、脉冲宽度和脉冲重复率随抽运功率的变化关系.当Cr4 :YAG的初始透射率为0.91,输入功率是5.7 W时,得到的拉曼光的最高功率为244.6 mW,相应的转换效率为4.3%.通过数值求解基频光和拉曼光空间分布的速率方程并应用到被动调Q自拉曼Nd:GdYO4激光器.获得的理论结果与实验结果大致相符.     

激光二极管抽运Tm,Ho:YLF晶体声光调Q激光器

对激光二极管端面抽运Tm,Ho：YLF晶体声光调Q激光器的激光特性进行了研究。根据粒子跃迁和能量传递过程,在考虑能级传递上转换的前提下,建立了Tm,Ho：YLF脉冲激光器的速率方程,得到了初始反转粒子数的解析表达式,分析了能量传递上转换效应对激光上能级反转粒子数的影响。在室温下实现了2μm波长激光的脉冲输出。实验上给出并分析了Tm,Ho：YLF脉冲激光器的平均输出功率、单脉冲能量和脉冲宽度随抽运功率以及声光Q开关调制频率的变化关系。在抽运功率为2．8W．重复频率为9kHz时,获得了平均输出功率为189mW的激光脉冲,光-光转换效率为6．8％。在重复频率为1kHz时,得到最大单脉冲能量为65μJ,峰值功率为0．17kW。     

调频微片Nd:YAG激光器光回馈特性的研究

研究了调频微片Nd：YAG激光器的光回馈特性.在没有光回馈的情况下，激光频率每改变一个纵模间隔，激光器输出功率变化一个条纹.有光回馈时，同时改变激光频率和外腔相位，激光器输出功率波动频率正比于内、外腔长度之比.基于三镜腔等效模型的理论分析和实验结果相符合.并且讨论了这一现象在精密测量领域的潜在应用.     

LD端面泵浦Cr~4∶YAG被动调Q激光器输出特性研究

对激光二极管端面泵浦Cr4+∶YAG被动调Q Nd∶YAG激光器输出特性进行了实验研究.实验研究发现,激光器输出功率及脉冲重复频率随谐振腔长度增大而增大.为解释这一实验现象,测量了泵浦光斑在激光晶体内尺寸,同时计算了激光晶体及Cr4+∶YAG晶体内的基模激光光斑半径随谐振腔长度变化.分析结果表明:激光晶体内泵浦光斑尺寸远小于激光晶体内基模光斑半径,腔模间交叠效率较低;当腔长增加时,激光晶体内的基模激光光斑减小,腔模间交叠效率增加,从而导致输出功率及脉冲重复频率随腔长增加而增加;另外,Cr4+∶YAG晶体内光斑半径也随谐振腔长度减小,引起Cr4+∶YAG晶体漂白时间缩短,导致脉冲重复频率随腔长增加而增加.     

自调Q光纤激光器的理论分析和数值模拟

基于自调Q光纤激光器的基本理论,结合速率方程理论与自调Q特点,借助简化的环形腔掺Er3+光纤激光器模型,分析了泵浦功率与自调Q脉冲周期、峰值功率的关系.随着泵浦功率的增加,光纤激光器自调Q脉冲的周期减小,峰值功率变大;当信号光强足够大时,激光器的自调Q现象消失,变为准连续激光输出.通过MATLAB编程对光纤激光器输出特性进行了数值模拟,模拟结果与实验结果基本相符.     

Investigation of cutting of engineering ceramics with Q-switched pulse CO2 laser

In this paper, the cutting of Si₃N₄ engineering ceramics with Q-switched pulse CO₂ laser is studied. Considering the influence of the cut front shape on the absorption of the laser beam, a simplified 2D mathematic model is developed based on a pulsed laser vaporization cut process. This model is based on the conservation of energy. The experimental results show that it would realize crack-free cutting by using high-speed and multi-pass feed cutting process.     

Model of CW pumped passively Q-switched laser

An analytical model of a CW pumped passively Q-switched laser in plane wave approximation is presented. The model was based on possibility to express the analytical solution of simplified rate equations with the help of LambertW function. The LambertW function is now commonly available in most of mathematical software and became to be easy to use. The significant simplification of saturable absorber dynamics is made and its presence is described only by its initial and saturated transmission. Using this model it is possible to estimate giant pulse parameters, like pulse length and energy density, the pulse repetition rate, and the laser input-output power characteristic. The validity limits of this model were verified using numerical solution of more complicated rate equations model which included nonlinear response of the modulator. The model was compared with experimental results obtained for passively Q-switched diode pumped Nd:YAG/V:YAG microchip laser.     

角锥棱镜腔激光二极管抽运被动调Q激光器

为了提高传导冷却条件下激光二极管(LD)侧向抽运被动调Q激光器的光束质量和输出稳定性,采用了两组半圆柱面激光二极管阵列侧向交错抽运两根串接的激光棒,实现了均匀抽运和散热。通过实验分析了横模结构对被动调Q稳定性的影响,设计了角锥棱镜-高斯输出镜非稳腔,在显著提高器件光束质量的同时,明显改善了被动调Q的稳定性,并保证了谐振腔的机械稳定性。在此基础上研制了一台重复频率20 Hz、单脉冲能量64 mJ、脉冲宽度7 ns、稳定性优于±5%、光束发散角0.6 mrad、光-光效率9.1%,且光轴指向稳定的工程实用器件。     

High energy and high stability Cr:YAG passively Q-switched laser with convex-ARR unstable resonator

A convex-ARR (Anti-resonant Ring) unstable resonator was introduced in a Cr⁴⁺:YAG passively Q-switched Nd:YAG pulsed laser. There are two novel features in this cavity, one is the unstable resonator increasing output energy and improving laser mode; the other is the ARR structure efficiently enhancing the laser stability. A high energy and high stability Q-switched pulse with a single pulse energy of 85.6 mJ, a pulse width of 38 ns and an energy stability of 99.6% was obtained. The experimental results were analyzed well by using the mechanism of transient grating and the properties of the unstable resonator.     

Diode-pumped doubly Q-switched mode-locked YVO4/Nd:YVO4 laser with AO and GaAs saturable absorber

By using both acousto-optic (AO) modulator and GaAs saturable absorber, a diode-pumped doubly Q-switched and mode-locked (QML) YVO₄/Nd:YVO₄ laser is presented. The average output power and the pulse width of the Q-switched envelope have been measured. The Q-switch pulse energy of the doubly QML laser are higher than that only with GaAs. The stability of the QML laser with the dual-loss-modulation is significantly improved if compared to that only with GaAs.The experimental results show that the doubly QML YVO₄/Nd:YVO₄ laser has nearly 80% modulation depth and deeper than that of the singly passively QML pulse. The doubly Q-switched mode-locked pulse inside the Q-switched envelope has a repetition rate of 111 MHz and its pulse width is estimated to be about 700 ps. By using a hyperbolic secant square function and considering the Gaussian distribution of the intracavity photon density, the coupled equations for diode-pumped dual-loss-modulated QML laser is given and the numerical solutions of the equations are in good agreement with the experimental results.     

新型电光调Q脉冲固体激光器的研究

针对传统的电光调Q脉冲固体激光器在高重复频率运转时易受热退偏振效应的影响,提出了一种利用方解石的自然双折射特性,将其作为起偏元件输出非线偏振激光脉冲的新型调Q方式。实验结果表明,采用这种调Q方案后,在20 Hz的重复频率运转时,激光输出能量较之1 Hz时平均降幅仅为2.3%,激光输出的稳定性得到较大的提高。     

Pulse symmetry and pulse duration compression in a diode-pumped doubly passively Q-switched Nd:YVO4 lasers with Cr4+:YAG and GaAs saturable absorbers

We present a simple technique to improve the symmetry of pulse emitted by doubly passively Q-switched lasers. Using both Cr⁴⁺:YAG and GaAs saturable absorbers in the same cavity, a diode-pumped doubly passively Q-switched Nd:YVO₄ laser is realized for the fist time. This laser can generate more symmetric pulse with shorter pulse width and higher peak power compared with the solely passively Q-switched laser with Cr⁴⁺:YAG saturable absorber or GaAs coupler. The pulse symmetry factor ε of such a doubly passively Q-switched laser is experimentally shown to reach 1.05. Simulations by a rate-equation model for doubly passively Q-switched laser are in close agreement with the experimental results.PACS 42.55.Xi; 42.55.Rz; 42.60.Gd     

Frequency-stabilized laser system at 1572 nm for space-borne CO_2 detection LIDAR

A frequency-stabilized laser system at 1572 nm for space-borne carbon dioxide(CO_2) detection LIDAR to realize the precise measurement of the global atmospheric CO_2 concentration is presented in this Letter.A distributedfeedback laser diode serves as the master laser(ML)and is wavelength locked to the CO_2 line center at 1572.0179 nm using the external frequency modulation technique.The root mean square frequency drift is suppressed to about 50 kHz at an average time of 0.1 s over 8 h.Based on optical phase-locked loops,an online seeder and an offline seeder are offset locked to the reference laser at 1572.024 and 1572.081 nm,respectively,retaining virtually the same frequency stability as the ML.     

负电子亲和势GaAs光电阴极中的三光子激发和发射的理论研究

将三阶微扰理论应用于单晶GaAs半导体,结合与实际相接近的能带结构,得到了GaAs中三光子吸收系数的解析式表达式,在考虑了激发电子的逃逸过程的情况下,进而推导了负电子亲和势GaAs光电阴极中三光子光电发射的发射系数的解析表达式.两表达式得到的理论数值分别与用ns量级脉宽、2.06μm波长的激光测得的GaAs中三光子吸收系数和GaAs(Cs,O)光电阴极中三光子发射系数的实验值相比较,吻合较好.     

Tomographic reconstruction of 2D-OH<Superscript>∗</Superscript>-chemiluminescence distributions in turbulent diffusion flames

A theoretical model on actively Q-switched Nd³⁺-doped quasi-three-level laser including the energy transfer upconversion and the ground state reabsorption is developed. The analytical expressions of the fractional thermal loading and the average output power are obtained, and the influence of ETU effects on laser performance for different repetition rate is analyzed. The average output power and the thermal focal length of the Q-switched 946 nm laser are acquired in experiment. The good agreement between the experimental data and theoretical results demonstrates the reliability of the theoretical model.