被动锁模复合环形腔掺饵光纤激光器的自启动分析

本文对被动锁模复合环形腔掺饵光纤激光器的自启动工作特性进行了分析，指出谐振腔内残余反射面的存在是阻碍激光器实现自启动锁模的主要原因。利用半导体激光器有源区的折射率随注入电流的变化而改变的特性，在谐振腔中获得了一个可移动腔镜，克服了腔内残余反射面的影响，实现了锁模的自启动。     

Effect of Ca2+ and Mg2+ ions on the sintering and spectroscopic properties of cr-doped yttrium aluminum garnet ceramics

In this work, we investigated the effects of Ca²⁺ and Mg²⁺ ions and annealing temperature on the spectroscopic parameters of chromium-doped yttrium aluminum garnet ceramics (Cr:YAG). Samples were obtained with either a separate or a simultaneous addition of calcium and magnesium oxides. To achieve this, aqueous suspensions were prepared using Y₂O₃, Al₂O₃, Cr₂O₃, MgO, and CaO high-purity powders as raw materials. The obtained suspensions were freeze-granulated, pressed into pellets, debinded, and subjected to reactive sintering in vacuum at 1715°C for 6 h. Each material was annealed in air with temperatures between 1300 and 1700°C. Samples were also compared to Cr:YAG ceramics with the addition of silica as a sintering aid. All the materials obtained were then exposed to 445 nm excitation, and emission spectra in the visible and infrared wavelengths were recorded. The results showed that the emission spectra of Cr:YAG ceramics varied according to the annealing conditions: as-sintered samples exhibited strong emissions of around 680 nm and, after air annealing, of around 1400 nm. This phenomenon is attributed to the Cr³⁺→Cr⁴⁺ transition. Samples doped solely with MgO exhibited the highest emission intensity in the infrared region. Thus, Mg²⁺ ions provided the best conversion efficiency of chromium ions.     

超声CO激光的现状和展望(续)

介绍了200kWCW超声电子束连续CO激光器（SSCO－EIL）开环实物模型的能量和光谱特征的实验研究结果，以及增加SSCO－EIL的输出功率，谱线选择性，Q－开关激光作用的数字计算结果，同时讨论了SSCO－EIL的特性对几种激光技术效率的影响，由于激光能量利用率的增加和能量成本的降低，SSCO－EIL拥有的无与伦比的能量和特有的特征，将大大拓宽激光技术的应用领域。     

Pump beam waist-dependent pulse energy generation in Nd:YAG/Cr4+:YAG passively Q-switched microchip laser

Abstract

The incident pump beam waist-dependent pulse energy generation in Nd:YAG/Cr⁴⁺:YAG composite crystal passively Q-switched microchip laser has been investigated experimentally and theoretically by moving the Nd:YAG/Cr⁴⁺:YAG composite crystal along the pump beam direction. Highest pulse energy of 0.4 mJ has been generated when the Nd:YAG/Cr⁴⁺:YAG composite crystal is moved about 6 mm away from the focused pump beam waist. Laser pulses with pulse width of 1.7 ns and peak power of over 235 kW have been achieved. The theoretically calculated effective laser beam area at different positions of Nd:YAG/Cr⁴⁺:YAG composite crystal along the pump beam direction is in good agreement with the experimental results. The highest peak power can be generated by adjusting the pump beam waist incident on the Nd:YAG/Cr⁴⁺:YAG composite crystal to optimize the effective laser beam area in passively Q-switched microchip laser.     

全光纤电光主动调Q激光器

利用马赫曾德尔Mach-Zehnder (M-Z)结构的尾纤型铌酸锂(LiNbO3)电光强度调制器作为Q开关元件,采用974nm半导体激光器作为泵浦源,峰值吸收系数为110dB/m的掺杂铒纤作为增益介质,实现了1550nm波长的全光纤主动调Q激光器。通过电光强度调制器对腔内损耗进行周期性调制,实现Q开关作用,获得了稳定的调Q脉冲输出。实验中通过改变泵浦功率和调制频率,研究了脉冲宽度和峰值功率的变化规律。获得输出脉冲重复频率50Hz-88kHz可调,重复频率1kHz时获得最窄脉冲宽度246ns,峰值功率近5W。     

被动调Q固体激光器的稳定性及增益预泵浦技术

研究了造成被动调 Q激光脉冲不稳定的原因 ,针对泵浦功率的起伏和饱和吸收体响应时间的影响 ,进行了深入的分析。提出了采用增益预泵浦方式提高被动调 Q激光器稳定性的方法 ,并就这种激光器进行了分析。结果表明 ,采用增益预泵浦 ,可提高被动调 Q激光器脉冲输出能量和工作效率。     

内腔倍频被动调Q Nd:YVO4/KTP绿光的脉宽控制

分别改变饱和吸收体在激光腔内的位置及抽运光的束腰在激光晶体中的位置，实现了对激光二极管（LD）抽运Nd：Nd：YVO4／KTP腔内倍频Cr^4＋：YAG被动调Q绿光的脉宽控制。在抽运功率1．52w的条件下，脉冲宽度可以控制在388～616ns之间，同时获得了激光脉冲的重复频率、单脉冲能量及峰值功率的变化范围分别为4．4～26．3kHz，0．52～4．19μJ和1．0～7．2w。考虑腔内光子数密度的高斯空间分布以及抽运光的空间分布，给出了描述调Q激光器工作原理的耦合速率方程组，其数值解与实验结果相符。     

一种全自动调节的锁模光纤激光器

通过在非线性偏振旋转环形腔中引入一种全光纤化的角度可调的起偏器,简化了被动锁模光纤激光器的结构,通过调节环形腔内的光纤起偏器和1/4波片的角度就能够实现锁模脉冲的输出。基于此简化结构,引入基于单片机的触发反馈电路,控制偏振片和波片的旋转状态,实现了腔内锁模脉冲的自动调节输出,得到平均功率为8mW的、重复频率为5.6 MHz的全自动锁模脉冲稳态输出。     

稳定的简单结构被动调Q单脉冲单纵模激光器

以激光二极管(LD)环形阵列侧面抽运Nd:YLF棒高增益放大器模块为基础，在经典的平凹驻波腔中加人一片Cr^4 ：YAG晶体作为被动Q开关，利用被动Q开关本身所具有的振荡选模功能以及两端不镀膜的Nd：YLF棒所具有的标准具效应，简便地实现了稳定的单脉冲、单纵模调Q输出。振荡器输出脉冲平均宽度为9．3ns，脉冲宽度稳定性达到8％(RMS)；输出脉冲平均能量为1．218mJ；单脉冲能量稳定度优于3％(RMS)，对应峰值功率达到O．13MW。同时该振荡器长时间工作过程中单纵模输出几率始终优于99％，这种单纵模振荡器结构简单，性能稳定可靠，适合于实际应用以及产品化。     

LD端面抽运掺Yb3+双包层光纤激光器自脉动行为的实验研究

本文对连续波半导体激光器端面抽运的Fabry-Perot腔掺Yb3 双包层光纤激光器的自脉动输出行为进行了研究．发现低Q值腔光纤激光器具有两种形式的自脉动输出，一种是饱和吸收被动调Q产生的自脉冲,另一种是与光纤中的受激Raman散射(SRS)效应相对应的阵发性巨脉冲．通过提高光纤激光器谐振腔的Q值并选择合适的抽运功率，可以有效地减小输出功率的自脉动，获得稳定的连续波激光输出．