高功率Nd∶YVO4/KTP腔内倍频晶体温度分布的半解析热分析

非线性晶体KTP采用Ⅱ类相位匹配腔内倍频时,不仅要求晶体满足基频光的偏振匹配条件,而且所选用的晶体要求符合λ/2波片的条件,才能使晶体的谐波转换效率达到最佳.由于倍频晶体吸收基频光能量引起晶体内部非均匀温升,改变晶体内部各点的折射率,也会使晶体产生不应有的热形变,破坏晶体初始的位相匹配条件,严重影响输出激光的品质和倍频效率.减弱、改善这种情况的关键是准确得出在实际工作条件下晶体内部温度场.利用半解析热分析方法得出了KTP晶体内部温度场的计算方法,分析了各种热参量变化对KTP晶体内部温度场的影响.得出的结果具有一定的普适性,可以应用到具有轴对称形式内热源的其它热模型温度场的计算分析中,对连续波腔内倍频激光系统的设计将起到指导作用.     

石墨烯在全固态激光器中的应用

正1.引言全固态激光器(all solid state lasers)是指用激光二极管(laser diode,LD)代替闪光灯泵浦固体激光增益介质的激光器,也称为激光二极管泵浦的固体激光器(laser diode pumped solid state lasers,LDPSSL或DPL)。它集两种激光器的优势于一体,具有转换效率高、输出能量大、峰值功率高、工作介质覆盖的波段广及运转方式多样等优点,与被动可饱和吸收体相结合,可以实现脉冲激光运转,已成为新的优质脉冲激光光源。     

Double Q-switched 946 nm laser with MgO:LN electro-optic crystal and MoSe_2 saturable absorber

We report a double Q-switched 946 nm laser with a magnesium-oxide-doped LiNbO_3(MgO:LN) electro-optic(EO) crystal and a monolayer molybdenum diselenide(MoSe_2) saturable absorber(SA). A pulsed laser diode side-pumped long neodymium-doped yttrium aluminum garnet rod(φ3 × 65 mm) is used as the gain medium.Large pulse energy up to 3.15 m J and peak power up to 346 kW are generated at the repetition rate of 550 Hz,corresponding to the beam quality factors of M_x~2=3.849, M_y~2=3.868. Monolayer MoSe_2 nanosheets applied in the experiment would be a promising SA for a passive Q-switching operation.     

波长可调谐的瓦级连续橙红光激光器

介绍了基于复合腔结构的全固态波长可调谐的连续橙红色激光的输出特性。该复合腔由一个使用周期极化晶体MgO:PPLN的信号光单谐振光参量振荡器和一个LD侧面泵浦Nd:GdVO₄晶体的1 062.9 nm基频光谐振腔构成。s-偏振1 062.9 nm泵浦光抽运单谐振光参量振荡器产生s-偏振信号光腔内独立振荡。通过复合腔结构的优化设计,使独立振荡的p-偏振1 062.9 nm基频光与s-偏振信号光在2个子腔的重叠区内通过Ⅱ类角度匹配KTP晶体的腔内和频过程获得橙红色激光。当MgO:PPLN晶体的调谐温度从30 ℃上升至200 ℃时,s-偏振信号光的中心波长产生红移,导致其与p-偏振1 062.9 nm基频光和频产生的橙红色激光的中心波长从620.2 nm红移至628.9 nm。同时测得中红外波段闲频光的中心波长从3 714.2 nm蓝移至3 438.3 nm。在30 ℃最低设定温度时, 中心波长620.2 nm的橙红色激光和中心波长3 714.2 nm的闲频光最大连续输出功率分别达到2.0 W和2.9 W。     

Experimental study on laser cleaning of paint layer on white marble surface北大核心CSCD

In order to effectively remove the surface paint of the cultural relic of white marble, the area extrapolation method and laser-induced plasma spectroscopy (LIPS) method were used to obtain the ablation threshold power of the gold, silver paint layer and white marble surface. On the basis of this, the optimal laser power for removing paint without damaging the white marble substrate was determined. The image processing method was used to study the cleaning degree and variation trend of cleaning rate of the gold and silver paint on the surface of 10 mm×10 mm white marble by laser cleaning, and the optimal laser spot overlap rate and the optimal cleaning times were obtained. Finally, the image processing method was used to evaluate the cleaning effect of laser cleaning of paint layer on the white marble surface. More than 93% of the cleaning degree shows that the synergistic use of the area extrapolation method, LIPS method and image processing method can effectively improve the laser cleaning efficiency of the paint layer on white marble surface. Copyright ©2022 Journal of Applied Optics. All rights reserved.     

KGW晶体外腔式高功率579nm喇曼黄光激光器

报道了579nm高功率KGd(WO4)2喇曼晶体外腔式喇曼黄光激光器的输出特性.基于808nm脉冲激光二极管侧面泵浦Nd∶YAG陶瓷、腔内BBO电光晶体同步延迟调Q和Ⅰ类临界相位匹配的LBO晶体腔外倍频方案,并通过外腔式KGW晶体Ng轴二阶斯托克斯喇曼频移,获得了579.54nm黄光激光输出.当脉冲信号重复频率为1kHz、532nm泵浦光最高平均功率为5.02W、脉冲宽度为10.1ns时,获得了最高平均功率2.58 W、脉冲宽度7.4ns、峰值功率348.6kW的579.54nm二阶斯托克斯喇曼黄光激光输出;532nm至579.54nm的光-光转化效率为51.4%、斜率效率为54.8%,光束质量因子Mx2-579.54=5.829、My2-579.54=6.336,输出功率不稳定性小于±2.35%.实验表明:外腔式喇曼结构能够高效地获得喇曼黄光,具有很高的光-光转化效率及良好的功率稳定性,并通过脉冲LD结合同步延迟电光调Q可获得高重复频率、高平均功率、窄脉冲宽度和高峰值功率的黄光激光输出.     

Continuous-Wave Green Laser of 9.9 W by Intracavity Frequency Doubling in Laser-Diode Single-End-Pumped Nd：YVO4／LBO

A maximum of 9.9 W cw TEM00 output at 532nm laser has been obtained by intracavity frequency doubling with LBO in laser-diode single-end-pumped Nd:YVO4. The Nd:YVO4/LBO green laser has a simple threemirror V-fold cavity structure. The optical-optical conversion efficiency was 34.8%. Based on the equation of thermal conduction, a general solution for the laser-crystal interior temperature distribution is obtained by the semi-analytical thermal analysis method. Using the software system, the cavity parameters have been optimized according to the stability condition and the astigmatic compensation principle. The astigmatism in the cavity has been effectively controlled and the resonator was insensitive to the thermal lens in the Nd:YVO4 crystal.     

碳化硅基底改性硅表面的磁流变抛光

为克服传统抛光方法在硅改性的碳化硅表面抛光存在的不足,采用磁流变抛光在精抛光阶段实现面形误差高效去除和快速收敛。基于实际应用中的对磁流变抛光液的需求,提出了磁流变液的性能要求,并配制了适合改性硅表面抛光的磁流变抛光液,检测所配制的抛光液体的流变特性和分散稳定性,证明了液体具有良好的性能。对口径为130 mm(有效口径为120 mm)的硅改性的同轴非球面碳化硅工件进行实际抛光。经过两个周期约3 h的抛光,面形误差均方根(RMS)从0.051λ(λ=632.8 nm)快速收敛至0.012λ,粗糙度Ra达0.618 nm。验证了所配制的磁流变抛光液满足碳化硅基底改性硅表面的抛光需求,证明了磁流变抛光技术在镜面硅改性后精抛光阶段具有独特的优势。     

全捷联激光半主动导引头线性视场研究

针对全捷联半主动导引头大线性视场的要求,分析了四象限光电系统线性视场与目标距离的关系。首先根据系统参数计算不同能见度、不同目标反射率下的目标距离与导引头接收光功率关系;通过建立光学系统的仿真模型,利用光线追迹方法获得不同视场对应的探测器光敏面光斑功率分布;最后结合探测器灵敏度阈值,得到线性视场与接收激光功率的关系:随着目标距离减小,线性视场从0°增大到光学设计理论值。实验测试结果表明,线性视场随着接收功率增大,从0°增大到±9°,与理论分析一致。因此,全捷联半主动激光制导系统设计应该考虑导引头线性视场变化规律。     

基于曲率滤波优化的遥感影像去雾算法

针对山区容易积聚云雾不利于遥感影像解译,且遥感影像因包含大量信息数据计算速率慢,在去雾过程中遇到雾量过多的情况去除效果差的问题,提出了一种曲率滤波优化与非局部去雾方法相结合的光学遥感影像去雾算法.首先通过曲率滤波降低了图像的总能量,从而减少了图像占用的内存,提高了计算效率.然后通过霍夫变换表决机制筛选出符合的大气光值,...