ALD氧化铝单层膜1 064 nm激光损伤特性研究

 采用原子层沉积技术(atomic layer deposition,ALD)在熔石英和BK7玻璃基底上镀制Al2O3单层膜。利用小口径损伤在线测试平台对膜层的1 064 nm激光损伤特性进行了实验测量,获得膜层损伤阈值约为10.3 J/cm2,对比了其与BK7基底损伤阈值之间的差异;利用Nomarski显微镜和原子力显微镜分析讨论了损伤形态的特点,结果表明损伤主要表现为膜层脱落和基片小孔烧蚀,其中小孔深度集中在70 nm～95 nm范围;讨论了损伤发生的诱因,得出膜基界面可能存在吸收源先驱的推断。     

超广角大工作面f-theta镜头的光学设计

 目前国内用于激光标刻机的f-theta镜头的视场角一般小于60°。采用望远镜结构,利用视觉放大率增大视场角,得到了超广角90°镜头。该方法具有简洁、可靠、易实现等特点。通过初级像差分析,确定系统的初级结构参数,利用ZEMAX软件优化得到了大工作面为285 mm的f-theta镜头,镜头线性畸变误差值不超过1 %,在半径为698 μm的圆内,能量集中度为80%,聚焦性能接近衍射极限。     

Broadband water window supercontinuum generation with a w ＋3w/2 multicycle two-colour pulse

We propose a method to generate a high-efficiency broadband water window supercontinuum with a w ＋ 3w/2 multicycle two-colour pulse. Our results reveal that the 3w/2 laser pulse can simultaneously modulate the acceleration step and the ionization step, which not only broadens the bandwidth but also enhances the yield of the generated supercontinuum. An ultra-broadband supercontinuum from 290 eV to 555 eV covering the whole water window is generated. Using this method, we expect that an isolated 62-as pulse with a minor pre-pulse can be directly obtained.     

电子俘获材料的研究现状及在红外检测方面的应用

电子俘获材料在辐射剂量测定、光信息处理、光存储、红外光检测等许多技术领域具有广泛的应用。本文详细介绍了电子俘获材料的发光原理、材料种类、制备方法以及研究现状,并针对该材料在红外光检测方面的应用,提出了在室温下该材料存在红外光检测上限的观点。针对电子俘获材料存在性质不稳定及在制备过程中需用到硫化类材料易造成污染等问题,建议进一步改进材料制备方法。最后,文中指出玻璃陶瓷类电子俘获材料会有很好的发展前景,并对该种材料未来的发展前景进行了展望。     

不同气体环境下532nm激光诱导硅表面形貌的研究

研究了在不同气体环境下,利用532nmNd：YAG纳秒脉冲激光累积辐照单晶硅表面形成的微结构,结果表明,在其他条件相同,背景气体不同的情况下,背景气体对硅表面形貌的形成起着重要的作用。具体分析了真空、N2和SF6 3种环境气氛下形成的微结构,结果显示,在sF6中形成的锥形微结构的数密度比在N2和真空中的大,并且锥形具有更大的纵横比;在N2、真空和sF6中形成的微结构尺寸依次减小。sF6气氛下,激光辅助化学刻蚀的效率比在真空和N2气氛中的高。另外,辐照区域边缘有波纹微结构形成,分析认为,该微结构的形成是由表面张力波的冷却导致的。     

基于GaSe和GaSe0.7S0.3单晶的单脉冲CO2激光倍频器

描述了使用电感储能发生器和半导体转换开关泵浦的工作波长为10.6μm的高效CO2激光器。给出了激光泵浦的非线性晶体GaSe和GaSe0.7S0.3的二次谐波振荡的实验数据和理论估算结果。结果显示,GaSe晶体在输入能量为180mJ时,最大能量转换效率为0.38%,倍频激光的峰值功率为8 kW。     

Studies on the mechanisms of powerful terahertz radiations from laser plasmas

A survey on the mechanisms of powerful terahertz (THz) radiation from laser plasmas is presented.Firstly,an analytical model is described,showing that a transverse net current formed in a plasma can be converted into THz radiations at the plasma oscillation frequency.This theory is applied to explain THz generation in a gas driven by two-color laser pulses.It is also applied to THz generation in a tenuous plasma driven by a chirped laser pulse,a few-cycle laser pulse,a DC/AC bias electric field.These are well verified by particle-in-cell simulations,demonstrating that THz radiations produced in these approaches are nearly single-cycles and linear polarized.In the chirped laser scheme and the few-cycle laser scheme,THz radiations with the peak field strength of tens of MV/cm and the peak power of gigawatt can be achieved with the incident laser intensity less than 10 17 W/cm 2.     

Radially polarized and passively Q-switched Nd:YAG laser with composite structure of gain medium

We report on a radially polarized and passively Q-switched Nd:YAG/Cr4+:YAG laser.The bulk Nd:YAG crystal is bonded with two undoped YAG crystal end caps to weaken the thermal lens e?ect and thus,enhance the extraction of stored energy in the bulk gain material.In the absence of active water cooling,the average laser power reaches 383 mW with 33% slope efficiency,and the laser pulse achieves 1.457-W peak power,18.9-ns duration,and 13.9-kHz repetition rate with 97.6% polarization purity.     

Study of diode-pumped Yb:YAG disk lasers at low temperature

A Yb:YAG disk laser with V-shaped stable resonator and active-mirror configuration,end-pumped by a 940-nm InGaAs laser diode array,is demonstrated.Performances and optimization of the disk laser at low temperature over a range of 130-200 K are investigated theoretically and experimentally.Laser output energy of 1.46 J/pulse operating at 10-Hz repetition rate is obtained with the optimum output coupler transmission of 30%,and the corresponding optical-to-optical efficiency is 48.7%.     

Microstructure evolution of laser solid forming of Ti-Al-V ternary system alloys from blended elemental powders

Morphology evolution of prior β grains of laser solid forming (LSF) Ti-xAl-yV (x 11,y 20) alloys from blended elemental powders is investigated. The formation mechanism of grain morphology is revealed by incorporating columnar to equiaxed transition (CET) mechanism during solidification. The morphology of prior β grains of LSF Ti-6Al-yV changes from columnar to equiaxed grains with increasing element V content from 4 to 20 wt.-%. This agrees well with CET theoretical prediction. Likewise, the grain morphology of LSF Ti-xAl-2V from blended elemental powders changes from large columnar to small equiaxed with increasing Al content from 2 to 11 wt.-%. The macro-morphologies of LSF Ti-8Al-2V and Ti-11Al-2V from blended elemental powders do not agree with CET predictions. This is caused by the increased disturbance effects of mixing enthalpy with increasing Al content, generated in the alloying process of Ti, Al, and V in the molten pool.