0.351μm激光辐照靶角度和时间分辨的侧向散射研究

 建立了一套角度和时间同时分辨的散射光诊断系统,利用星光Ⅱ装置输出的0.351μm激光辐照平面靶,研究了激光与靶作用产生的侧向散射光的时间行为,实验对金盘靶、CH膜靶和泡沫CH靶与激光作用产生的散射激光进行了研究,在多个角度获得了时间分辨的散射光信息,由角分布的结构得到了等离子体密度分布的一些重要信息。     

Characteristics of the crystalline and luminescence properties of a-plane GaN films grown on γ-LiAlO_2(302) substrates

A-plane GaN films are deposited on(302) γ-LiAlO 2 substrates by metalorganic chemical vapor deposition(MOCVD) . The X-ray diffraction(XRD) results indicate that the in-plane orientation relationship between GaN and LAO substrates is [010] LAO [0001] GaN and [203] LAO [1100] GaN with 0.03% and 2.85% lattice mismatch,respectively. Raman scattering results indicate that the strain in the films decreases along with the increase in the thickness of the films. In addition to the band edge emission at 3.42 eV,defects-related luminescence at 3.35 eV is observed in the photoluminescence(PL) spectra. The cathodoluminescence(CL) spectra indicate that the 3.35-eV emission is related to the V pits.     

过渡金属离子(Mn,Fe,Co)掺杂铝酸锂晶体的生长及光谱分析

采用提拉法分别生长了掺杂Mn、Fe以及Co元素的LiAlO2晶体,并对其结晶质量和光谱特性进行了研究.结果表明,LiAlO2:Mn、LiAlO2:Fe和LiAlO2:Co晶体的X射线双晶摇摆曲线半高宽分别为23.2 arcsec、12.9 arcsec和23.8 arcsec.LiAlO2:Mn与LiAlO2:Fe晶体在可见至近红外波段具有较高的透过率,而LiAlO2:Co晶体在500～700 nm波段存在吸收带;光致激发与发射光谱表明Mn2+在LiAlO2:Mn晶体中处于四面体晶体场内,而Fe3+替代Li+处于八面体格位;X射线激发发射光谱分析得出空气退火后γ-LiAlO2晶体出现了较强的缺陷发光,可归结为Li2O挥发后形成的F+心,而在同样退火条件下掺杂LiAlO2晶体中相应的缺陷发光不明显,说明Li2O的挥发被抑制,晶体的热稳定性得到了改善.     

Properties of long light filaments in natural environment

The multiple filamentation of terawatt femtosecond(fs) laser pulses is experimentally studied in a natural environment.A more than 30-m long plasma filament with a millimeter diameter is formed by the collimated fs laser pulse freely propagating in an open atmosphere. This study provides the first quantitative experimental data about the electron density of a long range light filament in the atmosphere. The electron density of such a filament is quantitatively detected by using an electric method, showing that it is at the 10~(11)-cm~(-3) level.     

基于大基模体积的10mJ飞秒钛宝石激光再生放大器

文章报导了基于大基模体积的高能量飞秒钛宝石激光再生放大器的设计与实验研究,在重复频率10 Hz、抽运能量60 mJ的激励下,得到了单脉冲能量17.4 mJ的种子脉冲放大结果,压缩后的脉冲宽度为40.6 fs,能量为13.9 mJ.借助于此大基模体积再生腔,仅增加一级多通放大,实现了峰值功率达1.9 TW飞秒激光脉冲输出.结果表明,大模体积再生放大不仅降低了后续放大对抽运能量的要求,也可以单独压缩实现再生腔直接输出10 mJ量级的飞秒激光脉冲,是大能量高峰值功率飞秒激光系统的优质前端.     

Generation of femtosecond laser pulses at 263 nm by K_3B_6O_(10)Cl crystal

The third harmonic generation(THG) of a linear cavity Ti:sapphire regenerative amplifier by use of a K_3B_6O_(10)Cl(KBOC) crystal is studied for the first time. Output power up to 5.9 mW is obtained at a central wavelength of 263 nm,corresponding to a conversion efficiency of 4.5% to the second harmonic power. Our results show a tremendous potential for nonlinear frequency conversion into the deep ultraviolet range with the new crystal and the output laser power can be further improved.     

Generation of femtosecond laser pulses at 396 nm in K_3B_6O_(10)Cl crystal

K_3B_6O_(10)Cl(KBOC), a new nonlinear optical crystal, shows potential advantages for the generation of deep ultraviolet(UV) light compared with other borate crystals. In this paper we study for the first time the second harmonic generation(SHG) of a femtosecond Ti:sapphire amplifier with this crystal. Laser power is obtained to be as high as 220 m W at the central wavelength of 396 nm with a 1-mm-long crystal, and the maximum SHG conversion efficiency reaches 39.3%. The typical pulse duration is 83 fs. The results show that second harmonic(SH) conversion efficiency has the room to be further improved and that the new nonlinear crystal is very suited to generate the high efficiency deep ultraviolet laser radiation below 266 nm.     

Frequency dependence of quantum path interference in non-collinear high-order harmonic generation

High-order harmonic generation(HHG) driven by two non-collinear beams including a fundamental and its weak second harmonic is numerically studied. The interference of harmonics from adjacent electron quantum paths is found to be dependent on the relative delay of the driving pulse, and the dependences are different for different harmonic orders.This frequency dependence of the interference is attributed to the spatial frequency chirp in the HHG beam resulting from the harmonic dipole phase, which in turn provides a potential way to gain an insight into the generation of high-order harmonics. As an example, the intensity dependent dipole phase coefficient α is retrieved from the interference fringe.     

射频磁控溅射法制备TiO2-xNx薄膜的结构性能研究

利用射频磁控溅射法室温下在Si(100)衬底上制备了N掺杂的TiO2薄膜,并且采用x射线衍射(XRD)、X射线光电子能谱(XPS)和透射光谱对薄膜进行了表征.XRD结果表明在纯Ar和N2(33.3;)/Ar气氛下制备的TiO2-xNx薄膜均为单一的金红石相,薄膜结晶性良好,呈高度(211)择优取向,而在N2(50.0;)/Ar下制备的薄膜结晶性明显变差;对于N掺杂的TiO2薄膜,XPS表明部分N原子进入TiO2晶格,并且以N-Ti-O、N-O键以及间隙式N原子形式存在;透射光谱表明掺N后的TiO2薄膜吸收边发生了红移.