Radiation-induced processes and defects in alkali and alkaline-earth borate crystals

The paper presents the results of a study of the radiation-induced processes and defects in nonlinear optical crystals Li₂B₄O₇ (LTB), LiB₃O₅ (LBO), CsLiB₆O₁₀, KB₅O₈·4H₂O, β-BaB₂O₄. It was revealed that a pulsed electron beam irradiation at 290 K forms the radiation-induced pairs of the ‘vacancy—interstitial atom’ defects in the cation sublattice of these crystals. This gives rise to a creation of metastable electronic (interstitial atom) and hole (small-radius polaron near the cation vacancy) centers in high concentrations. Optical hole-transitions from the local level of the trapped hole centers to the valence band states are responsible for the transient optical absorptions (TOA) of borates in the visible and UV spectral ranges. A sublattice of the weakly bound mobile lithium cations in LTB and LBO favors a spatial separation of the radiation-induced pair defects ‘hole polaron near Li-vacancy—mobile interstitial Li⁰ atom’. Their decay rated by the electron–hole nonradiative tunnel recombination determines a peculiar feature of the TOA decay kinetics in LTB and LBO.     

缓冲层对LBO晶体上1 064 nm，532 nm增透膜附着力的影响

 采用电子束蒸发方法在LBO晶体上制备了无缓冲层和具有不同缓冲层的1 064 nm,532 nm二倍频增透膜。利用分光光度计、纳米力学综合测试系统以及调Q脉冲激光装置对样品的光学性能、附着力以及抗激光损伤性能进行了测试分析。结果表明：所有样品在1 064 nm和532 nm波长的剩余反射率都分别小于0.1％和0.2％;与无缓冲层样品相比,预镀Al₂O₃缓冲层样品的附着力提高了43.1％,具有SiO₂缓冲层样品的附着力显著提高,而MgF₂缓冲层的插入却导致薄膜附着力降低。应用全塑性压痕理论和剪切理论对薄膜的附着力增强机制进行了分析。薄膜的抗激光损伤性能分析表明,SiO₂缓冲层也有助于改进薄膜的激光损伤阈值。     

高效转换的大功率皮秒脉冲激光器

本文描述我们设计的带抗共振环(ARR)的对撞脉冲锁模(CPM)非稳腔Nd:YAP和Nd:YAG激光器,该激光腔结合了CPM腔脉宽窄、工作稳定和非稳腔输出能量高的特点,是一理想的高功率激光器同时选择了KTP、BBO和LBO等优良非线性晶体作为腔内倍频元件,实现高效倍频转换获得×10mJ和5GW/cm²的高能量和高功率绿光皮秒脉冲输出,倍频转换效率高达(50～70)%.     

LD-pumped Nd:YAG/LBO 556 nm yellow laser

A new laser transition at 1112 nm was obtained after analyzing the parameters of the main laser transitions in Nd:YAG and calculating the transmission loss of the cavity at 1064, 1319, and 946 nm. The maximum output power of the fundamental wavelength was 610 mW, the fundamental wavelength light-to-light conversion efficiency was 38.1%, the maximum output at 556 nm was 109 mW intra-cavity frequency doubled by LBO, the SHG conversion efficiency was 17.8%, and the overall light-to-light efficiency was 6.8% for the pump power of 1.6 W.     

LD泵浦的高效率YVO4/LBO红光激光器

报道了用国产 L D泵浦 Nd∶YVO4产生的 1.34 2 μm的输出。首次用 类临界位相匹配 L BO腔内倍频实现了 6 71nm的红激光输出。当泵浦注入功率为 80 0 m W时 ,倍频红激光基模输出为 5 2 m W,光光转换效率达 6 .5 %。光束经扩束准直后测得偏振比高于 10 0∶ 1。在输出功率为 40 m W时 ,48h连续工作稳定性优于± 2 %     

LiB3O5参量调谐蓝紫光单脉冲皮秒激光器

利用Nd~(3+):YAG主被动锁模加晶体管雪崩吸收单选,再放大、倍频、混频,产生30ps,355nm激光单脉冲,用它泵浦Ⅱ类非临界相应匹配的LiB_3O_5光参量发生器,在精密温度控制下,获得415.9～482.6nm的蓝紫光可调谐输出,线宽0.15nm,最高参量转换效率37.6%,可输出能量为6.33mJ,峰值功率为211MW的皮秒激光单脉冲.     

高重复频率Nd∶GdVO4/LBO红光激光器

采用侧面泵浦Nd∶GdVO4晶体的方式,利用I类相位匹配LBO（LiB3O5）晶体进行腔内倍频。腔型采用平凹直腔,利用软件模拟优化谐振腔腔镜曲率半径、腔长以及晶体放置位置等参数,在最大注入电功率750 W时获得9.7 W的671 nm光输出,重复频率10 kHz,发散角7.9 mrad,电-光转换效率约为1.3%。     

Investigation of impurity transport using laser blow-off technique in the HL-2A Ohmic and ECRH plasmas

Impurity transports in two neighboring discharges with and without electron cyclotron resonance heating(ECRH)are studied in the HL-2A tokamak by laser blow-off(LBO) technique.The progression of aluminium ions as the trace impurity is monitored by soft x-ray(SXR) and bolometer detector arrays with good temporal and spatial resolutions.Obvious difference in the time trace of the signal between the Ohmic and ECRH L-mode discharges is observed.Based on the numerical simulation with one-dimensional(1D) impurity transport code STRAHL,the radial profiles of impurity diffusion coefficient D and convective velocity V are obtained for each shot.The result shows that the diffusion coefficient D significantly increases throughout the plasma minor radius for the ECRH case with respect to the Ohmic case,and that the convection velocity V changes from negative(inward) for the Ohmic case to partially positive(outward) for the ECRH case.The result on HL-2A confirms the pump out effect of ECRH on impurity profile as reported on various other devices.     

全固化自锁模飞秒Ti:S激光器实验研究

首次在国内系统报道了以腔内LBO倍频Nd:YVO₄激光器为泵浦源的全固化自锁模飞秒钛宝石激光器的实验结果.设计了一种热不敏腔内LBO倍频线性折叠腔结构,获得到了25.5%的光转换效率,泵浦功率为22W时得到了5.6W的基模绿光输出功率;以该激光器为泵浦源,在线性Z型腔的基础上,使用了一种能够通过改变腔内凹面聚焦镜折叠角消除象散的方法,直接由钛宝石激光器得到了脉冲宽度为22fs、功率为300mW的光脉冲.整个激光系统稳定性好,噪音明显低于Ar³⁺激光器的泵浦情况.     

全固态腔内倍频被动调Q绿光激光器的理论研究

将倍频过程视为一种随基波光子数变化而变化的非线性腔内损耗,对被动调Q四能级速率方程进行修正,总结出了被动调Q绿光激光器的四能级非线性速率方程.通过数值求解,对连续LD泵浦Nd:GdVO4 /Cr4+:YAG/KTP和Nd:YAG/ Cr4+:YAG/LBO腔内倍频被动调Q绿光激光器的输出特性进行了数值模拟.通过与实验数...