用于大口径钛宝石放大器的四路钕玻璃抽运源

研制了一套能量输出稳定、光斑分布均匀、时域近方波形的四路钕玻璃抽运源系统。系统能够输出4×180J的基频能量(波长为1053nm),4×80J的倍频能量(波长为526.5nm)。主要结构包括四部分:前端种子源、再生放大器、钕玻璃棒放链和KDP倍频晶体。利用偏振片实现了垂直偏振的两路基频光合束,经过第二类相位匹配KDP晶体倍频,获得了共线且同偏振的526.5nm倍频光,实现了用于150mm口径钛宝石放大器的结构紧凑的双脉冲抽运源。     

Optical property measurements of 235 mm large-scale Ti:sapphire crystal

A Ti:sapphire crystal with a diameter of 235 mm and thickness of 72 mm was grown by the heat exchange method(HEM). The absorption intensity of the crystal at 532 nm averaged at 91%. The figures of merit(FOMs)at different positions of the crystal were measured and the FOM value in the central region was found to reach 90.The transmittance laser beam was intact with no obvious distortions and had only a small deformation compared with the incident laser beam. A small-signal amplification experiment was performed on the Ti:sapphire crystal and a gain of more than 6 times was achieved with a pump energy density of 1.98 J∕cm~2. These tests indicate that the 235 mm Ti:sapphire crystal has excellent optical qualities and will further improve the energy output of a 10 PW laser system.     

10 PW级激光系统波前演变及分析

基于上海超强超短激光装置(SULF),选取各分系统关键节点进行波前测量,分析波前畸变的起源、演变及原因,并讨论了光学器件安装应力与钛宝石晶体质量对波前的影响。结果表明,激光波前畸变值随着大口径光学器件数量的增多而增大,光学镜片的面形加工误差、安装调试误差是影响钛宝石激光放大器中波前畸变的重要因素,对激光的聚焦性能有较大影响。对激光系统波前的测量有利于优化与控制整个系统的波前畸变,从而有助于提升光束质量和聚焦功率密度。     

FCBGA高铅凸块non-wet的失效机制及基于封装工艺的解决方案

FCBGA封装芯片中晶片凸块和基片凸块之间的non-wet问题是一个已知的能导致严重低良品率和引入可靠性隐患的问题。本文研究了FCBGA封装形式中non-wet的典型失效模式和揭示了其生成机制, 并确定了晶片凸块表面残留的铅和锡氧化物是导致晶片凸块和基片凸块之间non-wet的主要成因。晶片凸块回流工艺实验表明,优化后的回流时间和氢气流速能显著减少和去除晶片凸块表面的铅锡氧化物,从而能把non-wet引起的报废率降低90%左右。 失效分析结果和量产数据都验证了本文揭示的non-wet的失效机制是正确的。 研究确定的凸块回流工艺的优化参数显著降低了non-wet引起的报废率,从而大大地节省了制造成本和提高了产能利用率。