分析了口径为ф80 mm的钛宝石晶体内的增益特性,对大口径钛宝石晶体中的泵浦光能量密度和泵浦光口径进行了优化设计.对于ф80 mm×17 mm的晶体,最佳工作光束口径为ф55 mm,泵浦能量为50 J;对于ф80 mm×30 mm的晶体,最佳工作光束口径为ф60 mm,泵浦能量为90 J,且其横向小信号增益远小于ф80 mm×17 mm晶体的.对影响大口径钛宝石晶体放大的横向放大自发辐射(ASE)和寄生振荡采用折射率匹配的包边技术进行了抑制。实验表明,该方法把允许横向增益从13提高到了2 100.实验系统为100 J绿光台面泵浦激光器,100 TW主放大器采用四程空间构型放大光路.ф80 mm×17 mm钛宝石晶体c轴水平放置,泵浦光和主激光均为水平偏振.当以泵浦光能量为49 J对主放大器进行双端泵浦,注入信号光能量为1.2 J,光束口径ф60 mm时,获得了14.2 J的放大光输出和286 TW的最高峰值功率.

Gain characteristics of a large-aperture Ti:sapphire disk is studied in detail. To achieve large energy output, the pump energy fluence and beam size were analyzed and optimized. The results is that, for a Ti:sapphire crystal of ф80 mm×17 mm, the optimum beam size is about ф50 mm with 50 J pump energy, for a Ti:sapphire crystal of ф80 mm×30 mm, the optimum beam size is about ф60 mm with 90 J pump energy. To suppress the transverse parasitic oscillation and ASE across the large-aperture Ti:sapphire crystal, the periphery fo the disk is cladded with an index-matched thermoplastic polymer material, which increases the oscillation threshold from 13 to 2 100. The multihundred-terawatt amplifier is four-pass configured with a 17 mm long Ti:sapphire disk with 80 mm in diameter and. The pump energy of up to 100 J is provided by a newly built Nd:glass laser facility. Amplifier experimental results show that in the case of injected 1.2 J singal laser with 49 J pump energy, the amplifier has produced 14.2 J laser energy，which implies a peak power for the laser pulse of 286 TW.