双色场下紫外超短脉冲的频谱展宽

当共线传输的双色强激光脉冲满足时间重叠时，其等离子体通道间将出现强烈的耦合作用，由此引起的交叉相位调制可产生强烈的非线性效应，使紫外超短脉冲的频谱展宽效应得到增强.将由钛宝石激光系统经三倍频得到的能量为045 mJ、带宽为15 nm的紫外脉冲和能量为71 mJ的近红外脉冲共线聚焦后，在氩气样品池中分别诱导产生等离子体通道，发现紫外脉冲光谱受到明显调制.调制后的光谱半高全宽增至64 nm，为聚焦前谱宽的4倍，是单束紫外脉冲成丝时谱宽的25倍.实验着重研究在不同时间延迟、耦合位置和气体压强情况下，双 关键词： 紫外超快脉冲 双色光丝 非线性效应 光谱展宽

Spectrum broadening of ultrashort ultraviolet pulse in dual-color laser field

When collinear dual-color intense laser pulses are overlapped in time, a strong coupling interaction occurs between their plasma filaments. Due to the cross phase modulation, strong non-linear effects are generated and the spectrum width of the ultrafast ultraviolet (UV) pulse is further broadened. The original UV pulse with a bandwidth of 1.5 nm and energy of 0.45 mJ is obtained by tripling the frequency of a Ti:sapphire laser system. The UV pulse and the near inferred pulse of 7.1 mJ can induce plasma filaments separately after focusing within an argon gas cell, leading to an obvious modulation of the UV spectrum. The full width at half maximum of UV spectrum increases to 6.4 nm which is 4 times the width of spectrum before focusing and 2.5 times the width of single ultraviolet filament broadening. In this experiment, we mainly study the frequency spectrum evolution of dual-color co-filament in argon gas under the condition of different time delays, coupling locations and gas pressures. Optimizing these factors can yield a valid approach to achieving extremely ultrafast pulses in the range of ultraviolet.