Shim Bonggu, Schrauth Samuel E, Gaeta Alexander L
School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
Opt Express. 2011 May 9;19(10):9118-26. doi: 10.1364/OE.19.009118.
We theoretically investigate filamentation of ultrashort laser pulses in air in the mid-infrared regime under conditions in which the group-velocity dispersion (GVD) is anomalous. When a high-power, ultra-short mid-infrared laser beam centered at 3.1-μm forms a filament, a spatial solitary wave is stabilized by the plasma formation and propagates several times its diffraction length. Compared with temporal self-compression in gases due to plasma formation and pulse splitting in the normal-GVD regime, the minimum achievable pulse duration (∼70 fs) is limited by the bandwidth of the anomalous-GVD region in air. For the relatively high powers, multiple pulse splitting due to the plasma effect and shock formation is observed, which is similar to that which occurs in solids. Our simulations show that the energy reservoir also plays a critical role for longer propagation of the air filament in the anomalous-GVD regime.
我们从理论上研究了在群速度色散（GVD）为反常的条件下，中红外波段空气中超短激光脉冲的丝状化现象。当以3.1微米为中心的高功率、超短中红外激光束形成细丝时，空间孤波通过等离子体的形成而稳定，并传播其衍射长度的数倍。与由于等离子体形成导致的气体中的时间自压缩以及正常GVD区域中的脉冲分裂相比，在空气中反常GVD区域的带宽限制了可实现的最小脉冲持续时间（约70飞秒）。对于相对较高的功率，观察到由于等离子体效应和激波形成导致的多脉冲分裂，这与在固体中发生的情况类似。我们的模拟表明，在反常GVD regime中，能量储存器对于空气细丝的更长传播也起着关键作用。
