Experimental investigation of stochastic pulsation and formation oflight bullets in a laser-produced plasmas

摘要

Generation of an extremely stable light bullets in a preformedplasma near critical density has been observed experimentally. Opticalprobing measurements indicate the formation of a pulsating channel,typically of about 5 μm in diameter, directed towards to a heatinglaser beam, as well as a disconnected massive plasma blocks moving alsotowards to laser beam. The authors report time-resolved results obtainedby interferometric and absorption measurements for the interaction of a100 ps Nd:YAG laser beam at λ=1064 nm with a metallic target inair. The formation of density ripples, light bullets and their temporalevolution was investigated with high spatial and temporal evolution. Thevelocity of such dense plasma blocks reaches values of order of4.5×10 8 cm/s. And they are stable during the acceleration andpropagation in air. Self-generated magnetic fields up to 8 MG wereobserved by means of Faraday rotation of a probe laser beam. They are“frozen"” in moving plasma blocks