Evidence of localized heating in CO2-laser-produced plasmas

Abstract

Polyethylene foils and parylene disks have been irradiated by CO₂ (λ∼10.6 μm) and Nd : YAG‐glass (λ∼1.06 μm) laser pulses focused to flux levels in the 10¹³‐ and 10¹⁴‐W/cm² range. X‐ray pinhole photographs of the CO₂‐laser‐produced plasmas exhibit intense localized emission regions whose characteristic dimensions are smaller than the nearly diffraction‐limited focal spot of the laser. Corresponding photographs of the glass‐laser‐produced plasmas show no evidence of localized emission. These experimental results are consistent with theoretical predictions for laser‐beam trapping and/or filamentation in laser‐produced plasmas.