Jetlike Structures in the Visible Emission of Plasma Pumped by an Obliquely Incident Picosecond Laser

The observation of millimeter-long jetlike structures in the visible emission from laser-produced plasma is reported, which is produced by longitudinal pumping of preformed plasma with high-intensity 2 ps duration Nd:phosphate glass laser pulse. Clear jets are observed only for a relatively narrow range of the longitudinal pump intensity, from 5 ×10 14 W/cm 2 to 7 ×10 14 W/cm 2 . Spectral observation of the jets reveal that the spectrum is dominated by line emission, and not by the continuum. The dominant lines in the visible region originate from neutral and singly-ionized molybdenum ions. The decay time of the jetlike emission is found to be comparable to the typical radiative decay time of the line emission. The present observations are compared with those of plasma bullets by Vogel and Kochan [Phys. Rev. Lett. 86 (2001) 232] is discussed.