SUPPRESSION OF PARAMETRIC-INSTABILITY BY WEAKLY INCOHERENT LASER-BEAMS

The linearized coupled-mode equations in two dimensions are solved numerically within the paraxial approximation to find the absolute-mode threshold of parametric instabilities driven by an incoherent laser beam. The results show that, for plasma lengths only a few times threshold, a surprisingly small temporal bandwidth that is substantially less than the growth rate 0 is effective in suppressing absolute growth. Only if the plasma length greatly exceeds the threshold is the necessary temporal bandwidth the larger value obtained from homogeneous plasma theory. © 1990 The American Physical Society.