Thresholds of absolute instabilities driven by a broadband laser

Abstract

Absolute instability thresholds for stimulated Raman scattering (SRS) and two-plasmon decay (TPD) driven by a broadband laser pulse are evaluated numerically. The scalings of the calculated thresholds with the density scale length, temperature, and central wavelength are qualitatively similar to the existing analytical results. The threshold values, however, exhibit significant quantitative differences. Comparisons between the thresholds calculated for various broadband power spectra indicate a universal scaling of the threshold intensity with laser coherence time (τc). For SRS, Ithr∝τc-1/3, and for TPD, Ithr∝τc-1/2.