Intensity scaling of stimulated Raman forward scattering in laser-produced plasmas

Measurement of the intensity scaling of stimulated Raman forward scattering (SRFS) at one observation angle is presented. A single, high-intensity 527-nm laser beam excited the instability in a preformed plasma whose properties are such that the predicted gain for SRFS spans the range anticipated for high-gain laser-fusion experiments. At low intensities, the gain of the instability was consistent with convective theory. At intensities greater than 1×{}10¹⁵ W/cm², the instability saturated at a level of less than 10¹¹ W/sr nm cm².