We have observed strongly coupled stimulated Raman backscatter from the interaction of an intense, subpicosecond laser with an underdense plasma. The strongly coupled backscatter spectra have widths greater than the plasma frequency, extend to the blue side of the laser frequency, and at the highest densities, are shifted by less than ${\mathrm{\omega }}_{\mathit{p}}$. These observations are consistent with the predictions of a strongly coupled Raman theory, appropriately modified for short laser pulses.

• Received 24 April 1992

DOI:https://doi.org/10.1103/PhysRevLett.69.442