z-dependent absorption and stimulated backscatter processes in laser produced plasmas

Low- and high-atomic-number targets were irradiated at normal and oblique incidences with high focused intensity, 2.5-nsec duration of 1.06-μm laser pulses. Calorimetry and spectroscopy of ω and 2ω light reflected back into the focusing lens was performed. Results show a dramatic reduction in the specularly reflected light from high-atomic-number targets. Brillouin backscatter was observed throughout the range 1014–1016 W/cm2. 2ω spectra indicated the presence of an electron-ion decay instability with a threshold at 2×1015 W/cm2.