Energy absorption in plasmas produced by intense 10-μm laser radiation

Results are presented of measurements made of the fractional absorption of short (∼1 ns) intense (2×1014 W cm−2) 10.6-μm laser radiation by plasmas produced from massive plane targets. Two complementary techniques were used: infrared light accounting and plasma calorimetry. The methods are shown to provide consistent results, demonstrating peak absorptions of up to 50%. The beam-polarization and irradiance-angle dependence of the absorption is consistent with a resonance absorption model. Plasma calorimetry also yields a detailed spatial distribution of the particle emission, while infrared calorimetry shows that the scattered laser light distribution is strongly dependent on the polarization of the incident laser beam.