Intensity-dependent absorption in 10.6 μm laser-illuminated spheres
An intensity dependence of the absorption of 10-..mu..m laser light on CO/sub 2/ laser fusion targets has been observed. Absorption on gold spheres increases from 25%--30% at 10/sup 14/ W/cm/sup 2/ to 50%--60% at 10/sup 16/ W/cm/sup 2/, with most of the variation occurring above 10/sup 15/ W/cm/sup 2/. Concurrently, hot-electron temperature scales as T/sub hot/proportionalI/sup 0.43/ over the entire range. The absorption variation is interpreted as enhanced resonant absorption. It is suggested that as intensity is increased, the critical surface in the irradiated region becomes increasingly unstable, thereby permitting greater surface distortion and more favorable coupling conditions for resonant absorption.