DYNAMIC 193-NM OPTICAL-PROPERTIES OF WATER

Previous assumptions that water is not a 193-nm chromophore during ArF excimer laser tissue ablation are based on room-temperature data and ignore spectroscopic Literature that suggests a strong temperature dep endence of far-ultraviolet water absorption. By the use of a Q-switche d Er:YAG laser as a pump source and an ArF excimer laser as a probe so urce, thermal generation and rt laxation of 193-nm water absorption we re characterized under nonequilibrium high-temperature and high-pressu re conditions. At volumetric energy densities as small as 2 kJ/cm(3) r elative to room temperature, the 193-nm absorption coefficient of wate r was measured to increase by more than 5 orders of magnitude. These r esults are consistent with the hypothesis that the absorption of 193-n m radiation by water may play a role in ArF excimer laser ablation of tissue. (C) 1996 Optical Society of America