Thermal analysis of multiphoton absorption at 193nm in volume-absorbing glass

摘要

Two-photon absorption in volume-absorbing materials may be significant for high-power, short-pulse excimer laser irradiation. In the present work, the laser intensity in ultraviolet (UV) absorbing glass with one- and two-photon absorption is derived, and the effects of two-photon absorption on the intensity propagation and the penetration depth are investigated. The temperature histories for single- and multiple-pulse heating are predicted using an axisymmetric model. The heat generation rate caused by one- and two-photon absorption is determined for pulsed laser heating with Gaussian distributions in both space and time. The results show that the two-photon absorption can compress the volume-absorbing effect to surface absorption and increase the peak temperature on the glass surface. This will reduce the damage threshold, increase the energy loss, and reduce the accuracy of pulse-laser calorimeters.