A MODEL OF ULTRASHORT LASER-PULSE ABSORPTION IN SOLID TARGETS

A model for ultrashort laser pulse absorption and solid target heating has been developed. It combines a description of laser light absorpti on in the skin layer with a simple model of plasma heating. Heat wave propagation into the cold target material is the only loss mechanism b alancing energy deposition due to absorption. An absorption coefficien t is derived from the plasma conductivity and includes a description o f physical processes responsible for collisional and collisionless ski n layer absorption mechanisms. Comparison with recent femtosecond lase r pulse interaction experiment data show good agreement over a wide ra nge of pulse intensities. For laser intensities above 10(16) W/cm(2) p lasma hydrodynamical expansion, which is neglected in our model contri butes to a discrepancy between the calculated absorption and experimen tal data. (C) 1996 American Institute of Physics.