Abstract

Matter is ionized and very rapidly transformed into a plasma when subjected to electrical fields exceeding some critical value. Laser-induced breakdown of transparent solids in the nanosecond and picosecond time regime has been studied in detail by Bloembergen and his coworkers [1], who showed that breakdown is caused by avalanche impact ionization. More recently, Downer and coworkers [2] have investigated femtosecond laser-induced breakdown in rare gases and concluded that field or tunnelling ionization is the dominant physical mechanism in gases. There is great current interest in hot, dense microplasmas generated during the interaction of very intense femtosecond laser pulses with solids, because these short-lived plasmas represent an interesting point source of ultrashort x-ray pulses. However, to the best of our knowledge, detailed studies of femtosecond laser-induced breakdown in solids and the initial dynamics of plasma formation are still lacking.

© 1994 Optical Society of America