Temporal probing of an ultrafast plasma shutter driven by a KrF femtosecond laser system

Abstract.

A femtosecond high-power KrF-laser system was used to create a rapidly ionizing plasma on a BK7 glass slide and the plasma formation was probed by a second laser pulse at 497 nm. During the formation of the plasma the electron density reaches the critical density for 497 nm. Therefore, the reflectivity of the surface rises from a value given by the Fresnel formulas to a value close to 100% and the transmission decreases on the same time scale. It is shown that this method permits a precise timing of two femtosecond laser pulses at different wavelengths.