Using temporally and spectrally resolved diagnostics, we show that the pulse duration of laser-produced soft x rays emitted from solid targets can be controlled, permitting a reduction to as short as a few picoseconds. To enable this control, only a single parameter must be adjusted, namely, the intensity of the high-contrast ultrashort laser pulse (400 fs). These results are found to be in qualitative agreement with a simple model of radiation from a collisionally dominated atomic system.

• Received 23 February 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.2324