Abstract

Ultrashort x-ray pulses are powerful diagnostic tools, combining the temporal resolution typically reserved for optical (laser) pulses with atomic scale spatial resolution which, in principle, can be achieved using high energy electromagnetic radiation. Progress in the development of femtosecond x-ray sources has been hindered by an inability to measure x-ray pulses of femtosecond duration. Streak cameras are typically used to measure ultrashort x-ray pulses, however the ~ 1 ps resolution limit of these instruments abates their usefulness in the femtosecond regime. We report demonstration of a visible/x-ray cross correlation technique based on laser assisted x-ray photoionization which has been used to measure 50 fs soft x-ray pulses. The technique permits the first direct measurements on the duration of femtosecond high order harmonic radiation. Additionally, the free-free scattering inherent to the technique provides an important test for models of high power laser interaction with matter.

© 1996 Optical Society of America