Abstract

There has been considerable effort, both experimentally and theoretically, devoted to understanding the process of high harmonic generation. Much of this effort has been focused on understanding the existence of the plateau region, and the position of the cutoff. More recently, theoretical work has attempted to predict the spectral structure of the harmonic peaks, in order to better understand the mechanism of high harmonic generation. In this work, we present data from the first detailed experimental study of the fine spectral structure of high harmonic emission. We studied the harmonic lineshapes as a function of pressure, density and chirp, using 25 fs laser excitation pulses. We observed dramatic changes in the spectral shapes of the harmonic peaks as these experimental parameters were changed.

© 1997 Optical Society of America