Abstract

This paper experimentally examines the use of prism pairs and focusing elements to reversibly lengthen the duration of femtosecond pulses by means of spatial dispersion of the different frequency components of an ultrashort optical pulse in a direction transverse to the direction of propagation.¹ Unlike techniques based on a linear pulse chirp, this approach has the advantage of not favoring one part of the pulse spectrum over another in a nonlinear amplifier medium. The temporal lengthening described here, from the order of 50 fs to the order of 500 fs, is expected to have significant consequences because key mechanisms in amplifier media, such as spectral hole burning, have time constants of the order of 100 fs or less. The prism pairs also provide other useful features, such as a group velocity dispersion correction that can be adjusted from negative through positive values, low insertion loss, and easily adjusted spectral filtering. A comparison of the experimentally measured pulse broadening and its analytically calculated value for the experimental conditions shows good agreement between experiment and theory.² We will also discuss amplifier designs that take advantage of this pulse lengthening technique.

© 1990 Optical Society of America