Abstract

An instrument providing a complete signal diagnostic in the femtosecond-to-picosecond is important as a diagnostic tool for ultrashort sources and opens up new possibilities for studying nonlinear interactions. We apply this tool to various real and simulated femtosecond signals. The basic principle is to apply a known, reversible transformation to the pulse to be measured, in order to create a stretched signal that can be completely determined by means of interferometric cross-correlation with the original short signal. The latter is recovered by applying (numerically) the inverse transformation to its stretched-out version. Blocks of glass are used to provide dispersion in the femtosecond scale; a telescope between a grating pair serves the same purpose in the picosecond scale. The key function in determining the phase is the difference between the sum of the lower and upper envelopes, with (calculated function) and without (measurement) chirp. Fast Fourier transforms and appropriate filtering are used to determine these envelopes with maximum accuracy. The original pulse can easily be reconstructed from the complete characterization of the broadened pulse, if the transfer function of the broadening dispersion line is known.

© 1990 Optical Society of America