Abstract

Ultrafast optical pulses are useful for a range of scientific applications from spectroscopy to surface science. Since ultrafast lasers are limited in pulse duration to 5–7fs,¹ and high-energy laser amplifiers are limited to ~15fs,² shorter pulses must be created through external pulse compression techniques. The most common configuration is to use self-phase modulation to broaden the pulse spectrum, followed by a negative dispersion element to compress the pulse.^3,4 However, these techniques are limited in obtainable pulse duration, particularly at short-wavelengths, by high-order dispersion aberrations. In recent years, molecular modulation of light has been considered as an alternative source of phase modulation.^{5, 6} In this work, we demonstrate a new technique that uses the time-dependent index modulation of quantum revivals of molecular rotational wave packets in a molecular gas (CO₂). This technique has an inherent advantage over SPM techniques in that the spectral broadening can be induced with a negative chirp, allowing for simple pulse compression by propagating through a dispersive medium. This technique differs from Raman techniques previously demonstrated in that a wavepacket consisting of many rotational levels is used to obtain a single, self-compressed, pulse.

© 2002 Optical Society of America