Abstract

The technology of ultrashort-pulse measurement has been under development since the advent of short-pulse lasers over two decades ago. Early methods yielded only the intensity autocorrelation of the pulse.¹,² Later developments have allowed the determination of various phase distortions common to ultrashort pulses by either interferometric autocorrelations or degenerate-four-wave-mixing techniques.³,⁴ These methods do not yield the pulse shape or the phase (or, equivalently, the instantaneous frequency) evolution of the pulse, but instead yield traces that only roughly indicate each and require an assumed model of the pulse. Some work has been done to extract these quantities,^5-7 but general methods have not yet emerged; in most of these techniques, there remains a fundamental inherent ambiguity in the direction of time, and hence also in the sign of a chirp.⁶ In addition, nearly all techniques that provide more than a simple intensity autocorrelation are very difficult to implement. Interferometric autocorrelations, for example, require position stability to < .1 μm.

© 1991 Optical Society of America