Complete characterization of a chaotic optical field using a high-gain, self-amplified free-electron laser

For centuries chaotic light sources were the only available objects for optical science. Study of chaotic light led to the development of such important concepts as ensemble-average coherence. However, the detailed temporal structure of the underlying optical field has never been fully characterized. We report on a complete characterization of such a field from a high-gain, self-amplified spontaneous-emission (SASE) free-electron laser (FEL). The temporal structure of the amplitude and phase are measured for a single pulse and the statistics over multiple pulses is determined