Coherence and bandwidth measurements of harmonics generated from solid surfaces irradiated by intense picosecond laser pulses

We present measurements of the transverse and longitudinal coherence lengths of the fourth harmonic of a 1053-nm, 2.5-ps laser generated during high-intensity (up to ${10}^{19}$ W ${\mathrm{cm}}^{\mathrm{-}2}$) interactions with a solid target. Coherence lengths were measured by use of a Young’s double-slit interferometer. The effective source size, as defined by the Van Cittert–Zernicke theorem, was found to be 10–12 μm, and the coherence time was observed to be in the range 0.02–0.4 ps. © 1996 The American Physical Society.