Multi-frame interferometric imaging with a femtosecond stroboscopic pulse train for observing irreversible phenomena

Abstract

In this work a high-speed single-shot multi-frame interferometric imaging technique is presented. The technique enables multiple interferometric images with femtosecond exposure time over a 50 ns event window to be recorded for a single laser-induced excitation event. The stroboscopic illumination of a framing camera is made possible through the use of a doubling cavity which produces a pulse train that is synchronized to the gated exposure windows of the individual frames of the camera. The imaging system utilizes a Michelson interferometer to extract phase and ultimately displacement information.We demonstrate the method by monitoring laser-induced acoustic oscillations in a silicon nitride film.The propagation of the acoustic waves and the deformation of the film are tracked. The method is applicable to a wide range of dynamic and irreversible phenomena such as crack branching, shockinduced material damage, cavitation and dielectric breakdown.Topics: high-speed imaging, optical imaging, lasers, Michelson interferometry, multi-frame imaging, microscopy.

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