Single-shot ultrafast burst imaging using an integral field spectroscope with a microlens array.

Abstract

To fully utilize the functions of a center-wavelength-sweeping pulse train generated by a free-space angular-chirp-enhanced delay optical layout for a probe laser pulse in sequentially timed all-optical mapping photography (STAMP), we introduced an integral field spectroscopy (IFS) method using a microlens array (MLA) to produce hyperspectral images, referring to the technique as lens array (LA)-STAMP. Compared with the previous STAMP utilizing spectral filtering where a bandpass filter generated hyperspectral images, LA-STAMP achieved much higher optical throughput. In a prototype setup, we used a 60×60 MLA and demonstrated single-shot burst imaging of a femtosecond laser-induced ablation process on a glass surface with 300 ps frame intervals in a 1.8 ns time window. Each frame image was constructed by assembling spectrally dispersed 36×36 monochromatic segments distributed by each lenslet on 5×5 pixels of a CCD camera. The spatial resolution was ∼4.4µm, which was determined by the MLA's pitch and the magnification of the microscope lens. We limited the number of frames to seven in this prototype setup, although it can be scaled to ∼24 with a spatial resolution of ∼1µm by designing IFS with a fine pitch MLA.