Rapid Scan White Light Pump-Probe Spectroscopy with 100 kHz Shot-to-Shot Detection

Abstract

We demonstrate a femtosecond pump-probe spectrometer which utilizes a white light supercontinuum as input, and relies on mutual synchronization of acousto-optical chopper, pump-probe delay stage and the CCD camera to record shot-to-shot pump-probe spectra while the pump-probe delay is scanned synchronously with the laser repetition rate. The unique combination of technologies implemented here allows for electronically controllable and repetition-rate scalable detection throughput that is only limited by the camera frame rate. Despite RMS white-light probe fluctuations of ~5.5%, fully leveraging the temporal correlations in white light and fine sampling of pump-probe delay along with 30x reduction in equivalent data collection time compared to stepwise scanning leads to reduction of RMS noise without multichannel referencing down to ~0.33 mOD for a scattering nanotube sample. This demonstration opens door for impulsive pump-probe micro-spectroscopy of scattering samples with broadband spectral coverage and minimized sample exposure.