We propose a time-resolved optical measurement scheme for sampling transient charge and spin currents in a bulk centrosymmetric semiconductor. The technique relies on emission of second harmonic light triggered by a pulsed below-gap optical excitation and a spontaneous intraband polarization arising from spin or charge motion, mediated by a χ(3)-based nonlinear optical process. Our proposal uses homodyne amplification to boost the weak second harmonic signal, making it detectable with conventional electronics, calculated for charge current in a room temperature GaAs semiconductor. This all-optical technique requires neither electrical contact nor bias fields and the signal is estimated at a few percent relative to the shot noise of the probe. This proposal motivates a novel method for exploring thermal and quantum fluctuations in the solid state in a non-invasive manner.
@article{arxiv.2406.10397,
title = {Optical sensing of charge and spin current fluctuations in centrosymmetric semiconductors},
author = {Amin Lakhal and Stéphane Virally and Jacob B. Khurgin and Denis V. Seletskiy},
journal= {arXiv preprint arXiv:2406.10397},
year = {2024}
}