Recording THz waveforms in single-shot using femtosecond lasers: recent methods and challenges in accelerator physics and THz spectroscopy

Abstract:

Recording electric fields evolutions in single-shot, and with terahertz bandwidth, is needed in applications ranging from spectroscopy of irreversible processes, and quantum cascade lasers, to free-electron lasers. A standard strategy consists in probing the electric field under investigation, using ultrashort laser pulses, and to analyze the modified pulse in single-shot. Several variants have been investigated the last two decades, but the applications constantly require important challenges to be addressed.
We review here several advances in the field. In particular we present recent strategies aiming at high acquisition rates [1], high sensitivity [2], and high temporal and spectral resolution [3]. We will present recent achievements at accelerator-based light sources (SOLEIL, KARA, DESY, ELBE, and FERMI) as well as designs of table-top THz time-domain spectrometers. We will show how THz digitizers and Time-Domain Spectroscopy systems can now reach several terahertz bandwidth over recording lengths of tens of picoseconds, and at Megahertz repetition rates. We will also discuss some of the next challenges that remain to be solved.

[1] E. Roussel, Observing microscopic structures of a relativistic object using a time-stretch strategy, Sci. Reports 2015, https://doi.org/10.1038/srep10330

[2] C. Szwaj et al., High sensitivity photonic time-stretch electro-optic sampling of terahertz pulses, Rev. Sci. Instrum. 2017, https://doi.org/10.1063/1.4964702

[3] E. Roussel et al., Phase Diversity Electro-optic Sampling: A new approach to single-shot terahertz waveform recording, Light: Science & Applications 2022, https://doi.org/10.1038/s41377-021-00696-2