Correction of broadband terahertz electro-optic sampling with GaSe crystals

TL;DR

This paper investigates and corrects the distortions in broadband terahertz electro-optic sampling caused by lattice resonances in GaSe crystals, enabling more accurate measurements of multi-THz pulses.

Contribution

It provides an experimental evaluation of the frequency-dependent response in GaSe EO sampling and introduces a correction method for broadband terahertz measurements.

Findings

Phonon effects characterized using Faust-Henry coefficient

Corrected field amplitudes match additional power and beam measurements

Enhanced accuracy in multi-THz transient evaluation

Abstract

Gallium selenide (GaSe) is an efficient nonlinear crystal for electro-optic (EO) sampling in the multi-terahertz (THz) frequency range. However, the lattice resonance at several THz frequencies hampers broadband EO sampling, resulting in distorted pulse waveforms. In this work, we experimentally evaluated the frequency-dependent response function in EO sampling, considering the effects of phonons, phase mismatch, and gate pulse waveforms. The phonon effect is described using an effective Faust-Henry coefficient, which was determined to be $-0.21 \pm 0.02$. The corrected field amplitude of multi-THz pulses aligns with additional measurements of average power and a beam diameter. The successful compensation of the frequency characteristics in GaSe will contribute to a more accurate evaluation of multi-THz transients.