Mixed regime of light-matter interaction revealed by phase sensitive measurements of the dynamical Franz-Keldysh effect

TL;DR

This paper demonstrates that phase-sensitive measurements of electromagnetic pulses can reveal different regimes of light-matter interaction, including a novel quasi-static saturation regime, using ultrafast THz and optical techniques on GaAs.

Contribution

It introduces a phase-resolved measurement method to distinguish regimes of matter-light interaction, revealing a new quasi-static saturation regime in the Franz-Keldysh effect.

Findings

Identification of a quasi-static saturation regime

Phase content reveals interaction timescales

Enhanced understanding of ultrafast optical switching

Abstract

The speed of ultra-fast optical switches is generally limited by the intrinsic electronic response time of the material. Here we show that the phase content of selected electromagnetic pulses can be used to measure the timescales characteristic for the different regimes of matter-light interactions. By means of combined single cycle THz pumps and broadband optical probes, we explore the field-induced opacity in GaAs (the Franz-Keldysh effect). Our phase-resolved measurements allow to identify a novel quasi-static regime of saturation where memory effects are of relevance.