Nonlinear ultrafast modulation of the optical absorption of few cycle terahertz pulses in n-doped semiconductors

TL;DR

This paper demonstrates how intense few-cycle terahertz pulses induce nonlinear bleaching of absorption in n-doped semiconductors through intervalley scattering, with sub-picosecond resolution measurements aligning with theoretical models.

Contribution

It provides experimental evidence and theoretical analysis of ultrafast nonlinear optical absorption modulation in semiconductors driven by terahertz electric fields.

Findings

Nonlinear bleaching of absorption observed in n-doped semiconductors.

Agreement between experimental results and theoretical analysis.

Sub-picosecond resolution of conductivity dynamics achieved.

Abstract

We use an open-aperture Z-scan technique to show how intense few-cycle terahertz pulses can experience a nonlinear bleaching of absorption in an n-doped semiconductor due to terahertz-electric-field-driven intervalley scattering of electrons in the conduction band. Coherent detection of the transmitted terahertz pulse waveform also allows the nonlinear conductivity dynamics to be followed with sub-picosecond time resolution. Both the Z-scan and time-domain results are found to be in agreement with our theoretical analysis.