Fifth-order nonlinear optical response of excitonic states in an InAs quantum dot ensemble measured with 2D spectroscopy

TL;DR

This study measures excitonic dephasing rates in InAs quantum dots using 2D spectroscopy, revealing a fifth-order nonlinear response at high excitation densities, which was previously unobserved.

Contribution

It demonstrates the measurement of fifth-order nonlinear optical response in quantum dots, a novel observation in this context.

Findings

Dephasing rates are similar across all quantum dots and independent of excitation density.

A new spectral feature attributed to fifth-order nonlinear response appears at high excitation densities.

The fifth-order response was too weak to be observed in traditional time-integrated measurements.

Abstract

Exciton, trion and biexciton dephasing rates are measured within the inhomogeneous distribution of an InAs quantum dot (QD) ensemble using two-dimensional Fourier-transform spectroscopy. The dephasing rate of each excitonic state is similar for all QDs in the ensemble and the rates are independent of excitation density. An additional spectral feature -- too weak to be observed in the time-integrated four-wave mixing signal -- appears at high excitation density and is attributed to the $\chi^{\textrm{(5)}}$ biexcitonic nonlinear response.