Dynamically Dressed States of a Quantum Four-Level System

TL;DR

This paper investigates the dynamic dressed-state emission in a quantum dot's four-level system under pulsed excitation, revealing how sidebands depend on pulse parameters and providing insights into the emission dynamics.

Contribution

It presents the first detailed experimental and theoretical analysis of dynamic dressed states in a four-level quantum system under pulsed excitation, highlighting the dependence of sidebands on pulse characteristics.

Findings

Sidebands emerge from the biexciton-to-exciton transition, not from the exciton-to-ground state.

Number and width of sidebands depend on pulse duration and area.

Side peak emission occurs only during the presence of the excitation pulse.

Abstract

In this work, we experimentally and theoretically study the dressed-state emission of the biexciton-exciton cascade in a semiconductor quantum dot under pulsed, resonant, two-photon excitation. Building on the well-characterized steady-state dressed emission of the four-level system, we examine its dynamic counterpart under pulsed, resonant excitation, addressing both experimental observations and theoretical modeling. Here we report several sidebands emerging from the biexciton-to-exciton transition, whose number and spectral width depend on the excitation pulse duration and the effective pulse area, while no sidebands emerge from the exciton-to-ground-state transition. Since the biexciton state population follows a nonlinear pulse area function, sidebands with a small spectral nonlinearity result. Detuning- and time-dependent measurements provide deeper insight into the emission properties of the dressed states. They show that side peak emission only occurs in the presence of the excitation pulse. Moreover, when the system is excited by a Gaussian-shaped laser pulse, side peak emission takes place sequentially.