Second-order correlation function from asymmetric to symmetric transitions due to spectrally indistinguishable biexciton cascade emission

TL;DR

This study investigates photon bunching in biexciton cascade emission from quantum dots, revealing that spectral indistinguishability influences symmetric versus asymmetric photon correlation behaviors, supported by experimental and theoretical analysis.

Contribution

It demonstrates the transition from symmetric to asymmetric photon correlation functions depending on spectral distinguishability, supported by a three-level rate-equation model.

Findings

Photon bunching occurs regardless of biexciton binding energy.

Spectral indistinguishability leads to symmetric photon correlation.

Spectral distinguishability results in asymmetric cross-bunching.

Abstract

We report the observed photon bunching statistics of biexciton cascade emission at zero time delay in single quantum dots by second-order correlation function measurements under continuous wave excitation. It is found that the bunching phenomenon is independent of the biexciton binding energy when it varies from 0.59 meV to nearly zero. The photon bunching takes place when the exciton photon is not spectrally distinguishable from biexciton photon, and either of them can trigger the start in a Hanbury-Brown and Twiss setup. However, if the exciton energy is spectrally distinguishable from the biexciton the photon statistics becomes asymmetric and a cross-bunching lineshape is obtained. The theoretical calculations based on a model of three-level rate-equation analysis are consistent with the result of second-order correlation function measurements.