Single photon superradiance enhanced light–matter interaction in spatially ordered shape and volume controlled single quantum dots: enabling on-chip photonic networks

Abstract

On-chip photonic networks require adequately spatially ordered matter-photon interconversion qubit sources with emission figures-of-merit exceeding the requirements that would enable the desired functional response of the network. The mesa-top single quantum dots (MTSQDs) have recently been demonstrated to meet these requirements. The substrate-encoded size-reducing epitaxy (SESRE) approach underpinning the realization of these unique quantum emitters allows control on the shape, size, and strain (lattice-matched or mismatched) of these epitaxial single quantum dots. We have exploited this unique feature of the MTSQDs to reproducibly create arrays of quantum dots that exhibit single photon superradiance, a characteristic of the SESRE-enabled delicate balance between the confinement potential volume, depth, the resulting exciton binding energy, and the degree of confinement of the center of mass (CM) motion of the exciton. Scanning transmission electron microscope (STEM) studies reveal the structural (atomic scale) and chemical (nanometer scale) nature of the material region defining the notion of the shape and volume (here large) of the electron confinement region (i.e. the QD). In the exciton’s weak CM confinement regime, owing to its coherent sampling of the large volume, an enhancement of the MTSQD oscillator strength to ∼30 is demonstrated. Theoretical modelling with input from the STEM findings provides corroboration for single photon superradiance causing enhancement of the oscillator strength by ∼2.5–3. Our findings allow fabricating and studying interconnected networks enabled by these unique matter qubit-light qubit interconversion units that can be realized for lattice matched and mismatched material combinations covering UV to mid-infrared wavelength range.