Direct and Indirect Cascade Photon Emission of Quantum Dots in the Telecom Band

Abstract

Semiconductor quantum dots (QDs) are promising sources of nonclassical light, such as single photons and entangled photon pairs for quantum information science. The performance of QD-based light sources is directly governed by the dynamics of the exciton complexes. Here, we focus on a bull’s-eye cavity-coupled QD system operating in the telecom band. By combining polarization-resolved photoluminescence, time-resolved photon correlation statistics, and rate equation analysis, we systematically investigate the cascaded emission processes of QDs. We clearly identify two distinct cascade photon emission pathways: one is a direct cascade from charged biexcitons to charged excitons, characterized by fast transition dynamics with a time scale of hundreds of picoseconds; the other is an indirect cascade involving charged excitons, charged biexcitons, and neutral excitons, governed by carrier capturing and relaxation processes on the nanosecond time scale. These findings provide a theoretical and technical foundation for designing efficient and stable telecom-band quantum emitters based on QDs, which are crucial for advancing practical photonic quantum technologies.