Emission quantum coherence and interference of excitons in cuprous oxide

Emission coherence is crucial for quantum photonic technologies like single-photon emitters. However, emission from most bulk semiconductors suffers from severely limited coherence times under non-resonant excitation, typically in the femtosecond to picosecond range. In this study, we investigate the temporal coherence properties of excitons in cuprous oxide (Cu2O) using interferometric Fourier spectroscopy. We reveal a coherence time of approximately 24 ps and a homogeneous linewidth of 0.017 nm (55 μeV) at 4.7 K under non-resonant two-photon excitation. We also analyze the impact of relaxation, scattering, and the experimental setup on the decrease in coherence time. The 1S orthoexciton shows robust photoluminescence intensity and negligible spectral diffusion over 120 min. These results suggest that Cu2O presents itself as an exceptional material for generating indistinguishable single photons, demonstrating considerable potential for advanced applications in quantum photonics.