On-chip single-photon sources are key components for integrated photonic quantum technologies. Semiconductor quantum dots can exhibit near-ideal single-photon emission but this can be significantly degraded in on-chip geometries owing to nearby etched surfaces. A long-proposed solution to improve the indistinguishability is to use the Purcell effect to reduce the radiative lifetime. However, until now only modest Purcell enhancements have been observed.
In this seminar, I will show that by using pulsed resonant excitation, we avoid the slow relaxation paths present under non-resonant excitation, revealing a highly Purcell-shortened radiative lifetime (22.7 ps) in a waveguide-coupled quantum dot-photonic crystal cavity system . The quantum dot exhibits near-lifetime-limited single-photon emission with high indistinguishability (93.9%), indicating that a large Purcell enhancement significantly improves the measured coherence of quantum dots in on-chip geometries. When exciting the cavity and collecting from the waveguide, nearly background-free pulsed resonance fluorescence is achieved under p-pulse excitation. This enables the demonstration of an on-chip, on-demand single-photon source with very high potential repetition rates (~10 GHz).
 F. Liu, A. J. Brash, J. O’Hara, L. M. P. P. Martins, C. L. Phillips, R. J. Coles, B. Royall, E. Clarke, C. Bentham, N. Prtljaga, I. E. Itskevich, L. R. Wilson, M. S. Skolnick, and A. M. Fox, Nat. Nanotechnol. 13, 835 (2018).
Feng Liu is now a professor in Zhejiang University. He obtained his doctor degree from TU Dortmund, Germany in 2013. Then he worked as a postdoc in the University of Sheffield, UK and RWTH Aachen University, Germany. Since 2019, he joined the College of Information Science & Electronics Engineering of Zhejiang University via the Hundred Talents Program and 1000Plan for Young talents. His research interests include on-chip single photon source based on quantum dot-photonic crystal cavity system and its applications in semiconductor-integrated quantum optical circuit. His representative publications include Nature Nanotechnology, Physical Review Letters and PRB.