Overcoming power broadening of the quantum dot emission in a pure wurtzite nanowire

Overcoming power broadening of the quantum dot emission in a pure wurtzite nanowire

Reimer, M.E. (TU Delft QN/Quantum Transport; University of Waterloo)
Bulgarini, G. (TU Delft QN/Quantum Transport; Single Quantum)
Fognini, A.W. (TU Delft QN/Zwiller Lab)
Heeres, R.W. (TU Delft QN/Quantum Transport)
Witek, B.J. (TU Delft QN/Quantum Transport)
Versteegh, M.A.M. (TU Delft QN/Quantum Transport)
Rubino, A. (TU Delft QN/Quantum Transport)
Braun, T. (University of Würzburg)
Kamp, M. (University of Würzburg)
Höfling, S. (University of St Andrews; University of Würzburg)
Dalacu, D (National Research Council Canada)
Lapointe, J (National Research Council Canada)
Poole, Philip J. (National Research Council Canada)
Zwiller, V.G. (TU Delft QN/Zwiller Lab)

2016-05-25

One of the key challenges in developing quantum networks is to generate single photons with high brightness, purity, and long temporal coherence. Semiconductor quantum dots potentially satisfy these requirements; however, due to imperfections in the surrounding material, the coherence generally degrades with increasing excitation power yielding a broader emission spectrum. Here we overcome this power-broadening regime and demonstrate an enhanced coherence at exciton saturation where the detected count rates are highest. We detect single-photon count rates of 460 000 counts per second under pulsed laser excitation while maintaining a single-photon purity greater than 99%. Importantly, the enhanced coherence is attained with quantum dots in ultraclean wurtzite InP nanowires, where the surrounding charge traps are filled by exciting above the wurtzite InP nanowire band gap. By raising the excitation intensity, the number of possible charge configurations in the quantum dot environment is reduced, resulting in a narrower emission spectrum. Via Monte Carlo simulations we explain the observed narrowing of the emission spectrum with increasing power. Cooling down the sample to 300 mK, we further enhance the single-photon coherence twofold as compared to operation at 4.5 K, resulting in a homogeneous coherence time, T2, of 1.2 ns, and two-photon interference visibility as high as 83% under strong temporal postselection (∼5% without temporal postselection).

http://resolver.tudelft.nl/uuid:d63a0d15-d2fc-482f-ade2-9ccb6d33a4f9

https://doi.org/10.1103/PhysRevB.93.195316

2469-9950

Physical Review B, 93 (19)

Institutional Repository

journal article

© 2016 M.E. Reimer, G. Bulgarini, A.W. Fognini, R.W. Heeres, B.J. Witek, M.A.M. Versteegh, A. Rubino, T. Braun, M. Kamp, S. Höfling, D Dalacu, J Lapointe, Philip J. Poole, V.G. Zwiller