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August 2017

Universal Growth Scheme for Quantum Dots with Low Fine-Structure Splitting at Various Emission Wavelengths

Efficient sources of individual pairs of entangled photons are required for quantum networks to operate using fiber-optic infrastructure. Entangled light can be generated by quantum dots (QDs) with naturally small fine-structure splitting (FSS) between exciton eigenstates. Moreover, QDs can be engineered to emit at standard telecom wavelengths. To achieve sufficient signal intensity for applications, QDs have been incorporated into one-dimensional optical microcavities. However, combining these properties in a single device has so far proved elusive. Here, we introduce a growth strategy to realize QDs with small FSS in the conventional telecom band, and within an optical cavity. Our approach employs ‘‘droplet-epitaxy’’ of InAs quantum dots on (001) substrates. We show the scheme improves the symmetry of the dots by 72%. Furthermore, our technique is universal, and produces low FSS QDs by molecular beam epitaxy on GaAs emitting at ~900 nm, and metal-organic vapor-phase epitaxy on InP emitting at ~1550 nm, with mean FSS 4× smaller than for Stranski-Krastanow QDs.

Joanna Skiba-Szymanska, R. Mark Stevenson, Christiana Varnava, Martin Felle, Jan Huwer, Tina Müller, Anthony J. Bennett, James P. Lee, Ian Farrer, Andrey B. Krysa, Peter Spencer, Lucy E. Goff, David A. Ritchie, Jon Heffernan, and Andrew J. Shields. PhysRevApplied.8.01403 (2017).

Read full paper: PhysRevApplied, 8, 014013 (2017)