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

Abstract

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.

Quantum-Dot-Based Telecommunication-Wavelength Quantum Relay

“…Nevertheless, the experiment made use of a conventional QD emitting at short wavelength, suffering from high losses when being transmitted over a long optical fiber and, therefore, not suitable for a scalable architecture. Great effort has been put into the development of QDs emitting at telecommunication wavelengths [21][22][23][24], culminating in independent demonstrations of entangled photon emission [25] and interference with laser photons [26]. Here, we report the implementation of a quantum-relay experiment in the telecommunication O band (close to 1310 nm), suitable for secure quantumcommunication applications and, at the same time, fully compatible with the existing communication infrastructure regarding networks and sources.…”

High‐Purity Triggered Single‐Photon Emission from Symmetric Single InAs/InP Quantum Dots around the Telecom C‐Band Window

“…MOCVD‐grown structures allowed also for realization of single‐photon emission under electrical carrier injection . However, all of them lead to strongly anisotropic structures with FSS well above 20 µeV therefore limiting their applicability. Recently, another technological approach for realization of InP‐based QDs, namely the droplet epitaxy growth has been reported .…”

Generation of Non‐Classical Light Using Semiconductor Quantum Dots

“…In addition to the SK growth, droplet epitaxy and droplet etching methods have been established which result in strain‐free QDs. Here, demonstrated material combinations are GaAs/AlGaAs QDs emitting at 780 nm, InAs/GaAs QDs emitting around 900 nm, and InAs/InP QDs emitting at 1550 nm . Also, pyramidal QDs grown in tetrahedral recesses etched in GaAs have recently demonstrated strong potential for scalable non‐classical light sources .…”