Engineering of Quantum Emitter Properties

The investigation of semiconductor quantum dots (QDs) that can emit single photons directly in the wavelength range of existing fiber communication networks is of key interest in order to harness the quantum properties of photonic qubits for everyday applications. While the first big achievements in fabricating highly efficient quantum light sources and the generation of spin-photon or multi-photon entangled states utilizing QDs were performed in a wavelength range around 900 nm, the past few years have shown a rapid technological evolution that enables the transfer to the telecom range.
Here, we report on our progress studying photoluminescence from QDs in the telecom C-Band. In detail, we present the quantum-optical properties of InAs QDs grown by molecular beam epitaxy on an InP substrate around which circular Bragg gratings are fabricated. The observed lines exhibit Purcell enhanced emission featuring high raw Hong-Ou-Mandel visibility and low multi-photon probability. Furthermore, we investigate excitonic complexes in QDs grown by metal-organic vapor-phase epitaxy on a metamorphic buffer layer on a GaAs substrate, the spectral properties of which are enhanced by a hybrid cavity consisting of a semiconductor mirror on the bottom and a dielectric mirror on top. Full polarization tomography capability and picosecond-time resolution, together with an in-plane magnetic field enables us to study spin dynamics and to analyze and control the interplay between electron/hole spins and the polarization of the emitted photons.