"Towards scalable sources of entangled photon pairs relying on GaAs quantum dots embedded in circular Bragg resonators"
Towards scalable sources of entangled photon pairs relying on GaAs quantum dots embedded in circular Bragg resonators
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In the recent decade of research, semiconductor quantum dots have proven to be promising candidates for the use as node points in quantum information networks, as tunable on-demand sources of pairs of polarization-entangled photons featuring a near unity degree of entanglement, quasi-perfect single photon purity and a high indistinguishability. However, as-grown quantum dots lack a sufficient photon yield and suffer from total internal reflection within their embedding matrix. To enhance the extraction efficiency, the implementation of photonic cavities seems to be inevitable. The circular Bragg resonator photonic cavity has been reported to show outstanding results in extraction efficiency while also enhancing the spontaneous radiative emission rate, taking advantage of the Purcell effect. The cavity can be fabricated deterministically on quantum dots with pre-recorded positions through a reactive-ion dry etching process. In this thesis, an already existing quantum dot position mapping system was optimized, achieving a state-of-the-art detection precision and patterning accuracy. Furthermore, processing techniques were improved for an enhanced membrane fabrication success rate near 100 % and a recipe for dry-etching electron beam lithography patterned structures on GaAs membranes was established. The resulting circular Bragg resonators show broadband cavity modes in -reflectivity measurements, carried out polarization-resolved and in a temperature series.