Photonic Jet Writing of Quantum Dots Self-Aligned to Dielectric Microspheres

Owing to their ability to generate non-classical light states, quantum dots (QDs) are very promising candidates for the large-scale implementation of quantum information technologies. However, the high photon collection efficiency demanded by these technologies may be impossible to reach for "standalone" semiconductor QDs, embedded in a high-refractive index medium. In this work a novel laser writing technique is presented, enabling the direct fabrication of a QD self-aligned-with a precision of +/- 30 nm-to a dielectric microsphere. The presence of the microsphere leads to an enhancement of the QD luminescence collection by a factor 7.3 +/- 0.7 when an objective with 0.7 numerical aperture is employed. This technique exploits the possibility of breaking the N-H bonds in GaAs1-xN(x):H by a laser light, obtaining a lower-bandgap material, GaAs1-xN(x). The microsphere, deposited on top of a GaAs1-xN(x):H/GaAs quantum well, is used to generate a photonic nanojet, which removes hydrogen exactly below the microsphere, creating a GaAs1-xN(x) QD at a predefined distance from the sample surface. Second-order autocorrelation measurements confirm the ability of the QDs obtained with this technique to emit single photons.