Single photon emitters

Single photon emitters (SPEs) are the most promising candidates for the implementation of Quantum Information Technologies (QIT). A SPE is a light source that emits, on demand, one photon at a time in a pure quantum state. The possibility to control the properties of the emitted photon makes them perfectly suitable for applications in Quantum Cryptography and Quantum Computing. Among the different processes to generate single photons, the most promising ones are solid-state SPEs. They consist in emitters embedded in a solid-state matrix which makes them easily identifiable, controllable and integrable in photonic circuits. Solid-state SPEs can be divided in two main groups: luminescent point defects and quantum dots (QDs). The former are defects formed in the crystalline structure, whose presence leads to the formation of energy levels within the energy gap of the hosting material. The latter are small volumes of semiconductor embedded in a material with a higher energy gap. This leads to a 3D confinement of the charges and thus to an atom-like energy level structure. In this thesis work we have focused on two different solid-state SPEs: isolated GaAs1−xNx QDs and ensemble of G-centers (luminescent point defects in silicon). Regarding the former, we present the results of a recently developed fabrication technique for the realization of GaAs1−xNx QDs. Exploiting the properties of GaAs1−xNx and the use of photonic jets (PJ), which are intense light beam characterized by a sub-diffraction lateral size, we were able to laser-write QDs of different sizes. The PJs were obtained illuminating dielectric microsphere deposited on the sample, which had the additional advantage of increasing the collected luminescence emitted by the fabricated QDs. The QDs realized were thoroughly characterized by means of micro-photoluminescence (micro-PL) spectroscopy and their SPE nature was proved. Finally, we have reported the results of a novel set of simulations as a basis to achieve a better control over the fabrication process. Concerning the G-centers, we present the results of a novel technique to tune their emission with strain. The technique is based on the realization of silicon suspended membranes, which are then strained depositing a silicon nitride layer on top. The presence of strain causes a splitting of the G-centers zero phonon line in two peaks. The energy difference between the peaks is directly related to the amount of strain introduced, which, in our technique, is controlled by changing the membranes size. Indeed, the realization of smaller membranes results in a stronger strain and vice versa. Therefore, by simply engineering the material we were able to tune the G-centers emission. Moreover, we have proved that these manipulations do not affect the optical properties of the emitters. It is worth mentioning that both techniques presented in this work can be applied to other SPEs that share similarities with the ones studied in this work. Moreover, these technique represent innovative approaches to solving know problems related to SPEs such as their realization, their limited brightness and the control over their emission.