Single Photon Sources Based on Colloidal Nanocrystals and Two Photon Polariton Laser

When scaled down up to nanometer size, semiconductors can exhibit quantum confinement effects for both electrons and photons. One interesting feature of nano-sized materials is the strong size dependence of their optical properties, that allows to master classical and non-classical light generation. This work concerns the development and the characterization of new sources for the gener- ation of classical and non-classical light states with isolated and coupled confined systems for photons and electrons. In particular: (i) a new type of semiconductor colloidal nanocrystals (NCs) is studied with the goal to obtain an efficient single photon generation at room temper- ature in the visible spectral range and (ii) NCs coupling with photonic crystals nanocavities has been obtained by using several methods; finally, (iii) in the last part of the manuscript the development of a two-photons excitation technique for microcavity polaritons is discussed with the final goal to obtain non-classical light generation. The first part of the manuscript is focused on the emission properties of a particular type of colloidal nanocrystals, called dot-in-rod (DR), in which a spherical cadmium selenide (CdSe) core is surrounded by a rod-like cadmium sulfide (CdS) shell. By virtue of their electronic properties, colloidal nanocrystals can emit single photons at room temperature. However the application of colloidal nanocrystals has been so far limited by two phenomena: the blinking of their photoluminescence and a non-polarized emission. The streaky point of dot-in-rods is that their emission properties are strongly dependent on their geometrical parameters. Here we show that by carefully choosing the diameter of the core, as well as the thickness and the length of the shell, the blinking behavior can be strongly reduced and a high degree of linear polarization of the emitted photons obtained. The second part of the thesis is devoted to the development of a silicon nitride photonic crystals cavity platform for applications in the visible spectral range. The weak coupling of these nanocavities with dot-in-rods has been achieved by using several deposition methods and we obtained a modification of the spontaneous emission by means of the Purcell effect. The possibility to reach the strong coupling regime by using this technology is also discussed from the theoretical point of view. The last part of the work studies a semiconductor system in which the strong coupling between quantum well excitons and a cavity mode gives rise to quasi-particles called polaritons. When polaritons experience a sufficiently strong three-dimensional confinement, they can exhibit a quantum blockade phenomenon. Indeed, in the case of ultra small cavity modal volume just one polariton at time can exist in the structure, while the injection of other po- laritons is forbidden by virtue of strong polariton-polariton repulsive interactions. With the purpose to reach this operation regime, an original excitation technique based on a resonant two-photon absorption (TPA) process has been developed. Moreover, TPA has been exploited to resonantly inject high polariton density in pillar microcavities, reaching an emission regime called two-photon polariton laser.