ROOM TEMPERATURE LIGHT-MATTER INTERACTION USING QUANTUM DOTS AND PHOTONIC CRYSTAL CAVITIES

Abstract

Control over spontaneous emission is important for many applications in photonics, including efficient light-emitting diodes, photovoltaics, single-photon sources and low-threshold nanolasers. Photonic crystals can modify the spontaneous emission by creating cavities with extremely small mode-volumes, and are an ideal platform for integrated devices because of their scalable planar architecture. For developing photonic devices at room temperature using such cavities, colloidally synthesized quantum dots are excellent emitters because they exhibit high photoluminescence efficiency and emission wavelength tunability. In this thesis, I present experimental and theoretical work on enhancing light-matter interaction at room temperature, using colloidal quantum dots and nanobeam photonic crystal cavities. Using time-resolved optical spectroscopy, we observed enhanced spontaneous emission rate of the quantum dots coupled to the cavity mode. We also demonstrated saturable absorption of the quantum dots coupled to the cavity mode by pump-intensity dependent cavity-linewidth, which is a nonlinear phenomenon with potential applications in optical switching at room temperature. Using the quantum optics framework, we developed a theoretical model to show that cavity-enhanced spontaneous emission can be used to overcome Auger recombination (an ultrafast nonradiative process that quenches optical gain) in colloidal quantum dots to develop low-threshold nanolasers. In the end, I will also discuss our current efforts towards deterministic deposition of quantum dots on photonic crystal cavities using atomic force microscopy for effective fabrication of quantum dot devices.