Coupling single molecules to cryogenic optical fibre microcavities

Abstract

Placing single emitters inside optical cavities provides a way of drastically modifying their interaction with the electric field. Such systems can be used to test our fundamental understanding of quantum electrodynamics and to develop devices that exploit this new found knowledge. This thesis describes work towards coupling single dye molecules to optical fibre microcavities at cryogenic temperatures. I present the design of an oven growth chamber and develop a method to grow cosublimated crystals of anthracene doped with dibenzoterrylene. I then describe the characterisation of these samples using a confocal microscope setup both at ambient and cryogenic temperatures. The samples grown show bright, stable, single emitters in a defined orientation in the anthracene crystals. By varying the growth parameters of the homebuilt crystal growing chamber, we can control the density of dibenzoterrylene molecules and grow at an optimum density to use these crystals in conjunction with optical fibre microcavities. I show how optical fibre microcavities have been developed that can be cooled to the liquid helium temperatures required to take advantage of the lifetime-limited emission from single dibenzoterrylene molecules, that only occurs below 4K. I also present cavity quantum electrodynamic simulations of the cavities, showing what we expect to see when we take reflection spectra of single molecules coupled to these cavities. In addition, I describe the optical setup that has been developed to take these measurements. I conclude with proposed improvements to the cavity setup that will enable these reflection spectra to be more easily taken. This will allow these molecule-cavity systems to be used as infrared single photon sources for quantum optics experiments.