Dibenzoterrylene as a single photon source

Abstract

Deterministic single photon generation is of huge interest for quantum research and this thesis will begin by outlining the properties of interest for a single photon emitter. I then outline the theory behind the interaction of light and Dibenzoterrylene (DBT), an organic dye molecule that I use for the generation of single photons. DBT is used in the solid-state, and I present fabrication processes for producing host matri- ces with DBT embedded. The physical properties of the organic crystals produced by these methods are described, along with the optical properties of the DBT molecules within. The development of a new method for preparing DBT containing polymer encapsulated nanocrystals that show stable single photon emission at cryogenic temperatures is presented. Interactions between DBT and the vibrations, or phonons, in its host environment are then studied. The effect of thermal dephasing on a DBT molecule will be modelled to predict the probability of excitation as a function of excitation wavelength. Measurements at both room and liquid nitrogen temperatures will verify these predictions. A cryogenically cooled DBT molecule is then used to observe the effects of vibrations on the emitted photons as temperature increases. This allows the temperature dependance of the branching ratio and photon linewidth to be measured. I use the emission of a single DBT molecule to measure two-photon interference and draw parallels between pulsed and continuous-wave excitation measurements. I find an indistinguishability of 53% using continuous-wave excitation and verify this using pulsed excitation, proving this method works for measuring full photon wavepacket indistinguishability. This is also in line with the expected maximum value given the temperature. To increase the efficiency of photon collection from DBT molecules I will finish by looking at integration of molecules with nanophotonic devices. Measurements of a 9% coupling of a molecule to a waveguide will be presented, which is the highest cryogenic coupling of a molecule to a waveguide structure measured. Integration of DBT into circular Bragg gratings will also be discussed.