Waveguide coupling of single photons from a solid state emitter

The organic dye molecule dibenzoterrylene (DBT) in an anthracene crystal matrix is a promising candidate for single photon emission. At cryogenic temperatures, this system presents a narrow lifetime-limited transition at 785nm, with a quantum yield close to unity. Moreover, DBT molecules have been shown to act as a mediator for photon-photon interactions, by inducing a phase-shift on a passing photon when another photon is present. These features make DBT
molecules a powerful tool for quantum information purposes, including use as single photon sources and controlled quantum gates. For these to be achieved, the interaction between the molecule and the radiation field must be enhanced.

We plan to accomplish this task by integrating single molecules in nano-photonic structures. We have designed and fabricated single mode ridge waveguides, optimised to have maximum overlap between their evanescent field and the molecule. To further enhance the interaction, we have inserted a nanotrench in a waveguide, further increasing the coupling to the structure. Simulations shown an expected 52% of the light radiated from to the molecule to be harnessed in the waveguide. A growth method developed in our group allows deposition of a thin film of anthracene doped with DBT on top of the structures. To move beyond the diffraction limit, we have designed a plasmonic hybrid waveguide. These waveguides provide an adiabatic transition to the plasmonic regime, while minimising the losses typically associated with interactions between light and metals. Since most quantum information protocols require direct manipulation of the state of the molecule, we have studied its coherent dynamics in the presence of dephasing. By solving analytically the optical Bloch equation, we are now able to model the response of any two-level system, a result we have validated experimentally with our molecules.