Novel Method of Sub-Wavelength Thin Film Growth for Single Photon Emission from Dye Molecules

Single photons are very attractive for quantum information processing, given their long coherence time and their ability to carry information in many degrees of freedom. A current challenge is the generation of single photons in a photonic chip in order to scale up the complexity of quantum operations. Solid state emitters could offer this possibility. Quantum dots are one promising approach, but photons produced by different dots are generally distinguishable. Nitrogen-vacancy (N-V) centres in diamond are also promising, however it is challenging to place these in photonic circuits and the emitted photons have many frequencies. By contrast, dibenzoterrylene (DBT) molecules embedded in a thin film of anthracene (AC) at cryogenic temperatures produce a high yield of indistinguishable photons [1, 2]. DBT acts as a two-level system with a narrow 30 MHz near-infrared (785 nm) zero-phonon line [1]. We have proposed that a DBT molecule, deposited in the vicinity of a nanoscale waveguide, could emit these photons efficiently into the waveguide [3]. Conventional spin-coating methods [1] do not offer sufficient control over the surface coverage and the morphology of the AC crystal for deposition on photonic structures, while crystals grown with sublimation are too thick. Another method is needed.