Enhanced spontaneous emission in proximity of a plasmonic nano-slit antenna

We investigate enhancement in the spontaneous emission (SE) rate of CdSe/ZnS core–shell quantum dots (QDs) by a semi-infinite plasmonic nano-slit antenna. Long Al2O3 filled nano-slits having ∼15 nm width, ∼250 nm height, and >50 μm length in a silver film exhibit strong Fabry–Pérot like resonances associated with gap plasmon modes. For the QDs located on top or in proximity of the nano-slit, we observe ∼15 times enhanced SE relaxation rate compared to the free-space environment. The faster relaxation is attributed to Purcell enhancement resulting from the strong field confinement within the nano-slit and the associated increase in the optical density of states. The experimental results are supported by COMSOL simulations. Our findings demonstrate the ability of the plasmonic nano-slit antenna to strongly enhance the SE rate of emitters in proximity.