Large Spontaneous Emission Enhancement with Silver Nanocube Dimers on Silver Substrates

Nanoantennas and nanocavities are widely used for at-source manipulation of quantum emission based on the well-known Purcell effect. Here, the configuration is explored consisting of silver (Ag) nanocube dimers positioned on Ag substrates to realize large Purcell enhancement of molecular spontaneous emission. The relationship is investigated between the cube sizes and separation gap of a nanocube dimer and the resulting Purcell enhancement, and shows the possibility of achieving the enhancement of up to 6.4 × 10⁶. Furthermore, to experimentally demonstrate large Purcell enhancements, atomic force microscopy is used to assemble Ag nanocube dimers in the corner-to-corner configuration with the help of prefabricated corner-to-corner dielectric bricks. The decrease of the lifetime of Ru dye molecules from 91.7 ns (on a glass substrate) to the instrument response function limit (1.5 ns) after coupling with nanocube dimers is observed. This work provides a promising design and realization method for advanced photon sources, e.g., atom-like single-photon emitters with extremely large decay rates.