Silver Columnar Thin-Film-Based Half-Wavelength Antennas for Bright Directional Emission from Nanodiamond Nitrogen-Vacancy Centers

A plasmonic nanoantenna offers directionality and a large photonic density of states to a nearby emitter. Here researchers create antennas based on silver columnar thin film for bright, directional emission from N-$V$ centers in nanodiamonds (NDs). By simply drop-casting the NDs from aqueous solution on top of the film, order-of-magnitude enhancement of emittance is attained. The silver nanocolumns couple to an N-$V$ center's emission via the optical near field, and out-couple the excitation energy effectively into the far field. As the approach is not restricted to these emitters, it offers a broad way to practical implementation of solid-state single-photon sources.