Deesha Shah

Ultrabright Room-Temperature Sub-Nanosecond Emission from Single Nitrogen-Vacancy Centers Coupled to Nanopatch Antennas

Solid-state quantum emitters are in high demand for emerging technologies such as advanced sensing and quantum information processing. Generally, these emitters are not sufficiently bright for practical applications, and a promising solution consists in coupling them to plasmonic nanostructures. Plasmonic nanostructures support broadband modes, making it possible to speed up the fluorescence emission in room-temperature emitters by several orders of magnitude. However, one has not yet achieved such a fluorescence lifetime shortening without a substantial loss in emission efficiency, largely because of strong absorption in metals and emitter bleaching. Here, we demonstrate ultrabright single-photon emission from photostable nitrogen-vacancy (NV) centers in nanodiamonds coupled to plasmonic nanocavities made of low-loss single-crystalline silver. We observe a 70-fold difference between the average fluorescence lifetimes and a 90-fold increase in the average detected saturated intensity. The nanocavity-coupled NVs produce up to 35 million photon counts per second, several times more than the previously reported rates from room-temperature quantum emitters.

Ultra-thin transition metal nitrides for tailorable plasmonic devices (Conference Presentation)

As a result of recent developments in nanofabrication techniques, the dimensions of metallic building blocks of plasmonic devices continue to shrink down to nanometer range thicknesses. The strong spatial confinement in atomically thin films is expected to lead to quantum and nonlocal effects, making ultra-thin films an ideal material platform to study light-matter interactions at the nanoscale. Most importantly, the optical and electronic properties of ultra-thin plasmonic films are expected to have a strong dependence on the film thickness, composition, strain, and local dielectric environment, as well as an increased sensitivity to external optical and electrical perturbations. Consequently, unlike their bulk counterparts which have properties that are challenging to tailor, the optical responses of atomically thin plasmonic materials can be engineered by precise control of their thickness, composition, and the electronic and structural properties of the substrate and superstrate. This unique tailorability establishes ultra-thin plasmonic films as an attractive material for the design of tailorable and dynamically switchable metasurfaces. While continuous ultra-thin films are very challenging to grow with noble metals, the epitaxial growth of TiN on lattice matched substrates such as MgO allows for the growth of smooth, continuous films down to 2 nm. In this study, we present both a theoretical and an experimental study of the dielectric function of ultrathin TiN films of varying thicknesses. The investigated ultrathin films remain highly metallic, with a carrier concentration on the order of 1022 /cm3 even in the thinnest film. Additionally, we demonstrate that the optical response can be engineered by controlling the thickness, strain, and oxidation. The observed plasmonic properties in combination with confinement effects introduce the potential of ultra-thin TiN films as a material platform for tailorable plasmonic metasurfaces.

Ultra-thin plasmonic metal nitrides: Tailoring optical properties to photonic applications

In this study, we present recent developments on growing epitaxial quality, ultra-thin titanium nitride films that exhibit very good metallic/plasmonic properties, comparable with their bulk counterparts. The potential of these films for extreme light confinement and electrical control is discussed.

Optical properties of ultrathin plasmonic TiN films

Epitaxial, ultrathin (<10 nm) plasmonic TiN films are characterized using spectroscopic ellipsometry and Hall measurements. Thin films with thicknesses down to 2 nm remain highly metallic with a carrier concentration on the order of 10²² cm⁻³.