Plasmonic gap mode nanocavities at telecommunication wavelengths

We analyze a plasmonic gap-mode Fabry-Perot nanocavity containing a metallic nanowire. The proper choice of the cladding layer brings about a decent confinement inside the active region for the fundamental and first-order plasmonic gap modes. We numerically extract the reflectivity of the fundamental and first-order mode and obtain the optical field inside the cavity. We also study the dependence of the reflectivity on the thickness of Ag reflectors and show that a decent reflectivity above 90 % is achievable. For such cavities with a cavity length approaching 1.5 pm, a quality factor near 150 and threshold gain lower than 1500 cm-1 are achievable.