Room-temperature high-Q channel-waveguide surface plasmon nanocavity.

A low-loss plasmonic cavity is proposed comprising of channel waveguides of different widths. Numerical simulations show that surface plasmons are strongly confined by a mode-gap mechanism in the cavity that has a mode volume of 0.0040 (λ/n)3 and a room temperature quality (Q) factor of 125. The introduction of low-index material can enhance the room temperature Q factor by 2.5 times to 350, while maintaining the mode confinement of 0.040 (λ/n)3- well below the wavelength-scale in free space. The suppression of losses from radiation and metallic absorption in the cavity would allow room temperature plasmonic laser operation, and constitutes significant progress towards practical coherent light sources for such lasers.