Lasing in metallic nano-structures with Fano resonance (Conference Presentation)

Abstract

Recently, plasmon laser has been attracted great attention at length scales below diffraction limit. It has been demonstrated not only in single nanocavity systems, but also been observed in periodic nanoplasmonic structures. We propose a kind of lasing scheme in a nano-grating with three slits and three metal strips (one fat metal strip and two thin metal strips) in each supercell. There exists a bright mode and a dark mode in the nano-grating, due to the inter-couple among the cavity modes in the slits. The most interesting issue is that such two modes can be independently controlled by tuning the widths of the fat and thin metal stripes. It enables the flexibility to choose the gain medium and the corresponding cavity surrounding in nanoscale. Based on such guideline, we investigate a lasing system consisting of nano-grating and Rhodamine dye molecules by using self-consistent finite element method. We show the lasing dynamic process with both the matched and mismatched nano-grating. As a result, when it well matches, the dark mode will provide higher feedback and amplification than those of the mismatched system. Consequently, when the same optical pump power is applied, the matched case will have shorter lasing onset time and higher output power than the mismatched structure. More calculations can conclude that the perfect-matched nano-grating system will have minimum threshold and maximum lasing slope efficiencies. Our findings may provide a new way on plasmon laser with low threshold and high efficiency.