Multiple Fano resonances in bimetallic layered nanostructures

Plasmonic Fano resonances arise in bimetallic layered nanostructures (metal–dielectric–metal and dielectric–metal–dielectric–metal) are studied theoretically as the function of their geometrical parameters. Multiple Fano resonances are generated in these nanostructures where several subradiant dark modes appear due to the geometrical symmetry breaking induced by offsetting different layers. The plasmonic responses of the proposed nanoparticles with equal volumes are compared and multiple Fano resonances with large modulation depths are obtained in metal–dielectric–metal structure which is highly suitable for multi-wavelength sensing and plasmon line shaping. However, the dielectric–metal–dielectric– metal nanostructure is found to provide a slightly better tunability of higher-order plasmonic modes compared to metal–dielectric–metal nanostructure due to which it can be useful for biomedical applications.