Curvature effects in surface plasmon dispersion and coupling

We have studied the resonant coupling of surface plasmons in curved thin-film tunneling geometries by obtaining the dispersion relations for the system. The surface plasmon dispersion relations are calculated for a metal-coated dielectric probe above a dielectric half space with and without metal coating. The system is modeled in the prolate spheroidal system, and the dispersion relations are studied as functions of the parameter that defines the boundaries of the tip and the corresponding coating, and as functions of the involved coating thicknesses. Using this type of probe-substrate configuration, the nonradiative surface plasmon coupling mechanism is investigated in the visible spectrum at frequencies relevant to scanning probe microscopy. The simulations of the results predict optical access to the resonant surface modes of the system.