Electromagnetic modes in metal-insulator-metal structures

Metal-dielectric-metal structures are constructed by depositing Ag films on CaF2 thin films that coat Ag surfaces. The reflectance of such structures was measured for several angles of incidence in the 1-5-eV spectral range. The minima observed in the reflectance are due to the excitation of electromagnetic modes inside an optical cavity. These observed electromagnetic modes are discussed and compared to computed dispersion.