Electromagnetic properties of periodic multilayers of ultrathin metallic films from dc to ultraviolet frequencies

Ultrathin metallic films have an interesting electromagnetic behavior as th e frequency of the incident field is varied over several orders of magnitud e, because of the dramatic dispersion exhibited by the metal permittivity. We study a finite multilayer of periodically placed planar conducting films for frequencies varying from the de limit to the far ultraviolet. We provi de the optimized reflectivity and transmittivity of the system for the vari ous frequency regimes involved. Further, we produce the dispersion diagrams of the corresponding photonic bandgap structures, which clearly show the t ransition of the system from a metallic (low frequencies) to a dielectric ( optical frequencies) behavior. In addition, simple design formulas for maxi mum reflectivity of finite film number N are presented in terms of film thi ckness and film spacing in each of the representative frequency ranges. (C) 1999 Optical Society of America [S0740-3232(99)00808-X] OCIS codes: 310.68 60, 290.4210, 220.4830, 230.1480, 260.3910.