Optical properties of subwavelength metallic-dielectric multilayers

We present studies on the optical properties of periodic metallic-dielectric (MD) multilayers and numerical results show that there exists, insensitive to the lattice scaling, a transparent band as long as the layer thickness is in the subwavelength ranging. It illustrates the transparent band is controlled by mechanisms beyond the Bragg scattering: the shorter-wavelength band edge comes from the intensive resonant absorption behavior of the metals, while the longer-wavelength band edge is determined by zero (volume) averaged permittivity εeff=0. Moreover, a Lorentz-Drude model for the permittivity of a ε-negative (ENG) metamaterial is used to show that a transparent band may be obtained in a subwavelength structure consisting of ENG multilayers with total length less than both the center wavelength and the half width of the band.