Zero-reflection metal slabs: A mechanism of light tunneling in metamaterials

Thick metals are nearly opaque due to high reflectance and the huge third-order nonlinear susceptibility of metals is hardly utilized. In the present paper, zero-reflection phenomena in a thick metal (M) slab covered with one-dimensional dielectric photonic crystals (PC’s) (CD) _n are studied in heterostructures M(DC) _n and sandwiched structures (CD) _n M(DC) _n . Visible-light tunneling modes can be realized in M(DC) _n or (CD) _n M(DC) _n in which the optical epsilon-negative medium (metal) is paired with the PC, which mimics a lossless optical mu-negative medium in the gap region. The transmittance as high as 33% and 38% are observed at wavelength of 589 nm for M = Ag, with thickness d=60.2 nm in a heterostructure and d=83.1 nm in a sandwiched structure, respectively. The transmittance is more than 200 times larger than that of a single Ag layer with the same thickness in the latter case. Possible applications on metal-based nonlinearity enhancement and optical absorber are also discussed.