Engineering the structure-induced enhanced absorption in three-dimensional metallic photonic crystals

Order-of-magnitude enhancement of light absorption can take place near the photonic band gaps in three-dimensional layer-by-layer metallic photonic crystals in the mid-infrared wavelength regime where a conventional bulk metallic material shows weak absorption. In this paper we investigate the dependence of this enhanced absorption on several structural parameters of the crystal by means of a plane-wave-based transfer-matrix method in combination with an analytic model expansion approach. We find that when the metallic layers are brought out of touch, the magnitude of the absorption peaks grows rather than decays, in contrast with the conventional wisdom that the connectivity of metallic structure can enhance the absorption. Besides, the increase in the metallic layer separation distance will result in redshifts of absorption peak. The position of the absorption peak can also be engineered conveniently by simply changing the refractive index of the dielectric material filling the open domain between metal walls. Due to the approximate scalability of Maxwell's equations, the absorption peak shows a nearly linear dependence in position on this refractive index.