Surface Tamm states in a photonic crystal slab with asymmetric termination

Abstract

The reflection and transmission spectra of a finite thickness 2D Photonic Crystal Slab (PCS) based on macroporous silicon are investigated. Periodic photonic crystal region is separated from air by homogeneous silicon interfacial layers. These interfacial layers at the silicon/air boundary being defects of the photonic-crystal lattice, define the properties of surface Tamm states in the Photonic Stop-Bands (PSBs). It is demonstrated experimentally and theoretically that the reflection spectra of a structure with different thicknesses of the interfacial layers on both sides of the PCS depend on the illuminated side. At the same time, the transmission spectra are identical for both light directions in agreement with the reciprocity princi-ple. Analysis shows that the dependence of the reflection spectrum on the side of light entrance is due to scattering losses in the real structure.