Reciprocally tailored transparent artificial media for frequency and direction dependent light trapping

Abstract

We propose a quasiperiodic leveled-wave structure whose reciprocal space is represented by spherical belt sections, designed to achieve scattering only for the defined wavelength and direction of incident light. At the same time light is scattered only towards directions of k-vectors for which the waves are trapped by total internal reflection in the structured slab. The trapped light is only weakly scattered and thus spends a long time inside the slab and is attenuated by weak absorption in the slab. The incident light of other direction and/or wavelength is transmitted through the slab almost undisturbed. We quantitatively estimated the scattering mean free paths for incident and trapped light from the first-order Born approximation and develop an analytical model which predicts the absorption for a given slab thickness, refractive index contrast and spherical belt parameters. Reducing the refractive index contrast and thickness of the belt, the selectivity can be increased and the absorption contrast for incident light of different wavelengths can reach 70%. We present numerical simulations with absorption contrast of 63% for refractive index contrast of 0.1, which is in good agreement with our analytical model.