Optical Characterization of Very Thin Films for Nanotechnological Basis of Sensors

Abstract

Thin films and photonic crystals are used as elements of a nanotechnological basis for sensors due to their well-defined optical properties such as transmittance, reflectance, or diffraction. Key issue is the optical characterization of structures obtained by nanotechnological methods, i.e. a determination of the physical thickness of each individual layer, its dielectric permittivity, magnetic permeability as well as the evaluation of its homogeneity and corrugation. Herein, we focus on a specific problem of great importance to fundamental and applied science: we analyze the case of very thin films, meaning that the ratio ‘layer thickness to wavelength’ is much less than 1/50. We also demonstrate the potential of a new direct approach developed by us to inverse optical problems, based on a position estimation of the probability density function of partial solutions.