Modeling Method for Characterization of Absorptive Planar Interference Resonators

The development of mathematical models for both resonant systems and their environment with structural and material parameters based on experimental measurements of optical spectra is widely used, for example, in optical sensing, fi ltering, and spectroscopy. In sensing or infrared spectroscopy, the estimation of absorption in continuous media is an important problem, where the accuracy decreases as the characteristic dimensions of structures become smaller. In the present work, the possibility of implementation of planar dielectric and metal-dielectric resonance structures that support the excitation of interference modes for investigating absorption in materials is considered. Conventionally, the relationship between spectral values and parameters of layered dielectric and metal-dielectric structures is determined through numerical approximation of recorded spectra. For analytical description and interpretation of resonant effects in the spectra of resonant structures, coupled-mode theory approaches are used, which, however, do not reveal the conditions for eigenmodes excitation. In the present work, to describe the infl uence of optical and geometric parameters of interference structures supporting the excitation of waveguide, Fabry-Pérot, symmetric and antisymmetric plasmonic normal modes on the characteristics of the resonance profi le, a mathematical method for modeling optical characteristics of absorbing layers in interference resonators based on changing the excitation conditions of their eigenmodes has been developed. Within the framework of the developed method, dispersion relations describing the behavior of propagation constants of interference modes are used to obtain analytical expressions relating individual parameters of layered resonant systems. The developed method can be used for the estimation of material characteristics of the examined media eliminating the need for iterative spectral approximations.