Oscillator Chain: A Simple Model for Universal Description of Excitation of Waveguiding Modes in Thin Films

There is no simple and universal analytical description of various micro-optical systems related with Fano resonances. This especially concerns modulated thin films, which, when coupled to external fields, show Fano resonances. Usually, such micro-optic schemes are simulated numerically, frequently by the use of commercial software. The study fills this gap of the lack of universal analytical description by introducing and exploring a simple mechanical equivalent, the oscillator chain, which mimics such schemes involving Fano resonances. The model does not necessarily provide the rigorous description of complicated micro-optical schemes, however does capture the main properties of such Fano-related micro-optical systems. The model captures different modifications of the thin film arrangement as well: thin film with amplification, non-Hermitical thin films, and others. It also covers the case of multiple Fano resonances in a thin film. The model is validated by comparing with the rigorously calculated wave propagation in the thin films.