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.