Tunable Filtering via Lossy Mode Resonance in Integrated Photonics

This study explores an integrated tunable filter based on lossy mode resonance (LMR) in TiOx thin films, modeled in COMSOL Multiphysics using the Wave Optics and Semiconductor modules. By exploiting the electro-optic (EO) modulation of free carrier concentration in TiOx, the LMR wavelength can be actively tuned under an applied electric field. The results demonstrate a tuning efficiency of 4.0 nm/V, which surpasses many reported EO tunable filters. Optimization studies reveal that thinner ITO electrodes and TiOx layers enhance tuning efficiency, while the initial bulk free carrier concentration has limited influence due to the compensating effect of the Debye length. These findings extend the applicability of LMR beyond sensing, highlighting its potential for active photonic components in integrated optics.