Dual-Mode Electro-Optic Modulation Based on BaTiO 3 Guided-Mode Resonances Assisted by Spatial Filtering

Abstract Liquid crystal spatial light modulators suffer from slow response, while conventional electro-optic (EO) thin-film devices exhibit limited modulation depth, hindering high-speed programmable optical systems. Here, we numerically propose a dual-mode EO spatial modulation scheme enabled by barium titanate guided-mode resonance (BaTiO3-GMR) combined with spatial filtering. A SiN photonic crystal structure integrated with a continuous BaTiO3 thin film uses GMR to convert weak electrically induced refractive index perturbations into pronounced complex reflection changes. To overcome the intrinsic amplitude-phase (AP) coupling of single resonant pixels, a two-pixel coherent field synthesis strategy expands the accessible complex field state space, enabling programmable joint AP encoding. Amplitude-type and phase-type trajectories are then selected as two representative constrained modes via 4f spatial-filtering readout. The numerical model yields a broad range near amplitude-only modulation (0 to 0.668) and phase modulation exceeding 2.443 rad. Simulations using MNIST handwritten digits further evaluate 2D amplitude and phase pattern reconstruction. These results establish a simulation-based proof of concept for dual-mode amplitude and phase modulation and provide a numerical basis for future development of programmable optical modulation systems.