Quasi-periodic MoS 2 -based absorber for angular and polarization-selective narrowband filtering

Optical filtering, sensing, and integrated photonic systems require high-Q narrowband absorbers with angular and polarization selectivity. However, most visible-near-infrared dual-band absorbers rely on plasmonic metasurfaces, multiple defect layers, or lithography-intensive fabrication, which limits angular robustness and increases structural complexity. This article presents a theoretical demonstration of a lithography-free inverse Fibonacci one-dimensional photonic crystal absorber with a single lossy MoS 2 defect layer. Two cavity-supported absorption resonances within the photonic bandgap are revealed by transfer-matrix analysis. At 910.5 nm, near-perfect absorption of 99.5% is achieved with quality factors greater than 100 and linewidths less than 2 nm. Perfect absorption is demonstrated to be governed by impedance-matching and critical-coupling conditions, which are reinforced by prominent resonant dispersion with group delays up to ∼6 ps and strong defect-localized electric-field enhancement. Polarization-independent at normal incidence with narrow angular tolerance (