Design of a tunable photonic crystal narrowband filter with a mirror-symmetric heterostructure based on the anisotropic 2D vdW material α-MoO₃

This work establishes a mirror-symmetric quasi-1D photonic crystal (PC) heterostructure for tunable high-efficiency narrowband filtering. The narrowband filter (NBF) architecture employs a Fabry-Perot-type configuration with mirror elements realized by quasi-1D PCs of alternating <i>α</i>-phase molybdenum trioxide (<i>α</i>-<i>M</i><i>o</i><i>O</i>₃) and <i>S</i><i>i</i><i>O</i>₂ multilayers. A centrally positioned junction layer within this structure breaks the intrinsic periodicity, functioning as a defect layer. For the tunable NBF, simulations reveal a 95.81% transmittance maximum at 1550 nm. Additionally, the tunability of <i>α</i>-<i>M</i><i>o</i><i>O</i>₃ and the effects of dielectric layer periodicity and thickness on the filtering characteristics of the tunable NBF were numerically investigated. The superior optical properties of the tunable NBF enable promising applications in detection and photonic systems.