Wavelength calibration using MEMS-enabled double filter configuration for air gap sensing in the tunable Fabry–Pérot filter

We fabricate a microelectromechanical systems (MEMS)-based device configuring the tunable air gap Fabry–Pérot filter (FPF) with a static gradient thickness filter on the same platform. The proposed double filter configuration offers a wavelength calibration approach that accurately estimates the air gap dimension in the tunable air gap FPF. The wavelength calibration is performed by utilizing the spectrally-selective and spatially-resolved transmission characteristics of the tunable air gap FPF and the static gradient thickness filter, respectively. The MEMS-compatible chip-level integration of the static gradient thickness filter facilitates device miniaturization to enable its use in handheld devices.