Description
Tunable long-wave infrared (LWIR) optical filters are key enabling components for compact multispectral and polarization-sensitive thermal imaging systems. Here, we demonstrate geometry-driven polarization engineering in microelectromechanical systems (MEMS)-integrated extraordinary optical transmission (EOT) filters based on a dual-membrane plasmonic metamaterial platform. Resonant EOT modes supported by subwavelength apertures in a perforated gold membrane provide wavelength-selective transmission, while electrostatic modulation of the separation to a patterned silicon membrane tunes the resonance through modification of the local electromagnetic environment. By modifying only the in-plane metamaterial geometry, both polarization-selective and polarization-insensitive spectrally tunable optical responses are realised within a common MEMS architecture without changes to the material stack, fabrication process, or actuation mechanism.
Finite-element simulations were used to investigate the influence of aperture geometry on resonance linewidth, transmission efficiency, polarization extinction, and spectral tuning behaviour. Three polarization-selective slit geometries with varying aperture widths and aspect ratios together with a polarization-insensitive architecture were considered. The results reveal that slit width and slit length act as largely independent design parameters governing different aspects of device performance. Narrower apertures improve polarization selectivity and spectral resolution, while elongated apertures enhance transmission and spectral tunability at the expense of broader resonances. Polarization-insensitive operation is achieved through introduced in-plane symmetry of the metamaterial pattern while preserving favorable tuning characteristics.
The simulated designs were subsequently fabricated using a common MEMS process and characterized using polarization-resolved Fourier-transform infrared spectroscopy under electrostatic actuation. Despite fabrication-induced geometric deviations from the intended layouts, the measured optical responses closely followed the predicted trends. Geometry-corrected simulations incorporating experimentally determined dimensions and intermembrane separations showed good agreement with the measured transmission spectra, validating the modelling framework.
The results establish practical design guidelines for geometry-based polarization engineering in tunable EOT filters and demonstrate a versatile platform for compact infrared sensing, multispectral thermal imaging, and polarization-sensitive imaging applications.
| I am the presenting author | Yes |
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