Tunable Leaky-Mode MEMS Filters for Multispectral Imaging Applications

When an incident electromagnetic wave is properly coupled to a waveguide's leaky eigenmode by a subwavelength grating, a guided-mode resonance takes place. This phenomenon can manifest itself as sharp, high quality resonances in the reflection spectra. Since these resonances are highly sensitive to the device structural parameters (-grating thickness, period, and filling factor), a tunable resonance can be implemented if one or more of these parameters are suitably varied. In this paper, the micro-electro-mechanical system (MEMS) concept is applied for tuning the spectral response of resonant filters through mechanical microscale alteration of the grating profile. We provide numerical solutions based on exact electromagnetic models of MEMS-tuned resonance gratings designed with common materials. Computed results for an example tunable element with 6.0 μm period and 2.4 μm thickness show MEMS tuning of ~3.4 μm in the ~9-12 μm band with ~100 nm resonance linewidth. These elements are promising candidates for MWIR (3-8 μm) and LWIR (8-15 μm) multispectral imaging applications.