According to one embodiment, a micro-electrical mechanical system apparatus includes first and second mirrors that define a cavity. Moreover, a photonic band-gap structure coats a surface of at least one of the first or second mirrors to improve reflectivity. Another embodiment includes a third mirror, wherein the second and third mirrors form a second cavity. The spaces between the mirrors might comprise, for example, a pair of Fabry-Perot filter cavities for a spectrometer.