1. A thermal sensor comprising a plurality of pixels disposed on an upper surface of a substrate, each said pixel comprising: a reflector disposed on the upper substrate surface; a pair of legs protruding from the upper substrate surface; and a membrane including an infrared (IR) absorbing material and mounted on the pair of legs, wherein the membrane is disposed over and separated from the reflector such that coupling between the membrane and the reflector forms a Fabry-Pérot cavity, wherein the membrane defines a plurality of spaced-apart openings, and wherein each adjacent pair of said openings is separated by a micron-level distance.