A sensor and methods of making a sensor are disclosed. The sensor may include a substrate including an opening, an optical source disposed in the substrate and configured to generate an optical source signal, an optical detector disposed in the substrate so that the opening is disposed between the optical source and the optical detector, a plurality of optical cavity structures disposed in the opening wherein each of the plurality of optical cavity structures contains an enclosed cavity so that the respective enclosed cavities are not in gas communication with each other, wherein the plurality of optical cavity structures are arranged in an optical path between the optical source and the optical detector, and a processing circuit coupled to the optical detector and configured to process an optical signal received by the optical detector.