A review is made of the physics and technology of spectrally selective thermal detectors, especially those operating at non-cryogenic temperatures. The background radiation noise fluctuations are rederived for arbitrary spectral characteristics. Infrared absorption due to phonons and free carriers is discussed followed by a review of published works on artificial infrared absorption materials such as patterned grids, nanoparticles, plasmonic structures, metamaterials and others. Subsequently, the literature of the spectral characteristics of broadband thermal detectors and spectrally selective thermal detectors is reviewed. Finally, the authors speculate on the directions that future research and development in the area will take regarding architectures, sensitivity and spectral characteristics.

The performance of thermal detectors is derived for devices incorporating materials with non-uniform spectral absorption. A detector designed to have low absorption in the primary thermal emission band at a given temperature will have a background-limited radiation noise well below that of a blackbody absorber, which is the condition typically assessed for ultimate thermal detector performance. Specific examples of mid-wave infrared (ʎ ∼ 3-5 μm) devices are described using lead selenide as a primary absorber with optical cavity layers that maximize coupling. An analysis of all significant noise sources is presented for two example room-temperature devices designed to have detectivities up to 4.37 × 10(10) cm Hz(1/2) W(-1), which is a factor 3.1 greater than the traditional blackbody limit. An alternative method of fabricating spectrally selective devices by patterning a plasmonic structure in silver is also considered.

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Investigation of capillary adhesion between the microcantilever and the substrate with electronic speckle pattern interferometry Appl.