Abstract: The present invention provides apparatuses comprising a plurality of junctions providing a Seebeck effect, configured as alternating hot and cold junctions. The apparatus can be configured such that the cold junctions exhibit a different thermal behavior than the hot junctions in response to incident radiation. The junctions can be connected in series, such that the sum of the Seebeck effect from the plurality of junctions provides a sensitive, inherently calibrated indication of heating of the apparatus responsive to incident radiation, and therefore of the radiation itself.