Metamaterial thermopile beyond optical diffraction limit

A radiation thermopile detector that converts radiant thermal energy into electricity is capable of remote temperature measurement without the need for a cooling system. However, due to its operating mechanism, its active area needs to be larger than the wavelengths of thermal radiation, i.e. >10 mu m. Here, we report calculation results of a metamaterial thermopile that operates beyond the optical diffraction limit. The metamaterial thermopile has a physical active area of only seven square microns but absorbs thermal energy from the environment equivalent to that of a significantly larger detector owing to the large absorption cross-section of the metamaterial elements. The metamaterial absorbs thermal radiation emitted from the surrounding media, creating a thermal gradient across a silicon nanowire, resulting in thermoelectric conversion. We numerically evaluated the responsivity and specific detectivity of the metamaterial thermopile at temperature ranging from 273 to 373 K. The calculated specific detectivity of the metamaterial thermopile was 2.38 x 10(7) (cm center dot Hz(1/2)center dot W-1/2). This metamaterial thermopile that enables highly miniaturized thermometry sensors surpassing the optical diffraction limit, opens new avenues for microscale temperature measurement, leading to new discoveries in physics and thermodynamics.