Abstract
Metal-based thermal metasurfaces exhibit stable spectral characteristics
under temperature fluctuations, in contrast to more traditional gray- and near
black-bodies, as well as some dielectric metasurfaces, whose emission spectra
shift with changing temperatures. However, they often suffer from limited
quality (Q) factors due to significant non-radiative ohmic losses. In this
study, we address the challenge of achieving high emissivity and Q-factors in
metal-based thermal emitters. By leveraging the coupling between a magnetic
dipole resonance and two bound-state-in-continuum (BIC) resonances to achieve
electromagnetically induced absorption (EIA) in an asymmetric metallic ring
structure, we design a metal-based thermal metasurface with a near-unity
emissivity (0.96) and a Q factor as high as 320 per simulations. Experimental
validation yields an emissivity of 0.82 and a Q factor of 202, representing an
approximately five-fold improvement in the experimentally measured Q factor
compared to the state-of-the-art metal-based thermal metasurfaces. Our work
offers a promising approach for developing efficient, narrow-band, directional
thermal emitters with stable emission spectra across a wide temperature range.