Engineering thermal emission with enhanced emissivity and quality factor using bound states in the continuum and electromagnetically-induced absorption

Metal-based thermal metasurfaces offer stable spectral characteristics under temperature fluctuations, unlike their dielectric counterparts whose emission spectra shift with temperature. However, these metal-based emitters typically suffer from limited quality factors due to significant non-radiative ohmic losses. In this study, we overcome this challenge of achieving both high emissivity and high quality factors in metal-based thermal emitters. By leveraging the coupling between a magnetic dipole resonance and two bound states in the continuum (BIC) resonances to induce electromagnetically induced absorption (EIA), we design a thermal metasurface with a near-unit emissivity of 0.96 and a quality factor of 320 numerically. Experimental validation confirms an emissivity of 0.82 and a quality factor of 210, which is approximately a fivefold improvement over the current state-of-the-art metal-based thermal metasurfaces. Our work paves the way for the development of efficient, narrow-band, directional thermal emitters with stable emission spectra across a wide temperature range.