Fig. 5

Engineered mode symmetries in thermal photonics: Fano resonance and BICs for thermal emission control. a Fano-resonant optical coatings for the application of hybrid thermal-electric power generation, enabling the splitting of solar spectrum band for both photovoltaics and photothermal applications, respectively. b Fano resonance-based thermal emission control in a MDM grating structure. A very narrow emission peak (dashed white circle) is shown in the angle-resolved thermal emission spectra. c Fano resonance-based near-field radiative heat transfer. The Fano resonance is formed by the coupling between gap-plasmon modes in porous Bi and surface phonon modes in NaBr. The color map shows a dispersion diagram of the energy transmission coefficient. d Highly directional and extremely narrow thermal emission due to accidental BICs operated at the plasma frequency of SiC. e Complete switching of optical absorption based on vertical symmetry-breaking BICs in Si metasurfaces with elliptical meta-atoms. f Quasi-BIC-based thermal metasurface for thermal emission with designed orbital angular momentum. Figures adapted from: a, ref [89]; b, ref [91]; c, ref [92]; d, ref [100]; e, ref [109]; f, ref [74]