Spectral Control of Near-Field Thermal Radiation With Periodic Cross Resonance Metasurfaces

Near-field thermal spectra can be engineered using periodic cross resonance metasurfaces. Structures consisting of single crosses, double crosses, and multiple crosses are proposed to control the spectral heat flux from narrow band to broadband with the Fabry-Pérot-cavity-like effect and the interaction between the emitter and receiver. Radiation peaks originating from the cross structures split into two adjacent peaks in the near-field, due to the separate contributions of s- and p-polariton modes. Their frequency can be manipulated by adjusting the length of the crosses. Multiple radiation peaks can be generated by double crosses, and due to the strong coupling of resonance modes, multiple crosses can yield a broadband thermal spectrum ranging from 100-180 THz, with the total heat flux two orders of magnitude above the blackbody limit. The inherent physical mechanisms are illustrated by analyzing the energy transmission coefficients of the cross structures. The features of the radiation peaks and spectra are robust to the change of the gap distance or the temperature, which is advantageous for both the experimental design and fabrication of thermal radiation devices.