Directional thermal emission control by coupling between guided mode resonances and tunable plasmons in multilayered graphene

摘要

Directional thermal radiation is attracting interest because of its applicability to thermal management systems and mid-infrared light sources. Plasmons in a single graphene layer are tunable by the chemical potential, while the lateral wavenumber of the plasmon dispersion is too large for the directional coupling to the far field. In this paper, we achieve directional thermal radiation by utilizing tunable plasmons in multilayered graphene. The lateral wavenumber of the plasmon is shown to be reduced as the number of graphene layers increases, and the reduction is analytically explained. The thermally excited graphene plasmon couples to the guided mode resonance in a silicon grating through evanescent waves so as to realize angular-selective far-field emission. We develop a modal analysis in order to investigate the coupling condition. In addition, the directional thermal emission including asymmetric one can be tuned by varying the chemical potential of graphene layers. The calculated emissivity obtained by changing both the chemical potential and the height of the grating suggests the control of the angular heat flux profile.