A strong controllable absorber using graphene-metal nanostructure

In this paper, a strong absorption is obtained by a graphene-metal nanostructure at near-infrared wavelengths. The proposed absorber consists of a single graphene layer on a metal film array with semicircle and L-shaped grooves. There are two absorption peaks of 0.48 and 0.86 at 1488 nm and 1538 nm wavelengths, respectively, in the absorption spectrum of the structure without the graphene layer. The absorption is enhanced to 0.89 at 1498 nm wavelength and the full-width at half-maximum (FWHM) is increased as the graphene layer is used. Also, the absorption value of 0.99 can be attained as three graphene layers are utilized and the FWHM can be enhanced to 173 nm when four graphene layers are on the structure. Moreover, the effects of geometrical parameters of the structure and graphene chemical potential on the absorption spectrum are studied to tune the absorption value and wavelength. By tuning the geometrical parameters, a three-band absorber is proposed.