Magnetic coupling metasurface for achieving broad-band and broad-angular absorption in the MoS_2 monolayer

A magnetic coupling metasurface with a structure of a Ag nanograting/space layer/Ag reflector is proposed to achieve broad-band and broad-angular absorption response for 2D materials such as a MoS2 monolayer. By reducing the size of the Ag nanograting and thickness of the spacer into deep subwavelength, strong magnetic coupling effects occur within the metasurface. The magnetic coupling effects can confine large energy density and reduce the metallic optical loss to a relatively low value in the structure. Correspondingly, broadband absorption enhancement is achieved for the MoS2 monolayer. The average absorption within the visible wavelength range reaches as high as 72.7% and the value still remains over 40% when the incident angle increases up to 80°. It is revealed that the magnetic coupling effects are more efficient than both the plasmonic and the magnetic resonant effects to achieve broad-band and broad-angular absorption in ultrathin 2D material absorbers.