Abstract
Broadband optical absorption structures in the near infrared by coupling monolayer-graphene with periodical metal structures are proposed and demonstrated numerically. Optical absorption of graphene with over-50%-absorption bandwidth up to hundreds of nanometer caused by magnetic dipole resonances and magnetic coupling effect are investigated in detail, and the demonstrated bandwidths are one order higher than those caused by dielectric guiding mode resonances. In addition, the influences of geometrical parameters of structures are fully analyzed and these demonstrated structures show angular-insensitive absorption for oblique incidence in a large angular range. The demonstrated absorption structures in this work provide new design ideas in the realization of advanced graphene-based optoelectronic devices.
Highlights
Graphene has been widely applied in different kinds of optoelectronic devices due to its excellent physical properties[1,2,3], such as stable optical response in broad spectrum[4] and ultra-high carrier mobility[5]
In the mid-infrared to THz range, graphene absorption is normally enhanced by exciting surface plasmonic resonance of graphene[7,8,9,10,11,12,13]
The full width at half maximum (FWHM) of total absorption is beyond 150 nm, one order higher than that of graphene-dielectric coupling structures[15,16,17,18], and the over-50% absorption bandwidth of graphene is about 46 nm
Summary
Graphene has been widely applied in different kinds of optoelectronic devices due to its excellent physical properties[1,2,3], such as stable optical response in broad spectrum[4] and ultra-high carrier mobility[5]. Research results show that the bandwidth of graphene absorption over 50% can exceed 200 nm at center wavelength near 1550 nm by using magnetic dipole resonances[40,41,42] or magnetic coupling effects[43]. All these proposed structures could work in a large incident angle range. The demonstrated structures would be of valuable applications in advanced graphene-based optoelectronic devices
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