Photonic surface waves enabled perfect infrared absorption by monolayer graphene

The low absorptivity of monolayer or few-layer graphene is one of the key limitations for high performance. To improve the graphene absorption, highly nanostructured or metallic systems have been usually employed, which however rely on the advanced nanofabrication with high cost or strong metallic parasitic absorption. In this study, via thin-film optics, the photonic surface waves based on purely dielectric planar system are proposed to realize perfect optical absorption by monolayer graphene with the thickness of similar to 0.34 nm. The Bloch surface wave (BSW) is found to be excited efficiently from 7-layer dielectric system by carefully addressing the admittance matching conditions, electric/magnetic field confinement, and band structure. Coupling with the strongly localized BSW field, a monolayer graphene shows an absorption similar to 100% at the designed infrared band (1310 nm, which can be tuned readily). With detailedly addressing the excitation condition of BSW, it is found that the perfect absorber can also be realized based on the more generalized surface waves from aperiodic structure. It is believed that the thin-film and purely dielectric surface wave system provides two-dimensional devices a promising opportunity for low-cost and high-performance applications.