Enhancement of light absorption in a WS_2 monolayer using spacer and Au layers

摘要

Among ultrathin transition metal dichalcogenides, WS_2 monolayers with a direct bandgap have attracted intensive attention because of their narrow optical absorption centered at 619 nm. However, these layers with stronger absorption are needed in applications such as photonic devices. In this paper, an increase in absorption is achieved through plasmonic coupling of a nearby Au thin layer directly or through a spacer to the WS_2 monolayer. The optical properties of the designed structures are investigated by the transfer matrix method in the visible wavelength region. In the structure consisting of a WS_2 monolayer with Au and spacer layers, the absorption at 619 nm was increased to 61%. Sharp optical absorption as high as 40% for a large range of incidence angles in both polarizations was retained. Our study provides useful information for the design of WS_2 monolayers in photonic devices for practical applications.