Perfect absorption in transition metal dichalcogenides-based dielectric grating

Abstract

The low absolute absorption of monolayer transition metal dichalcogenide severely restricts their available applications due to its atomic thickness, despite their large absorption coefficients. We investigate theoretically, the absorption properties of a hybrid structure which combines dielectric grating and photonic crystal together, where monolayer transition metal dichalcogenide is placed on the top. The guide mode resonances associated with waveguide mode resonances grant the multifold enhancement of the absorption of the hybrid structure, leading to two perfect absorption peaks as well as another high absorption peak with the amplitude of 95%. In particular, strong absorption of the hybrid structure with monolayer transition metal dichalcogenide appears in the visible frequency regime. This is in contrast to those with monolayer graphene always in terahertz and near-infrared range and facilitates their promising applications in photodetectors or solar cells. Our findings offer monolayer transition metal dichalcogenide unique opportunities for applications in optoelectronics and nano-photonics devices and this strategy of achieving high absorption can be applicable to other two-dimensional layered semiconductors.