Enhanced optical absorption of monolayer WS2 using Ag nanograting and distributed Bragg reflector structures

A hybrid novel structure of monolayer WS2 with Ag nanograting and distributed Bragg reflector (DBR) on Si substrate has been proposed to obtain broad-band absorption response for two-dimensional (2D) materials. It is effective to reduce light loss and reflect the incident light efficiently for monolayer WS2 absorption with DBR dielectric layers. Moreover, by combining Ag nanograting with DBR structure, the average absorption achieves as high as 52.9% within broad wavelength ranging from 420 to 700 nm, which is attributed to the plasmonic resonant effect of metal nanostripes. The absorption would be influenced by the period and height of the Ag nanograting, and shows incident angle dependent characteristics, while an average absorption higher than 50% has been obtained at the incident angle around 40°. These results indicate that 2D WS2 in combination with DBR and metal nanograting have a promising potential applications for optical nano-devices.