Polarization-insensitive dielectric metamaterial absorber for near-unity UV-light trapping in monolayer graphene

With the aim of improving UV light trapping capability in monolayer graphene, a nanomesh metamaterial absorber is proposed, which exhibits the polarization-insensitive feature due to the geometrical symmetry. Through the functional combination of magnetic resonance and UV mirror, the absorption of unpolarized UV light in monolayer graphene can reach 99.5% under normal incidence. The absorption enhancement is induced by the magnetic resonance mode between the dielectric silica nanomesh and the calcium fluoride base layer. The effects of geometric parameters on the absorption spectra are systematically investigated. The proposed structure shows insensitive to manufacturing deviations, which can maintain at a high UV absorption rate of more than 99% within the nanomesh width ranging from 50 nm to 90 nm. Furthermore, after delicate optimization of the geometric parameters, two sharp resonances with absorbance more than 90% can be excited simultaneously inside the absorber. Our work provides an important theoretical guide for the design of optoelectronic devices based on two-dimensional materials in the UV range. • Near-unity UV-light absorption is achieved in the monolayer graphene. • The proposed structure is insensitive to manufacturing deviations. • Two sharp resonances with absorbance over 90% can be excited inside the absorber.