Broadband enhancement of absorption by two-dimensional atomic crystals modeled as non-Hermitian photonic scattering

We report the design and fabrication of a vertical structure using a distributed Bragg reflector and dielectric material layer to achieve optimized optical absorption enhancement for a stack of monolayer WS2 and MoS2, namely, a tenfold increase in absorption over a 100 nm spectral range. Our research indicates that we can approach over 50% absorption by finely tuning the thickness of the spacer layer. Our theoretical model shows that the dependence of the absorption coefficient on the spacer thickness can be understood as a solution of a non-Hermitian Schrödinger equation. These results advance the development of broadband optical devices, including solar energy conversion and sensitive optical sensors, by using two-dimensional excitonic materials.