Embodiments described herein relate to flat optical devices with a coating layer including monolayers selected from the group consisting of molybdenum disulfide (MoS2), tungsten disulfide (WS2), tungsten diselenide (WSe2), molybdenum diselenide (MoSe2), molybdenum ditelluride (MoTe2), titanium disulfide (TlS2), zirconium disulfide (ZrS2), zirconium diselenide (ZrSe2), hafnium disulfide (HfS2), platinum disulfide (PtS2), tin disulfide (SnS2), or combinations thereof. The coating layer is disposed over a plurality of optical device structures of the optical device. The monolayers may alternate between the materials to form the coating layer or may be a uniform coating layer of a single material. The coating layer is disposed over each optical device structure of the plurality of optical device structures.