obtaining a substrate having an exterior above which the optical surface is to reside, the exterior including laterally spaced-apart asperities having peaks which are spaced <1000 nm apart and affect optical performance of the produced optical surface absent a smoothing of the exterior surface;

smoothing the exterior of the substrate using an atomic layer deposition process to sequentially deposit a first plurality of ALD layers to produce an ALD film that fills spaces between the laterally spaced-apart asperities existing on the exterior surface; and

depositing a reflective material on a surface of the ALD film to produce the optical surface, the smoothing resulting from depositing the ALD film on the exterior of the substrate causing the grain size of the reflective material to be reduced in comparison to the grain size that would otherwise exists without having deposited the ALD film on the exterior of the substrate, the reduction in grain size of the reflective material causing a reduction in plasmon absorption in the optical surface in comparison to the plasmon absorption that would otherwise occur in the optical surface without having reduced the grain size of the reflective material.