Smoothing surface roughness using atomic layer deposition

A method of producing an optical surface, the method comprising:

• obtaining a substrate having an exterior above which the optical surface is to reside, the exterior including laterally spaced-apart asperities;
• 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;
• a first step of determining the power spectral density of a surface topography of the exterior of the substrate that includes the ALD film surface as a function of spatial frequency after the smoothing of the exterior of the substrate using the atomic layer deposition process;
• a second step comparing the power spectral density determined in the first step to a predetermined target power spectral density at one or more of the spatial frequencies, the predetermined target power spectral density at one or more spatial frequencies corresponding to a target roughness of the exterior of the substrate that includes the ALD film surface;
• and
• only upon a determining that the exterior of the substrate that includes the ALD film surface has a roughness equal to or less than the target roughness, depositing a reflective material on the smoothed exterior of the substrate that includes the ALD film surface to produce the optical surface.

A method of producing an optical surface, the method comprising:

• obtaining a substrate having an exterior on 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;
• processing the exterior of the substrate using an atomic layer deposition process to sequentially deposit a first plurality of ALD layers to produce a first ALD film that fills spaces between the laterally spaced-apart asperities existing on the exterior surface;
• depositing one or more layers of a metal onto a surface of the first ALD film using a physical vapor deposition process to form a metal film over the surface of the first ALD film;
• smoothing a surface of the metal film using an atomic layer deposition process to sequentially deposit a second plurality of ALD layers to produce a second ALD film over the metal film;
• and
• depositing a reflective material on a surface of the second ALD film to produce the optical surface.