Surface Roughness (Surface Finish)

Surface roughness, or high frequency error, is a measure of smoothness, or the quality of the polish on an optic’s surface. Surface roughness can effect scatter and the ability to withstand high laser power on the surface. They are usually an unfortunate by-product of the polishing process. Rough surfaces tend to wear faster than smooth surfaces and may not be suitable for some applications, especially those with lasers or intense heat, due to possible nucleation sites that can appear in small cracks or imperfections. Manufacturing tolerances for surface finish range from 50Å RMS for typical quality, 20Å RMS for precision quality, and 5Å RMS for high quality.