Qualification of supermirrors for ring-laser-gyros based on surface roughness and scatter measurements

We report on experiments performed to investigate the quality of supermirrors for ring-laser-gyroscopes. The principle measurement techniques employ an interferometric profilometer to probe surface roughness and a laser scatter meter to measure total scatter loss of supermirror coatings. Measured scatter losses are compared with those expected, given typical roughness measurements both of pre-coated substrates as well as the coated mirrors. The measurements offer insight into the general usefulness of profilometer data for the efficient qualification of substrates before cleaning and coating procedures.