Measurements are reported on the optical absorption of Various samples
of monocrystalline sapphire from various manufacturers, at 1 mu m wav
elength. The lowest observed absorption coefficient was 3.1 ppm/cm com
parable to the best optical glass materials. The absorption coefficien
t showed variations within samples similar to 30% and was not correlat
ed with metal impurity concentration. (C) 1997 Elsevier Science B.V.