Improved surface quality of Nd:YAG monitored by second harmonic generation

In ongoing efforts to improve the surface quality of insulating materials, particularly when used for waveguide lasers, there has been significant progress in removing surface layer dislocations caused by cutting and polishing. However, the new surfaces, together with the subsurface material within a waveguide region, require quality assessment and characterisation by a non-destructive route. Surface generated second harmonic intensity measurements satisfy this requirement and data are reported for Nd:YAG samples. There are correlations between improvements in the second harmonic intensity and both the depth dependent cathodoluminescence signals and scanning electron microscope images of the surface. The wider implications of the second harmonic test procedure, and the technique used to achieve the improvements, are mentioned. (C) 1999 Elsevier Science B.V. All rights reserved.