Ellipsometric analysis of refractive index profiles produced by ion implantation in silica glass

An experimental method for measuring directly refractive index profiles, produced by ion implantation, is described. This uses surface-stripping techniques to enable a series of ellipsometric measurements to be made through the altered surface layer. The data are translated into a complex refractive index profile using a FORTRAN IV computer program. Sensitivities and error limits are discussed and results obtained for 300 keV Ar implant in vitreous silica are presented to demonstrate the capabilities of the technique. The technique is compared with other published work, where either profiling techniques or homogeneous layer approximations have been used, to show that the method described has advantages in determining the relative contributions of radiation damage and implanted species to the refractive index modification.