Abstract

GRIN-rod lenses currently have a variety of applications including imaging systems and microoptic lightwave components. Effective implementation of these lenses in such devices requires accurate evaluation of their optical properties. Transverse geometrical^1,2 and interferometric³ techniques have been reported for the determination of the refractive index profile of GRIN-rod lenses and fiber preforms. These methods may be useful for initial measurements of lens rods, however, it is unlikely that they would adequately determine the quality of finished lenses. A fundamental limitation of transverse methods is that rays used to test the lens must pass through the entire lens cross section. It has been reported⁴ and we have confirmed that the index distribution at large radii frequently has relatively large deviations from the desired distribution. For microoptic lightwave components, lenses are used at subaperture values so the index profile beyond a certain maximum radius is incidental. Therefore, it is likely that results from transverse techniques may be distorted by unused portions of the lens.

© 1981 Optical Society of America