Measurement of the optical properties of gradient index materials

Abstract

The measurement and manufacture of gradient index optical materials has been studied. The geometries of the samples are several centimeters in aperture and are applicable to high quality lens systems for the visible portion of the spectrum. The measurements of the index of refraction as a function of spatial coordinate are done using a new type of interferometer. The ac interferometer with its electronics provides an electrical signal which is proportional to the index of refraction at the point being measured. This system is ideally suited for interfacing to a computer. Measurements of the index of refraction profile have been been made on over 60 samples manufactured by Bausch & Lomb (Rochester, New York), Schott Optical (Duryea, Pennsylvania) and University of Rochester. Further, several samples have been measured at many wavelengths within the visible portion of the spectrum. The maximum slope of the gradient is 10% steeper in the blue than in the red. The effects of time and temperature of ion diffusion have been studied. Numerous gradient index materials have been made by Bausch & Lomb. The samples have been used to characterize the ion exchange of silver into soda-rich crown glass. A series of diffusions were performed to detemine the effect of time (13 to 100 h) and temperature (450 to 650° C) on the index change and the index of refraction profile. A gradient index glass map is presented.