Radial distribution of the refractive index in light-focusing rods: determination using Interphako interference microscopy

Abstract

An interferometric technique for the determination of the radial distribution of the refractive index in light-focusing plastic rods (LFR) has been developed using the shearing method of Interphako interference microscopy. We have derived mathematical expressions for the shape of interference fringes across the rod assuming the index distribution of LFR is described by n(r) = n₀(I − ar² + br⁴ + cr⁶ + dr⁸) in which a, b, c, and d are distribution constants. The dsitribution constants were determined using a least-squares technique on a computer from the actual shape of fringes. Results for the representative cases are shown.