Refractive Index Distribution of Graded Index Poly(methyl methacrylate) Preform Made by Interfacial-Gel Polymerization

Abstract

A graded index poly(methyl methacrylate) (PMMA) preform has been made by a novel interfacial-gel polymerization procedure, in which polymerization was performed in a PMMA tube and a dopant, bromobenzene (BB), was used as a higher refractive index molecule. A detailed mechanism of the graded index formation is given and simulated according to the free volume theory and its application in a high-conversion polymerization system. Under the assumption that polymer concentration distributes in the form of ω = a exp(r) + b at the radial direction of the tube, a quadratic distribution of refractive index on the cross section of the preform is obtained. The result is identical with experiments performed by the interfacial-gel polymerization.