Antiresonant ring interferometry as a sensitive technique for measuring nonlinear optical properties of thin films

There is a critical need for a simple technique for the accurate measurement of weak optical nonlinearities such as the nonlinear coefficients of thin films. We discuss the experimental set-up and provide a realistic analysis for a sensitive and single beam technique based on an antiresonant ring interferometer for measuring nonlinear optical coefficients in thin films. The technique was benchmarked using toluene and its superiority was demonstrated by measuring the effective nonlinear absorption coefficient of a 1.3 mum thick CdS film, which could not be detected using standard techniques such as z-scan. We show that this technique can, in principle, be used for films with thickness down to the nanometer regime. (C) 2004 Elsevier B.V. All rights reserved.