Integrated Optical Technique for Detection of Electro-Optical Non-Linearities in Thin Films

A simple method for detection of electro-optical non-linearities in thin films is presented. The method involves an easily fabricated structure and a little practice in integrated optical techniques. It is also possible to detect small induced variations of refractive index, using lower voltage with respect to those applied in a conventional Kerr cell. We have sucessfully tested our method using two different polymer materials as thin films. In both of these we have observed an induced Δn ≃ 3 10^-5 with an electric field of 60 V/μ, with a response time round about 300 nsec. The experimental values of induced Δn versus electric field fit very well a parabola, proving the quadratic behavior of Kerr effect.