Novelty filtering with a photorefractive lithium-niobate crystal

In this letter we present a technique which employs a photorefractive lithium-niobate crystal for novelty filtering. Due to the minimal trail formation exhibited by this novelty filter, it can be used for reliable quantitative phase measurement for time intervals of the order of a few hours. We present a simplified theoretical description of this filter based on a coupled wave theory [ N. V. Kukhtarev , V. B. Markov , S. G. Odulov , M. S. Soskin , and V. L. Vinetskii , Ferroelectrics 22 , 949 ( 1979 ) ; N. V. Kukhtarev , V. B. Markov , S. G. Odulov , M. S. Soskin , and V. L. Vinetskii , Ferroelectrics 22 , 961 ( 1979 ) ]. We also demonstrate the first experimental results of employing this device in the field of microfluid dynamics for measuring the concentration changes produced due to the mixing of two transparent liquids in a microchannel.