Photonic circuit design of adaptive two-wave mixing photorefractive interferometer

Two-wave mixing interferometry based on photorefractive crystals stands out among many techniques for monitoring dynamic strain because it can provide multiple dynamic sensing and does not require electronic feedback to actively compensate for any quasi-static drift. However, the traditional optical signal sensing processing system has shortcomings such as large, occupied space, various types of optical components, and complex optical path structure, which is not conducive to practical applications. Thanks to the development of photonic integrated circuits, photonic integrated can effectively solve these shortcomings. In this paper, based on the experimental study of two-wave mixing interferometry in InP:Fe spatial optics configuration, a photonic integrated two-wave mixing photorefractive interferometer is designed, which consists of curved waveguide, directional couple, unbalanced Mach-Zehnder interferometer structure, crossed waveguide, electrodes, etc. To minimize the loss of light in transmission and achieve the best demodulation performance for a two-wave mixing photorefractive interferometer, each structure is optimized by finite element method simulations. The feasibility of the optimized structure is verified in theory and the demodulation curve of transmitted signal light varying with time is obtained.