Integrated Mach–Zehnder Interferometer Based on Liquid Crystal Evanescent Field Tuning

In this work, the performance of a Mach–Zehnder interferometer manufactured in silicon nitride with a liquid crystal cladding is studied. The device consists of two multi-mode interference couplers linked by two rectangular waveguides, the cladding of one of which is a liquid crystal. The structure demonstrates the potential of using liquid crystals as tunable cladding material in simple waveguides as well as in more complex coupling or modulating structures. Liquid crystal cladding permits a local fine-tuning of the effective refractive index of the waveguide, avoiding coarse global temperature control. The study is realized in the visible region (632.8 nm), for its intrinsic interest region in (bio-)sensing or metrology.