Integrated optical refractometer based on waveguide bend loss

This paper reports on a refractometer, which is based on measuring the throughput of a bent channel waveguide. A new type of channel waveguide, designed in SiON technology makes the throughput strongly dependent on the refractive index of a measurand fluid. This new waveguide can be designed for any measurand refractive index range between 1.00<n<2.00. In addition, monomode input and multimode output waveguides matching the sensor waveguide were designed which significantly simplify the fabrication process by eliminating the occurrence of critical alignment steps during the processing. Preliminary measurements on the device show a high sensing resolution of Δn=1×10^-5 in an aqueous solution with a refractive index of n=1.37. The sensor characteristics, make this simple sensor very interesting for controlling a chemical concentration during chemical processes, e.g., in the food and beverages industry