Refractive index sensing in aqueous environment using three different polymeric waveguide interferometers

In this work, the performances of three developed polymer integrated optical sensors based on different waveguide configurations were evaluated for homogeneous refractive index (RI) sensing in aqueous environment. Young interferometer configuration with reference and sensing waveguide arms was utilized in sensor chips. Light from a laser source was end-fire coupled into the chips and interference pattern produced by the out coupled light was investigated. External fluidic pump was used to produce the analyte flow. The homogeneous bulk refractive index change was characterized by applying DI-water with varying glucose concentrations. With an interaction length of 1 cm a detection limit in the order of 10-5 ~ sub-10-6 refractive index unit (RIU) was determined. The sensing performances are compared among the sensors in terms of sensitivity, stability, multiparameter sensing ability, and fabrication and operation simplicity. The polymeric-inorganic composited rib waveguide configuration showed the highest performance and relatively simple fabrication process amongst the evaluated sensors.