Wide-Range Refractometric Sensor Using Differently Sensitive Y-Branched Waveguides

Abstract

A surface sensor rendering an extended detection range was proposed and demonstrated, taking advantage of a Y-branch structure. The sensing and reference waveguides, comprising the Y-branch structure, were overlaid with TiO2 films of different thicknesses; thus, they show unequal sensitivities. The phase change experienced by the two waveguides was in situ monitored through a birefringence analyzer. The interference number for the sensing waveguide was derived from the response of the reference waveguide. The implemented sensor was evaluated by varying the concentration of glucose solution, confirming that the proposed sensing scheme is useful for efficiently extending the detection range.