Refractive index sensor employing PVA-coated long period grating technology

Abstract

The sensitivity of a Long Period Grating (LPG)-based refractive index (RI) sensor has been enhanced through an appropriate coating of a thin polymer layer, with a higher RI than that of the cladding, on the LPG. The performance of the coated sensor, together with a bare LPG, was evaluated as a chemical sensor when the sodium chloride concentration in water varies from 0.01% to 2%. The corresponding attenuation band shifts of both sensors in response to the RI change were observed. The experimental results confirmed that the coated LPG sensor has higher sensitivity than that of the bare LPG sensor.