<title>Integrated optic chemical sensor for environmental monitoring</title>

Abstract

An integrated optic chemical sensor has been developed to monitor benzene, toluene, ethylbenzene and xylene (BTEX) in water. The sensor uses planar waveguide interferometry, where the evanescent field associated with a guided wave probes the refractive index changes immediately above the waveguide surface. Currently, up to thirteen interferometers are fabricated on a 1 X 2 cm glass chip. One arm of each interferometer is coated with a chemically interactive film, and the other arm is buried under an inert layer of silicon dioxide (SiO₂). The interference pattern formed by combining the guided waves from the two arms is read by a linear photodiode array, and onboard electronics convert the raw optical intensities into analyte concentrations. The sensor is packaged in a 1.5 inch diameter, 18 inch long stainless steel housing suitable for use in monitoring wells of with cone penetrometers. It is plug-and-play compatible with E-SMART^TM monitoring networks.