Fiber-optic chemical sensing with Langmuir-Blodgett overlay waveguides

Fiber-optic chemical sensing has been demonstrated with a side-polished sin gle-mode optical fiber, evanescently coupled to chemically sensitive Langmu ir-Blodgett (LB) overlay waveguides. The sensors exhibit a channel-dropping response centered on a wavelength that is dependent on the thickness and t he refractive index of the overlay waveguide. It has been shown that pH-sen sitive organic dyes proved to be suitable materials fur the formation of an overlay waveguide whereas LB deposition provides the required thickness co ntrol. A theoretical model of the sensor response, based on the Kramers-Kro nig relations and phase matching of the guided modes within the optical fib er and overlay waveguide, shows good agreement with experimental results. ( C) 1999 Optical Society of America OCIS codes: 060.0060, 060.2370.