Fiber-optic chemical sensing has been demonstrated with a side-polished single-mode optical fiber, evanescently coupled to chemically sensitive Langmuir–Blodgett (LB) overlay waveguides. The sensors exhibit a channel-dropping response centered on a wavelength that is dependent on the thickness and the refractive index of the overlay waveguide. It has been shown that pH-sensitive organic dyes proved to be suitable materials for the formation of an overlay waveguide whereas LB deposition provides the required thickness control. A theoretical model of the sensor response, based on the Kramers–Kronig relations and phase matching of the guided modes within the optical fiber and overlay waveguide, shows good agreement with experimental results.
© 1999 Optical Society of America
Original Manuscript: March 3, 1999
Revised Manuscript: August 23, 1999
Published: December 20, 1999
Damien Flannery, Stephen W. James, Ralph P. Tatam, and Geoffery J. Ashwell, "Fiber-optic chemical sensing with Langmuir–Blodgett overlay waveguides," Appl. Opt. 38, 7370-7374 (1999)