Instrumentation for Cylindrical Waveguide Evanescent Fluorosensors

Abstract

This chapter contains a description of the physical principles of a cylindrical evanescent-wave fluorosensor and a discussion of some practical considerations for use of the sensor. Evanescent fluorosensors are based on the principle of total reflection fluorescence, first described by Hirschfeld (1), wherein fluorescence is excited by the evanescent wave on or near the boundary of a totally reflecting element, such as a prism or waveguide. Early investigators(2–4)used evanescent excitation, but collected fluorescent emission in free propagation. Block and Hirschfeld(5–7)first proposed evanescent excitation and evanescent collection (i.e., collection of the fluorescence that is tunneled back into trapped modes of the waveguide) using an optical fiber or rod as the sensing element. Subsequently, Sutherland et al. in 1984(4-8)at Battelle and Andrade et al. in 1985 (9)at the University of Utah described similar research approaches. The topic of evanescent-wave theory is reviewed by Harrick (10)(good introduction) and supplemented by Carniglia, Mandel, and Drexhage’s treatment(11)