OPTICAL WAVE-GUIDE SENSORS IN ANALYTICAL-CHEMISTRY - TODAYS INSTRUMENTATION, APPLICATIONS AND TRENDS FOR FUTURE-DEVELOPMENT

Current concepts for chemical and biochemical sensing based on detecti on with optical waveguides are reviewed. The goals are to provide a fr amework for classifying such sensors and to assist a designer in selec ting the most suitable detection techniques and waveguide arrangements . Sensor designs are categorized on the basis of the five parameters t hat completely describe a light wave: its amplitude, wavelength, phase , polarization state and time-dependent waveform. In the fabrication o f a successful sensor, the physical or chemical property of the determ ined species and the particular light wave parameter to detect it shou ld be selected with care since they jointly dictate the sensitivity, s tability, selectivity and accuracy of the eventual measurement. The pr inciple of operation, the nature or the detected optical signal, instr umental requirements for practical applications, and associated proble ms are analyzed for each category of sensors. Two sorts of sensors are considered: those based on direct spectroscopic detection of the anal yte, and those in which the analyte is determined indirectly through u se of an analyte-sensitive reagent. Key areas of recent study, useful practical applications, and trends in future development of optical wa veguide chemical and biochemical sensors are considered.