ANALYSIS OF THE DOUBLE EXPONENTIAL BEHAVIOR IN ALEXANDRITE FOR OPTICAL-TEMPERATURE SENSING APPLICATIONS

An analysis of the fluorescence decay behavior of alexandrite emission , al higher dopant concentrations, has been undertaken for optical sen sor application purposes. A double exponential decay behavior of the f luorescence emission has been observed, which differs from the single exponential behavior of alexandrite at lower concentrations of the act ive Cr3+ ion. Thr origin of the phenomenon has been investigated bath experimentally and theoretically and found to be produced by the joint contribution from the Cr3+ dopant In both the mirror, as well as in t he inversion sites of that ion. The two lifetimes resulting, each havi ng a different temperature dependence, both call be represented throug h the use of the configurational coordinate model which considers the effect of thermal quenching. The intensity ratio of these two aspects is seen to change regularly with tile temperature within the important region for sensing of 273-773 K, and thus provides an alternative mea ns to produce a calibrated fluorescence-based sensor. (C) 1997 America n Institute of Physics.