THERMAL-CHARACTERISTICS OF ALEXANDRITE FLUORESCENCE DECAY AT HIGH-TEMPERATURES, INDUCED BY A VISIBLE LASER DIODE EMISSION

Resulting from an experimental study to develop a fiber-optic temperature sensor based on the fluorescence decay of Cr3+-doped crystalline alexandrite, a simple configurational coordinate model is proposed to describe the kinetics of alexandrite fluorescence over the temperature region from 20 to 700-degrees-C, to link experimental and theoretical work. This model fits well the experimental fluorescence lifetime data over the above region and successfully explains the observed phenomenon that a sharp reduction in the fluorescence lifetime occurs beyond approximately 400-degrees-C. The model was also used to study the temperature dependence of the intensity of the fluorescence emission induced by light from a visible laser diode, and as a result it is suggested that a phonon-assisted absorption is involved in a specific absorption process, where the energy of a single incident photon is below that of the primary absorption band 4T2.