FLUORESCENCE DYNAMICS IN TM,HO-YLF FOLLOWING 800 NM PULSED-LASER EXCITATION

We have performed spectroscopic studies that examined the time evoluti on of the fluorescence at wavelengths between 400 and 2500 nm, emitted from an optically excited Tm,Ho:YLF crystal in response to pulsed las er excitation at 780 nm. The fluorescence intensity decay patterns hav e been analyzed in terms of their time and amplitude characteristics, paying attention to the dependence of these characteristics on excitat ion laser fluence. With the aid of a simplified model for numerical si mulations, we have been able to quantify and evaluate the effects of a number of processes whose relative importance varies with excitation fluence, such as upconversion losses and ground-state depletion.