Excited state absorption spectroscopy of ZBLAN:Ho3+ glass—experiment and simulation

The excited state absorption (ESA) spectra of ZBLAN glass activated by trivalent holmium ions have been measured in a wide spectral range (550–1750 nm) and simulated using such theoretical tools as the Judd–Ofelt formalism and McCumber theory of stimulated emission. We also propose a systematic approach for prediction of various types of up-conversion mechanisms in a given type of material. Experimental results on ESA up-conversion processes in ZBLAN:Ho3+ under red and infrared laser excitation, which confirm theoretical analysis, are presented. The optical linewidths were studied using high resolution laser spectroscopy at low temperatures and the existence of different crystallographic sites for Ho3+ ions was revealed.