Energy level decay and excited state absorption processes in dysprosium-doped fluoride glass

Abstract

The primary excited state decay processes relating to the 6H13/2→6H15/2 3 m laser transition in singly Dy3+-doped fluoride ZBLAN glass have been investigated in detail using time-resolved f luorescence spectroscopy. Selective laser excitation of the 6F9/2, 6H7/2 energy levels at 1125 nm and 6F11/2, 6H9/2 energy levels at 1358 nm established that the energy levels above the 6H11/2 level, excluding the 4F9/2 level, are entirely quenched by multiphonon emission in ZBLAN glass. The 6H11/2 and 6H13/2 energy levels emit luminescence with peaks at 1700 and 2880 nm, respectively, but at low quantum luminescence efficiencies. The quantum efficiency of the 6H11/2 level and 6H13/2 level is 9 10−5 and 1.3 10−2, respectively, for Dy3+=0.5 mol % based on calculations of the radiative lifetimes using the Judd–Ofelt theory. Excited state absorption ESA was detected by monitoring the rise time of the 1700 nm luminescence after tuning the probe wavelength across the spectral range from 1100 to 1400 nm. As a result of nonradiative decay of the higher excited states, ESA contributes to the heating of 3 m fiber lasers based on Dy3+-doped f luoride glass. For Dy3+ up to 4 mol %, we found no evidence of energy transfer processes between Dy3+ ions that influence the decay characteristics of the 6H11/2 and 6H13/2 energy levels.