Quadrature frequency resolved spectroscopy (QFRS) of radiative transitions of Er3+ and Nd3+ ions in chalcogenide glasses (ChGs)

Abstract

Wideband quadrature frequency resolved spectroscopy (QFRS) of photoluminescence (PL) lifetime distributions from 2 ns to 160 s is shown to be very effective in elucidating the characteristic features of radiative transitions of Er3+ ions in GeGaSe and GeGaS chalcogenides glasses (ChGs). Undoped GeGaSe ChGs show triple-peak lifetime distributions of which two short-lifetimes are associated with singlet-triplet excitons and longest-lifetime, ∼20 s, with radiative tunnelling (RT) of distant-pairs (DPs). Er-doped GeGaSe and GeGaS ChGs exhibit a double-peak lifetime distribution, consisting of a peak at ∼3.3 and ∼5.3 ms, respectively, a characteristic of the Er3+ luminescence centre and another peak at ∼20 s, similar to that of undoped GeGaSe ChGs. It is shown that the QFRS can separate and analyse two mixed radiative transitions of Nd3+ ions, 4F3/2V4I15/2 and 4F5/2,2H9/2V4I15/2 in GaLaS ChGs. From the QFRS results we can experimentally extract the branching ratio βJ and lifetime τ ≈ 77 (μs for 4 lasing transitions 4F3/2→4IJ(J = 9/2, 11/2, 13/2, 15/2) of Nd3+ ions in GaLaS ChGs, in particular, the weakest transition 4F3/2→4I15/2.