Spectroscopy of upper energy levels in an Er^3+-doped amorphous oxide

Abstract

A spectroscopic study of the population mechanisms in erbium-doped amorphous aluminum oxide up to the 2 H 112 4 S 32 levels is performed. Via luminescence decay measurements, absorption and emission spectra, and a Judd-Ofelt analysis, we determine luminescence lifetimes, radiative and nonradiative decay-rate constants, and branching ratios of the Er 3 intermanifold transitions. With a continuous-wave pump-probe technique, the excited-state absorption (ESA) spectrum is recorded between 900 and 1800 nm and the cross sections of the ESA transitions 4 I 132 4 I 92 , 4 I 132 4 F 92 , and 4 I 112 4 F 72 are determined. The microparameters and efficiencies of resonant and phonon-assisted energy-migration and energy-transfer upconversion (ETU) processes among Er 3 ions occurring from the first and second excited states are evaluated. From the ratio of the 4 S 32 and 4 F 92 luminescence intensities as a function of Er 3 concentration, we prove the existence and quantify the macroscopic ETU coefficient of the two-phonon-assisted ETU process 4 I 132 ; 4 I 112 4 I 152 ; 4 F 92 .