Infrared-to-visible upconversion of Er^3+ ions in GeO_2–PbO–Nb_2O_5 glasses

Abstract

We report the infrared-to-visible upconversion luminescence of Er 3ϩ -doped lead-niobium-germanate glasses (GeO 2 -PbO-Nb 2 O 5 ) with different Er 2 O 3 concentrations (0.5, 1, 2, and 3 wt.%) under continuous-wave and pulsed-laser excitation in the near-infrared region inside the 4 I 9/2 level. Intense green emission due to the ( 2 H 11/2 , 4 S 3/2 ) → 4 I 15/2 transitions was observed at room temperature together with a weak red emission corresponding to the 4 F 9/2 → 4 I 15/2 transition. These upconversion emissions are attributed to a two-photon process. The time evolution of the green emission from the 4 S 3/2 level indicates that energy-transfer upconversion and excited-state absorption are responsible for the upconversion luminescence. The increase of the weak red emission with increasing Er 2 O 3 concentration, together with its temporal behavior under infrared excitation, suggests that for Er 2 O 3 concentrations higher than 1 wt.%, the upconverted red emission is the result of multiphonon relaxation from the 4 S 3/2 level and energy-transfer processes.

Strong visible up-conversion emissions and thermometric applications of Er3+–Yb3+ codoped Al2O3 prepared by the sol–gel method

“…In the near-infrared spectral region, Er 3+ has a favorable energy level structure with 4 I 15/2 ? 4 I 11/2 transition, which can be easily excited when using a 978 nm semiconductor laser diodes (LD) as excitation source [4]. However, the relatively low absorption cross-section of about 1.7 9 10 -21 cm 2 made the ground state absorption (GSA) of Er 3+ at 978 nm very weak, leading to reduction of the emission intensity and pump efficiency.…”

Near-infrared to visible up-conversion emissions of Er3+ doped Al2O3 powders derived from the sol-gel method

“…In the near-infrared spectral region, Er 3+ has a favorable energy level structure with 4 I 15/2 → 4 I 11/2 transition which can be easily excited by using a 978 nm semiconductor LD as the excitation source. Now, there are also considerable increasing interests to the characteristics of up-conversion emission of the Er 3+ doped materials for their potential applications in the fields of color display, optical data storage, biomedical diagnostics and temperature sensors [3][4][5][6] . Developing the Er 3+ doped optical devices, the influence factors of matrix being doped must be preferably considered, such as the dispersion of Er 3+ , luminescence efficiency, decay time, chemical durability, thermal stability, and mechanical strength.…”

Spectroscopic excitation and quenching processes in rare-earth-ion-doped AI203 and their impact on amplifier and laser performance

“…By taking into account both, spectral overlap and phonon energy of the host material, we evaluate their efficiency. F 9/2 ), whose existence has previously been proposed [85,132], and quantify its macroscopic ETU coefficient. Because of the rather high phonon energies in oxide host materials, such as Al 2 O 3 , the lifetimes of higher-lying Er 3+ levels are quenched by multiphonon relaxation, thereby diminishing the influence of processes originating in those levels on practical device performance.…”

“…In a number of publications [47,85,132,[136][137][138], the presence of the additional upconversion process ( Fig. 2.4 of Chapter 2, was suggested.…”

“…However, in most cases its existence was only assumed (and not thoroughly investigated) or the presented proof was quantitatively not entirely convincing. To the best of our knowledge, only Balda et al [132] provide persuasive evidence with a quantitative analysis of luminescence decay curves from the 4 F 9/2 and 4 S 3/2 levels.…”