Different dominant transitions in holmium and ytterbium codoped oxyfluoride glass and glass ceramics originating from varying phonon energy environments

Abstract

Transparent oxyfluoride glass and glass ceramics doped with 0.5% Ho and 1.0% Yb ions have been prepared. X-ray diffraction and transmission electron microscopy demonstrated the formation of NaYF nanocrystals during the heat treatment process. Raman spectra indicated the variation of glass structure brought about by the formation of NaYF nanocrystals. XRD curves and Judd-Ofelt intensity parameters confirmed the incorporation of Ho into NaYF nanocrystals. Significantly enhanced visible upconversion and 2.85 μm emissions were achieved in glass ceramic under 980 nm laser diode pumping. A broadband spectrum with a full-width at half-maximum close to 132 nm was obtained in the glass ceramic. Besides, the calculated peak emission cross section was 0.6 × 10 cm, suggesting that the glass ceramic is a promising gain material that can be applied to broadband amplifiers in the mid-infrared region. Furthermore, energy transfer mechanisms in glass and glass ceramics were proposed based on visible to mid-infrared emission spectra. It was found that the change in the photon energy environment around rare earth ions induced different dominant transitions in glass and glass ceramic. Finally, the influence of phonon energy on the transition processes was further quantitatively investigated, which may provide useful guidance for obtaining highly efficient 2.85 μm emission of holmium.

Structural evolution, crystallization behaviour and mid-infrared emission properties in Yb/Ho codoped oxyfluoride germanosilicate glass ceramics with varied Si/Ge ratio

“…The calculation results showed that the peak absorption cross section reached 9.93×10 -21 cm 2 at 2880 nm, while the peak emission cross section reached 11.18×10 -21 cm 2 at 2888 nm which is higher than that of oxyfluoride silicate GC(6.0×10 -21 cm 2 ) 4 . Obviously, it can be attributed to the higher density of oxyfluoride germanosilicate GC, as there is a positive correlation between density and absorption and emission cross sections.…”

“…For SiO 2 -rich glass and glass ceramics, the upconversion emissions and NIR emission are both enhanced with the heat-treatment temperature. This is because more rare earth ions located at fluoride nanocrystals with low phonon energy, in which the multi-phonon assisted non-radiative decay rates is significantly reduced so that the radiative emission is enhanced 4,22,23 . For GeO 2 -rich glass and glass ceramics, the upconversion emission and NIR emission of glass ceramics are stronger than those of the precursor glass, but not shown a positive correlation with the heat-treatment temperature because there is no similar fluoride nanocrystallization.…”

“…Mid-infrared laser has been gaining momentum in the recent years due to their appeal and potential applications in eye-safe laser radar, laser surgery, remote sensing and pump source for far-infrared lasers 1-3 . Among various rare earth ions (REs), Ho 3+ is an important active ion to achieve 2μm and 3μm emission by its 5 I 7 → 5 I 8 and 5 I 6 → 5 I 7 transitions, respectively 4 . Codoping proper sensitized ions is the most efficient way to address the problem that Ho 3+ has no suitable pump bands overlap with commercially available laser diode.…”

“…However, when introducing fluoride into them, there are obvious differences between oxyfluoride silicate glass and oxyfluoride germanate glass in crystallization behaviour and luminescent properties. For instance, NaLnF 4 NCs with low phonon energy are readily precipitated in oxyfluoride silicate glasses 4,18 , but there is not yet any report on oxyfluoride germanate glass ceramic containing NaLnF 4 NCs. It is significant to understand why varied crystallization behaviour occur in these two conventional and important glasses, and investigation on a series of glasses changing with the content of SiO 2 and GeO 2 may help reveal the potential reasons.…”

Multiligand Europium Complexes Incorporated Polyvinylpyrrolidone for Enhanced Solar Cell

“…Stimulated emission cross section σ em is one of the most basic physical quantities to evaluate the energy extraction e ciency from rare-earth doped optical materials, not only for a fundamental understanding of the excitation and depopulation process but also for the optimization of laser materials, which is determined through the Fuchtbauer-Ladenburg equation [60]:…”