Abstract
The infrared to visible upconversion processes have been investigated for ${\mathrm{Nd}}^{3+}$-doped chalcohalide glasses with different halide modifiers by using steady-state and time-resolved laser spectroscopy. Two different upconversion mechanisms have been identified depending on the infrared excitation wavelength. When the excitation wavelength is resonant with the ${}^{4}{F}_{3/2}$ state, three main bands at 538, 600, and 675 nm are observed and attributed to emissions from the ${}^{4}{G}_{7/2}$ level. These upconverted emissions occur via energy-transfer upconversion involving two neodymium ions in the ${}^{4}{F}_{3/2}$ state. However, nonresonant excitation at higher energies than that of ${}^{4}{F}_{3/2}$ state (between states ${}^{4}{F}_{3/2}$ and ${}^{4}{F}_{5/2})$ or in resonance with the ${}^{4}{F}_{5/2}$ state, causes an additional blue emission to originate from the ${}^{2}{P}_{1/2}$ state. This latter upconverted emission can be attributed to excited-state absorption of the pump radiation. The proposed upconversion mechanisms responsible for the different emissions from levels ${}^{2}{P}_{1/2}$ and ${}^{4}{G}_{7/2}$ are supported by both the time evolution of the upconversion luminescence after infrared pulsed excitation and the upconversion luminescence excitation spectra.
Highlights
Neodymium has been recognized as one of the most efficient rare-earthREions for solid-state lasers in different hosts[1,2] due to its intense emission at 1.06 m
Infrared-to-visible upconversion in Nd3ϩ-doped chalcohalide glasses has been investigated under continuous-wave and pulsed-laser excitation for different halide modifiers
Similar upconverted emission spectra are found with different halideCl, Br, Imodifiers; glass modified with CsCl shows the highest intensity for the blue emission
Summary
Neodymium has been recognized as one of the most efficient rare-earthREions for solid-state lasers in different hosts[1,2] due to its intense emission at 1.06 m. The germanium-gallium-sulfideGGSglass system has been studied for its potential as a low phonon energy glass for lasers and fiber-optic amplifier applications.[21,22,23,24] Sulfide glasses, usually show a low-energy band gap that causes strong absorption of visible light, as in Ga-and Gebased glasses,[25,26] which can limit applications such as upconversion. This drawback is partly circumvented in Ge-
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