Abstract
The foremost limitation of an oxide based crystal or glass host to demonstrate mid- infrared emissions is its high phonon energy. It is very difficult to obtain radiative mid-infrared emissions from these hosts which normally relax non-radiatively between closely spaced energy levels of dopant rare earth ions. In this study, an intense mid-infrared emission around 2.9 μm has been perceived from Ho3+ ions in Yb3+/Ho3+ co-doped oxide based tellurite glass system. This emission intensity has increased many folds upon Yb3+: 985 nm excitation compared to direct Ho3+ excitations due to efficient excited state resonant energy transfer through Yb3+: 2F5/2 → Ho3+: 5I5 levels. The effective bandwidth (FWHM) and cross-section (σem) of measured emission at 2.9 μm are assessed to be 180 nm and 9.1 × 10−21 cm2 respectively which are comparable to other crystal/glass hosts and even better than ZBLAN fluoride glass host. Hence, this Ho3+/Yb3+ co-doped oxide glass system has immense potential for the development of solid state mid-infrared laser sources operating at 2.9 μm region.
Highlights
Emission from Ho3+/Yb3+ ions co-doped Tellurium-Barium-Lanthanum oxide glass system having low phonon energy
There is a clear dependence of excitation wavelength on emission intensity where an ~8 fold enhancement in ~2 μm emission has been demonstrated under Yb3+ (985 nm)excitation compared to direct Ho3+ ion excitations
The experimental emission data suggests, this emission transition is only possible with second photon absorption from 5I7 to 5F5 state through Excited State Absorption (ESA) process
Summary
Emission from Ho3+/Yb3+ ions co-doped Tellurium-Barium-Lanthanum oxide glass system having low phonon energy. Visible up-conversion emissions from Ho3+ ions on account of bi-photonic absorption by Yb3+ ions under 980 nm excitation in the same host has been reported[19]. The present work mainly aims to investigate the MIR emission transitions from Ho3+ ions by considering the extended IR transparency (upto ~6 μm) and low phonon energy (Fig. 1 of Supplementary data) of this oxide based glass system. The dependence of emission transition strengths on pump wavelengths, role of Yb3+ co-doping on the enhancement of Ho3+ mid-infrared emissions and the possible energy transfer mechanisms were discussed in detail and reported here
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