Role of Yb3+ ions on enhanced ∼2.9 μm emission from Ho3+ ions in low phonon oxide glass system

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 mu m 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+:F-2(5/2) -> Ho3+:I-5(5) levels. The effective bandwidth (FWHM) and cross-section (sigma(em)) of measured emission at 2.9 mu m are assessed to be 180 nm and 9.1 x 10(-21) cm(2) 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 mu m region.