Role of Yb ³⁺ ions on enhanced ~2.9 μm emission from Ho ³⁺ ions in low phonon oxide glass system

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 Ho ³⁺ ions in Yb ³⁺/Ho ³⁺ co-doped oxide based tellurite glass system. This emission intensity has increased many folds upon Yb ³⁺: 985 nm excitation compared to direct Ho ³⁺ excitations due to efficient excited state resonant energy transfer through Yb ³⁺: ²F _5/2 → Ho ³⁺: ⁵I ₅ levels. The effective bandwidth (FWHM) and cross-section (σ _em) of measured emission at 2.9 μm are assessed to be 180 nm and 9.1 × 10 ⁻²¹ cm ² respectively which are comparable to other crystal/glass hosts and even better than ZBLAN fluoride glass host. Hence, this Ho ³⁺/Yb ³⁺ co-doped oxide glass system has immense potential for the development of solid state mid-infrared laser sources operating at 2.9 μm region.