Transition intensities and excited state relaxation dynamics of Dy3+ in crystals and glasses: A comparative study

A comparative spectroscopic investigation of dysprosium-doped YAl3(BO3)4, LiNbO3 single crystals, fluorosilicate glass and fluorogermanate glass was performed with special attention directed to laser potential associated with the 4F9/2 → 6H13/2 transition of Dy3+ near 570 nm in the visible. Optical absorption spectra were acquired and analysed in the framework of the Judd–Ofelt theory. Values of radiative transition rates and luminescence branching ratios calculated using phenomenological intensity parameters Ωt were compared to corresponding experimental values derived from measurement of luminescence decay curves and luminescence spectra. Importance of the self-quenching of the 4F9/2 emission was assessed for the systems under study based on results of lifetime measurement with samples containing different Dy3+ concentrations. Feasibility of the visible laser operation was considered taking into account availability of bands accessible for optical pumping, the 4F9/2 quantum efficiency and emission cross-section for the potential 4F9/2 → 6H13/2 transition. It was concluded that among considered systems the Dy:YAl3(BO3)4 is the most promising material for the visible laser operation. It shows advantageously low matrix absorption in the optical pump region between 400 and 340 nm. The 4F9/2 quantum efficiency is close to unity for a low Dy3+ concentration and it is weakly affected by the self-quenching effect at increased concentration. The 4F9/2 → 6H13/2 emission consists of narrow lines with high peak emission cross-section with maximum value of 1.9 × 10−20 cm2 at 575.5 nm for π-polarisation.