Optical absorption and emission characteristics of Pr3+-doped RTP glasses

Judd–Ofelt (J–O) parameters are calculated for Pr3+ions doped alkaline earth potassium titanium phosphate (RTP, where R=Mg, Ca, Sr) glasses. The best fit for the oscillator strengths has been obtained by omitting the 3H4→3P2 hypersensitive transition. In all the three glasses, the J–O parameters follow the same trend as Ω2<Ω4>Ω6. These J–O intensity parameters are then used to compute the radiative properties such as the radiative transition probabilities (AR), branching ratios (βR) and radiative lifetimes (τR) for the observed fluorescence bands. The fluorescence spectra obtained upon 445 nm excitation exhibited an intense emission band centered at 484 nm (3P0→3H4), four medium intense bands at 525 nm (3P1→3H5), 598 nm (1D2→3H4), 608 nm (3P0→3H6) and 641 nm (3P0→3F2) and one weak band at 669 nm (3P1→3F3). The experimental branching ratios (βexp) obtained from steady state fluorescence are compared with the calculated values. The decay curves measured from the 3P0 excited metastable state are found to be single exponential in all the glasses. The gain bandwidths (σe×ΔλP) and optical gain (σe×τm) parameters suggest that the RTP glasses could be used for laser active materials to emit intense blue emission at 484 nm.