Increase of the pumping range in rare-earth glass lasers

A germanate lasing glass doped with Bi(plus 3) and Eu(plus 3) ions was examined to observe increases in pumping efficiency. A stronger F to D and D to F transition was determined for germanate rather than silicate or phosphate glasses due to covalency effects, and ground levels were calculated. Bi-doped glass displayed peaks at 3250 and 2860 A, with shifts toward higher energies at higher temperatures. Laser-induced fluorescent band narrowing and time resolved spectroscopic techniques were employed to establish the spectral dependence of the radiative lifetime, the time evolution of the bandwidth, and the redshift of the 3P to 1S transition. A resonance was detected in the 3P to 1S transition of Bi and the 7F to 5D transition of Eu, which was concluded to be due to strong spin coupling. Both radiative and nonradiative energy transfer were present at a temperature of 4 K, and the diffusion process was found to be inefficient.