Fluorescence lifetime and 980nm pump energy transfer dynamics in erbium and ytterbium co-doped phosphate laser glasses
Solid State Lasers XII
Phosphate glasses are attractive laser oscillator/amplifier materials because unlike fluoride, silicate, and other laser glass materials they combine such useful properties as good chemical durability, ionexchangeability, high gain, low concentration quenching, and low upconversion losses. Phosphate glasses also exhibit a very high solubility for rare earth ions. This feature permits the introduction of large concentrations of active ions into relatively small volumes resulting in smaller laser
... ng in smaller laser devices with highenergy storage capabilities. These high dopant concentrations also result in very rapid and efficient energy transfer between rare earth ions. This allows for the effective use of Yb 3+ as a sensitizer for the Er 3+ laser ion. Effective Er:Yb:Glass pumping, energy storage, and energy extraction involves the population of the 2 F 5/2 level of Yb 3+ (~2ms fluorescence lifetime); a moderately rapid and efficient nonradiative transfer of energy to the 4 I 11/2 level of Er 3+ (about 500 µsec transfer time); and a very rapid (< 1µsec) nonradiative decay of the Er 3+ from the 4 I 11/2 to the metastable 4 I 13/2 state (with an 8ms fluorescence lifetime). In this study we measured the fluorescence lifetime for the 4 I 13/2 level of Er +3 on different glass samples with various concentrations of erbium. The data indicate that for doping levels up to 7 wt.% Er 2 O 3 the lifetime remains above 7.0 ms. Theoretically, this highly doped glass could produce over 18 dB gain in a 1cm path length. In additional fluorescence lifetime testing, ytterbium doped and erbium/ytterbium co-doped glasses were evaluated for concentration quenching and energy transfer rate as a function of the Er 3+ concentration. The effect on the energy transfer efficiency and laser efficiency was analyzed.