Spectroscopic properties of ytterbium, praseodymium-codoped fluorozirconate glass for laser emission at 3.6 μm

摘要

Excitation of the ~2F_(7/2) → ~2F _(5/2) transition of the Yb~(3+) ion in Yb~(3+), Pr ~(3+)-doped fluorozirconate glass at 974 nm results in efficient excitation of the ~1G)4 level of Pr~(3+) ion that in turn emits in the middle infrared at ～3.6 μm. The energy transfer (ET) process Yb~(3+)(~2F_(5/2)) → Pr ~(3+)(~1G)4) is assisted by fast excitation migration among the Yb~(3+) ions. An upconversion process involving ET from the ~2F_(5/2) level to the ~1G)4 excited state populates the ~3P_0 excited state that produces emission at 481, 521, 603, 636, and 717 nm. A study of the behavior of the fluorescence from the ~1G)4 level at 1325 nm and from the ~3P_0 level at 603 nm allowed the estimation of the ET rate constants for the processes involved after short-pulsed laser excitation at 974 nm. A rate-equation model was employed to evaluate the population inversion relating to the ~1G)4 → ~3F_4 transition of the Pr~(3+) ion at 3.6 μm under continuous wave pumping.