Sensitized Ho3+ up-conversion luminescence in Nd3+-Yb3+-Ho3+ co-doped ZrF4-based glass

As previously reported, a selectively strong green emission due to the Ho3+: (F-5(4), S-5(2))-->I-5(8) transitions is observed in Nd3+-Ho3+ co-doped ZrF4-based fluoride glasses under 800 nm excitation. As an attempt to more enhance Ho3+ up-conversion luminescences in the Nd3+-Ho3+ co-doped ZrF4-based glasses, Yb3+ ions were added to the glasses. As a result it was found that, in 800 nm excitation of 60ZrF(4). 30BaF(2).(8-x)LaF3. 1NdF(3). xYbF(3). 1HoF(3) glasses (x=0 to 7), sensitized up-conversion luminescences are observed at around 490 nm (blue), 545 nm (green), and 650 nm (red), which correspond to the Ho3+: F-5(3)-->I-5(8), (F-5(4), S-5(2))-->I-5(8), and F-5(5)-->I-5(8) transitions, respectively. The intensities of the green and red emissions in a 3 mol % YbF3-containing glass were about 50 times stronger than those in no YbF3-containing glass. This is based on sensitization due to Yb3+ ions. In particular, the green emission is extremely strong so that the Nd3+-Yb3+ -Ho3+ co-doped ZrF4-based glasses have a high possibility of realizing a green up-conversion laser glass. Up-conversion processes for the blue, green, and red emissions were two-photon processes assisted by Nd3+-->Yb3+-->Ho3+ energy transfer. The up-conversion mechanism in the glasses is discussed. (C) 1999 American Institute of Physics. [S0021-8979(99)03714-7].