Photon avalanche up-conversion in Ho3+ doped fluoride glasses

Photon avalanche-induced up-conversion green emission centered at 545 nm was observed in Ho3+ doped, and Ho3+, Tm3+ co-doped ZrF4-based heavy metal fluoride glasses, when excited near 585 nm, which is off resonance with any ground state absorption bands of either Ho3+ or Tm3+ ions. Analyses of spectral measurements suggest that the 545 nm emission occurs from the 5S2 and 5F4 states of Ho3+ that are populated by excited-state absorption from the 5I7 state of Ho3+. Multi-channel cross-relaxation processes that efficiently populate the 5I7 state make the photon avalanche process efficient in this system. The photon avalanche dynamics are discussed in detail by comparing the experimental results from the Ho3+ doped and Ho3+, Tm3+ co-doped samples. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)