Laser-induced, Er3+ trace-sensitized red-to-blue photon-avalanche up-conversion in Tm3+:KY3F10

We report here the first results of a spectroscopic study of anti-Stokes emissions from a Tm3+-doped KY3F10 crystal demonstrating the sensitization effect of Er3+ ions, present as trace impurities, on the ESA (3F4 → 1G4) lines of Tm3+. We have also detected Ho3+ traces in Tm3+:KY3F10. Contrary to the Er3+ ion, the Ho3+ ion does not increase the possibilities of resonant transfer with the Tm3+ ion. The Tm3+ → Ho3+ → Tm3+ transfers are much less probable than the Tm3+ → Er3+ → Tm3+ transfers. The majority of the Tm3+ ions excited by sensitized photon-avalanche absorption are exclusively located in the immediate neighbourhood of Er3+ ions. Red-to-green up-conversion mechanism is, for Er3+ either a two-step absorption process or a photon-avalanche absorption process, depending on whether the excitation wavelength is tuned on the 4I13/2 → 4F5/2 or 3F4 → 1G4 transitions.