Infrared-laser induced photon avalanche upconversion in Ho3+-Yb3+ codoped fluoroindate glasses

An intense green upconversion emission due to a photon avalanche mechanism has been observed in Ho3+-Yb3+ codoped fluroindate glasses, measured at 200 K, under excitation at around 750 nm. The influence of the Yb3+ concentration on the photon avalanche process has been studied. The pump power threshold of the avalanche mechanism decreases as the Yb3+ concentration is increased. A reduction by about a factor of 3 is observed from the 2.25 mol % Ho3+ single doped glass to the 2.25 mol % Ho3+-2.25 mol % Yb3+ codoped glass. This effect has been related to an extra feeding of the I-5(7) intermediate level of Ho3+ ions via Ho3+-->Yb3+ and Yb3+-->Ho3+ energy transfer and back transfer processes, respectively. (C) 2004 American Institute of Physics.