PHOTON AVALANCHE UP-CONVERSION IN ER3+YALO3

The results of an investigation of photon avalanche upconversion pumpi ng in Er3+:YAlO3 are reported. Five pump wavelengths corresponding to transitions from the metastable I-4(13/2) state to the H-2(11/2) State generated upconversion laser emission at 549.8 nm. The dependence of the laser output power on pump power near laser threshold is discussed in terms of a four-level kinetics model and is shown to reflect the t hreshold power requirement for photon avalanche. The maximum output po wer at 7K was 33 mW, giving an optical conversion efficiency of 3.5% a nd a conversion efficiency of 28% based on absorbed power. Pumping Er: YALO by cross relaxation energy transfer produced 166 mW of laser outp ut with an optical conversion efficiency of 17%.