Upconversion lasing of a thulium-ion-doped fluorozirconate glass microsphere

Blue and red upconversion lasing of a Tm3+-doped fluorozirconate glass microsphere was demonstrated. Tens-of-micrometer-sized, genuinely spherical glass particles were produced by a melting method with a burner. The single microsphere was pumped by a focused beam of a Nd:YAG laser operating at 1064 nm. Three-photon-excited lasing emission could be observed in 480 and 800 nm regions at room temperature, and their lasing thresholds were determined to be 20 and 5 mW, respectively. Applications of the microspherical upconversion laser to near-field scanning optical microscopy are also discussed.