Blue continuously pumped upconversion lasing in Tm:YLiF₄

Blue upconversion laser operation in Tm at 450.2 nm on the 1D2→3F4 transition, and at 483.0 nm on the 1G4→3H6 transition has been achieved using cw pumping with Ti Sapphire and DCM dye lasers. The 450.2-nm laser was excited by sequential two-photon absorption with 784.5-nm and 648-nm laser sources and was operated at temperatures up to 70 K. The 483.0-nm laser was pumped with a single red-dye laser using a wavelength resonant only with absorption from a metastable intermediate state but not with absorption from the ground state. With this avalanche absorption pumping scheme, 483.0-nm laser emission was observed up to 160 K.