Ultraviolet upconversion signals at 293, 351, and 366 nm were observed from thulium-doped fluorozirconate fiber pumped with a 458-nm Ar<sup>+</sup> laser. The upconversion signal's intensity was enhanced 5× when the fiber was simultaneously pumped with a 458-nm Ar<sup>+</sup> laser and a 585-nm dye laser. There is evidence of the formation of defect centers under simultaneous excitation by visible and near-infrared lasers (458 and 750 nm), and there is no evidence of color-center formation when both of the exciting beams are in the visible (458 and 585 nm).
© 2001 Optical Society of America
(060.2310) Fiber optics and optical communications : Fiber optics
(160.5690) Materials : Rare-earth-doped materials
(190.7220) Nonlinear optics : Upconversion
(300.6360) Spectroscopy : Spectroscopy, laser
Wenyan Tian and B. Rami Reddy, "Ultraviolet upconversion in thulium-doped fluorozirconate fiber observed under two-color excitation," Opt. Lett. 26, 1580-1582 (2001)