Abstract

Infrared-pumped upconversion lasing of praseodymium ions in a fluorozirconate glass fiber at room temperature has been observed in our laboratory at 491,520,605,635, and 715 nm. For all these transitions the initial state is the ³P₀ level at 21 000 cm^-1, populated by a two-step pumping process using Ti:sapphire lasers at diode compatible wavelengths; 1.01 μm and 835 nm. The observed threshold powers suggest that diode-pumped operation of these upconversion laser transitions should be readily achievable. Elsewhere the use of codoping to pump this system at a single wavelength has also been demonstrated. In waveguide geometry modest pump powers can achieve large transition rates, an important advantage in this system where the intermediate pump level has a lifetime limited by nonradiative decay to 100 μs. The 4-level 635-nm transition, which exhibited the highest gain, yielded a maximum output of 185 mW when pumped by a total of 2.7 W of infrared power. The efficiency of the pumping process was further demonstrated by operation on the quasi-3-level blue transition at 491 nm. Output powers of up to 40 mW have been achieved at this wavelength.

© 1991 Optical Society of America