Abstract

The unique features of fiber lasers have stimulated interest in this new class of lasers. Rare-earth-doped fluorozirconate fibers are often superior to their silica-based counterparts owing to their multiphonon spectrum. This permits radiative transitions from levels that suffer nonradiative de-excitation in silica glasses. The potential number of lasingwave-lengths in fluoride glasses is thus large. This topic is still being studied, and many fundamental phenomena remain to be clarified. Major advances in the field have been recently published: new lasing wavelengths in erbium, holmium, thulium, neodymium, samarium, and praseodymium; Q-switched operation; diode-laser pumping; and cw-tunable operation. The upconversion laser is one of the most promising devices, and it has already been demonstrated with thulium at 480 nm and with holmium at 550 nm, for which a slope efficiency of 36% and an extracted power of more than 10 mW have been obtained at room temperature.

© 1990 Optical Society of America