Characterization of a Ho3+-doped fluoride fiber laser with a 3.9-mu m emission wavelength

The fluoride fiber laser with the longest emission wavelength, the Ho3+-transition at 3.9 mu m in the attenuation minimum of the 3-5-mu m atmospheric window, is characterized. After reviewing the importance of fluoride fibers due to their low phonon energies, we describe room-temperature fluorescence and laser action with Liquid-nitrogen cooling. Continuous-wave laser action at 3.9 mu m is presented for the 640- and the 890-nm pump ranges. A shift of the emission wavelength is achieved by varying the resonator mirrors. Laser characteristics and temperature dependence are discussed. (C) 1997 Optical Society of America.