Laser properties of holmium and erbium in thorium-, zinc- and yttrium-based fluoride glass

Optical properties of Ho(III)- and Er(III)-doped thorium-, zinc- and yttrium-based fluoride glasses are determined. Due to the large number of luminescent levels, it is possible to determine the multiphonon relaxation rates even for energy gaps smaller than 1900 cm^-. Peak cross sections for laser action and threshold powers for infrared laser emissions are calculated and compared with literature data. It is shown that addition of other lanthanides significantly decreases the threshold power for laser action. The results indicate that a rare-earth-doped fluoride glass is a promising candidate for an integrated fiber optics system in which the rare earth laser is a part of the fiber.