Spectroscopic and laser properties of Nd3+ doped fluoride crystals in 1.3-um region

For a number of neodymium doped fluoride crystals both with regular and disordered structure the Judd-Ofelt analysis of absorption spectra have been performed, and fluorescence and lasing spectra were studied in order to reveal the most promising materials for optical amplification in a 1.3 micrometers telecommunication window. The most suitable crystalline media investigated was found to be cubic disordered fluorides based on (50 - 70%) SrF2 - (50 - 30%) CaF2 solid solutions with Nd3+ optical centers having tetragonal local symmetry. These crystals have (1) low value of excited state absorption line strength, (2) high metastable level lifetime (1.2 - 1.3 ms), (3) high enough emission cross section for fluorescence (approximately 4 X 10-21 cm2), and (4) proper fluorescence peak at about 1310 nm wavelength and comparatively wide fluorescence band with about 20 nm FWHM.