Rare earth doped tellurite glasses and fibres for photonics

Tellurite glasses are promising host materials for fibre lasers emitting in the 2 micron wavelength region, thanks to the low phonon energy and high rare earth solubility of this glass system. In this paper novel heavily rare earth doped tellurite glasses are presented as candidates for fabricating short cavity single frequency mid-infrared optical fibre lasers. Glasses were prepared by melt quenching from mix powder batches, inside a glove box in a dry atmosphere with water content of about 7 ppm. Glass melting was carried out in Pt crucibles, then pouring on a preheated brass plate and annealing followed. Tm-doping allows emission at 1800 nm under excitation at 790 nm, Yb co-doping is explored in order to assess the possibility of efficiently pumping at 980 nm and emitting at 1800 nm through energy transfer from Yb to Tm. Ho co-doping is explored to extend emission wavelength up to 2 micron through energy transfer from Tm to Ho. Assessment of optimum glass composition for each rare earth system is carried out by means of optical and spectroscopic characterization of the prepared glasses. Refractive index measurements were carried out by means of prism coupling technique. The optical absorption spectra were measured for all prepared glasses in the wavelength range from 180 to 2300 nm by means of a UV-VIS-IR spectrophotometer (Fig. 1). Level lifetime values and fluorescence spectra of prepared glasses were measured using a spectrometer and laser diode as excitation sources.