Thermal and Optical Properties of ${hbox {Yb}}^{3+}$- and ${hbox {Nd}}^{3+}$-Doped Phosphate Glasses Determined by Thermal Lens Technique

摘要

In this work, we study the thermal and optical properties of ion-doped phosphates glasses using the thermal lens (TL) technique. Three samples were characterized: ${hbox {Nd}}^{3+}$ -doped Q-98; ${hbox {Nd}}^{3+}$ -doped Q-100; and ${hbox {Yb}}^{3+}$ -doped QX. We report multiwavelength TL measurements for a more accuracy determination of the fluorescence quantum efficiency and temperature coefficient of the optical path length change ($ds/dT$ ). In Nd-doped glasses, it was carried out using four discrete excitation wavelengths (between 514 and 872 nm) chosen to match with the ion absorption lines. In Yb-doped glass, the spectrum of heat generated along the ${hbox {Yb}}^{3+}$ transition $(^{2}F_{5/2}rightarrow^{2}F_{7/2})$ was obtained. In addition, parameters as thermal diffusivity and conductivity, thermal loading, etc were achieved. The advantages to obtain fluorescence quantum efficiency using the TL technique, mainly in ${hbox {Yb}}^{3+}$ doped materials, which are normally overestimated due to radiation trapping effect, are presented. The accuracy knowledge of these parameters is very important for design of high-power solid-state lasers, since these properties are directly related to the heat generation.