Analysis of Tungstates and Sesquioxides, Two of the Best Yb3+-Doped Laser Crystals According to Different Evaluations.

Abstract

ABSTRACTThe development of reliable InGaAs laser diode pump sources emitting in the 900-980 nm spectral range is stongly influencing the field of lasers based on Yb3+-doped solid state crystals. Ca5(PO4)3F (C-FAP) and S-FAP (Sr5(PO4)3F) were soon recognized to be favourable hosts for Yb3+ lasing in the nanosecond pulse regime. This fact was supported by an evaluation of the spectroscopic properties of several Yb3+-doped crystals useful for laser action. This evaluation is based on two parameters known from spectroscopy, the emission cross-section at the laser wavelength and the minimum pump intensity required to achieve transparency at the laser wavelength.We think there is a need of a new evaluation of Yb3+-doped crystals in order to predict the laser efficiency in a more realistic manner in different kinds of regimes. We present here the main spectroscopic properties of two Yb3+-doped laser crystals which are grown in our Group: (i) KY(WO4)2 double tungstates by the Floating Crystal method and (ii) Y2O3sesquioxides by the Laser Heated Pedestal Growth method. The approach, based on a quasi-three level laser model, leads to compare all known Yb3+-doped crystals in a two-dimensional diagram considering the laser extracted power and the slope efficiency. We shall show that tungstates and sesquioxides belong to the highest laser crystal potential in CW-end pumping configuration.