Spectroscopic investigation and laser behaviour of Yb-doped laser ceramics based on mixed crystalline structure (ScxY1-x)(2)O-3

We report on the spectroscopic and laser characterization of Yb-doped (ScxY1-x)(2)O-3 ceramics with different Y3+/ Sc3+ balance (x=0, 0.273, 0.508 and 0.742) and similar to 6 at.% Yb concentration, fabricated by solid-state vacuum sintering of laser-ablated mixed sesquioxide nanoparticles. The optical transmittances of 2-mm-thick samples with x=0, 0.273 and 0.508 were above 80% at a wavelength of 600 nm and 82% at 1100 nm which is very close to the theoretical limit. The lifetime of the F-2(5)/(3+)(2 Yb) energy level, absorption and emission cross sections result to be influenced by the Sc3+ content. In particular, the upper state lifetime decreased from 781 mu s to 614 mu s with an increase in Sc2O3 concentration from 0 mol.% to 74.2 mol.%. Moreover, the main emission peaks of Yb3+ near 1040 nm and 1080 nm shift toward longer wavelength with an increase in Sc3+ content and progressively broaden until Y3+/Sc3+ balance reaches-1. Concerning the laser tests, all samples showed good performance under quasi-CW laser diode end-pumping at 929 nm. For the mixed compositions, a maximum output power of 5.95 W with an optical-to-optical conversion efficiency of 58.8% was achieved in (Yb0.058Sc0.508Y0.434)(2)O-3 ceramics. Most interestingly, we measured an end-to-end tuning range of 117.7 nm for the sample (Yb0.062S-c(0.273)Y(0.665))(2)O-3, which is to the best of our knowledge the broadest tuning range found in literature for an Yb doped laser ceramics. This represents the first highly efficient laser operation of compositionally disordered Ybdoped (ScxY1-x)(2)O-3 ceramic matrices.