Yb:Lu₂O₃ single-crystal fiber: spectroscopy, amplification, and lasing

For the first time, to our knowledge, a lutetium oxide (Lu₂O₃) single-crystal fiber (SCF) laser is demonstrated. The laser heated pedestal growth (LHPG) technique was used to pull Yb-doped Lu₂O₃ SCFs between 10 and 50 mm long and with diameters between 150 and 225 µm. Spectroscopic properties are first reported in detail, as the two-site nature of the host demands careful attention. Short 10 mm long, unclad fibers were used as amplifier media in a single pass copropagating configuration. Then, a 50 mm long 0.1%Yb:Lu₂O₃ SCF with a 180 µm diameter was configured to lase by butt-coupling mirrors on the ends and pumping at 976 nm. Lasing occurred at the 1033 nm peak of Yb, and a maximum output of around 300 mW is reported. The results indicate there is no, at least obvious, fundamental reason that should deter future interest in Lu₂O₃ as a SCF platform, which has been considered to have high potential for power scaling based on its beneficial intrinsic properties.