Diode-pumped solid-state lasers emitting in the near-IR provide an attractive range of applications such as optical-frequency stabilization, pumping of indium gallium arsenide laser diodes, and molecular spectroscopy of chemical compounds including water, carbon dioxide, and nitrogen dioxide. Researchers at Politecnico di Milano (Milan, Italy) and Università di Pisa (Pisa, Italy) reported the results of an experiment using various concentrations of thulium (Tm) doping of lithium lutetium fluoride (LiLuF4) crystal to achieve efficient laser action spanning the near-IR from 1.82 to 2.06 µm.
Principal author Nicola Coluccelli and the team found the best performance resulted from a Tm-doped concentration of 12% (1.72 × 1021 ions/cm3), which bested 8% and 16% doping values. When paired with 1% output coupling, the 12% Tm:LiLuF produced an output power of 1.05 W and achieved a 230 nm tuning range from 1826 to 2056 nm. While other fluoride hosts such as barium yttrium fluoride have achieved tuning ranges of up to 245 nm, Tm:LiLuF offers larger emission cross sections, lower phonon-cutoff energy, and more-congruent crystal growth. The slope efficiency of 46% is the highest value ever obtained with diode-pumped Tm-doped fluoride crystals. Contact Nicola Coluccelli at [email protected].