Self-Q-switched and widely tunable continuous-wave operation of a Tm³⁺:Lu₂O₃ ceramic laser near 2 μm

We report, for the first time to our knowledge, self-Q-switched (SQS) operation of a Tm³⁺:Lu₂O₃ ceramic laser near 2 μm based on the ³F₄→³H₆ optical transition. By careful optimization of cavity focusing, SQS operation could be achieved at several curved mirror separations without any external modulator and the laser delivered 9.7-μs pulses at the wavelength of 2091 nm with a pulse repetition rate of 26 kHz. In the experiments, a tight-focusing resonator design was further employed to achieve low-threshold continuous-wave (CW) operation of the laser with lasing threshold pump powers as low as 33 mW. With an incident pump power of 590 mW at 776 nm, a maximum output power of 164 mW was obtained at 2097 nm with a slope efficiency of 30% with respect to the incident pump power. The tuning range of the CW Tm³⁺:Lu₂O₃ ceramic laser could be extended up to the wavelength of 2235 nm.