2  µm lasing from Tm³⁺-doped PbO-PbF₂-Bi₂O₃-Ga₂O₃ glass microspheres

Whispering gallery mode (WGM) lasers at ∼2µm are demonstrated in PbO-PbF₂-Bi₂O₃-Ga₂O₃ (PBG) heavy metal oxyfluoride glass microspheres. A 793 nm diode laser is used to pump the PBG microsphere and achieve single-mode and multimode WGM lasing. The fluorescence spectra of Tm³⁺-doped PBG glasses are measured under 793 nm diode laser pumping. The maximum absorption and emission cross sections of Tm³⁺:³F₄→³H₆ are calculated to be 8.23×10^-21 and 4.42×10^-20cm², respectively. The experimental results indicate that these PBG glass microspheres could become an important photonic component for infrared laser applications.