Tm3+-doped fluorotellurite glass microsphere resonator laser at 2.3 µm

In this Letter, we report lasing at 2.3 µm in Tm 3 + -single-doped and Tm 3 + / Ho 3 + -codoped fluorotellurite glass microsphere resonators. By employing a 793 nm diode laser as a pump and exploiting whispering gallery mode microresonators (WGMRs), dual-wavelength lasing at 1.9 and 2.3 µm and triple-wavelength lasing at 1.9, 2.07, and 2.3 µm are achieved in Tm 3 + -doped and Tm 3 + / Ho 3 + -codoped microspheres, respectively. The introduction of Ho 3 + ions significantly reduces the lasing threshold of Tm 3 + at 2.3 µm because of energy transfer.