Tm-doped fluorotellurite glass microsphere resonator laser at 2.3 µm.

In this Letter, we report lasing at 2.3 µm in Tm-single-doped and Tm/Ho-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-doped and Tm/Ho-codoped microspheres, respectively. The introduction of Ho ions significantly reduces the lasing threshold of Tm at 2.3 µm because of energy transfer.