An Experimental and Theoretical Investigation of a 2 μm Wavelength Low-Threshold Microsphere Laser

We present our results on an experimental and theoretical investigation into a glass microsphere laser emitting at 2 μm wavelength. First, we fabricated Ho
³⁺
-doped tellurite glass fiber and measured the absorption and emission spectra, and the fluorescence lifetime. Using this fiber, a tellurite glass microsphere with a Q-factor of 2 × 10
⁶
was also prepared, and a single-mode laser output with a low threshold of 342 μW was observed using a 1150 nm laser as the pump source. The dynamic characteristics of the microsphere laser were studied theoretically by considering rare-earth ion spectroscopy, the rate equation of the rare-earth energy level, and the light-matter interactions in the microsphere. This work can be used to study laser emissions with low thresholds in rare-earth doped compound glass microresonators for a wide range of applications, such as gas sensing, integrated photonics, and medical surgery.