Single-mode low threshold lasing at ∼2.1 μm in Ho3+/Yb3+ codoped fluorotellurite glass microspheres

In this work, we report a single-mode Ho ³ +/Yb ³ + codoped fluorotellurite (HYCF) microsphere laser at ∼2.1 μm with low threshold of 96.2 μW. Fluorotellurite glass microspheres exhibit a high Q -factor, reaching up to 10 ⁶ . Furthermore, we demonstrate the thermal tunability of the microsphere lasers, with a temperature sensitivity of 38 pm/℃ for the lasing wavelength. These research findings showcase highlight the potential of HYCF glass microsphere lasers as a miniature photonic element in the emerging field of compact IR lasers, low-threshold, as well as for high-precision temperature sensing applications.