Single-mode Low Threshold Lasing at ∼2.1 μm in Ho3+/Yb3+ Codoped Fluorotellurite Glass Microspheres

In this work, we report a single-mode Ho³⁺/Yb³⁺ 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 10⁶. Furthermore, we demonstrate the thermal tunability of the microsphere lasers, with a temperature sensitivity of 38 pm/°C 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.