A Tm3+-doped ZrF4-BaF2-YF3-AlF3 glass microsphere laser in the 2.0 μm wavelength region

This work reports a microsphere laser at ∼2.0 μm in a Tm³⁺-doped ZrF₄-BaF₂-YF₃-AlF₃ (ZBYA) fluoride glass. The ZBYA glass microsphere was fabricated by reflowing the tip of a 1.0 mol% Tm³⁺-doped ZBYA glass fiber with a CO₂ laser. By using a fiber taper for input and output coupling in the Tm³⁺-doped ZBYA microsphere, single and multi-mode laser outputs at around 2.0 μm were observed under 808 nm laser excitation. The radiation lifetime and emission cross-section of Tm³⁺ ions in ZBYA glass were calculated to be 6.42 ms and 5.86 × 10⁻²¹ cm², respectively. Our results indicate that the Tm³⁺-doped ZBYA fluoride glass has potential applications for 2.0 μm lasers.