Low threshold, high-power Tm/Ho co-doped double-clad single-mode silica fiber operation at 2.08 μm

The 2.0 μm fiber laser remains a key research focus in medical applications. Here, a Tm/Ho co-doped double-clad single-mode silica fiber was prepared using the chelate-assisted modified chemical vapor deposition (MCVD) method, whose cladding absorption was 2.36 dB/m@793 nm, and the saturated gain coefficient was up to 8.0 dB/m under 793 nm pumping. The fluorescence lifetime of the 1900 nm emission of Tm/Ho co-doped glass slice was 430.01 μs, obviously shorter than that of a singly Tm doped glass slice (985.38 μs). Therefore, the energy transfer efficiency between Tm (³F₄) and Ho (⁵I₇) reached approximately 56.35%. At 2080 nm, the slope efficiency and output power achieved 46.84% and 38.9 W under 793 nm cladding pumping. More importantly, the M-squared factor was less than 1.19; the laser operated in a narrow 3 dB bandwidth, 0.45 nm, and low threshold, 3.0 W. In addition, the fluctuation of output power (FOP) was 0.21% of the average power. The performance of this fiber laser paves the way for its application in areas such as medical systems, radar, and remote sensing.