4.3 μm CO₂-filled hollow-core fiber laser with a ring-cavity structure

In recent years, gas-filled hollow-core fibers (HCFs) have been studied as an extraordinary method for generating mid-infrared (MIR) light. However, most demonstrations have focused on single-pass amplified spontaneous emission (ASE) sources rather than cavity-based lasers. Here, for the first time, we demonstrate a continuous-wave (CW) and self-Q-switched pulsed laser at 4.3 μm from a CO₂-filled HCF with a ring-cavity structure. A maximum CW laser output power of 1.09 W was achieved. Self-Q-switched pulse laser at 4.3 μm was realized by utilizing the ground-state self-absorption effect of CO₂. An average power of 244 mW, a pulse width of 142 ns, and a repetition rate of 2.8 MHz were obtained for the self-Q-switched operation. This study paves the way for Q-switched and mode-locked pulse generation in gas-filled HCFs, offering a novel, to the best of our knowledge, platform for MIR pulsed laser research.