Mid-infrared pulsed fiber laser source at 4.3 µm based on a CO₂-filled anti-resonant hollow-core silica fiber

Fiber lasers in the mid-infrared (mid-IR) band are of great interest due to their wide range of applications such as manufacturing, defense, spectroscopy, and free-space communication. Due to the immaturity of the soft glass fiber fabrication technology and the limitation of the type of doped rare earth, laser power scaling and wavelength expansion above 4 µm are greatly limited. Lasers based on gas-filled hollow-core fibers (HCFs) have proved to be an effective way of generating mid-IR lasers. We demonstrate a pulsed 4.3 µm laser source based on a CO 2 -filled HCF for the first time. The pulse energy characteristics and output spectrum of the mid-IR laser have been investigated. The maximum pulse energy of the mid-IR laser is 236 nJ. The maximum average power of the mid-IR laser is 297.8 mW with a slope efficiency of 17.3%. A step-tunable mid-IR output is achieved from 4293.718 nm to 4392.085 nm including 8 emission lines. Furthermore, the time-domain and frequency-domain properties of the mid-IR laser have been studied to understand laser operation better. This work has an important reference value for the development of pulsed mid-IR fiber gas laser sources.