Fiber gas amplifier in CO₂-filled hollow-core fiber and its self-absorption phenomenon

Fiber gas laser based on hollow-core fiber is a novel and potential method to emit mid-infrared output. Here, we firstly demonstrate the fiber gas amplifier in CO ₂ -filled hollow-core fiber. Through the research of the fiber gas amplifier, self-absorption phenomenon is observed. 4.3 μm locates near the strong absorption wavelength band of CO ₂ . As the increase of gas pressure and the injected pump power, 4.3 μm laser generated by four absorption lines from 00001-20012 can be absorbed. The strength of the absorption depends on the wavelength difference between the output wavelength and the absorption wavelength. This research proves the way for improving the conversion efficiency of fiber gas lasers filled with CO ₂ by avoiding the self-absorption effect of CO ₂ .