Fiber tapering technology has been used to realize low-loss coupling from solid-core fibers to antiresonant hollow-core fibers (AR-HCFs) at low-power level, by inserting the tapered solid-core fibers into the hollow-core of AR-HCFs. Here, we have demonstrated the high-power coupling capacity of this way. For ice-cream type AR-HCF, a transmission efficiency of ~47% is achieved with injected 1080 nm laser power of ~90 W in a ~2 m HCF; for nodeless type AR-HCF, a transmission efficiency of ~40% is achieved with injected 1550 nm laser power of ~32 W in a ~2 m HCF. The output mode field with good beam quality shows the mode filtering characteristics of AR-HCFs.
Lasing from HBr-filled hollow-core fiber (HCF) based on population inversion is demonstrated and characterized. Usually, there are two emission lines corresponding to each absorption line. Here, by controlling the gas pressure in the HCF, a single emission line P(7) of 4.26 μm is efficiently achieved when pumping with line R(5) of 1958 nm, and the other emission line R(5) of 3.91 μm is totally suppressed. The maximum 4.26 μm laser output power of 350 mW is obtained with a slope efficiency of about 11%.
Hollow-core fibers (HCFs) provide an ideal environment for the interaction of light and gases, which gives birth to a novel kind of lasers, namely fiber gas lasers (FGLs). Although there is a rapid development of FGLs in the past years, highly efficient and stable coupling of the pump light is still a key limit for their applications in the future. Here, we propose and fabricate the HCF end-cap for the first time. The measured results show that the HCF end-cap can bear several hundreds of watt laser power, and the coupling efficiency is around 70%. This work opens new opportunity for the development of high-power FGLs.
We report here a novel two-stage approach Raman cascade laser source operating at 2.8 μm. In the first stage, a pulsed pump laser at 1064.6 nm is coupled into a methane-filled hollow-core fiber and efficiently transfer to 1st Stokes wave at 1543.9 nm. The quantum efficiency is ~ 87%, which is achieved in 2 bar methane pressure and 2 m fiber length. In the second stage, the 1st Stokes wave is coupled into another methane-filled hollow-core fiber as the pump source, 2nd Stokes wave at 2.8 μm is obtained with a high quantum efficiency of ~75%, which is achieved in 11 bar methane and 2.2 m fiber length. The record total quantum efficiency (from the 1064 nm pump laser to Stokes wave at 2.8 μm) of ~ 65% is achieved, which is 1.6 times the previous reported value. This kind of gas filled hollow-core cascade Raman laser source provides a potential method to obtain high efficiency mid-infrared laser sources with low threshold in various applications.
Based on a method for coupling of guided light from tapered single-mode fibers to hollow-core fibers, we report midinfrared emission around 3.1-3.2 μm from acetylene-filled hollow-core fiber gas laser system. The laser operating at both CW and pulsed regime is investigated. The maximum pulse average power of ~0.125 W (~250 nJ pulse energy) at both P(11) and P(13) pump transitions is obtained with a 2 m length of fiber. And the maximum CW power is 185 mW by P(15) pump transition at 1.1 mbar gas pressure with a power conversion efficiency of ~14% when the fiber is 10 m.
We report here the characteristic of a 1.55-μm fiber gas Raman amplifier worked in an ethane-filled hollow-core fiber (HCF). This amplifier is composed of a CW C-band tunable, narrow linewidth seed laser, and a pulsed 1064.6-nm microchip pump laser. Through a dichroic mirror, the seed laser, together with a 1064.6-nm pump source, is coupled into the ethane-filled HCF and then efficient 1553-nm Raman laser generates by the stimulated Raman scattering of ethane molecules. A maximum Raman laser average power of 43.8 mW (pulse energy 87.6 μJ) with a Raman conversion efficiency of 47.5% (quantum efficiency of ∼70 % ) is obtained using 8.7-m HCF filled with 1.4-bar ethane. A method to obtain efficient 1.55-μm fiber laser sources is demonstrated.
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