Fiber oscillator of 5 kW using fiber Bragg gratings inscribed by a visible femtosecond laser

We fabricate a pair of fiber Bragg gratings(FBGs)by a visible femtosecond laser phase mask scanning technique on passive large-mode-area double-cladding fibers for multi-kilowatt fiber oscillators.The bandwidth of high-reflection(HR)and lowreflection(LR)FBG is~1.6 nm and 0.3 nm,respectively.The reflection of the HR-FBG is higher than 99%,and that of the LR-FBG is about 10%.A bidirectional pumped all-fiber oscillator is constructed using this pair of FBGs,a record output power of 5027 W located in the signal core is achieved with a slope efficiency of~82.1%,and the beam quality factor M2is measured to be~1.6 at the maximum power.The FBGs are simply fixed on a water cooling plate without a special package,and the thermal efficiency of the HR-FBG and the LR-FBG is 2.76℃/kW and 1℃/kW,respectively.Our research provides an effective solution for robust high-power all-fiber laser oscillators.

A 110 W fiber gas Raman laser at 1153 nm

We report here the first hundred-watt continuous wave fiber gas laser in H_(2)-filled hollow-core photonic crystal fiber(PCF)by stimulated Raman scattering.The pump source is a homemade narrow-linewidth fiber oscillator with a 3 dB linewidth of 0.15 nm at the maximum output power of 380 W.To efficiently and stably couple several-hundred-watt pump power into the hollow core and seal the gas,a hollow-core fiber end-cap is fabricated and used at the input end.A maximum power of 110 W at 1153 nm is obtained in a 5 m long hollow-core PCF filled with 36 bar H2,and the conversion efficiency of the first Stokes power is around 48.9%.This work paves the way for high-power fiber gas Raman lasers.