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

Abstract

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 M 2 is 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°C/kW and 1°C/kW, respectively. Our research provides an effective solution for robust high-power all-fiber laser oscillators.

Wavelength selective bending sensitive multi-ring fiber for suppressing stimulated Raman scattering

“…Fiber lasers have various applications owing to their high conversion efficiency, beam quality, compactness, and reliability 1 – 5 However, with an increase in the optical power, a series of unwanted nonlinear effects emerge. Specifically, stimulated Brillouin scattering (SBS) is the primary obstacle in scaling the power of narrow-linewidth lasers 6 , 7 .…”

3.8 kW high brightness MOPA fiber laser

“…For the single-stage fiber laser oscillators, in 2021, an industrial 6 kW single-stage all-fiber laser oscillator based on 30/600-μm fiber was posted with M 2 of ~2.6 [7]. And in 2023, researchers achieved 5 kW single-mode (M 2 ~ 1.6) laser output on a 20/400-μm fiber, based on femtosecond laser grating rapid manufacturing technology [8]. Maintaining a good beam quality while raising the output power is still a big challenge.…”