Abstract
We report a high power, narrow linewidth fiber laser based on oscillator one-stage power amplification configuration. A fiber oscillator with a center wavelength of 1080 nm is used as the seed, which is based on a high reflection fiber Bragg grating (FBG) and an output coupling FBG of narrow reflection bandwidth. The amplifier stage adopted counter pumping. By optimizing the seed and amplifier properties, an output laser power of 2276 W was obtained with a slope efficiency of 80.3%, a 3 dB linewidth of 0.54 nm and a signal to Raman ratio of 32 dB, however, the transverse mode instability (TMI) began to occur. For further increasing the laser power, a high-power chirped and tilted FBG (CTFBG) was inserted between the backward combiner and the output passive fiber, experimental results showed that both the threshold of Stimulated Raman scattering (SRS) and TMI increased. The maximum laser power was improved to 2576 W with a signal to Raman ratio of 42 dB, a slope efficiency of 77.1%, and a 3 dB linewidth of 0.87 nm. No TMI was observed and the beam quality factor M2 maintained about 1.6. This work could provide a useful reference for obtaining narrow-linewidth high-power fiber lasers with high signal to Raman ratio.
Highlights
In the past years, owing to the great improvement of laser diodes (LDs) brightness and high-quality large mode area (LMA) fiber as well as beam combining technology, the output power of continuous-wave (CW) fiber lasers has been scaled rapidly [1,2,3,4].the further improvement of single fiber output power is limited by various nonlinear effects, transverse mode instability (TMI), thermal effect, etc
Spectral beam combining (SBC) is a promising approach to break through the limitations of the fiber lasers [5,6]
In SBC, the key is that the sub beam needs to be a narrow linewidth fiber laser (NLFL) with high beam quality, which usually realize by a main oscillator power amplifier (MOPA) configuration [7]
Summary
In the past years, owing to the great improvement of laser diodes (LDs) brightness and high-quality large mode area (LMA) fiber as well as beam combining technology, the output power of continuous-wave (CW) fiber lasers has been scaled rapidly [1,2,3,4]. The further improvement of single fiber output power is limited by various nonlinear effects, transverse mode instability (TMI), thermal effect, etc. For the present single fiber lasers, further power scaling is even difficult with compromise in bandwidth, beam quality, and so on. Spectral beam combining (SBC) is a promising approach to break through the limitations of the fiber lasers [5,6]. In SBC, the key is that the sub beam needs to be a narrow linewidth fiber laser (NLFL) with high beam quality, which usually realize by a main oscillator power amplifier (MOPA) configuration [7]. For MOPA structure, there are two main types of seeds, namely few longitudinal mode fiber oscillator laser (FOL)
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