2.43 kW narrow linewidth linearly polarized all-fiber amplifier based on mode instability suppression

Abstract

We demonstrate an experimental study on scaling mode instability (MI) threshold in fiber amplifiers based on fiber coiling. The experimental results show that coiling the active fiber in the cylindrical spiral shape is superior to the coiling in the plane spiral shape. When the polarization maintained Yb-doped fiber (PM YDF: with a core/inner-cladding diameter of 20/400 µm) is coiled on an aluminous plate with a bend diameter of 9-16 cm, the MI threshold is ~1.55 kW. When such a PM YDF is coiled on an aluminous cylinder with diameter of 9 cm, no MI is observed at the output power of 2.43 kW, which is limited by the available pump power. The spectral width and polarization extinction ratio is 0.255 nm and 18.3 dB, respectively, at 2.43 kW. To the best of our knowledge, this is the highest output power from a linear polarized narrow linewidth all-fiberized amplifier. By using a theoretical model, the potential MI-free scaling capability in such an amplifier is estimated to be 3.5 kW.

2.5 kW Narrow Linewidth Linearly Polarized All-Fiber MOPA With Cascaded Phase-Modulation to Suppress SBS Induced Self-Pulsing

“…In 2016, P. Ma et al based on three-level sinusoidal phase modulation and PM fiber amplifier, obtained a 1.89kW linearly polarized laser output with the linewidth of 45 GHz [20]. In 2017, R. Su et al obtained a 2.43 kW output laser power with 68 GHz linewidth based on WNS phase modulation [33]. In 2018, N. Platonov reported 2 kW, 22 GHz linearly polarized all-fiber laser [26], the further increasing of laser power is limited by the MI effect.…”

“…For example, ref. [33] using the aluminous cylinder for bending mode selection to achieve a 2.43 kW PM laser output. In this work, in order to suppress the MI effect, the gain fiber in PM-amplifier is coiled with a plum blossom shape on the aluminous plate with the minimum coiled diameter of 9 cm and the maximum coiled diameter of 11 cm, respectively, it is shown in Fig.…”

Comparison and Optimization on Transverse Mode Instability of Fiber Laser Amplifier Pumped by Wavelength-Stabilized and Non-Wavelength-Stabilized 976 nm Laser Diode

“…Because of its far-reaching influence, after the first report of the TMI phenomenon, the researchers put forward lots of effective methods to mitigating the TMI effect [11][12]. Such as designing the structure of active fiber [13][14][15][16], optimizing the structure of the fiber laser [17][18][19][20], shifting the pump and signal wavelength and pump power distribution [21][22][23], and so on. Among these suppression methods, optimizing the pumping wavelength to increase the TMI threshold is easy to realized and proved very effective.…”

Thermally Induced Mode Amplification Characteristics of Large Mode Area Segmented Cladding Fiber

“…In high-power fiber lasers and amplifiers, fewmode or multi-mode propagation can degrade the beam quality because output power dynamically exchanges between the fundamental mode (FM) and high order modes (HOMs) when transverse mode instability (TMI) occurs. In recently TMI is considered as a severe limitation on power scaling [4,5], so it is essential to keep single-mode operation in high-power amplification.…”