3.96 kW All-Fiberized Linearly Polarized and Narrow Linewidth Fiber Laser with Near-Diffraction-Limited Beam Quality

Abstract

In this paper, we realize a 3.96 kW all-fiberized and polarization-maintained (PM) amplifier with narrow linewidth and near-diffraction-limited beam quality. Based on a master oscillator power amplifier (MOPA) configuration seeded with phase-modulated single-frequency laser, a 3.96 kW signal laser is achieved with a 3 dB linewidth of 0.62 nm at the pump power of 5.02 kW. At the maximum output power, the polarization extinction ratio (PER) is ~13.9 dB, and the beam quality (M2 factor) is M2x = 1.31, M2y = 1.41. As far as we know, this is the maximum output power of PM narrow linewidth fiber laser with near-diffraction-limited beam quality and all-fiber format.

3.2 kW, 0.22 nm narrow-linewidth MOPA configuration fiber laser with a homemade polarization-maintaining Yb-doped fiber

“…This result mainly can be explained by the fact that the increased NA leads to the increasing number of modes supported by the core, which reduces the proportion of FM, so MI is more likely to occur. For the first time, accurate experimental data is given to illustrate the relationship between NA and MI threshold in 20/400 PMYDF, which is urgently needed for current power scaling in high-power narrow-linewidth linearly polarized fiber amplifiers [14,19]. Although the gain fiber lengths employed in the amplifier have meter-scale differences, the previous experimental results show that the SBS threshold was affected little.…”

“…High-power narrow-linewidth fiber lasers or amplifiers with linearly polarized have been a major area of interest within the field of gravitational wave detection (GWD), non-linear frequency conversion (NFC), spectral beam combining (SBC), coherent beam combining (CBC) [1][2][3][4][5][6], and ultrafast lasers [7][8][9][10][11][12], etc., Over the last decade, ytterbium (Yb)-doped master oscillator power amplifiers (MOPAs) with linearly polarized ones have made great progress, and the power scaling has reached the muti-kilowatt level [13][14][15]. However, a number of destructive non-linear phenomena, including stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), and thermal mode instability (MI), can jeopardize the stability of the laser system because of the high intensity in the fiber core [6,[16][17][18].…”

“…Taking the various strategies of seed sources into consideration, some typical approaches to realize high-power narrow-linewidth linearly polarized fiber amplifiers are to use phase-modulated singlefrequency laser (PMSFL) seeds [14,15], super-fluorescent (SF) seeds [33,34], random fiber laser (RFL) seeds [35,36], and fiber oscillator laser (FOL) seeds [5,13,32]. And the multi-stage pre-amplifier and main-amplifier schemes based on the PMSFL seeds, SF seeds, and RFL seeds make the entire system complex and expensive while the scheme based on the FOL seeds is straightforward and practical due to its one-stage amplification.…”

“…And the multi-stage pre-amplifier and main-amplifier schemes based on the PMSFL seeds, SF seeds, and RFL seeds make the entire system complex and expensive while the scheme based on the FOL seeds is straightforward and practical due to its one-stage amplification. However, it is well known that the SBS effect is easily stimulated in amplifiers based on a FOL seed due to its temporal instability [14,36]. Previous theoretical studies have shown that broadening the output linewidth of the laser can effectively suppress the SBS effects [37].…”

Homemade polarization maintaining Yb-doped fibers for high power fiber amplifier

“…High-power narrow-linewidth linearly polarized fiber amplifiers have important research significance in the fields of nonlinear frequency conversion, spectral beam combining (SBC), and coherent beam combining (CBC) [1][2][3][4]. The output power of linearly polarized all-fiber lasers has made impressive progress in recent years.…”