Liu, C.-H.C.-H.LiuGalvanauskas, A.A.GalvanauskasKhitrov, V.V.KhitrovSamson, B.B.SamsonManyam, U.U.ManyamTankala, K.K.TankalaMachewirth, D.D.MachewirthHeinemann, S.S.Heinemann2022-03-032022-03-032006https://publica.fraunhofer.de/handle/publica/21162910.1364/OL.31.000017Conventionally, large-mode-area (LMA) fiber lasers use free-space polarizing components to achieve linear polarization output. External components, however, significantly limit laser robustness and power scalability. We demonstrate, to the best of our knowledge, the first high-power all-fiber cavity single-polarization single-transverse-mode LMA fiber laser, without the use of free-space polarizing components. This has been achieved by using tightly coiled high-birefringence 20 mu m core LMA fiber. The lasing spectrum at 1086 mn has been stabilized by a fiber grating, spliced at one end of a LMA fiber. Up to 405 W of single-polarization output with a polarization extinction of > 19 dB with a narrow spectrum (1.9 nm FVMM) and in a single-transverse mode (M-2 < 1.1) has been demonstrated. The simplicity of a monolithic-cavity approach is highly beneficial for a number of applications, including the use of a fiber laser for nonlinear wavelength conversion and for coherent and spectral beam combining.en621535High-power single-polarization and single-transverse-mode fiber laser with an all-fiber cavity and fiber-grating stabilized spectrumjournal article