Extinction ratio

Double-clad fiber

Laser power scaling

Materials science

Optical fiber

Amplifier

Fiber optic sensor

Wavelength

Laser

Physics

Laser beams

Optics

Single-mode optical fiber

Dispersion-shifted fiber

Brillouin scattering

Laser beam quality

Polarization-maintaining optical fiber

CMOS

Fiber laser

Optoelectronics

Optics Express

In this paper, we report a high power single frequency 1030 nm fiber laser with near-diffraction-limited beam quality based on a polarization-maintaining tapered Yb-doped fiber (T-YDF). The T-YDF has advantages of effectively suppressing stimulated Brillouin scattering (SBS) while maintaining good beam quality. As a result, a record output power of 379 W single frequency, linearly polarized, nearly single-mode fiber amplifier operating at 1030 nm is demonstrated. The polarization extinction ratio is as high as 16.3 dB, and the M2 is measured to be 1.12. Further, the dependence of the thermal-induced mode instability (TMI) threshold on the polarization state of an input signal laser is investigated for the first time. By changing the polarization state of the injected seed laser, the output power can increase to 550 W while the beam quality can be maintained well (M2=1.47). The slope efficiency of the whole amplifier is about 80%. No sign of SBS appears even at the highest output power and the further brightness scaling of both situations is limited by the TMI effect. To the best of our knowledge, this result is the highest output power of all-fiberized single frequency fiber amplifiers.

550 W single frequency fiber amplifiers emitting at 1030 nm based on a tapered Yb-doped fiber