Double-clad ytterbium-doped tapered fiber with circular birefringence as a gain medium for structured light.

Amplifying radially and azimuthally polarized beams is a significant challenge due to the instability of the complex beam shape and polarization in inhomogeneous environment. In this Letter, we demonstrated experimentally an efficient approach to directly amplify cylindrical-vector beams with axially symmetric polarization and doughnut-shaped intensity profile in a picosecond MOPA system based on a double-clad ytterbium-doped tapered fiber. To prevent polarization and beam shape distortion during amplification, for the first time to the best of our knowledge, we proposed using the spun architecture of the tapered fiber. In contrast to an isotropic fiber architecture, a spun configuration possessing nearly circular polarization eigenstates supports stable wavefront propagation. Applying this technique, we amplified the cylindrical-vector beam with 10 ps pulses up to 22 W of the average power at a central wavelength of 1030 nm and a repetition rate of 15 MHz, maintaining both mode and polarization stability.

Stabilization of the mean wavelength of an erbium-doped fiber source as part of high-accuracy FOG with increased spectrum width.

The mean wavelength, spectrum width, and optical power of the output light of an erbium-doped fiber source (EDFS) are key parameters for navigation systems based on navigation-grade and strategic-grade fiber optic gyroscopes (FOGs). We propose a method of simultaneous stabilization for EDFS parameters. The essence of this method is to stabilize the constant values of the mean wavelength and optical power by real-time adjustment of the two laser diodes' pump ratios during temperature changes using an EDFS double-pass bidirectional optical scheme with the unpumped erbium-doped fiber. The achieved temperature stability of the EDFS mean wavelength as a component of the FOG was 0.32 ppm/°C, and the spectrum width at half-maximum was more than 16.5 nm.