We performed a comparative study of Yb-doped double-clad large mode area (${\rm{MFD}} = {{31}}\;{\rm{\unicode{x00B5}{\rm m}}}$) spun tapered fibers with different pitch lengths. A novel type of spun tapered fibers with constant pitch lengths of 7.5, 15, and 30 mm, internal birefringence as low as ${\sim}{{10}^{- 8}}$, and perfect output beam quality (${{\rm{M}}^2}\; \lt \;{1.2}$) has been manufactured and investigated. We demonstrated the efficient direct amplification of a picosecond pulsed signal (95 ps/100 MHz, 1064 nm) in the spun active tapered fiber with optimized geometry providing an average output power of 71 W (gain 32 dB, 74% slope efficiency). Efficient green light generation ($\lambda = {{532}}\;{\rm{nm}}$) with 17 W average power (1.7 µJ) and 80 pm linewidth was demonstrated using the developed master oscillator power amplifier system.

中文翻译：

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大模场双包层掺镱纺丝锥形光纤

我们对掺镱双包层大模式面积进行了比较研究（${\rm{MFD}} = {{31}}\;{\rm{\unicode{x00B5}{\rm m}}}​​$）纺成具有不同节距长度的锥形光纤。一种新型纺丝锥形光纤，具有 7.5、15 和 30 毫米的恒定节距长度，内部双折射低至${\sim}{{10}^{- 8}}$和完美的输出光束质量 ( ${ {\rm{M}}^2}\; \lt \;{1.2}$ ) 已经制造和调查。我们展示了在旋转有源锥形光纤中对皮秒脉冲信号 (95 ps/100 MHz, 1064 nm) 的有效直接放大，该光纤具有优化的几何形状，平均输出功率为 71 W（增益 32 dB，斜率效率为 74%）。高效的绿光产生（$\lambda = {{532}}\;{\rm{nm}}$) 具有 17 W 平均功率 (1.7 µJ) 和 80 pm 线宽，使用开发的主振荡器功率放大器系统进行了演示。