We here reported a single wavelength second order vortex mode lasing in optical fiber system. For this, we implemented a high efficient mode conversion between the fundamental guiding mode(LP₀₁ mode) and the second azimuthal order guiding mode(e.g.LP₂₁ mode), and an appropriate mode modulation that converted the mode from LP₂₁ mode to the second order optical vortex(OV) mode. The high efficient mode conversion was realized by utilizing a single intra-cavity strong modulated long-period fiber grating (SM-LPFG) that enables a higher than 20 dB($>99\%$) direct mode conversion efficiency over a bandwidth range of 3 nm. And the mode modulation was fulfilled with high-order mode polarization controller that control the polarization state of the resonating mode to transform the LP₂₁ mode to the 2nd order OV mode. Experiment results showed that a single wavelength of 1542.88 nm of the 2nd order OV mode laser was obtained with a 3 dB bandwidth 0.22 nm and over 27 dB signal to noise ratio. As far as we know, this was the first report on the implementation of the 2nd order OV mode lasing in optical fiber system by only one intra-cavity SM-LPFG in the laser cavity.

我们在这里报告了光纤系统中的单波长二阶涡旋模式激光。为此，我们在基本引导模式（LP ₀₁模式）和二阶方位角阶引导模式（例如LP ₂₁模式）之间实现了高效模式转换，以及将模式从LP ₂₁模式转换为二阶引导模式的适当模式调制。订购光学涡流（OV）模式。利用单个腔内强调制长周期光纤光栅 (SM-LPFG) 实现了高效模式转换，该光栅可实现高于 20 dB($>99\%$) 3 nm 带宽范围内的直接模式转换效率。并且通过控制谐振模式的偏振态将LP ₂₁模式转换为2阶OV模式的高阶模式偏振控制器来实现模式调制。实验结果表明，获得了单波长1542.88 nm的二阶OV模式激光器，具有3 dB带宽0.22 nm和超过27 dB的信噪比。据我们所知，这是第一篇关于在光纤系统中仅通过一个腔内SM-LPFG在激光腔内实现二阶OV模式激光的报道。