He Jun, Wang Yiping, Liao Changrui, Wang Qiaoni, Yang Kaiming, Sun Bing, Yin Guolu, Liu Shen, Zhou Jiangtao, Zhao Jing
Opt Lett. 2015 May 1;40(9):2008-11. doi: 10.1364/OL.40.002008.
We demonstrate a highly birefringent phase-shifted fiber Bragg grating (PS-FBG) inscribed in H2-free fiber with a near-infrared femtosecond Gaussian laser beam and uniform phase mask. The PS-FBG was fabricated from an ordinary fiber Bragg grating (FBG) in a case in which overexposure was applied. The spectral evolution from FBG to FS-FBG was observed experimentally with a decrease in transmission loss at dip wavelength, blueshift of the dip wavelength, decrease in the cladding mode loss, and an increase in the insertion loss. A high birefringence was demonstrated experimentally with the existence of PS-FBG only in TM polarization. The formation of the PS-FBG may be due to a negative index change induced by the higher intensity in the center of the Gaussian laser beam.
我们展示了一种使用近红外飞秒高斯激光束和均匀相位掩膜写入无氢光纤中的高双折射相移光纤布拉格光栅（PS-FBG）。该PS-FBG是在对普通光纤布拉格光栅（FBG）进行过曝光的情况下制成的。通过实验观察到从FBG到FS-FBG的光谱演变，包括凹陷波长处传输损耗的降低、凹陷波长的蓝移、包层模损耗的降低以及插入损耗的增加。实验证明，仅在TM偏振中存在PS-FBG时具有高双折射。PS-FBG的形成可能是由于高斯激光束中心较高强度引起的负折射率变化。
