Baker Chams, Gao Song, Chen Liang, Bao Xiaoyi
Opt Express. 2017 May 29;25(11):12409-12414. doi: 10.1364/OE.25.012409.
We report for the first time that transmission of optical pulses centered at a wavelength of 1550 nm through a tapered dual-core AsSe-PMMA fiber inscribes an antisymmetric long-period grating. The pulse power is equally divided between even and odd modes that superpose along the dual-core fiber to form an antisymmetric intensity distribution. A permanent refractive-index change that matches the antisymmetric intensity distribution is inscribed due to photosensitivity at the pulse central wavelength. The evolution of the transmission spectrum of the dual-core fiber is experimentally measured as the accumulated time that the fiber is exposed to the pulse is increased. A theoretical model of an antisymmetric long-period grating in a dual-core fiber computationally reproduces the experimentally observed evolution of the transmission spectrum. Experimental results indicate that antisymmetric long-period gratings induce effective group-velocity matching between the even and odd modes of the dual-core fiber, and reveal for the first time that long-period gratings can lead to slow light propagation velocities.
我们首次报道，中心波长为1550 nm的光脉冲通过锥形双芯AsSe-PMMA光纤传输时会刻写出一个反对称长周期光栅。脉冲功率在沿双芯光纤叠加形成反对称强度分布的偶模和奇模之间平均分配。由于在脉冲中心波长处的光敏性，会刻写出与反对称强度分布相匹配的永久性折射率变化。随着光纤暴露于脉冲的累积时间增加，对双芯光纤的传输光谱演变进行了实验测量。双芯光纤中反对称长周期光栅的理论模型通过计算再现了实验观察到的传输光谱演变。实验结果表明，反对称长周期光栅在双芯光纤的偶模和奇模之间诱导了有效的群速度匹配，并首次揭示了长周期光栅可以导致慢光传播速度。
