Bound States in the Continuum in Fiber Bragg Gratings
Bound States in the Continuum in Fiber Bragg Gratings
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DOI：
10.1021/acsphotonics.9b01202
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发表时间：
2019-11-01
期刊：
影响因子：
7
通讯作者：
Hsu, Chia Wei
中科院分区：
文献类型：
--
作者：
Gao, Xingwei;Zhen, Bo;Hsu, Chia Wei
光纤通常通过全内反射或通过光子带隙来限制光。在这里，我们展示了光可以通过一种不同的机制在光纤中被完美地引导，这种机制基于连续统中的束束态(BIC)。在周期布拉格光栅光纤中，我们预测了纯极化模式下的真BIC和混合偏振模式下的准BIC。这些BIC和准BIC在拓扑上受到保护，不需要精细的结构调整就可以稳健地存在。通过对折射率对比度较小的光栅特别精确的耦合波框架，我们分析证明，即使在实际光纤布拉格光栅中常见的非常小的折射率对比度下，这些BIC也是持续存在的。辐射损耗的抑制是由于弱辐射局域模和强辐射局域模之间的相消干涉而产生的。这一发现开启了用光纤中的BIC引导光的可能性，以及它们在光纤传感器、滤光器和高功率光纤激光器中的应用。
Optical fibers typically confine light through total internal reflection or through photonic band gaps. Here, we show that light can be perfectly guided in optical fibers through a different mechanism based on bound states in the continuum (BICs). In fibers with periodic Bragg gratings, we predict bona fide BICs in pure-polarization modes as well as quasi-BICs in hybrid-polarization modes. These BICs and quasi-BICs are topologically protected and exist robustly without the need for fine structural tuning. With a coupled-wave framework that is especially accurate for gratings with small index contrasts, we analytically prove that these BICs persist even with the very small index contrasts that are common in realistic fiber Bragg gratings. The suppression of radiation loss arises from the destructive interference between a weakly radiating local mode and a strongly radiating one. This finding opens the possibility of guiding light with BICs in optical fibers and their applications in fiber sensors, filters, and high-power fiber lasers.