Hao Tianyi, Berini Pierre
Opt Express. 2022 Feb 14;30(4):5167-5176. doi: 10.1364/OE.450960.
Parity-time symmetric Bragg gratings produce unidirectional reflection around the exceptional point. We propose and explore directional coupling of gain and loss modulated waveguide Bragg gratings operating at around 880 nm with long-range surface plasmon polaritons. Step-in-width modulation of a Ag stripe supporting long-range plasmons combined with a periodic modulation of the cladding were used to balance the real and imaginary index perturbation of the gratings. IR140 dye molecules in solvent forms a portion of the uppercladding, providing gain under optical pumping. We investigate directional coupling between a pair of parity-time symmetric waveguide Bragg gratings operating near their exceptional point, arranged in various configurations - duplicate, duplicate-shifted and duplicate-flipped. We also investigate coupling to a bus waveguide and to a conventional waveguide Bragg grating. Unidirectional multi-wavelength reflection and coupled supermode conversion are predicted.
宇称-时间对称布拉格光栅在奇异点附近产生单向反射。我们提出并研究了工作在880nm左右的增益和损耗调制波导布拉格光栅与长程表面等离激元极化激元的定向耦合。支持长程等离激元的银条纹的步长宽度调制与包层的周期性调制相结合，用于平衡光栅的实折射率微扰和虚折射率微扰。溶剂中的IR140染料分子构成上包层的一部分，在光泵浦下提供增益。我们研究了一对在其奇异点附近工作的宇称-时间对称波导布拉格光栅之间的定向耦合，它们以各种配置排列——重复、重复移位和重复翻转。我们还研究了与总线波导和传统波导布拉格光栅的耦合。预测了单向多波长反射和耦合超模转换。
