Roy Nicolas, Lou Beicheng, Fan Shanhui, Mayer Alexandre, Lobet Michaël
Namur Institute for Complex Systems, University of Namur, Namur, 5000, Belgium.
Namur Institute for Structured Matter, University of Namur, Namur, 5000, Belgium.
Light Sci Appl. 2025 Aug 7;14(1):263. doi: 10.1038/s41377-025-01942-7.
Twisted bilayer photonic crystals introduce a twist between two stacked photonic crystal slabs, enabling strong modulation of their electromagnetic properties. The change in the twist angle strongly influences the resonant frequencies and available propagating diffraction orders with applications including sensing, lasing, slow light or wavefront engineering. In this work, we design and analyze twisted bilayer crystals capable of steering light in a direction controlled by the twist angle. To achieve beam steering, the device efficiently routes input power into a single, twist-dependent, transmitted diffraction order. The outgoing light then follows the orientation of this diffraction order, externally controlled by the twist angle. Our study shows, using systematic exploration of the design space, how the device resembles blazed gratings by effectively canceling the undesired diffraction orders. The optimized devices exhibit a shared slant dependent on the selected diffraction order and that proves robust to the twist angle. Our analysis is supported by a classical blazing model and a data-oriented statistical analysis. The data-oriented approach is steered by high-efficiency heuristic optimization method, which enabled the design of optimized devices demonstrating an efficiency above 90% across twist angles ranging from 0 to 30° for both TE and TM polarizations. Extending the optimization to include left- and right-handed polarizations yields overall accuracy nearing 90% when averaged across the entire 0 to 60° control range. Finally, with the identification of the blazing effect in this initially black box structure, we show one can consider simpler design for a first prototype.
扭曲双层光子晶体在两个堆叠的光子晶体平板之间引入了扭曲，从而能够对其电磁特性进行强调制。扭曲角的变化强烈影响共振频率和可用的传播衍射级次，其应用包括传感、激光、慢光或波前工程。在这项工作中，我们设计并分析了能够将光导向由扭曲角控制的方向的扭曲双层晶体。为了实现光束转向，该器件将输入功率有效地路由到一个单一的、依赖于扭曲的透射衍射级次中。然后，出射光遵循这个衍射级次的方向，该方向由扭曲角外部控制。我们的研究通过对设计空间的系统探索表明，该器件如何通过有效地消除不需要的衍射级次而类似于闪耀光栅。优化后的器件表现出取决于所选衍射级次的共同倾斜，并且对扭曲角具有鲁棒性。我们的分析得到了经典闪耀模型和面向数据的统计分析的支持。面向数据的方法由高效启发式优化方法引导，这使得能够设计出优化的器件，在0至30°的扭曲角范围内，对于TE和TM偏振，效率均高于90%。将优化扩展到包括左旋和右旋偏振，在整个0至60°控制范围内平均时，总体精度接近90%。最后，通过在这个最初的黑箱结构中识别出闪耀效应，我们表明可以为第一个原型考虑更简单的设计。
