北京大学许秀来团队研究了光子分子超亚波长带隙中衰减波耦合光子的全偏振控制。相关论文于2025年3月5日发表在《光：科学与应用》杂志上。

光子的偏振在量子光学和光物质相互作用中起着关键作用，然而，在纳米系统中很难控制，因为纳米光子腔的本征态通常是固定的，并且是线性偏振的。

研究组揭示了使用光子分子（PM）对光子的偏振控制，PM承载了两个耦合纳米束腔的超级模型。与2D光子晶体板中的传统PM相比，对于两个1D光子晶体纳米束腔，它们之间的偏移和间隙可以连续调节。在超亚波长间隙的情况下，两个腔之间的耦合主要由周围环境中的渐逝波耦合主导，而不是传统PM的发射波耦合。因此，系统的非厄密性变得明显，超级模型由支持椭圆偏振的裸本征态之间的非平凡相位差组成。

研究组观察到，反对称模的偏振度和偏振角强烈依赖于两个腔之间的位移和间隙，表现出从线性到圆形的偏振态。这种全偏振控制表明了PM在量子光学器件和自旋分辨腔量子电动力学中的巨大潜力。

附：英文原文

Title: Full polarization control of photons with evanescent wave coupling in the ultra subwavelength gap of photonic molecules

Author: Zhu, Rui, Qian, Chenjiang, Xiao, Shan, Yang, Jingnan, Yan, Sai, Liu, Hanqing, Dai, Deyan, Li, Hancong, Yang, Longlong, Chen, Xiqing, Yuan, Yu, Dai, Danjie, Zuo, Zhanchun, Ni, Haiqiao, Niu, Zhichuan, Wang, Can, Jin, Kuijuan, Gong, Qihuang, Xu, Xiulai

Issue&Volume: 2025-03-05

Abstract: Polarization of photons plays a key role in quantum optics and light-matter interactions, however, it is difficult to control in nanosystems since the eigenstate of a nanophotonic cavity is usually fixed and linearly polarized. Here, we reveal the polarization control of photons using photonic molecules (PMs) that host supermodes of two coupled nanobeam cavities. In contrast to conventional PMs in a 2D photonic crystal slab, for the two 1D photonic crystal nanobeam cavities the shift and gap between them can be tuned continuously. With an ultra subwavelength gap, the coupling between the two cavities is dominated by the evanescent wave coupling in the surrounding environment, rather not the emission wave coupling for conventional PMs. As such, the non-Hermiticity of the system becomes pronounced, and the supermodes consist of a non-trivial phase difference between bare eigenstates that supports elliptical polarization. We observe that both the polarization degree and polarization angle of the antisymmetric mode strongly depend on the shift and gap between the two cavities, exhibiting polarization states from linear to circular. This full polarization control indicates the great potential of PMs in quantum optical devices and spin-resolved cavity quantum electrodynamics.

DOI: 10.1038/s41377-025-01794-1

Source: https://www.nature.com/articles/s41377-025-01794-1