Ma Wenbo, Chen Xuhuinan, Zhong Yuhan, Bian Chenxu, Wang Chan, Chen Hongsheng, Lin Xiao
Opt Lett. 2024 Oct 15;49(20):5862-5865. doi: 10.1364/OL.539647.
Near-field directional excitation of dipolar sources is crucial for many practical applications, such as quantum optics, photonic integrated circuits, and on-chip information processing. Based on theoretical analyses and numerical simulations, here we find that the near-field directionality of circularly polarized dipoles can be flexibly toggled by engineering the anisotropy of the surrounding matter, in which the dipolar source locates. To be specific, if the circularly polarized dipole is placed close to the interface between a hyperbolic matter and air, the main propagation direction of excited surface waves would be reversed when the location of the dipolar source is changed from the air region to the hyperbolic-matter region. The underlying mechanism is that the spatial-frequency spectrum of evanescent waves carried by the dipolar source in a homogeneous surrounding matter could be flexibly reshaped by the matter's anisotropy, especially when the isofrequency contour of the surrounding matter changes from the circular shape to the hyperbolic one.
偶极子源的近场定向激发对于许多实际应用至关重要，如量子光学、光子集成电路和片上信息处理。基于理论分析和数值模拟，我们在此发现，通过设计偶极子源所在周围物质的各向异性，圆偏振偶极子的近场方向性可以灵活切换。具体而言，如果将圆偏振偶极子放置在双曲型物质与空气的界面附近，当偶极子源的位置从空气区域改变到双曲型物质区域时，激发表面波的主要传播方向将会反转。其潜在机制是，在均匀周围物质中偶极子源携带的倏逝波的空间频谱可以被物质的各向异性灵活重塑，特别是当周围物质的等频率轮廓从圆形变为双曲线形时。
