基于广义希尔伯特变换的按需隐身
Invisibility on demand based on a generalized Hilbert transform
摘要：
在不使用极端材料的情况下设计隐形物体是光子应用长期追求的目标。迄今为止展示的隐形技术通常需要高各向异性、增益和损耗，同时也不灵活。在这里，我们提出了一个不可见的方法来抑制散射波从/到给定的方向和特定的频率范围内，即按需不可见。我们推导出一个玻恩近似为基础的广义希尔伯特变换的一个特定的不可见性安排有关的两个求积的复介电常数的对象。数值计算证实了理论上的建议，表明可以达到接近完美的隐形任意对象与低折射率对比度。我们进一步证明的情况下，这个想法可以扩展到高指数对象或限制在实际范围内，避免增益区。所提出的概念开辟了一条新的路线，为实际实施的复杂形状的物体与任意抑制的散射按需确定。
英文摘要：
Designing invisible objects without the usage of extreme materials is a long-sought goal for photonic applications. Invisibility techniques demonstrated so far typically require high anisotropy, gain and losses, while also not being flexible. Here we propose an invisibility approach to suppress the scattering of waves from/to given directions and for particular frequency ranges, i.e. invisibility on demand. We derive a Born approximation-based generalized Hilbert transform for a specific invisibility arrangement relating the two quadratures of the complex permittivity of an object. The theoretical proposal is confirmed by numerical calculations, indicating that near-perfect invisibility can be attained for arbitrary objects with low-index contrast. We further demonstrate the cases where the idea can be extended to high-index objects or restricted to within practical limits by avoiding gain areas. The proposed concept opens a new route for the practical implementation of complex-shaped objects with arbitrarily suppressed scatterings determined on demand.
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