Maegawa Yuki, Nakata Yosuke, Sanada Atsushi
Graduate School of Engineering Science, Osaka University, Toyonaka, Japan.
Center for Quantum Information and Quantum Biology, Osaka University, Toyonaka, Japan.
Nanophotonics. 2023 Jun 14;12(13):2623-2636. doi: 10.1515/nanoph-2022-0786. eCollection 2023 Jun.
In this article, we propose all-dielectric carpet cloaks composed of jungle gym shaped dielectric unit cells and present a design strategy for three-dimensional (3-D) anisotropy control based on the transformation optics. The carpet cloaks are 3-D printable and operate with polarization independent incident waves in arbitrary incident angles due to the 3-D anisotropy control. Realizable anisotropic permittivities of cubic and rectangular unit cells are numerically studied based on the relative permittivity and loss tangent of = 2.9 and tan = 0.02 of ultra-violet curing resin measured at the microwave frequency. It is shown that the unit cell has little frequency dependence even with the anisotropy in the low frequency range where the effective medium approximation is valid. A carpet cloak is designed based on the design method with a quasi-conformal coordinate transformation and implemented with the unit cells taking into account its realizable anisotropy. Polarization independent 3-D cloaking operations of the designed cloak are confirmed numerically. The designed cloak is fabricated by stereolithography 3-D printing technology and its cloaking performances are evaluated experimentally at 10 GHz. It is shown that non-specular reflections are well suppressed by the carpet cloak for both TE and TM incident waves with different incident angles of 30, 45, and 60°. Frequency independent cloaking operations are also shown experimentally in the X-band. The measured near-field distributions and bistatic radar cross sections are in good agreement with simulated predictions and the validity of the design method is confirmed.
在本文中，我们提出了由丛林健身房形状的电介质单元构成的全电介质地毯式隐身衣，并基于变换光学提出了一种三维（3-D）各向异性控制的设计策略。由于三维各向异性控制，地毯式隐身衣是三维可打印的，并且能在任意入射角下对偏振无关的入射波起作用。基于在微波频率下测得的紫外固化树脂的相对介电常数ε = 2.9和损耗角正切tanδ = 0.02，对立方和矩形单元的可实现各向异性介电常数进行了数值研究。结果表明，即使在有效介质近似有效的低频范围内存在各向异性，单元也几乎没有频率依赖性。基于准共形坐标变换的设计方法设计了一种地毯式隐身衣，并考虑其可实现的各向异性用单元实现。通过数值方法确认了所设计隐身衣的偏振无关三维隐身操作。所设计的隐身衣采用立体光刻三维打印技术制造，并在10 GHz下对其隐身性能进行了实验评估。结果表明，地毯式隐身衣对30°、45°和60°不同入射角的TE和TM入射波都能很好地抑制非镜面反射。在X波段也通过实验展示了频率无关的隐身操作。测得的近场分布和双站雷达截面与模拟预测结果吻合良好，证实了设计方法的有效性。
