To prevent the crosstalk between adjacent waveguides in photonic integrated circuits, the minimum thickness of the cladding layers is around half a wavelength, which imposes a fundamental limitation to further integration and miniaturization of photonic circuits. Here, we reveal that epsilon-near-zero claddings, either isotropic or anisotropic, can break the above bottleneck by prohibiting the crosstalk for the modes with magnetic field polarized in the z direction at a deep-subwavelength thickness (e.g., λ 0/30, λ 0 is the free-space wavelength), therefore bestowing ultra-compact waveguide systems. The physical origin of this remarkable effect attributes to the divergent impedance of epsilon-near-zero materials far beyond those of dielectric or epsilon-negative claddings. Through full-wave simulations and microwave experiments, we have verified the effectiveness of the ultrathin epsilon-near-zero cladding in crosstalk prohibition. Our finding reveals the significant impact of impedance difference in waveguide designs and opens a promising route toward ultra-compact photonic chips.

中文翻译：

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epsilon-near-zero 包层在深亚波长范围内的串扰抑制

为了防止光子集成电路中相邻波导之间的串扰，包层的最小厚度约为半个波长，这对光子电路的进一步集成和小型化施加了根本限制。在这里，我们揭示了 epsilon-near-zero 包层，无论是各向同性还是各向异性，都可以通过禁止磁场极化模式的串扰来打破上述瓶颈z在深亚波长厚度方向（例如，λ 0/30,λ 0是自由空间波长），因此赋予超紧凑的波导系统。这种显着效应的物理起源归因于 epsilon-near-zero 材料的发散阻抗远远超过电介质或 epsilon-negative 包层。通过全波模拟和微波实验，我们验证了超薄epsilon-near-zero包层在串扰抑制中的有效性。我们的发现揭示了波导设计中阻抗差异的重大影响，并为超紧凑型光子芯片开辟了一条有前途的途径。