We study metamaterials with an anisotropic permittivity tensor in which one component is near zero. We find that such an anisotropic metamaterial can be used to control wave propagation and construct almost perfect bending waveguides with a high transmission rate (>95%). This interesting effect originates in the power flow redistribution by the surface waves on the input and output interfaces, which smoothly matches with the propagating modes inside the metamaterial waveguide. We also find that waves in such anisotropic epsilon-near-zero materials can be reflected by small-sized perfect magnetic conductor defects. Numerical calculations have been performed to confirm the above effects.

We propose a method to realize directive emission using a layered metal heterostructure with around-zero average permittivity in the optical region. In the long-wavelength limit the heterostructure can be viewed as an epsilon-near-zero metamaterial. Our results show that when a transverse electric polarized source is placed in front of the heterostructure only the lights around the lines normal to the surfaces of the heterostructure can propagate through it. By exploiting constructive interference we can achieve good directivity and high transmission simultaneously. In addition, if the source is embedded in the heterostructure, the energy radiated by the source will be concentrated in a narrow cone.

Optical logic gates are important elements in optical computing and optical circuits. In this study, all-optical logic gates, including OR, XOR, XNOR, NAND, and NOT gates, are obtained in a composite structure composed of gyroelectric material and metal based on the interference and absorption of surface waves. In the composite structure, a Y-shaped channel through which surface plasmon polaritons propagate unidirectionally is formed. Through the ingenious one-way surface plasmon polaritons, backscattering and side-scattering generated by the composite structure and influencing the surrounding devices are prohibited effectively. The precisely controlled optical phase difference ensures the realization of five different logic gates with high contrast ratios. The maximum contrast ratios for XOR, XNOR, NAND, and NOT gates are 31.64 dB, 43.47 dB, 31.47 dB, and 43.47 dB, respectively. The output logic states “1”or “0” obtained by different logic inputs have nearly the same light intensity. Our research results provide the possibility for constructing all-optical integrated logic devices.

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