Amplifying Evanescent Waves by Dispersion-Induced Plasmons: Defying the Materials Limitation of the Superlens
Tie‐Jun Huang, Li‐Zheng Yin, Jin Zhao, Chao‐Hai Du, Pu‐Kun Liu
Abstract
Breaking the diffraction limit is always an appealing topic due to the urge for a better imaging resolution in almost all areas. As an effective solution, the superlens based on the plasmonic effect can resonantly amplify evanescent waves and achieve subwavelength resolution. However, natural plasmonic materials, within their limited choices, usually have inherent high losses and are only available from the infrared to visible wavelengths. In this work, we theoretically and experimentally demonstrate that arbitrary materials, when they are filled in a bounded metallic waveguide, can be used to enhance evanescent waves and build a low-loss superlens at the desired frequency. The operating mechanisms reside in the effective plasmons induced by the structural dispersion of the waveguide mode. On the basis of this, we construct hyperbolic metamaterials without negative dielectrics and experimentally verify their validity in the microwave range by directional propagation and imaging with a resolution of 0.087λ. By using several appropriate dielectrics, the extension of the imaging method to terahertz and infrared bands is also numerically discussed. The proposed method not only breaks the conventional barriers of plasmon-based lenses, but also bring possibilities in applications based on enhancing evanescent waves from microwave to infrared wavelengths, such as ultrasensitive optics, spontaneous emission, and light beam steering.