A waveguide metasurface based quasi-far-field transverse-electric superlens
基于波导超表面的准远场横向电超级透镜
導波路メタ表面ベースの準遠方場横電気スーパーレンズ
도파관 메타표면 기반 준 원거리 횡전기 슈퍼렌즈
Un superlente eléctrico transversal cuasi-campo lejano basado en una guía de ondas
Une superlentille électrique transversale quasi-champ lointain basée sur une métasurface de guide d'ondes
Квазидальнопольная поперечно-электрическая суперлинза на основе волноводной метаповерхности
¹ Shaanxi Province Key Laboratory of Micro and Nano Electro-Mechanical Systems, Northwestern Polytechnical University, Xi’an 710072, China
中国 西安 西北工业大学 陕西省微纳机电系统重点实验室
² Key Laboratory of Micro/Nano Systems for Aerospace (Ministry of Education), Northwestern Polytechnical University, Xi’an 710072, China
中国 西安 西北工业大学 空天微纳系统教育部重点实验室
³ Shaanxi Province Key Laboratory of Thin Films Technology and Optical Test, Xi’an Technological University, Xi’an 710021, China
中国 西安 西安工业大学 陕西省薄膜技术与光学检测重点实验室
⁴ Department of Optical Engineering, School of Electronic Science & Applied Physics, Hefei University of Technology, Feicui Road 420, Hefei 230601, China
中国 合肥 合肥工业大学 电子科学与应用物理学院 光学工程系
⁵ Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Hong Kong 999077, China
中国 香港 香港理工大学 应用生物及化学科技系
⁶ Department of Electrical and Electronic Engineering, Joint Appointment with School of Biomedical Sciences, The University of Hong Kong, Hong Kong 999077, China
中国 香港 香港大学生物科学学院/ 电气与电子工程系
⁷ Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong 999077, China
中国 香港 香港城市大学 材料科学及工程学系
The imaging capability of conventional lenses is mainly limited by the diffraction of light, and the so-called superlens has been developed allowing the recovery of evanescent waves in the focal plane. However, the remarkable focusing behavior of the superlens is greatly confined in the near-field regime due to the exponential decay of evanescent waves.
To tackle this issue, we design a waveguide metasurface-based superlens with an extraordinary quasi-far-field focusing capability beyond the diffraction limit in the present work. Specifically, we analyze the underlying physical mechanism and provide experimental verification of the proposed superlens. The metasurface superlens is formed by an array of gradient nanoslits perforated in a gold slab, and supports transverse-electric (TE) waveguide modes under linearly polarized illumination along the long axis of the slits.
Numerical results illustrate that exciting such TE waveguide modes can modulate not only optical phase but also evanescent waves. Consequently, some high-spatial-frequency waves can contribute to the focusing of the superlens, leading to the quasi-far-field super-resolution focusing of light. Under 405 nm illumination and oil immersion, the fabricated superlens shows a focus spot of 98 nm (i.e. λ/4.13) at a focal distance of 1.49 μm (i.e. 3.68λ) using an oil immersion objective, breaking the diffraction limit of λ/2.38 in the quasi-far field regime.
The developed metasurface optical superlens with such extraordinary capabilities promises exciting avenues to nanolithography and ultra-small optoelectronic devices.
