Millimeter-wave metalens with extended depth of focal on the short focal length

Abstract

Millimeter wave (mm-wave) metalens has shown significant progress in recent years. However, the existing works in the literature on the extended depth of focal (EDOF) metalens present limitations for mm-waves. More specifically, the good performance of the EDOF requires a focal length larger than the radius of the metalens, which limits its miniaturization applications. In this work, mm-wave metalens with EDOF on the short focal length was proposed. The focus distribution was equally divided and the spin Hall effect was employed to guarantee the uniform focus intensity. From our analysis, it was demonstrated that the designed metalens can work at mm-wave frequencies and also achieve extended focal depth at half the metalens’ radius. The proposed metalens has the unique characteristics of short focal length (The focal diameter ratio is 0.36) with EDOF. Moreover, it can be used in the mm-wave field for short-distance imaging and detection, also the development of high-power metalens applications may be facilitated.

Stretchable Dual-Axis Terahertz Bifocal Metalens with Flexibly Polarization-Dependent Focal Position and Direction

“…As an artificial design of subwavelength array, metamaterial processes unique characteristics such as the chiral effect, electromagnetically induced transparency, and perfect absorption. − Recently, metasurface, a two-dimensional manifestation of metamaterial has been widely explored to modulate the electromagnetic properties of incident waves such as amplitude, phase, and polarization. − Unlike traditional phase modulators based on phase accumulation, metasurface shapes the wavefront with precise arrangements of phase-shifting elements. − Meta-atoms are usually composed of dielectric or metal subwavelength structures, which could be modified to provide the phase coverage from 0 to 2π for incident wave under various polarization states including but not limited to circular or linear polarization. − Additionally, the research of metasurface has been explored in real-life applications, e.g., holography, invisible cloak, beam deflectors, and metalens. − Among these applications, metalens have aroused much interest from worldwide researchers. The booming developments of miniaturized optical systems indicate higher demands on the focusing and imaging components while a traditional lens is limited by its bulk volume, narrow working bandwidth, and fixed focal performance.…”

“…The booming developments of miniaturized optical systems indicate higher demands on the focusing and imaging components while a traditional lens is limited by its bulk volume, narrow working bandwidth, and fixed focal performance. Metalens break these bottlenecks and exhibit merits of achromatic aberration, subresolution, tunable focal length, and multifocus. − Specifically, the working spectrum of metalens is widely extended across extreme ultraviolet, visible light, infrared (IR) wave, and terahertz (THz) wave to microwave with proper arrangements of both geometry scale and material of the meta-atom. − ,− Along with low energy and high penetration, the THz metalens have become a hotspot of research topics with promising applications. , …”