Terahertz Fresnel-zone-plate film lens based on double-layer metamaterial phase shifter

Zhengli Han, Yuma Takida, Seigo Ohno, Hiroaki Minamide

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We have developed a thin THz-wave planar lens based on the phase-patterned Fresnel zone plate (FZP) concept to obtain a high transmittance and short focal length in free space. The FZP lens was designed for focusing THz waves at 1.0 THz (λ=300 μm) with a transmittance of more than 80% and a focal length of 24 mm (80λ). The developed FZP lens was made of polymer BCB as a flexible film substrate with concentric zones of metamaterial-based phase shifter patterns with a subwavelength thickness of approximately 48 μm (0.16λ). To obtain the THz-wave phase retardation of i€/2 compared to the naked polymer substrate, we employed the metamaterial unit structure consisting of double-layer unsplit ring resonators (USRRs) with a 32-μm distance between the two layers. The experimental result confirms that the FZP lens creates a focus by constructive interference of incident THz waves through concentric zones of metamaterial-patterned and un-patterned regions. By using a narrowband THz-wave beam from an injection-seeded THz-wave parametric generator, the measured focus spot size of 0.57 mm at full width at half maximum was obtained at the designed frequency of 1.0 THz. Using this FZP lens, the THz-wave imaging test in transmission geometry has also been demonstrated.

Original languageEnglish
Title of host publicationTerahertz Photonics
EditorsMona Jarrahi, Sascha Preu, Dmitry Turchinovich
PublisherSPIE
ISBN (Electronic)9781510634688
DOIs
Publication statusPublished - 2020
EventTerahertz Photonics 2020 - none, France
Duration: 2020 Apr 62020 Apr 10

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume11348
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Conference

ConferenceTerahertz Photonics 2020
CountryFrance
Citynone
Period20/4/620/4/10

Keywords

  • Film metamaterial
  • Fresnel zone plate
  • double-layer pattern
  • phase shifter
  • planar lens
  • terahertz wave

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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