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- Title
3-D Metamaterial Based Terahertz Planoconcave Lenses for Linearly and Circularly Polarized Waves.
- Authors
Marishwari, Muthusamy; Subramanian, Venkatachalam; Zhengbiao Ouyang; Yogesh, Natesan
- Abstract
A three-dimensional negative index (NI) metamaterial (MTM) is realized at terahertz (THz) frequencies. The structure is composed of orthogonally oriented cross-bars with arrows on each corner embedded in a dielectric cube. The proposed 3-D MTM is symmetric along all the principal axes and shows a polarization-insensitive, wide-incident-angle negative refractive index regime centered at 0.862 THz with an operational bandwidth of 0.234 THz (27.15%). Using staircase approximation, the proposed 3-D NI MTM has been designed into a THz parabolic planoconcave lens (PCL). A PCL made of a NI medium is a counterpart of a positive index planoconvex lens and focuses on the near-field region. The designed PCL shows 3-D focusing functionality for linearly and circularly polarized THz waves at 0.85 THz. The designed PCL has a short focal length and high numerical aperture (NA) with sub-wavelength focusing spot sizes. The computed FWHMs along transversal directions are 0:46λ(x) × 0:49λ(y) for transverse electric (TE) polarized wave, 0:46λ(x) × 0:49λ(y) for left-circularly polarized (LCP) wave, and 0:50λ(x) × 0:42λ(y) for right-circularly polarized (RCP) wave, respectively. The corresponding back focal lengths of the realized PCLs are 1:07λ, 1:03λ, and 0:98λ, and the focal depths are 0:40λ, 0:48λ, and 0:41λ for linear, LCP, and RCP waves, respectively. A short review of recent progress in manufacturing techniques for the fabrication of the proposed 3-D MTM is further highlighted. Since the proposed 3-D MTM PCL configurations show the far-field focusing of linearly/circularly polarized waves, imaging with high optical power requirements can be met for THz waveband applications.
- Subjects
NEGATIVE refraction; SUBMILLIMETER waves; FOCAL length; METAMATERIALS; NUMERICAL apertures; FABRICATION (Manufacturing)
- Publication
Progress in Electromagnetics Research B, 2023, Vol 98, p21
- ISSN
1937-6472
- Publication type
Article
- DOI
10.2528/pierb22101305