Asymmetry‐Based Plasmonic Phase Manipulation for a Compact Far‐Field Optical Lens. Issue 2 (4th October 2020)

• Record Type: Journal Article
• Authors: Darak, Mayur S.; Mote, Rakesh G.; Shukla, Shobha
• Is Part Of: Advanced photonics research. Volume 1:Issue 2(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-10-04
• Subjects: asymmetries -- nanofocusing -- optical components -- phase manipulation -- plasmonics; Photonics -- Periodicals; 621.36505
• DOI: 10.1002/adpr.202000018
• Languages: English
• ISSNs: 2699-9293

Abstract

Abstract : Fresnel zone plates (FZPs) enable diffractive focusing of light by controlling its in‐plane transmission. When a plasmonic FZP is illuminated with a linearly polarized light, the component of the electric field perpendicular to the structure yields a split focal spot at the desired focal region and the total electric field is observed to yield the broadened focal spot. Due to broadening of the focal spot, one of the most important characteristics of a focusing structure gets affected, i.e., its resolution. Herein, the concept of geometric asymmetry‐based plasmonic phase manipulation is proposed to obtain focusing in the far‐field domain using plasmonic zone plates (ZPs) with an improved resolution. By directly applying the concept, a 3D phase manipulative ZPs (PMZPs) is proposed. Further, a modified planar version with reduced fabrication complexity, planar phase manipulative ZPs (PPMZPs) is proposed. The finite‐difference time‐domain (FDTD) simulations are carried out to analyze the focusing properties of the lenses. Full width at half maximum (FWHM) of the focal spot for PPMZPs reduces by 410 nm, i.e., 0.77 λ 0 as compared with the FWHM of focal spot for conventional FZPs. The proposed lenses have potential applications in nanoimaging, nanosensing, and nanolithography. Abstract : Two configurations of phase manipulative plasmonic zone plates are proposed for far‐field focusing of a linearly polarized light. Lenses are designed via geometrical asymmetry‐based plasmon phase tuning. Lenses are investigated numerically. Electric fields are confined to a focal spot smaller by 0.77 times incident wavelength than conventional Fresnel zone plates. Proposed lenses have potential applications in nanoimaging, nanosensing, and nanolithography.