Indefinite metamaterials for optical applications

The resolution of conventional optical systems is limited because of Abbe’s diffraction limit, which dictates that objects placed closer than approximately half the wavelength of light used cannot be completely resolved. Hence, it becomes imperative to find means of performing near-field (Superlensi...

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Main Author: Bisht, Ankit
Other Authors: Wu Yongling, Linda
Format: Theses and Dissertations
Language:English
Published: 2016
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Online Access:https://hdl.handle.net/10356/68937
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-689372023-03-04T16:42:23Z Indefinite metamaterials for optical applications Bisht, Ankit Wu Yongling, Linda Li Shuzhou School of Materials Science & Engineering A*STAR Singapore Institute of Manufacturing Technology DRNTU::Science::Physics::Optics and light The resolution of conventional optical systems is limited because of Abbe’s diffraction limit, which dictates that objects placed closer than approximately half the wavelength of light used cannot be completely resolved. Hence, it becomes imperative to find means of performing near-field (Superlensing) and label-free real time far-field super-resolution imaging (hyperlensing) at the nanoscale. Although by utilizing anisotropic permittivities, metal-dielectric multilayers have been successful in reconstructing the high-frequency components from sub-λ objects, yet they remain cumbersome and expensive to make. Most of the multilayer structures require multiple vacuum deposition cycles and are plagued by stringent requirements on surface roughness of metallic layers. In contrast to the multilayer structure here we propose a 3D hyperbolic metamaterial model composed of metallic nanorods arranged in sea-urchin geometry as a hyper-lensing device, which is capable of projecting and magnifying diffraction limited information into the far-field at Near-infrared (NIR) frequencies. The hyperlens generates a band of flat hyperbolic dispersions in spherical coordinates, which in turn supports the propagation of high wave-vector spatial harmonics leading to far-field super-resolution imaging. Using full-wave Finite-difference time-domain (FDTD) simulations with diffraction limited trimer, quadrumer and ringed objects etched on thin perfect electric conductor (PEC) films, we show that the hyperlens model can achieve magnification factors of up to 10X in the far-field (~4.5λ from object’s surface) under a light source with a wavelength of 1 μm, with successful resolution down to 220 nm (~λ/5). The magnified image field distribution projected into the far-field is shown to follow the object under reduction in symmetry. A possible method for the fabrication of envisaged AuNWA-PDMS composite metamaterials is presented. The method shown is capable of yielding thin flexible polymer films embedded with free-standing metallic nanowires. Further, fabrication of diffraction-limited objects for both Superlensing (slits on film) and hyperlensing (slits on curved Cr-caps) are presented. These results are important for making progress in the realization of real-time bio-molecular imaging systems, eliminating the need for near-field scanning, destructive electron microscopy and various image post-processing techniques. DOCTOR OF PHILOSOPHY (MSE) 2016-08-15T02:36:01Z 2016-08-15T02:36:01Z 2016 Thesis Bisht, A. (2016). Indefinite metamaterials for optical applications. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/68937 10.32657/10356/68937 en 128 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Science::Physics::Optics and light
spellingShingle DRNTU::Science::Physics::Optics and light
Bisht, Ankit
Indefinite metamaterials for optical applications
description The resolution of conventional optical systems is limited because of Abbe’s diffraction limit, which dictates that objects placed closer than approximately half the wavelength of light used cannot be completely resolved. Hence, it becomes imperative to find means of performing near-field (Superlensing) and label-free real time far-field super-resolution imaging (hyperlensing) at the nanoscale. Although by utilizing anisotropic permittivities, metal-dielectric multilayers have been successful in reconstructing the high-frequency components from sub-λ objects, yet they remain cumbersome and expensive to make. Most of the multilayer structures require multiple vacuum deposition cycles and are plagued by stringent requirements on surface roughness of metallic layers. In contrast to the multilayer structure here we propose a 3D hyperbolic metamaterial model composed of metallic nanorods arranged in sea-urchin geometry as a hyper-lensing device, which is capable of projecting and magnifying diffraction limited information into the far-field at Near-infrared (NIR) frequencies. The hyperlens generates a band of flat hyperbolic dispersions in spherical coordinates, which in turn supports the propagation of high wave-vector spatial harmonics leading to far-field super-resolution imaging. Using full-wave Finite-difference time-domain (FDTD) simulations with diffraction limited trimer, quadrumer and ringed objects etched on thin perfect electric conductor (PEC) films, we show that the hyperlens model can achieve magnification factors of up to 10X in the far-field (~4.5λ from object’s surface) under a light source with a wavelength of 1 μm, with successful resolution down to 220 nm (~λ/5). The magnified image field distribution projected into the far-field is shown to follow the object under reduction in symmetry. A possible method for the fabrication of envisaged AuNWA-PDMS composite metamaterials is presented. The method shown is capable of yielding thin flexible polymer films embedded with free-standing metallic nanowires. Further, fabrication of diffraction-limited objects for both Superlensing (slits on film) and hyperlensing (slits on curved Cr-caps) are presented. These results are important for making progress in the realization of real-time bio-molecular imaging systems, eliminating the need for near-field scanning, destructive electron microscopy and various image post-processing techniques.
author2 Wu Yongling, Linda
author_facet Wu Yongling, Linda
Bisht, Ankit
format Theses and Dissertations
author Bisht, Ankit
author_sort Bisht, Ankit
title Indefinite metamaterials for optical applications
title_short Indefinite metamaterials for optical applications
title_full Indefinite metamaterials for optical applications
title_fullStr Indefinite metamaterials for optical applications
title_full_unstemmed Indefinite metamaterials for optical applications
title_sort indefinite metamaterials for optical applications
publishDate 2016
url https://hdl.handle.net/10356/68937
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