{"id":7405,"date":"2016-01-25T06:20:14","date_gmt":"2016-01-25T06:20:14","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=7405"},"modified":"2016-01-25T06:27:41","modified_gmt":"2016-01-25T06:27:41","slug":"nanoscale-sieves-snare-would-be-thieves","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/nanoscale-sieves-snare-would-be-thieves\/","title":{"rendered":"Nanoscale sieves snare would-be thieves"},"content":{"rendered":"

Bio-inspired algorithms enable a pattern of thousands of nanoscale holes into metal films for high-tech optical security.<\/strong><\/em><\/span><\/p>\n

\"Dense<\/a>
Dense arrays of light scattering nanoholes can make anti counterfeiting holograms more secure. \u00a9 2016 A*STAR Institute of Materials Research and Engineering<\/figcaption><\/figure>\n

Bank notes and credit cards may soon feature improved anti counterfeiting holograms thanks to a \u2018photon sieve\u2019 developed by Singapore’s Agency for Science, Technology and Research (A*STAR) researchers and co-workers.<\/span>

Holograms contain complex, three-dimensional image information that makes them difficult \u2014 but not impossible \u2014 to counterfeit. One way to improve their security is by using sophisticated devices that enhance holographic resolution. Nanophotonic devices deploy arrays of nanoscale light scattering pixels that encode additional layers of information through \u2018near field\u2019 optical interactions between lasers and the pixels.<\/span>

Recently, researchers have shown nanoscale holes carved into thin metal sheets to be effective light scattering pixels. Surprisingly, when these nanoholes are arranged randomly, instead of periodically, the generated hologram becomes more uniform. Designing devices with randomly arranged components, however, is technically challenging, as parameters such as nanohole radius and spacing can vary over a wide range of values.<\/span>

To overcome these obstacles, Jinghua Teng from the A*STAR Institute of Materials Research and Engineering and colleagues devised a theoretical method that deconstructs the complex diffracted field from a single nanohole into simple analytical expressions that can be solved exactly. By superimposing the solutions together, they can calculate local, specified electric fields instead of expending significant computational resources to numerically simulate the entire nanophotonic array.<\/span>

<\/p>\n

[pullquote]The researchers demonstrated another application of their approach by designing a \u2018superfocusing\u2019 system that can resolve objects smaller than the wavelength of light.[\/pullquote]<\/p>\n

The researchers turned to genetic algorithms to efficiently arrange the holes in a photon sieve arrangement. By repeatedly pairing, crossing, and mutating \u2018chromosomes\u2019 containing different \u2018genes\u2019 \u2014 labels of different nanohole sizes and positions \u2014 an aperiodic pattern evolves that optimizes holographic light control based on the simplified electric field calculations.<\/span>

<\/p>\n

Next, the team used electron-beam lithography<\/span>
Nanofabrication technique in which a focused beam of electrons is used to etch custom shapes on an electron-sensitive surface\u00a0<\/span>to turn their design into a practical device by etching over 34, 000 aperiodic nanoholes into a thin chromium film (see image). The resulting prototype boosted diffraction efficiency by nearly 50 per cent compared to conventional nanophotonic devices with image resolution hundreds of times better. Common holographic errors or \u2018artefacts\u2019 such as twin images were also eliminated through this technique.<\/span>

<\/p>\n

\"The<\/a>
The IMRE team working on the photon sieves (Jinghua Teng seated). \u00a9 2016 A*STAR Institute of Materials Research and Engineering<\/figcaption><\/figure>\n

\u201cThe high quality holographic images are promising for applications like anti counterfeiting, optical encryption and portable information identification system,\u201d says Teng. \u201cFor example, it could be used in anti counterfeiting in banknotes, with its ultra-compact size, high quality, and even multi level holographs.\u201d<\/span>

The researchers demonstrated another application of their approach by designing a \u2018superfocusing\u2019 system that can resolve objects smaller than the wavelength of light. With the nanoholes arranged into concentric rings, the photon sieve lens focuses light down to spots just 200 nanometers wide \u2014 scales useful for biological imaging and optical manipulations.<\/span>

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering and the Data Storage Institute.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Bank notes and credit cards may soon feature improved anti counterfeiting holograms thanks to a \u2018photon sieve\u2019 developed by Singapore’s Agency for Science, Technology and Research (A*STAR) researchers and co-workers.<\/p>\n","protected":false},"author":6,"featured_media":7406,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-7405","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252-238x300.jpg",238,300,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",286,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",52,65,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",300,378,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",76,96,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/01\/3252.jpg",150,189,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/7405","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=7405"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/7405\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/7406"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=7405"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=7405"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=7405"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}