Advanced Science<\/a>, represent the first full parametric analysis of helical structures for THz frequencies and show the potential of 3D printing for fabricating THz devices.<\/p>\nLending a handedness<\/p>\n
The THz frequency on the electromagnetic spectrum is the backbone of 5G\/6G telecommunications and a potential non-ionizing alterative to X-rays and gamma rays, in addition to being able to detect chemical and biological signatures that are inaccessible at other wavelengths. However, common optical components like waveplates and cameras are difficult to realize because the THz frequency is too high for electronics and its wavelength is too long for photonics. In the study, the team focused on one of these missing pieces: quarter waveplates to generate circularly polarized beams.<\/p>\n
\u201cMetamaterials are the most effective way to generate circularly polarized beams in the THz frequency range using optimized geometries, as there are currently no optical crystals available for such long electromagnetic wavelengths,\u201d said Materials Science Division scientist and Lawrence fellow Wonjin Choi, who led the project.<\/p>\n
Circularly polarized beams twist like a spiral staircase in a right-handed or left-handed direction, giving them a \u201chandedness\u201d property known as chirality. Chirality is a fundamental property of biomolecules like amino acids, DNA and proteins, and using a chiral beam to investigate their molecular vibrations can reveal critical information about structure, composition and biological activity. The THz regime supercharges this capability, making it possible to study much larger groups of atoms and detect vibrations resulting from long-range ordering and secondary-bonding networks. This can help quickly identify or characterize diseases and potentially hazardous materials like drugs and explosives.<\/p>\n
Creating circularly polarized beams involves using chiral structures as quarter waveplates, which introduce a 90-degree phase shift between two orthogonal components of a wave\u2019s electric field. Previous attempts at making THz chiral structures have resulted in limited transmission and frequency range, but the team saw an opportunity to make something much more optimal with two-photon polymerization (2PP), an ultrahigh resolution light-based 3D printing technique.<\/p>\n
\u201cAt around 300 \u00b5m, the wavelength of the THz frequency is a sweet spot [for 2PP], so we can create any geometries in that length scale comfortably and control it very nicely,\u201d said Materials Engineering Division (MED) staff engineer Xiaoxing Xia, who led the printing efforts for the project.<\/p>\n
Optimization to innovation<\/p>\n
With the flexibility to print nearly any shape, the team focused on optimizing helixes. Helixes are difficult to design because they have extra variables to consider like number of turns, radius, height and handedness, but their inherent circular geometry makes them ideal for creating strong circular polarization.<\/p>\n
\u201cOne of the most intuitive and powerful approaches to inducing chirality is to create a helix,\u201d said Choi. \u201cWe nearly perfectly optimized these parameters through simulations and then precisely 3D-printed the structures to achieve the desired functionality.\u201d<\/p>\n
The printed helixes demonstrated strong broadband activity in the THz range and reliably created circularly polarized beams at nearly any azimuthal angle. The team also discovered that single helixes have distinct left-handed or right-handed signals, and that arranging them in an array had a coupling effect that enhanced the response of both types. This inspired the world\u2019s first \u201cchiral QR code.\u201d<\/p>\n
\u201cI realized we can make pixelation if we make black pixels right-handed and white pixels left-handed,\u201d said Choi. \u201cA typical QR code encodes information in binary amplitude or brightness, but this one does so in phase with left- and right-handed polarization rotation.\u201d<\/p>\n
Made from a printed helical array, the chiral QR code\u2019s information is inaccessible unless viewed through a special \u201chandedness\u201d filter that is properly polarized and within the correct electromagnetic frequency. This makes it possible either hide or add an important layer of security in sensitive environments.<\/p>\n
\u201cFor hospitals or banks or military purposes, sometimes we might need to add encryption while maintaining the convenience of the rapid scan,\u201d said Choi.<\/p>\n
New applications<\/p>\n
For Xia\u2019s team, the study was an opportunity to test their innovative parallel printing technique, which uses novel optical materials called metalenses to tightly focus the laser for direct 2PP printing. A large metalens array can generate more than 100,000 focal spots at the same time, creating a 3D printing assembly line. The array can also be turned on and off to control printing path and create complex, layered and aperiodic structures significantly faster.<\/p>\n
\u201cBecause we have active control of the focal spots, we can selectively print helixes of different handedness in different locations,\u201d said Xia. \u201cIt would take a very long time to print on a commercial printer, but our parallel printer really improves the throughput to make the application tangible.\u201d<\/p>\n
Potential applications for the helixes include chiral molecular sensing, band-pass filtering for 5G\/6G telecommunications, as well detection and sensing for fields like medicine, biology, astronomy and more. The study also shows the potential of combining high-throughput 3D printing with materials science and optimization to create new THz technologies that take advantage of the frequency\u2019s full potential.<\/p>\n
Other co-authors include LLNL’s Widi Moestopo, Songyun Gu, Jae-Hyuck Yoo and Michael Armstrong, and Professor Taeil Lee from Gachon University in South Korea.<\/p>\n
-Noah Pflueger-Peters<\/p>\n","protected":false},"excerpt":{"rendered":"Newswise \u2014 Researchers at Lawrence Livermore National Laboratory (LLNL) have optimized and 3D-printed helix structures as optical materials…\n","protected":false},"author":2,"featured_media":237070,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77],"tags":[125573,7260,18,9656,19,17,125574,909,913,941,452,133,82],"class_list":{"0":"post-237069","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-3d-printinghelical-structurescircular-polarizationchiral-opticsqr-codestelecommunicationsmaterials-science","9":"tag-all-journal-news","10":"tag-eire","11":"tag-engineering","12":"tag-ie","13":"tag-ireland","14":"tag-lawrence-livermore-national-laboratory","15":"tag-materials-science","16":"tag-nanotechnology","17":"tag-newswise","18":"tag-physics","19":"tag-science","20":"tag-technology"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/115733786998265570","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/237069","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=237069"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/237069\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/237070"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=237069"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=237069"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=237069"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}