{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:47:34Z","timestamp":1760240854764,"version":"build-2065373602"},"reference-count":38,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2019,10,18]],"date-time":"2019-10-18T00:00:00Z","timestamp":1571356800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Johns Hopkins University Discovery Grant","award":["80046764"],"award-info":[{"award-number":["80046764"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Overcoming the diffraction limit, which enables focusing much less than the wavelength, requires tailoring the evanescent spectrum of an aperture\u2019s field distribution. We model and simulate a corrugated near field plate, which can generate a sub-wavelength focus in inhomogeneous background media. All reactive coupling, between the metasurface near field plate and the focusing domain and among the corrugations in the metasurface, is taken into consideration with the finite element method, which we solve in combination with a constraint to generate a desired focus. Various geometries for the near field plate are considered and we demonstrate that the proposed method can effectively create a deeply sub-wavelength focus within a layered medium having properties resembling brain tissue. Such a device could find use as a detector of biological signals or for hyperthermic treatment near the skin surface.<\/jats:p>","DOI":"10.3390\/s19204534","type":"journal-article","created":{"date-parts":[[2019,10,18]],"date-time":"2019-10-18T11:24:15Z","timestamp":1571397855000},"page":"4534","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Sub-Wavelength Focusing in Inhomogeneous Media with a Metasurface Near Field Plate"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8212-5891","authenticated-orcid":false,"given":"Andrew C.","family":"Strikwerda","sequence":"first","affiliation":[{"name":"Johns Hopkins Applied Physics Lab, 11100 Johns Hopkins Road, Laurel, MD 20723, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1448-817X","authenticated-orcid":false,"given":"Timothy","family":"Sleasman","sequence":"additional","affiliation":[{"name":"Johns Hopkins Applied Physics Lab, 11100 Johns Hopkins Road, Laurel, MD 20723, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"William","family":"Anderson","sequence":"additional","affiliation":[{"name":"Johns Hopkins School of Medicine, 733 N Broadway, Baltimore, MD 21205, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ra\u2019id","family":"Awadallah","sequence":"additional","affiliation":[{"name":"Johns Hopkins Applied Physics Lab, 11100 Johns Hopkins Road, Laurel, MD 20723, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,10,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1016\/S0079-6638(07)50005-3","article-title":"The history of near-field optics","volume":"50","author":"Novotny","year":"2007","journal-title":"Prog. 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