Blok, H.

Gbur, G.

Lenstra, D.

Schouten, H.F.

Visser, T.D.

English

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 Phase singularities and enhanced transmission at asubwavelength slitCitation for published version (APA):Schouten, H. F., Visser, T. D., Gbur, G., Lenstra, D., & Blok, H. (2003). Phase singularities and enhancedtransmission at a subwavelength slit. Optics and Photonics News, 14(12), 23-23.Document status and date:Published: 01/01/2003Document Version:Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can beimportant differences between the submitted version and the official published version of record. Peopleinterested in the research are advised to contact the author for the final version of the publication, or visit theDOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and pagenumbers.Link to publicationGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, pleasefollow below link for the End User Agreement:www.tue.nl/taverneTake down policyIf you believe that this document breaches copyright please contact us at:openaccess@tue.nlproviding details and we will investigate your claim.Download date: 08. Jul. 2024December 2003 ■ Optics & Photonics News 23NEAR-FIELD OPTICSPhase Singularities and Enhanced Transmission at aSubwavelength SlitH.F. Schouten, T.D. Visser, G. Gbur, D. Lenstra and H. BlokR ecent research has demonstrated aconnection between two seeminglydisparate and blossoming fields of opti-cal science, namely, singular optics andthe anomalously high transmission of light through subwavelength sizeapertures.Anomalous light transmission,first demonstrated experimentally byEbbesen et al.,1 is the surprising prop-erty that subwavelength size aperturesin metal plates can transmit much morelight than predicted by the standardtheory of aperture diffraction. It hasbeen suggested that this enhancedtransmission is due to the coupling of light to surface plasmons. A goodunderstanding of the origins ofenhanced transmission could lead tonovel near-field optical measurementdevices, among other things.It has also been known for sometime that the phase of a wave field canexhibit unusual yet physically relevantbehavior in the neighborhood of pointsat which the field amplitude is zero. Thesystematic study of such singular pointshas developed into the vibrant field nowreferred to as singular optics.2 Thephase of the field in the neighborhoodof a singular point can exhibit a richvariety of behaviors, such as a vortexstructure, and such points possess cer-tain conserved quantities such as topo-logical charge.We have undertaken two-dimen-sional numerical calculations of theelectromagnetic field in the neighbor-hood of a subwavelength size slit in athin metal plate. In particular, thebehavior of the time-averaged Poyntingvector was analyzed by use of a rigorousintegral equation method.3,4 We foundthat the field of power flow typicallypossesses numerous phase singularities;an example of such a field is shown inFig. 1. More importantly it was foundthat, by increasing the slit width, theannihilation of phase singularities andthe resulting smoother power flow coincide with the onset of anomalouslight transmission through the slit. Thisanalysis was done in a configurationthat does not support surface plasmons,indicating that anomalous transmissioncan occur even in their absence.Our results give new insight into thestudy of transmission through subwave-length size apertures and show that agood understanding of the phenomenonrequires that the behavior of the phasesingularities of the field be taken intoaccount.References1. T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio and P.A. Wolff, Nature 391, 667-9 (1998).2. M. S. Soskin and M. V. Vasnetsov, “Singular optics,” inProgress in Optics, E. Wolf, ed. (Elsevier, Amsterdam,2001), Vol. 42, pp. 219-76.Figure 1. Illustration of the power flow in the neighborhood of a 200-nm-wide slit in a 100-nm-thick plate of evaporated silver (with refractive index n = 0.05 + i 2.87). The incident field (coming from below) has a wavelength of =500 nm. Features (a) and (d) are left-hand vortices, (b) and (c) are right-hand vortices and (e) and (f) are saddles. For thisexample the transmission coefficient T = 1.11. The color coding indicates the modulus of the (normalized) Poynting vector.(a)(f)(e)(c) (d)100 nm 0 1(b)3. H. F. Schouten, T. D. Visser, D. Lenstra and H. Blok,Phys. Rev. E 67, 036608 (2003).4. H. F. Schouten, T. D. Visser, G. Gbur, D. Lenstra and H.Blok, Opt. Express 11, 371-80 (2003), www.opticsex-press.org.H.F. Schouten, T.D. Visser (tvisser@nat.vu.nl), G. Gbur and D. Lenstra are with the  Department ofPhysics and Astronomy, Free University, Amsterdam,The Netherlands. H. Blok is with the Department ofElectrical Engineering, Delft University ofTechnology, Delft, The Netherlands.Tell us what you think: http://www.osa-opn.org/survey.cfm

Phase singularities and enhanced transmission at a subwavelength slit

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Phase singularities and enhanced transmission at a subwavelength slit

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