Subscriber access provided by University of Sunderland
Communication
Active Two-dimensional Steering of Radiation from a Nano-Aperture Laura S Dreissen, Hugo F Schouten, Wim Ubachs, Shreyas B Raghunathan, and Taco visser Nano Lett., Just Accepted Manuscript • DOI: 10.1021/acs.nanolett.8b03319 • Publication Date (Web): 29 Oct 2018 Downloaded from http://pubs.acs.org on October 30, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Nano Letters
Active Two-dimensional Steering of Radiation from a Nano-Aperture Laura S. Dreissen,1 Hugo F. Schouten,1 Wim Ubachs,1,2 Shreyas B. Raghunathan,3 and Taco D. Visser1,4,∗ 1
Department of Physics and Astronomy, LaserLaB, Vrije Universiteit De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands 2
Advanced Research Center for Nanolithography, Science Park 110, 1098 XG Amsterdam, The Netherlands 3
ASML, De Run 6501,
5504 DR Veldhoven, The Netherlands 4
Department of Physics and Astronomy, University of Rochester Rochester, NY 14627, USA
∗
Corresponding author:
[email protected] Abstract We experimentally demonstrate control over the direction of radiation of a beam that passes through a square nano-aperture in a metal film. The ratio of the aperture size and the wavelength is such that only three guided modes, each with different spatial symmetries, can be excited. Using a spatial light modulator, the superposition of the three modes can be altered, thus allowing for a controlled variation of the radiation pattern that emanates from the nano-aperture. Robust and stable steering of 9.5◦ in two orthogonal directions was achieved. Keywords: Nano–apertures, Radiation steering, Diffraction, Guided modes, Optical switch
1
ACS Paragon Plus Environment
Nano Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 2 of 12
Since the seminal work by Bethe1 , many studies have been devoted to understanding the physical mechanisms that underly the transmission of radiation through nano-apertures2−11 , a topic of both fundamental and technical interest. Several methods have been proposed to dynamically control the total transmission, in order to achieve all-optical switching12−14 . A useful next step would be to actively steer the radiation, something of great importance for applications such as selective probing of nano-samples, and all-optical circuits for telecommunication. Directional transmission has been achieved, for example, by using a single sub-wavelength slit surrounded by surface corrugations or grooves15−16 , and by varying the refractive index of neighboring sub-wavelength slits17 . However, all these approaches lead to a static asymmetry of the radiated field. What has not been achieved so far, is the possibility to dynamically steer the transmitted field in two orthogonal directions. Here we report an experiment in which such steering is clearly demonstrated. Central to our approach is the selective excitation of guided modes in a wavelength-sized aperture in a metal film. We previously used a similar technique to control the direction in which surface plasmons polaritons are launched18 , and to obtain one-dimensional beam steering from a narrow slit19 . A non-trivial extension to two-dimensional steering has now been realized by using a square aperture illuminated by light with a wavelength such that only three guided modes can be excited. Using a spatial light modulator the phase of each of the three modes is controlled. The transmitted field, which is a coherent superposition of these modes, can thus be altered, leading to a change in the directionality of the emanating field. The radiation from an aperture can be understood by analyzing the guided (i.e., nonevanescent) modes that it can sustain. Consider a square hole with sides a, in a perfect conductor, such that
√ λ
