Helical structures have attracted considerable attention due to their inherent optical chirality. Here, we report a unique type of 3D Janus plasmonic helical nanoaperture with direction-controlled polarization sensitivity, which is simply fabricated via the one-step grayscale focused ion beam milling method. Circular dichroism in transmission of as large as 0.72 is experimentally realized in the forward direction due to the spin-dependent mode coupling process inside the helical nanoaperture. However, in the backward direction, the nanoaperture acquires giant linear dichroism in transmission of up to 0.87. By encoding the Janus metasurface with the two nanoaperture enantiomers having specified rotation angles, direction-controlled polarization-encrypted data storage is demonstrated for the first time, where a binary quick-response code image is displayed in the forward direction under the circularly polarized incidence of a specified handedness, while a distinct grayscale image is revealed in the backward direction under linearly polarized illumination with a specified azimuthal angle. We envision that the proposed Janus helical nanoapertures will provide an appealing platform for a variety of applications, which will range from multifunctional polarization control, enantiomer sensing, data encryption and decryption to optical information processing.


Mechanical and Aerospace Engineering

Research Center/Lab(s)

Intelligent Systems Center

Second Research Center/Lab

Center for Research in Energy and Environment (CREE)


The authors acknowledge support from the Office of Naval Research under Grant no. N00014-16-1-2408 and the National Science Foundation under Grants nos. ECCS-1653032 and DMR-1552871.

Keywords and Phrases

Dichroism; Digital storage; Enantiomers; Ion beams; Optical data processing; Plasmonics; Plasmons; Polarization, Circularly polarized incidence; Controlled polarization; Focused ion beam milling methods; Helical structures; Linearly polarized; Optical chirality; Polarization control; Quick response code, Cryptography

International Standard Serial Number (ISSN)


Document Type

Article - Journal

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Final Version

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© 2019 The Author(s), All rights reserved.

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Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Publication Date

01 Dec 2019