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Article

Free-Space Nonreciprocal Transmission Based on Nonlinear Coupled Fano Metasurfaces

1
Department of Electrical Engineering, City College of The City University of New York, New York, NY 10031, USA
2
Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY 10031, USA
3
Department of Electrical Engineering, Wayne State University, Detroit, MI 48202, USA
4
Physics Program, Graduate Center, City University of New York, New York, NY 10016, USA
*
Author to whom correspondence should be addressed.
Photonics 2021, 8(5), 139; https://doi.org/10.3390/photonics8050139
Received: 6 April 2021 / Revised: 19 April 2021 / Accepted: 20 April 2021 / Published: 23 April 2021
(This article belongs to the Special Issue Advances in Complex Media Electromagnetics)
Optical nonlinearities can enable unusual light–matter interactions, with functionalities that would be otherwise inaccessible relying only on linear phenomena. Recently, several studies have harnessed the role of optical nonlinearities to implement nonreciprocal optical devices that do not require an external bias breaking time-reversal symmetry. In this work, we explore the design of a metasurface embedding Kerr nonlinearities to break reciprocity for free-space propagation, requiring limited power levels. After deriving the general design principles, we demonstrate an all-dielectric flat metasurface made of coupled nonlinear Fano silicon resonant layers realizing large asymmetry in optical transmission at telecommunication frequencies. We show that the metrics of our design can go beyond the fundamental limitations on nonreciprocity for nonlinear optical devices based on a single resonance, as dictated by time-reversal symmetry considerations. Our work may shed light on the design of flat subwavelength free-space nonreciprocal metasurface switches for pulsed operation which are easy to fabricate, fully passive, and require low operation power. Our simulated devices demonstrate a transmission ratio >50 dB for oppositely propagating waves, an operational bandwidth exceeding 600 GHz, and an insertion loss of <0.04 dB. View Full-Text
Keywords: nonlinear metasurface; nonreciprocal metasurface; nonreciprocity; Fano resonance nonlinear metasurface; nonreciprocal metasurface; nonreciprocity; Fano resonance
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MDPI and ACS Style

Mekawy, A.; Sounas, D.L.; Alù, A. Free-Space Nonreciprocal Transmission Based on Nonlinear Coupled Fano Metasurfaces. Photonics 2021, 8, 139. https://doi.org/10.3390/photonics8050139

AMA Style

Mekawy A, Sounas DL, Alù A. Free-Space Nonreciprocal Transmission Based on Nonlinear Coupled Fano Metasurfaces. Photonics. 2021; 8(5):139. https://doi.org/10.3390/photonics8050139

Chicago/Turabian Style

Mekawy, Ahmed, Dimitrios L. Sounas, and Andrea Alù. 2021. "Free-Space Nonreciprocal Transmission Based on Nonlinear Coupled Fano Metasurfaces" Photonics 8, no. 5: 139. https://doi.org/10.3390/photonics8050139

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