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Ultrathin Nonlinear Metasurface for Optical Image Encoding
journal contribution
posted on 2017-04-14, 00:00 authored by Felicitas Walter, Guixin Li, Cedrik Meier, Shuang Zhang, Thomas ZentgrafSecurity of optical
information is of great importance in modern society. Many cryptography
techniques based on classical and quantum optics have been widely
explored in the linear optical regime. Nonlinear optical encryption
in which encoding and decoding involve nonlinear frequency conversions
represents a new strategy for securing optical information. Here,
we demonstrate that an ultrathin nonlinear photonic metasurface, consisting
of meta-atoms with 3-fold rotational symmetry, can be used to hide
optical images under illumination with a fundamental wave. However,
the hidden image can be read out from second harmonic generation (SHG)
waves. This is achieved by controlling the destructive and constructive
interferences of SHG waves from two neighboring meta-atoms. In addition,
we apply this concept to obtain gray scale SHG imaging. Nonlinear
metasurfaces based on space variant optical interference open new
avenues for multilevel image encryption, anticounterfeiting, and background
free image reconstruction.
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quantum opticsmeta-atominformationOptical Image Encoding Securityinterferenceimage encryptionSHG wavesNonlinear metasurfacesUltrathin Nonlinear Metasurfacescale SHG imagingultrathin nonlinear photonic metasurfacespace variantnonlinear frequency conversionsimage reconstructionMany cryptography techniques
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