Plasmonic Nanoantenna Encoding for Miniature Security Marking
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Solution Overview
Problem
Existing optical security elements, such as plasmonic devices with metal-dielectric interfaces, are not suitable for creating miniature marking devices for small objects due to the requirement of large dimensions and angular dependence of visual effects, which limits their application in protecting small valuables like gems or jewelry.
Innovation Solution
A device using plasmonic nanoantennas of the metal-dielectric-metal type, arranged on a supporting structure to encode spatial information, where each pixel is defined by a position and value, allowing for efficient optical encoding in a spectral band, enabling miniature marking devices with dimensions on the order of the wavelength, independent of observation angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional plasmonic devices with metal-dielectric interfaces are used, then optical security effects are achieved, but the device dimensions become too large and angular dependence becomes strong, making them unsuitable for miniature marking devices
Solution Approach 1:
The patent divides the conventional large-scale plasmonic grating into discrete plasmonic nanoantennas, each with dimensions on the order of the wavelength. This segmentation allows the device to achieve the required optical security effects while reducing the overall device dimension to suitable sizes for miniature marking devices on small objects.
Solution Approach 2:
The patent changes the dimensional parameters of the plasmonic structures from conventional grating dimensions (dozen or so wavelengths) to nanoantenna dimensions (on the order of wavelength). This parameter change enables the device to maintain security effects while achieving miniature scale suitable for gems and jewelry.
2Reliability
If conventional plasmonic gratings are used, then optical encoding is achieved, but strong angular dependence of visual effect limits application in gems or jewelry where angle-independent colors are sought
Solution Approach 1:
The patent assigns different optical responses to different plasmonic nanoantennas based on their local geometrical parameters (shape, dimensions, orientation). By carefully designing the local properties of each nanoantenna, the device achieves angle-independent optical encoding, as each nanoantenna's response is inherently tied to its specific geometric configuration rather than external observation angle.
3Length of stationary object
If plasmonic nanoantennas with dimensions on the order of wavelength are used, then miniature marking devices are achieved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs parameter changes through material selection and geometric design to achieve the required optical responses. By optimizing the geometrical parameters of the nanoantennas within manufacturable tolerances and selecting appropriate materials, the device achieves miniature dimensions while maintaining feasibility for standard manufacturing processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the creation of miniature optical encoding devices that can securely mark small objects by varying the geometrical parameters of plasmonic nanoantennas to generate specific optical responses, achieving effective counterfeiting protection without angular dependence, thus suitable for small valuables.
Implementation Method 1
each plasmonic nanoantenna is resonant to at least one wavelength comprised in said first spectral band of observation
Implementation Method 2
the plasmonic nanoantennas are arranged spatially on the supporting structure so that at one pixel of the image, a subset of one or more plasmonic nanoantenna(s) is associated, whose optical polarization response and in a spectral band comprised in the first spectral band of observation corresponds to a value of said pixel
Data Source
AI summary
According to a first aspect, the present description relates to a device for optically encoding an image, which device is intended to be observed in at least one first spectral band of observation. The encoding device comprises a supporting structure and a set of metal-dielectric-metal plasmonic antennae formed on said supporting structure, each plasmonic antenna being resonant at at least one wavelength comprised in said first spectral band of observation, the plasmonic antennae being arranged spatially on the supporting structure in such a way as to form at least one first spatial encoding of said image in said first spectral band of observation.