Miniature 3D Displacement Sensor Using Plasmonic Metasurfaces
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Solution Overview
Problem
Existing extrinsic Fabry-Perot Interferometer (EFPI) sensors face challenges with low reflectivity, fragile alignment, and limited directional measurement capabilities, which hinder their accuracy and applicability in measuring displacement and rotation in three-dimensional spaces.
Innovation Solution
A miniature, micrometer-accuracy 3D position-to-optical and rotation-to-optical displacement sensor is developed, utilizing a single-mode optic fiber with plasmonic metasurface resonators and a glass tube for robust measurements, and a tri-interferometer configuration for comprehensive displacement analysis, including three-component translational and rotational measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional EFPI sensors use fiber core reflection, then the sensor structure is simple, but the reflectivity is low resulting in low Q-factor
Solution Approach 1:
The patent changes the reflection mechanism from fiber core reflection to metasurface reflection, fundamentally altering the optical parameter to achieve high reflectivity and Q-factor while maintaining sensor functionality
Solution Approach 2:
The patent employs composite metasurfaces combining multiple materials with different optical properties to achieve both high reflectivity and wavelength selectivity, resolving the contradiction between simple structure and high Q-factor
2Volume of moving object
If traditional EFPI sensors use small core diameter fiber (8.2 μm), then the sensor can be compact, but the alignment and installation become time-consuming and fragile
Solution Approach 1:
The patent introduces a glass tube as an intermediary component that mechanically supports and protects the optical fiber, facilitating easier alignment and installation while maintaining compact sensor dimensions
Solution Approach 2:
The patent uses a disposable glass tube that simplifies the alignment process, where the tube serves as a temporary alignment aid during installation and can be discarded afterward, reducing the complexity of precise fiber alignment
3Device complexity
If traditional EFPI sensors measure only cavity change in light propagation direction, then the sensor structure is simple, but the measurement capability is limited to one direction
Solution Approach 1:
The patent transitions from one-dimensional cavity length measurement to three-dimensional displacement measurement by incorporating metasurfaces with wavelength-selective properties that respond to displacements in X, Y, and Z directions, enabling multi-axis sensing capability
Solution Approach 2:
The patent designs the metasurface to perform multiple functions simultaneously: providing high reflectivity for interferometric measurement, enabling wavelength-selective response for directional discrimination, and facilitating three-dimensional displacement sensing, thereby achieving universal measurement capability
4Manufacturing precision
If traditional EFPI sensors are aligned in collimated capillary tube, then the fiber alignment is precise, but the installation process becomes fragile and time-consuming
Solution Approach 1:
The patent performs preliminary alignment by positioning the fiber within the glass tube before final sensor assembly, pre-establishing the correct geometric relationship and reducing the time required during actual installation
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
The solution achieves high accuracy in 3D displacement measurements with a maximum error of 5.4 μm, enabling precise assessment of structural conditions under combined loads and overcoming the limitations of traditional EFPI sensors.
Implementation Method 1
the two surfaces generate two reflection waves with a time delay, inducing an interference fringe pattern in the output spectrum
Implementation Method 2
a series of plasmonic metasurface resonators with distinctive wavelength-selective characteristics in X- and Y-directions
Data Source
AI summary
A miniature, micrometer-accuracy, three-dimensional (3D) position-to-optical displacement sensor that has at least one extrinsic Fabry-Perot interferometer (EFPI) in Z direction and a series of plasmonic metasurface resonators with distinctive wavelength-selective characteristics in X and Y directions. The interferometer comprises at least one single mode optic fiber for light propagation, and a substrate mirror to create a light interference fringe as a function of distance between the mirror and the distal end of the optic fiber. Each plasmonic resonator is capable of modifying the substrate mirror and comprises an array of multiple unit nanostructure unit cells that are arranged in a two-dimensional (2D) square lattice or array in the X-Y plane. The nanostructure unit cells are preferably inscribed in the top layer of a three-layer thin film via the focused ion beam (FIB).