Optical Characterisation of Particles via Phase and Intensity Imaging
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Solution Overview
Problem
Existing methods struggle to quantitatively determine the complex dipolar optical polarizability and scattering, absorption cross sections of particles made from materials other than gold, as they rely on macroscopic permittivity measurements that do not account for surface effects, and require complex experimental setups.
Innovation Solution
A method using phase and intensity imaging, combined with multilateral shift interferometry, to measure complex dipole optical polarizability and cross sections without prior knowledge of particle composition or geometry, employing a simpler setup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If macroscopic permittivity measurements are used to characterize particles, then the characterization is effective for gold nanoparticles, but it is not suitable for particles made of other materials exhibiting dominant surface effects or surface oxidations
Solution Approach 1:
The invention changes the measurement parameters from macroscopic permittivity to complex dipole polarizability and cross sections, which can be determined through phase and intensity imaging. This parameter transformation enables accurate characterization of particles made from diverse materials including metals, semiconductors, oxides, and nitrides, resolving the limitation of material-specific characterization methods
2Measurement precision
If different measurement systems are used to determine scattering and absorption cross sections, then complete optical characterization is achieved, but the experimental setup becomes complex and requires different systems for each measurement
Solution Approach 1:
The invention merges the measurement of phase and intensity information into a single optical imaging system, from which both scattering and absorption cross sections can be simultaneously determined. This unified approach eliminates the need for separate complex measurement systems while achieving complete optical characterization
Solution Approach 2:
The optical imaging system is designed to perform multiple functions: measuring phase, measuring intensity, and from these measurements, determining complex dipole polarizability, scattering cross section, and absorption cross section. This multi-functional system replaces multiple specialized instruments with a single versatile platform
3Loss of information
If complex polarizability extraction methods are used, then complete optical information including phase is obtained, but the polarizability extraction procedure becomes complex requiring inversion algorithms
Solution Approach 1:
The invention replaces complex mechanical inversion algorithms with a direct optical measurement approach. By measuring both phase and intensity directly through optical imaging, the system obtains complex polarizability information without requiring mathematical inversion procedures, thereby simplifying the data processing while retaining complete optical information
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
Accurately determines the complex dipole optical polarizability and cross sections of various particles, including metallic and dielectric types, with improved signal-to-noise ratio and robustness against focus and numerical aperture variations.
Implementation Method 1
Some particles, such as metallic nanoparticles (NPs), exhibit localized plasmon resonance effects around the visible/infrared range and have been widely studied for nanophotonic applications such as light confinement or heat generation at the nanoscale
Implementation Method 2
A method using phase and intensity imaging, combined with multilateral shift interferometry, to measure complex dipole optical polarizability and cross sections
Data Source
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AI summary
According to a first aspect, the present description concerns a method for measuring optical properties of at least one particle in a sample (10) and can be used, for example, for the quantitative determination of the complex dipole polarisability of at least one particle present in a sample. The optical characterisation method comprises illuminating the sample (10) by means of a light beam, the sample (10) being positioned in the object space of an optical system (120); acquiring at least one phase image and at least one intensity image of the at least one particle illuminated by the light beam, the acquisition being carried out in an analysis plane arranged in the image space of the optical system (120); and determining at least one optical property of the at least one particle based on the at least one phase image and at least one intensity image.