Institut Fresnel

keywords : quantitative phase imaging, nanoplasmonics, gold nanoparticles, 2D materials, metasurfaces

QLSI is a quantitative phase imaging technique, capable of measuring both the intensity and the phase of a light beam, with high spatial resolution, and high sensitivity, in a particularly simple manner. When implemented on an optical microscope, QLSI can optically characterize nano- and micro-objects.

QLSI is based on the simple use of a so-called wavefront sensor that consists of the association of a 2-dimensional diffraction grating with a regular camera, as schematized in the figure (a) below. The grating is positioned at a millimetric distance from the camera sensor. Any distortion of the incoming optical wavefront impinging on the grating yields a distortion of the fringes on the camera. Then, using a demodulation algorithm in the Fourier space of the acquired image, one can retrieve both the intensity and the phase distribution of the light beam.

In 2017-2020, the Fresnel Institute has shown that QLSI represents a powerful tool to optically characterize nanophotonic objects, such as nanoparticles [3,4], 2D-materials such as graphene and metasurfaces [2] and metasurfaces [5]. Relevant properties such as the complex polarizability, susceptibility, the extinction, scattering, absorption cross sections, and more, can all be measured quantitatively. QLSI also enables the photothermal characterization of plasmonic nanoparticles. QLSI represents thus a powerful tool for metrology in nanophotonics [1].

Publications

2023

2022

2021

2020