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PLEOM microscopy

Electro-Optical (EO) Microscopy is one of the key experiments in our nonlinear imaging platform, allowing to map the EO properties of a sample.

Point by point with optical resolution, The ability of  a material to change its refractive index under the application of a static Electric field (Pockels effect) is measured by interferometry, in an imaging mode driven by piezo motors.
This property is related to the electronic polarizability and  symmetry features of materials, complementary to the parent quadratic nonlinear susceptibility at the origin of Second harmonic generation (SHG).

Whereas SHG requires high intensity pulsed lasers (cf nonlinear nanophotonics platform), PLEOM requires a  simple He-Ne laser source, which is a major asset in terms of portability and cost.

EO Microscopy is a new imaging method based on the Pockels linear electrooptic effect, well known in the context of optical communications to provide the key modulation function. By applying via a microelectrode array a known low frequency electric field , the spatial distribution of electrooptic properties can be measured and imaged. An inverse approach consists in using a pre-characterized material to detect, measure and image a (quasi)-static electric field, opening the way to a non invasive optical detection and imaging scheme for membrane or neuronal potentials.

As their SHG counterpart, EO properties are expressed by a rank-3 tensor with its coefficients singled-out by adequate polarization schemes for both the electric field and probe beam. These properties result from multi-scale collective organizational features of constituent materials or bio-tissues. In the case of biological systems, such as cell membranes, the arrangement of biomolecules is governing biological functions, which can be read-out locally via the electrooptic tensor

PLEOM (Pockels linear EO Microscopy) is an evolving prototype set-up entirely developed and patented by LPQM and applied successfully so far to the characterization and study of several materials such as ferroelectric crystals and nano-crystals, molecular crystals, artificial lipid membranes doped with nonlinear dyes and polypeptides.

A key-project run in collaboration with Institut Gustave Roussy (Pr . Lluis Mir), and the SATIE Lab of Institut d'Alembert (Pr. Le Pioufle) is aiming at understanding the EO properties of cell membranes and inferring their organization and properties from EO images. This project is part of a general endeavor towards the improvement of  drug delivery by electroporation into cancer cells and in particular, a better understanding of the role of membranes in drug vectorization and related theranostic approaches.
Another project, in collaboration with Tel Aviv University (Pr. Ellenbogen), deals with a new generic family of electrooptic materials based on self-assembled polypeptides. Preliminary experiments have demonstrated that such materials exhibit EO coefficients of magnitudes comparable to the best inorganic ferroelectric crystals.

Achievements :

In collaboration with the Laboratoire SATIE (Pr. Le Pioufle), artificial phospholipidic bi-layer membranes  have been studied in order to calibrate the experiment for real cell measurements.
First EO signals have been seen with the addition of nonlinear dyes in one of side of the membrane. 

B. Hajj et al. Biophysical Journal, 97, 2913-2921 (2009)

Available  equipements :


- Laser He-Ne stabilisé 633 nm

- "home made" microscopes

- 2 photodiodes

Localisation :

Bât. IDA (room B36)