Place : 1 avenue Augustin-Fresnel, 91767 Palaiseau, France
Manager : Elzbieta Gradauskaite, elzbieta.gradauskaite@cnrs-thales.fr
Scientific Context
Layered Carpy-Galy oxides (general formula AₙBₙO₃ₙ₊₂, e.g. La2Ti2O7) are a versatile family of ferroelectric materials consisting of perovskite blocks separated by additional oxygen planes. Their uniaxial in-plane polarization, arising from cooperative oxygen octahedral rotations, makes them fundamentally different from conventional ferroelectric perovskites and potentially valuable for electro-optic applications (e.g. photonic integrated circuits). In our laboratory, through epitaxy we stabilized high-quality, single-crystalline thin films of these compounds, with nearly fourfold increase in ferroelectric polarization [1]. This opens the way to investigate their electro-optic properties, in particular, the Pockels effect, which describes the linear modulation of refractive index of a material under an applied electric field. Studying this effect in layered ferroelectrics will provide insight into how their uniaxial in-plane polarization influence electro-optic coefficients, thus evaluating their potential for compact on-chip electro-optic
modulators [2].
Work program & skills acquired during internship
During the internship, the student will learn the basics of thin-film structural characterization (X-ray diffraction, atomic force microscopy) to determine film orientation and quality; perform ellipsometry measurementsto extract the refractive indices and assess the material’s birefringence; set up and carry out electro-optic coefficient measurements using a laser, Soleil-Babinet compensator, polarizer, and photodiode combined with lock-in amplifier detection [3] to quantify the effective electro-optic coefficients; compare results with theoretical predictions/canonical ferroelectric materials and uncover how the anisotropic layered structure and uniaxial in plane polarization affect electro-optic properties.
The project will primarily focus on thin-film optical characterization and data interpretation, with a brief
introduction to material properties. The knowledge in optical measurements (ellipsometry, birefringence, etc.) is a plus.
- Gradauskaite, E. et al. Adv. Mater. 37 (12), 2416963 (2025).
- Abel, S. et al. Nat. Mater. 18, 42 (2019).
- Sando, D. et al. Phys. Rev. B 89, 195106 (2014).
Work environment
You will be working under the supervision of: Elzbieta Gradauskaite (elzbieta.gradauskaite@cnrs-thales.fr , CNRS), Manuel Bibes (CNRS), Jérôme Bourderionnet (Thales), Gilles Feugnet (Thales).