Fundamental electromagnetic approach to complex optical systems – FRAXOS

We will address the above described issues on several levels, taking advantage of both the expertise of Prof. Ingve Simonsen in theoretical and numerical approaches to the light scattering problems and the know-how of SVI and SGR in elaboration of complex structures and their optical characterization. With the help of Prof. Ingve Simonsen, we aim to develop pertinent modeling of several geometries with respect to light scattering and to simulate numerically their response. These models will be applied to understand the optical properties of existing products of SGR and samples of SVI. With this project we aim to reinforce optical activities of SVI. At the same time, in SVI the structures similar to those considered theoretically will be produced and optical characterization, namely, light scattering (in reflection and transmission) spectroscopic study of plasmon resonances, will be performed and compared to the simulations. In addition, regular monitoring by engineers of Saint-Gobain Recherche will provide the opportunity for direct application of the results of the research, identification of new structures and materials relevant for applications. Project contains three axes: light scattering from rough surfaces, light scattering from from nano-particles on a dielectric substrate, and finally bulk scattering of light caused by inclusions or defects (a random medium), and its coupling to the surface scattering. In all the three parts of the project, we aim at achieving a deeper understanding of the process of light scattering by nano-structures and disordered systems, which is a major axis of contemporary science. In addition, for simpler structures (nano-particles, simpler rough surfaces) we will develop practical tools (publically available software as GranFilm), which are able to predict the light scattering response. Such tools will be directly accessible to the applied scientific laboratories and R&D industrial centers.

The works that have been published so far as part of the FRAXOS project are devoted to surface random systems and surface periodic systems. In the first group of studies the goal was to reconstruct the statistical properties of the surface from the in-plane and co-polarized intensity scattered from it. To this end, the so-called phase perturbation theory was used and good results were achieved for s-to-s polarization for the scattering from dielectric surfaces ; see Phys. Rev. A 93, 043829 (2016). In parallel to these theoretical studies, one of the PhD students affiliated with the project has worked on the conception, fabrication and morphological characterization of model rough surfaces. The second group of studies are dealing with the reflection and transmission of polarized light through two-dimensional randomly rough surfaces. The simulations were performed on the basis of the reduced Rayleigh equation. By performing non-perturbative, purely numerical solutions of this equation, the mean differential reflection or transmission coefficients were be calculated. These quantities can directly be compared to what can be obtained in experimental studies. The final group of studies deal with periodic system of metallic particles supported by a dielectric substrate. Such system shows complex Mueller matrix response caused by localized surface plasmon resonances and Rayleigh anomalies. In a recent combined experimental and theoretical study we demonstrated that this optical response can be used for critical dimension metrology of a plasmonic photonic crystal; see Opt. Lett. 42, 2631 (2017). In addition to these published papers and ongoing experiments, work has been performed on the development of the GranFilm software for the calculation of the optical response of nano-particles supported by a planar substrate. Here both the core of the software and the python interface to it has been developed further.

We aim to use the characterization and measurements that we have performed on model rough surfaces to test various algorithms on experimental data for the extraction of statistical information on the sample morphologies. Such work is now in progress and we will be reported later on the results. A publication on the optical response of truncated supported particles is in the pipeline. Meanwhile, one of the PhD students affiliated with the project, has started accumulating optical data necessary for the validation and further development of GranFilm.

1. A.K. Gonzalez-Alcalde, J.-P. Banon, Ø.S. Hetland, A.A. Maradudin, E.R. Mendez, T. Nordam, and I. Simonsen, «Experimental and numerical studies of the scattering of light from a two-dimensional randomly rough interface in the presence of total internal reflection: Optical Yoneda peaks«, Opt. Express 24, 25995 (2016). 2. Ø. S. Hetland, A. A. Maradudin, T. Nordam, P. A. Letnes, and I. Simonsen «Numerical studies of the transmission of light through a two-dimensional randomly rough interface«, Phys. Rev. A 95, 043808 (2017). 3. V. Perez-Chavez, I. Simonsen, A. A. Maradudin, S. Blaize, and E. R. Mendez «Effective optical properties of supported silicon nanopillars at telecommunication wavelengths«, Opt. Commun. 399, 127 (2017). 4. T. Nesse, S. D. Eder, T. Kaltenbacher, J. O. Grepstad, I. Simonsen, and B. Holst, «Neutral-helium-atom diffraction from a micron-scale periodic structure: Photonic-crystal-membrane characterization«, Phys. Rev. A 95, 063618 (2017). 5. J.-P. Banon, T. Nesse, Z. Ghadyani, M. Kildemo, and I. Simonsen «Critical dimension metrology of a plasmonic photonic crystal based on Mueller matrix ellipsometry and the reduced Rayleigh equation«, Opt. Lett. 42, 2631 (2017).

Optical properties of high tech Saint-Gobain glass products are in the scope of this project. The technology of surface functionalization through thin films or coatings has matured and is now evolving towards the third dimension and including the role of interface roughness or patterning in light control. Prof. I. Simonsen (NTNU: Norwegian University of Science and Technology) is invited as chair of FRAXOS project in order to advance theoretical understanding of the impact of this third dimension on the optical behavior.

This project will follow three closely connected axes of research:
- the role of surface roughness in light scattering;
- the plasmonics properties of metallic nano-objects of complex shapes;
- the coupling between bulk and surface light scattering.
Thorough understanding of light-surface interaction along these three axes will allow for solving applied problems:
- design of new materials with prescribed optical properties;
- the use of optical response of real surface as a tool to discover its physical properties (such as topography).
The key outcome of the project will be the development of simulation toolboxes, released to the scientific community. Along with the simulations, elaboration and optical characterization of complex structures will allow for validation of theoretical approach.
FRAXOS will create a unique scientific environment around Prof. Ingve Simonsen contsisting of industry (Saint-Gobain Recherche) and the academic laboratory SVI (Laboratoire Mixte CNRS/Saint-Gobain “Surface du Verre et Interfaces”), supported by collaborating groups from INSP (Institut des NanoSciences de Paris) and ESPCI (Ecole Supérieure de Physique-Chimie Industrielles, Institut Langevin). For that aim a specialist in theoretical optics (Prof. Ingve Simonsen) will work with researchers having strong background in surface functionalization.