Phd : Engineering surface roughness for light absorbers

CNRS; France; Sur place; EUR 25 000 - 35 000; Plein temps

Résumé du poste

A leading research institute in France is looking for a First Stage Researcher in optics engineering to tackle challenges related to stray light in optical systems. The successful candidate will develop simulations in Matlab and explore the relationship between surface properties and absorption. A background in physics or engineering is required, along with skills in optics, photonics, and programming. This is a full-time PhD position with a start date of September 1st, 2026.

Qualifications

• Experience in physics and engineering.
• Strong understanding of optics and photonics.
• Programming skills in Matlab.

Responsabilités

• Conduct research on surface roughness and absorption in optical systems.
• Develop software and simulations in Matlab.
• Study the relationship between surface properties and absorption.

Connaissances

Physics

Optics

Photonics

Electromagnetism

Programming

Formation

Engineering school or Master 2

Outils

Matlab

Description du poste

Organisation/Company CNRS Department Institut Fresnel Research Field Physics » Optics Engineering » Simulation engineering Researcher Profile First Stage Researcher (R1) Positions PhD Positions Country France Application Deadline 15 Feb 2026 - 12:00 (Europe/Paris) Type of Contract Temporary Job Status Full-time Hours Per Week 35 Offer Starting Date 1 Sep 2026 Is the job funded through the EU Research Framework Programme? Not funded by a EU programme Is the Job related to staff position within a Research Infrastructure? No

Offer Description

In many fields, the elimination of stray light remains a major challenge. In particular, stray light is one of the main factors limiting the performance of onboard matrix detectors and the resolution of next-generation gravitational wave interferometers.

The classic approach to increasing substrate absorption involves depositing a stack of thin optical layers that act as an anti-reflective coating. This technology is now extremely effective and has led to the development of metal-dielectric components that reduce stray light, combining achromaticity with insensitivity to both the angle of incidence and polarization.

However, the requirements of optical systems necessitate further improvements in the performance of light absorbers, particularly in the infrared range, where thin film control is more problematic. In this context, an alternative technology consists of texturing the surface of the substrate. This texturing was first observed on the eyes of certain insects: it is known as the moth-eye effect (Kryuchkov, M. et al. Reverse and forward engineering of Drosophila corneal nanocoatings. Nature 585, 2020). Since the 1980s and the rise of ion etching techniques for semiconductors, black silicon, with its monocrystalline silicon needles, has also exhibited increased absorption properties. Finally, black coating (https://www.rp-photonics.com/black_coatings.html ) is a market where photonics start-ups that have developed manufacturing processes sell their products and offer services.

These manufacturing processes have been developed empirically over a few years; they do not currently benefit from accurate modeling of electromagnetic wave-matter interaction. In particular, none of the models developed to date apply to black coatings. This is because the extreme geometries (including very steep slopes) and high index jumps of these structures place them well outside the validity range of the approximate methods. As for the rigorous methods, which are necessarily numerical, they require computing resources and calculation times that quickly become prohibitive.

Black coatings often combine surface roughness with porosity or volume inhomogeneities. In this work, we focus on surface roughness, for which the most appropriate rigorous method is the boundary integral method. This technique for numerically solving Maxwell's equations was developed (Tsang, L, et al. Scattering of electromagnetic waves: numerical simulations. John Wiley & Sons, 2004) in the 1990s for microwave remote sensing and optically rough surfaces. These rough surfaces had moderate slopes, which ensured the convergence of iterative algorithms (Krylov methods).

The proposed research therefore begins with the case of two-dimensional electromagnetic scattering, where the systems of equations derived from the boundary integral method can be solved directly (LU decomposition). In this context, we will study the relationship between surface roughness, medium absorption, and surface reflectance. In particular, we will seek to identify the parameters that govern absorption processes, a subject that has yet to be explored. These results will be used to guide manufacturing processes toward optimal performance.

The increase in absorption is undoubtedly linked to the appearance of very steep slopes, due to the phenomenon of multiple reflections. This observation leads us to study parameterized surfaces that cannot be described by functions of the type z=h(x). This class of surfaces constitutes an original area of research, which will enable us to get closer to porous media and determine the existence of micro-light wells.

Software development, simulations, and other parametric studies will be carried out in the Matlab environment, on personal computers and on a laboratory computing server.

Engineering school or Master 2, skills in physics and engineering, Optics, photonics, electromagnetism, and programming