Valentin Allard will defend his thesis entitled “Optical Nearfield Microscopy : from qualitative analysis of biomaterials towards quantitative characterization of dielectric thin films” on Thursday, october 30th at 11:00 a.m. in room Pierre Coton of our Lab.
The jury is composed of :
– Benoît Cluzel, ICB, Reviewer
– Davy Gérard, L2n, Reviewer
– Anne Charrier, CINaM, Examiner
– Baptiste Fix, ONERA, Examiner
– Aude Lereu, Institut Fresnel, Thesis Supervisor
– Julien Lumeau, Institut Fresnel, Co-supervisor
– Philip Schaeffer, Neaspec-Attocube, invited member
Abstract : Near-field optical microscopy enables overcoming the diffraction limit and achie-ving nanometric resolution, independent of the illumination wavelength. Among its configurations, scattering-type Scanning Near-field Optical Microscopy (s-SNOM) is distinguished by the use of an illuminated nanometric tip that generates a confined field whose coupling with the sample provides local information. These complex inter-actions make it difficult to convert the detected signal into reliable quantitative data. Thus, despite its strong potential, the technique is still mainly employed for qualitative measurements. This manuscript presents two complementary parts. The first focuses on the development of a quantitative analysis methodology applied to dielectric thin films in the visible range. Reference samples with controlled thicknesses and refractive indices were fabricated to study the influence of these parameters on near-field inter-actions. Measurements were compared with numerical models, allowing a physical interpretation of the results. This work stands out by proposing a quantification ap-proach adapted to a domain where studies remain scarce and technically demanding. The second part addresses a qualitative study of lignin recalcitrance mechanisms in wood cell walls. Biomimetic samples were analyzed using infrared s-SNOM to visualize lignin distribution and to assess its interaction with cellulose-hemicellulose fibrils. Overall, this work highlights the potential of s-SNOM for both quantitative analysis and qualitative exploration of complex materials.
Keywords : s-SNOM, nearfield optics, dielectric thin films, quantification, lignin recal-citrance.
