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TOM Metrology S3: Frontiers in Optical Metrology: Materials and thin films
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2:30pm - 3:00pm
INVITED Advances in 3D OCT Metrology using Wavelength-Swept Lasers Pusan National University, Korea, Republic of (South Korea) Optical coherence tomography (OCT) is a non-invasive imaging modality capable of providing high-resolution, three-dimensional visualization for both biomedical and metrological applications. Compared to classical time-domain OCT (TD-OCT), swept-source OCT (SS-OCT) offers faster imaging speeds and a better signal-to-noise ratio due to advancements in wavelength-swept laser (WSL) light sources. The performance and application range of a WSL are primarily determined by the laser’s linewidth, tuning range, linearity, and repetition rate. This presentation reviews the development and current status of WSL light sources and their imaging applications, with a focus on achieving higher speeds and improved precision in 3D metrology. 3:00pm - 3:15pm
Rapid Thickness Determination of Optical Thin Films from X-ray Diffraction Eastern Switzerland University of Applied Science, Switzerland A rapid, non-destructive method for determining thin film thickness from standard X-ray diffraction (XRD) data is introduced, called WHEATT (Williamson–Hall Estimation and Analysis of Thin-film Thicknesses). The approach applies Williamson–Hall analysis to routine 2θ/ω scans to extract crystallite size, which directly correlates with thickness in coherently grown epitaxial films. Validation on La0.5Sr0.5CoO3 demonstrates excellent agreement with Rutherford backscattering spectrometry (RBS), with errors below 1% in the coherent regime. WHEATT thus provides a simple, efficient, and broadly accessible route for accurate thickness estimation using conventional XRD measurements. 3:15pm - 3:30pm
A spectrometer sharper than its own encoder 1University of Eastern Finland, Finland; 2Tampere University, Finland We introduce a reconstructive spectrometer based on a deterministic single encoder scheme, where spectral information is encoded via angle–wavelength mapping and recovered by means of a physics aware deconvolution. The experimental implementation consists of a resonant metasurface on a rotation stage, together with a single pixel detector, resulting in a compact, self calibrated centimeter scale system. Despite an effective spectral point spread function of approximately 1.5 nm, the spectrometer achieves a spectral resolution of 37.4 pm over a bandwidth of about 20 nm. Direct benchmarking against a conventional high resolution spectrometer confirms the resolution and wavelength accuracy. 3:30pm - 3:45pm
Angle-resolved second harmonic generation for thin film characterisation 1Institute of Plasma Physics of the Czech Academy of Sciences; 2Faculty of Mechatronics, Informatics and Interdisciplinary Studies, Technical University of Liberec We present an all-optical method for the characterisation of thin centrosymmetric films based on second-harmonic generation (SHG), a nonlinear optical phenomenon highly sensitive to interfaces and symmetry breaking. This work reports on angle-resolved SHG measurements of dielectric centrosymmetric thin films together with data analysis based on theoretical modelling. The experiments are performed in reflection geometry using various polarisation combinations of the incident fundamental beam and the detected second-harmonic signal. Samples with varying film thicknesses, material compositions, and substrate types are investigated. The results show the potential of SHG as a non-destructive optical probe for thin-film characterisation. At the same time, we address the current challenges of this method, including physical limitations, fitting ambiguities, and other factors influencing the reliable interpretation of measured data. 3:45pm - 4:00pm
Fibre direction estimation in composite tapes using phase gradients of laser speckle Aerospace Faculty, Delft University Technology. Accurate estimation of fibre orientation in composite materials is essential for ensuring structural performance, particularly in aerospace applications. However, optical inspection methods are challenged by strong scattering and anisotropic surface properties, which obscure structural information in intensity based measurements. In this work, we demonstrate a noninterferometric approach for fibre direction estimation based on phase information extracted from laser speckle fields. Using experimentally acquired intensity measurements, the phase gradient information is reconstructed and analysed through gradient based techniques to extract directional features. Experiments on unidirectional GFRP tapes show that, although speckle patterns appear random in intensity, the phase gradients exhibit a clear directional bias aligned with fibre orientation. The method demonstrates reliable a estimation of fibre orientation, highlighting its potential for non-contact and inline inspection of composite materials. | ||
