Hodaya Klimovsky | Searcharxiv

arXiv2026

Label-Free Microrefractometry of Interfacial Processes Using Fluorescent Smart Coverslips

Molecular dipoles near interfaces emit highly directional radiation due to near-field interactions, making surface-bound fluorophores sensitive probes of local physicochemical changes. We introduce smart coverslips, stably coated with uniform, brightly fluorescent nanobead films, that exploit refractive-index-dependent emission shifts for sensitive micro-refractometry in small volumes. Supercritical-angle fluorescence refractometry uses single back-focal-plane images to allow us real-time RI sensing and nanometric thin-film height measurements without the need for multi-angle or multi-wavelength acquisition. Our fast, label-free, and non-invasive approach allows measurements of thin-film properties and monitoring of interfacial dynamics on a standard inverted microscope and is broadly applicable to nanobiophotonics, chemical sensing, and in-situ materials analysis.

physics.optics↗

arXiv2025

Combinatorial Sample-and Back-Focal-Plane (BFP) Imaging. Pt. I: Instrument and acquisition parameters affecting BFP images and their analysis

The back-focal plane (BFP) of a high-numerical aperture objective contains the fluoro-phore radiation pattern, which encodes information about the axial fluorophore position, molecular orientation and the local refractive index of the embedding medium. BFP image acquisition and analysis are common to conoscopy, k-space imaging, supercritical-angle fluorescence (SAF) and single-molecule detection, but they are rarely being used in biological fluorescence. This work addresses a critical gap in quantitative microscopy by enabling reliable, real-time BFP imaging under low-light conditions and/or short exposure times, typical of biological experiments. By systematically analyzing how key parameters - such as Bertrand lens position, defocus, pixel size, and binning - affect BFP image quality and SAF/UAF ratios, we provide a robust framework for accurate axial fluorophore localization and near-membrane refractive-index measurements. The described hardware- and software integration allows for multi-dimensional image-series and online quality control, reducing experimental error and enhancing reproducibility. Our contributions lay the foundation for standardized BFP imaging across laboratories, expanding its application to dynamic biological systems, and opening the door to machine learning-based analysis pipelines. Ultimately, this work transforms BFP imaging from an expert-dependent technique into a reproducible and scalable tool for surface-sensitive fluorescence microscopy.

physics.optics↗