arXiv subjects

Omer Shavit

Publications and source records attributed to Omer Shavit.

3 recordsLinked to original sources

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↗

arXiv2023

A Colour-Encoded Nanometric Ruler for Axial Super-Resolution Microscopies

Recent progress has boosted the resolving power of optical microscopies to spatial dimensions well below the diffraction limit. Yet, axial super-resolution and axial single-molecule localisation typically require more complicated implementations than their lateral counterparts. In the present work, we propose a simple solution for axial metrology by providing a multi-layered single-excitation, dual-emission test slide, in which axial distance is colour-encoded. Our test slide combines on a standard microscope coverslip substrate two flat, thin, uniform and brightly emitting fluorophore layers, separated by a nanometric transparent spacer layer having a refractive index close to a biological cell. The ensemble is sealed in an index-matched protective polymer. As a proof-of-principle, we estimate the light confinement resulting from evanescent-wave excitation in total internal reflection fluorescence (TIRF) microscopy. Our test sample permits, even for the non-expert user, a facile axial metrology at the sub-100-nm scale, a critical requirement for axial super-resolution, as well as near-surface imaging, spectroscopy and sensing.

physics.optics↗

arXiv2019

Nanoporous Metallic Network as a Largescale 3D Source of Second Harmonic Light

Second harmonic generation (SHG) is forbidden from most bulk metals, because metals are characterized by a net zero electric-field in equilibrium. This limit breaks down when reaching nanoscale dimensions, as have been shown for metallic nano-particles and nano-cavities. Yet, nonlinear response from a three-dimensional (3D) macroscale metallic piece comprising sub-optical wavelength features remains a challenge for many years. Herein, we introduce a largescale nanoporous metallic network whose building-blocks are assembled into an effective nonlinear conductive material, with a considerable conversion efficiency in a wide range of optical wavelengths. The high nonlinear response results from the network structure having a large surface area on which the inversion symmetry is broken. In addition, because of the 3D structure, hot-spots can be formed also in deeper focal plans of the metallic network, and thus can give rise to coherent addition of the signal. The solid connectivity between the nanoscale building-blocks also plays a role, because it forms a robust network which may respond in a collective manner to form very intense hot-spots. Broadband responses of the metallic network are observed both by SHG and cathodoluminescence (CL). The large-scale dimension and generation of randomized hot-spots make this 3D metallic network a promising candidate for applications like photocatalysis, sensing, or in optical imaging as structured illumination microscopy.

physics.app-ph↗