Enhanced Quantitative Wavefront Imaging for Nano-Object Characterization.

Quantitative phase imaging enables precise and label-free characterizations of individual nano-objects within a large volume, without a priori knowledge of the sample or imaging system. While emerging common path implementations are simple enough to promise a broad dissemination, their phase sensitivity still falls short of precisely estimating the mass or polarizability of vesicles, viruses, or nanoparticles in single-shot acquisitions. In this paper, we revisit the Zernike filtering concept, originally crafted for intensity-only detectors, with the aim of adapting it to wavefront imaging. We demonstrate, through numerical simulation and experiments based on high-resolution wavefront sensing, that a simple Fourier-plane add-on can significantly enhance phase sensitivity for subdiffraction objects─achieving over an order of magnitude increase (×12)─while allowing the quantitative retrieval of both intensity and phase. This advancement allows for more precise nano-object detection and metrology.

3D nanoparticle superlocalization with a thin diffuser.

We report on the use of a thin diffuser placed in the close vicinity of a camera sensor as a simple and effective way to superlocalize plasmonic nanoparticles in 3D. This method is based on holographic reconstruction via quantitative phase and intensity measurements of a light field after its interaction with nanoparticles. We experimentally demonstrate that this thin diffuser can be used as a simple add-on to a standard bright-field microscope to allow the localization of 100 nm gold nanoparticles at video rate with nanometer precision (1.3 nm laterally and 6.3 nm longitudinally). We exemplify the approach by revealing the dynamic Brownian trajectory of a gold nanoparticle trapped in various pockets within an agarose gel. The proposed method provides a simple but highly performant way to track nanoparticles in 3D.