Fadwa Joud

Imaging gold nanoparticles in living cell environments using heterodyne digital holographic microscopy

This paper describes an imaging microscopic technique based on heterodyne digital holography where subwavelength-sized gold colloids can be imaged in cell environments. Surface cellular receptors of 3T3 mouse fibroblasts are labeled with 40 nm gold nanoparticles, and the biological specimen is imaged in a total internal reflection configuration with holographic microscopy. Due to a higher scattering efficiency of the gold nanoparticles versus that of cellular structures, accurate localization of a gold marker is obtained within a 3D mapping of the entire samples scattered field, with a lateral precision of 5 nm and 100 nm in the x,y and in the z directions respectively, demonstrating the ability of holographic microscopy to locate nanoparticles in living cell environments.

Imaging a vibrating object by Sideband Digital Holography

We obtain quantitative measurements of the oscillation amplitude of vibrating objects by using sideband digital holography. The frequency sidebands on the light scattered by the object, shifted by n times the vibration frequency, are selectively detected by heterodyne holography, and images of the object are calculated for different orders n. Orders up to n = 120 have been observed, allowing the measurement of amplitudes of oscillation that are significantly larger than the optical wavelength. Using the positions of the zeros of intensity for each value of n, we reconstruct the shape of vibration the object.

Fringe free holographic measurements of large amplitude vibrations

In the measurement of the amplitude of vibration of objects, holographic imaging techniques usually involve fringe counting; because of the limited resolution of the images, measurements of large amplitudes are not accessible. We demonstrate a technique that suppresses the necessity of fringe counting--frequency sideband imaging--where the order of the sideband is considered a marker of the amplitude. The measurement is completely local: no comparison with another reference point on the object is necessary. It involves a sharp variation of a signal, which makes it robust against perturbations. The method is demonstrated in an experiment made with a vibrating clarinet reed; phase modulations as large as 1000 rad have been measured.

Two-step distortion-free reconstruction scheme for holographic microscopy

We propose a three-dimensional holographic reconstruction procedure applicable with no a priori knowledge about the recording conditions enabling distortion-free three-dimensional object reconstruction.

Vibration motions studied by Heterodyne Holography

Playing with amplitude, phase and frequency of both reference and signal arms, heterodyne holography is well adapted to vibration analysis. Vibration sidebands can be imaged and stroboscopic measurement sensitive to mechanical phase can be made

Holographic microscopy for the three-dimensional exploration of light scattering from gold nanomarkers in biological media

The 3D structure of light scattering from dark-field illuminated live 3T3 cells marked with 40 nm gold nanomarkers is explored. For this purpose, we use a high resolution holographic microscope combining the off-axis heterodyne geometry and the phase-shifting acquisition of the digital holograms. Images are obtained using a novel 3D reconstruction method providing longitudinally undistorted 3D images. A comparative study of the 3D reconstructions of the scattered fields allows us to locate the gold markers which yield, contrarily to the cellular structures, well defined bright scattering patterns that are not angularly titled and clearly located along the optical axis. This characterization is an unambiguous signature of the presence of the gold biological nanomarkers, and validates the capability of digital holographic microscopy to discriminate them from background signals in live cells.

Three dimensional tracking of gold nanoparticles using digital holographic microscopy

In this paper we present a digital holographic microscope to track gold colloids in three dimensions. We report observations of 100nm gold particles in motion in water. The expected signal and the chosen method of reconstruction are described. We also discuss about how to implement the numerical calculation to reach real-time 3D tracking.

Digital Holography at Ultimate Shot Noise Level

We present an Off-Axis Phase-Shifting Digital Holographic technique able to make digital holography at shot noise level. We discuss the advantages of this technique and we give application examples.

Off-axis phase-shifting holographic interferometry for the 3D localization of cellular transmembrane receptors tagged with gold nanomarkers

In this communication, we show that off-axis digital holography combined to phase-shifting acquisition of holograms is an effective microscopic tool to fully localize, in three dimensions, transmembrane receptors of living cells tagged with Gold nanocolloids. Gold nanoparticles, known for their interesting optical properties as well as for their noncytotoxicity are used here as biomarkers to target the cellular receptors.