Digital holographic microscopy at fundamental and second harmonic wavelengths

Christian Depeursinge, Etienne Shaffer
SPIE, 2009
Conference paper

Optical second harmonic generation, thanks to its coherent nature, is a suitable signal for interferometric measurements, such as digital holography: a well-established imaging technique that allows recovering of the complex diffraction wavefields from which it is possible to extract both amplitude- contrast and quantitative phase images. We believe that application of digital holography to non-linear optical fields might ultimately be the key to phase- related functional imaging. In a first approach, we report here on second harmonic generation digital holographic microscopy, and present its application to (1) discrimination of nanoparticles of different nature - here polystyrene microspheres and barium titanate (BaTiO3) nanoparticles - and to (2) 3D-mapping of a distribution of BaTiO3 nanoparticles.

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Christian Depeursinge, Etienne Shaffer
SPIE, 2009
Conference paper

Abstract

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https://infoscience.epfl.ch/record/140420?ln=en

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Second-harmonic generation

Second-harmonic generation (SHG, also called frequency doubling) is a nonlinear optical process in which two photons with the same frequency interact with a nonlinear material, are "combined", and g

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FORCETOC Quantitative phase contrast microscopy or quantitative phase imaging are the collective names for a group of microscopy methods that quantify the phase shift that occurs when light wave

Digital holographic microscopy investigation of second harmonic generated at a glass/air interface

Christian Depeursinge, Jonas Kühn, Nicolas Pavillon, Etienne Shaffer

Optical second harmonic generation, thanks to its coherent nature, is a suitable signal for interferometric measurements, such as digital holography: a well-established imaging technique that allows recovering complex diffraction wavefields from which it is possible to extract both amplitude- contrast and quantitative phase images. Here, we report on a new, multi-functional form of microscopy: second harmonic generation digital holographic microscopy. As a proof of concept, we have investigated the second harmonic signal generated at the glass/air interface of a microscope slide under focused femtosecond laser illumination and propose for the first time a representation and interpretation of the recovered phase. In this simple, yet very educative case study, we observe that the second harmonic is generated by the axial component of the incident field polarization

2009

Digital holography for second harmonic microscopy

Christian Depeursinge, Etienne Shaffer

Quantitative phase images make digital holographic microscopy (DHM) an excellent instrument for metrological, but also for biological applications, where it can reveal deformations and morphological details at ultrahigh resolution in the order of a few nanometers only, while also precisely determining the refractive index across a sample (e.g. cell or neuron). On the other hand, non-linear light-matter interactions have also proved very useful in microscopy. For instance, second harmonic generation (SHG) allows marker-free identification of cell structures, tubulin or membranes and, because of its coherent nature, SHG is very sensitive to the local sample structure and to the direction of the laser polarization. In addition, since SHG does not result from light absorption and subsequent re-emission, in opposition to fluorescence, photo-bleaching of the studied material can be avoided by a judicious selection of the laser wavelength. These characteristics make SHG very interesting for biomedical imaging. We have designed and built a microscope that combines the fast and precise DHM imaging with tagging capabilities of non-linear light-matter interactions. Here, we present the technique and look into its possible applications to biological and life sciences. Among promising applications is the 3D tracking of colloidal gold nanoparticles.

SPIE2010

Digital Holographic Microscopy applied to Metrology

Florian Charrière, Tristan Colomb, Etienne Cuche, Christian Depeursinge, Jonas Kühn, Pierre Magistretti, Mihaela Marian, Pierre Marquet, Frédéric Montfort

We report on a method called Digital Holographic Microscopy (DHM) for the numerical reconstruction of digital holograms taken with a microscope. It allows for simultaneous amplitude and quantitative phase contrast imaging. The reconstruction method computes the propagation of the complex optical wavefront diffracted by the object and is used to determine the refractive index and/or shape of the object with an accuracy in the nanometer range along the optical axis. A single hologram is needed for reconstruction. The method requires the adjustment of several reconstruction parameters. The adjustment is performed automatically by using a suitable algorithm. The method has been applied to the measurement of several integrated optics devices, MOEMS, and integrated micro-optical components: microlenses.

SPIE2004