134 research outputs found
Ultra-thin rigid endoscope: Two-photon imaging through a graded-index multi-mode fiber
Rigid endoscopes like graded-index (GRIN) lenses are known tools in
biological imaging, but it is conceptually difficult to miniaturize them. In
this letter, we demonstrate an ultra-thin rigid endoscope with a diameter of
only 125 microns. In addition, we identify a domain where two-photon endoscopic
imaging with fs-pulse excitation is possible. We validate the ultra-thin rigid
endoscope consisting of a few cm of graded-index multi-mode fiber by using it
to acquire optically sectioned two-photon fluorescence endoscopic images of
three-dimensional samples.Comment: 17 pages, 15 figures, submitted to Opt. Expres
Temperature Imaging using Quadriwave Shearing Interferometry. Applications in Thermoplasmonics
International audienceThe use of illuminated gold nanoparticles as ideal nanosources of heat is the basis of numerous research activities and applications in physics, chemistry, biology and medicine. This field defines the area recently named Thermoplasmonics [1]. In most of the activities related to Thermoplasmonics, probing the temperature at the vicinity of the metal nanoparticles is not an easy task. In this context, we recently developed a novel optical microscopy technique, named TIQSI, aimed at mapping the temperature around plasmonic nanoparticles [2]. The approach is based on the measure of the thermal-induced variation of the refractive index surrounding the sources of heat. The TIQSI technique cumulates all the advantages a thermal microscopy technique may require: i) high resolution (diffraction limited), ii) high readout rate (less than one image per second), iii) high temperature sensitivity (<1°C), iv) large accessible temperature range, v) temperature can be measured without fluorescence labelling or any other kind of thermal probe, v) no need to use sophisticated devices such as heterodyne detection, acousto-optic modulator, spectrometer, etc, like previous thermal imaging techniques. In this presentation, we will first introduce the TIQSI technique, its principle and capabilities. We will then present several recent applications made it possible by this new thermal imaging technique. In particular, we shall explain how this technique have been already used to quantitatively measure the absorption cross section of gold nanoparticles [3] and graphene sheets, how it can be used to map the temperature in real time in living cells [4], how it can help to design temperature distributions at will at the microscale using gold nanoparticles [5,7], and how it can be used to investigate thermal-induced phenomena in hydro- dynamics and phase transitions [6]
Metasurface optical characterization using quadriwave lateral shearing interferometry
An optical metasurface consists of a dense and usually non-uniform layer of
scattering nanostructures behaving as a continuous and extremely thin optical
component, with predefined phase and intensity transmission/reflection
profiles. To date, various sorts of metasurfaces (metallic, dielectric,
Huygens-like, Pancharatman-Berry, etc.) have been introduced to design
ultrathin lenses, beam deflectors, holograms, or polarizing interfaces. Their
actual efficiencies depend on the ability to predict their optical properties
and to fabricate non-uniform assemblies of billions of nanoscale structures on
macroscopic surfaces. To further help improve the design of metasurfaces,
precise and versatile post-characterization techniques need to be developed.
Today, most of the techniques used to characterize metasurfaces rely on light
intensity measurements. Here, we demonstrate how quadriwave lateral shearing
interferometry (QLSI), a quantitative phase microscopy technique, can easily
achieve full optical characterization of metasurfaces of any kind, as it can
probe the local phase imparted by a metasurface with high sensitivity and
spatial resolution. As a means to illustrate the versatility of this technique,
we present measurements on two types of metasurfaces, namely Pancharatnam-Berry
and effective-refractive-index metasurfaces, and present results on uniform
metasurfaces, metalenses and deflectors
Thermal Imaging of Nanostructures by Quantitative Optical Phase Analysis
International audienceWe introduce an optical microscopy technique aimed at characterizing the heat generation arising from nanostructures, in a comprehensive and quantitative manner. Namely, the technique permits (i) mapping the temperature distribution around the source of heat, (ii) mapping the heat power density delivered by the source, and (iii) retrieving the absolute absorption cross section of light-absorbing structures. The technique is based on the measure of the thermal-induced refractive index variation of the medium surrounding the source of heat. The measurement is achieved using an association of a regular CCD camera along with a modified Hartmann diffraction grating. Such a simple association makes this technique straightforward to implement on any conventional microscope with its native broadband illumination conditions. We illustrate this technique on gold nanoparticles illuminated at their plasmonic resonance. The spatial resolution of this technique is diffraction limited, and temperature variations weaker than 1 K can be detected
Imagerie de phase quantitative appliquée à l’analyse de l’interaction laser matière dans les matériaux et composants optiques
National audienc
Characterization of potential energy landscapes in holographic optical tweezers
International audienc
- …