337 research outputs found
Complementary Speckle Patterns : deterministic interchange of intrinsic vortices and maxima through Scattering Media
Intensity minima and maxima of speckle patterns obtained behind a diffuser
are experimentally interchanged by applying a spiral phase delay of charge to the impinging coherent beam. This transform arises from the intuitive
expectation that a tightly focused beam is so-changed into a vortex beam and
vice-versa. The statistics of extrema locations and the intensity distribution
of the so-generated "complementary" patterns are characterized by numerical
simulations. It is demonstrated experimentally that the incoherent
superposition of the three "complementary speckle patterns" yield a synthetic
speckle grain size enlarged by a factor . A cyclic permutation of
optical vortices and maxima is unexpectedly observed and discussed.Comment: 9 pages, 9 figure
Photonic Methods to Enhance Fluorescence Correlation Spectroscopy and Single Molecule Fluorescence Detection
Recent advances in nanophotonics open the way for promising applications towards efficient single molecule fluorescence analysis. In this review, we discuss how photonic methods bring innovative solutions for two essential questions: how to detect a single molecule in a highly concentrated solution, and how to enhance the faint optical signal emitted per molecule? The focus is set primarily on the widely used technique of fluorescence correlation spectroscopy (FCS), yet the discussion can be extended to other single molecule detection methods
Compressive Raman imaging with spatial frequency modulated illumination
We report a line scanning imaging modality of compressive Raman technology
with spatial frequency modulated illumination using a single pixel detector. We
demonstrate the imaging and classification of three different chemical species
at line scan rates of 40 Hz
Filtering of matter symmetry properties by circularly polarized nonlinear optics
International audienceWe propose a direct readout of symmetry information in matter using nonlinear optics. From combinations of circularly and longitudinally polarized optical fields, we construct irreducible spherical field tensors for second- and third-order nonlinear processes. The coupling of these field tensors to the matter susceptibility tensors allows filtering out of the susceptibility symmetries independently of the sample orientation in the laboratory frame. Experimental demonstrations are conducted on microcrystals, in a microscopy configuration compatible with symmetry order imaging
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
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