43 research outputs found
Thermal emission from a single glass fiber
In this article, we study the thermal light emission from individual fibers
of an industrial glass material, which are elementary building blocks of glass
wool boards used for thermal insulation. Thermal emission spectra of single
fibers of various diameters partially suspended on air are measured in the
far-field by means of infrared spatial modulation spectroscopy.These
experimental spectra are compared with the theoretical absorption efficiency
spectra of cylindrical shaped fibers calculated analytically in the framework
of Mie theory taking as an input the measured permittivity of the industrial
glass material. An excellent qualitative agreement is found between the
measured thermal radiation spectra and the theoretical absorption efficiency
spectra.Comment: 25 pages, 5 figures, JQSRT, 201
Anisotropy in s-wave Bose-Einstein condensate collisions and its relationship to superradiance
We report the experimental realization of a single-species atomic four-wave
mixing process with BEC collisions for which the angular distribution of
scattered atom pairs is not isotropic, despite the collisions being in the
-wave regime. Theoretical analysis indicates that this anomalous behavior
can be explained by the anisotropic nature of the gain in the medium. There are
two competing anisotropic processes: classical trajectory deflections due to
the mean-field potential, and Bose enhanced scattering which bears similarity
to super-radiance. We analyse the relative importance of these processes in the
dynamical buildup of the anisotropic density distribution of scattered atoms,
and compare to optically pumped super-radiance.Comment: 13 pages, 10 figures, added a fuller discussion of timescales,
otherwise some minor changes in the text and the formatting of Figures 5-
Thermal emission from a single glass fiber
International audienceIn this article, we study the thermal light emission from individual fibers of an industrial glass material, which are elementary building blocks of glass wool boards used for thermal insulation. Thermal emission spectra of single fibers of various diameters partially suspended on air are measured in the far field by means of infrared spatial modulation spectroscopy. These experimental spectra are compared with the theoretical absorption efficiency spectra of cylindrical shaped fibers calculated analytically in the framework of Mie theory taking as an input the measured permittivity of the industrial glass material. An excellent qualitative agreement is found between the measured thermal radiation spectra and the theoretical absorption efficiency spectra
Sub-Poissonian number differences in four-wave mixing of matter waves
We demonstrate sub-Poissonian number differences in four-wave mixing of
Bose-Einstein condensates of metastable helium. The collision between two
Bose-Einstein condensates produces a scattering halo populated by pairs of
atoms of opposing velocities, which we divide into several symmetric zones. We
show that the atom number difference for opposing zones has sub-Poissonian
noise fluctuations whereas that of nonopposing zones is well described by shot
noise. The atom pairs produced in a dual number state are well adapted to sub
shot-noise interferometry and studies of Einstein-Podolsky-Rosen-type
nonlocality tests.Comment: 4 pages, 3 figure
One-shot measurement of the three-dimensional electromagnetic field scattered by a subwavelength aperture tip coupled to the environment
International audienceNear-field scanning optical microscopy (NSOM) achieves subwavelength resolution by bringing a nanosized probe close to the surface of the sample. This extends the spectrum of spatial frequencies that can be detected with respect to a diffraction limited microscope. The interaction of the probe with the sample is expected to affect its radiation to the far field in a way that is often hard to predict. Here we address this question by proposing a general method based on full-field off-axis digital holography microscopy which enables to study in detail the far-field radiation from a NSOM probe as a function of its environment. A first application is demonstrated by performing a three-dimensional (3D) tomographic reconstruction of light scattered from the sub-wavelength aperture tip of a NSOM, in free space or coupled to transparent and plasmonic media. A single holographic image recorded in one shot in the far field contains information on both the amplitude and phase of the scattered light. This is sufficient to reverse numerically the propagation of the electromagnetic field all the way to the aperture tip. Finite Difference Time Domain (FDTD) simulations are performed to compare the experimental results with a superposition of magnetic and electric dipole radiation
Imaging light scattered by a subwavelength nanofiber, from near field to far field
We present a direct experimental investigation of the optical field
distribution around a suspended tapered optical nanofiber by means of a
fluorescent scanning probe. Using a 100 nm diameter fluorescent bead as a probe
of the field intensity, we study interferences made by a nanofiber (400 nm
diameter) scattering a plane wave (568 nm wavelength). Our scanning
fluorescence near-field microscope maps the optical field over 36 m,
with resolution, from contact with the surface of the nanofiber
to a few micrometers away. Comparison between experiments and Mie scattering
theory allows us to precisely determine the emitter-nanofiber distance and
experimental drifts