5,334 research outputs found
Ultrasensitive interferometric on-chip microscopy of transparent objects
Light microscopes can detect objects through several physical processes, such as scattering, absorption, and reflection. In transparent objects, these mechanisms are often too weak, and interference effects are more suitable to observe the tiny refractive index variations that produce phase shifts. We propose an on-chip microscope design that exploits birefringence in an unconventional geometry. It makes use of two sheared and quasi-overlapped illuminating beams experiencing relative phase shifts when going through the object, and a complementary metal-oxide-semiconductor image sensor array to record the resulting interference pattern. Unlike conventional microscopes, the beams are unfocused, leading to a very large field of view (20 mm(2)) and detection volume (more than 0.5 cm(3)), at the expense of lateral resolution. The high axial sensitivity (<1 nm) achieved using a novel phase-shifting interferometric operation makes the proposed device ideal for examining transparent substrates and reading microarrays of biomarkers. This is demonstrated by detecting nanometer-thick surface modulations on glass and single and double protein layers.Peer ReviewedPostprint (published version
Broadening the bandwidth of entangled photons: a step towards the generation of extremely short biphotons
We demonstrate a technique that allows to fully control the bandwidth of
entangled photons independently of the frequency band of interest and of the
nonlinear crystal. We show that this technique allows to generate nearly
transform-limited biphotons with almost one octave of bandwidth (hundreds of
THz) which corresponds to correlation times of just a few femtoseconds. The
presented method becomes an enabling tool for attosecond entangled-photons
quantum optics. The technique can also be used to generate paired photons with
a very high degree of entanglement.Comment: 4 page
Heavy Quark Fluorescence
Heavy hadrons containing heavy quarks (for example, Upsilon-mesons) feature a
scale separation between the heavy quark mass (about 4.5 GeV for the b-quark)
and the QCD scale (about 0.3 GeV}) that controls effective masses of lighter
constituents. Therefore, as in ordinary molecules, the de-excitation of the
lighter, faster degrees of freedom leaves the velocity distribution of the
heavy quarks unchanged, populating the available decay channels in
qualitatively predictable ways. Automatically an application of the
Franck-Condon principle of molecular physics explains several puzzling results
of Upsilon(5S) decays as measured by the Belle collaboration, such as the high
rate of Bs*-anti Bs* versus Bs*-anti Bs production, the strength of three-body
B-anti B + pion decays, or the dip in B momentum shown in these decays. We
argue that the data is showing the first Sturm-Liouville zero of the
Upsilon(5S) quantum mechanical squared wavefunction, and providing evidence for
a largely b-anti b composition of this meson.Comment: 4 pages, 4 figures, Figure 2 updated and some typos corrected. To be
published in Physical Review Letter
Minimum of and the phase transition of the Linear Sigma Model in the large-N limit
We reexamine the possibility of employing the viscosity over entropy density
ratio as a diagnostic tool to identify a phase transition in hadron physics to
the strongly coupled quark-gluon plasma and other circumstances where direct
measurement of the order parameter or the free energy may be difficult.
It has been conjectured that the minimum of eta/s does indeed occur at the
phase transition. We now make a careful assessment in a controled theoretical
framework, the Linear Sigma Model at large-N, and indeed find that the minimum
of eta/s occurs near the second order phase transition of the model due to the
rapid variation of the order parameter (here the sigma vacuum expectation
value) at a temperature slightly smaller than the critical one.Comment: 22 pages, 19 figures, v2, some references and several figures added,
typos corrected and certain arguments clarified, revised for PR
Spatial wave intensity correlations in quasi-one-dimensional wires
Spatial intensity correlations between waves transmitted through random media
are analyzed within the framework of the random matrix theory of transport.
Assuming that the statistical distribution of transfer matrices is isotropic,
we found that the spatial correlation function can be expressed as the sum of
three terms, with distinctive spatial dependences. This result coincides with
the one obtained in the diffusive regime from perturbative calculations, but
holds all the way from quasi-ballistic transport to localization. While
correlations are positive in the diffusive regime, we predict a transition to
negative correlations as the length of the system decreases.Comment: 10 pages, 3 figures. Submitted to Physical Review Letter
Absolute dimensions of the G7+K7 eclipsing binary star IM Virginis: Discrepancies with stellar evolution models
We report extensive spectroscopic and differential photometric BVRI
observations of the active, detached, 1.309-day double-lined eclipsing binary
IM Vir, composed of a G7-type primary and a K7 secondary. With these
observations we derive accurate absolute masses and radii of M(1) = 0.981 +/-
0.012 M(Sun), M(2) = 0.6644 +/- 0.0048 M(Sun), R(1) = 1.061 +/- 0.016 R(Sun),
and R(2) = 0.681 +/- 0.013 R(Sun) for the primary and secondary, with relative
errors under 2%. The effective temperatures are 5570 +/- 100 K and 4250 +/- 130
K. The significant difference in mass makes this a favorable case for
comparison with stellar evolution theory. We find that both stars are larger
than the models predict, by 3.7% for the primary and 7.5% for the secondary, as
well as cooler than expected, by 100 K and 150 K, respectively. These
discrepancies are in line with previously reported differences in low-mass
stars, and are believed to be caused by chromospheric activity, which is not
accounted for in current models. The effect is not confined to low-mass stars:
the rapidly-rotating primary of IM Vir joins the growing list of objects of
near-solar mass (but still with convective envelopes) that show similar
anomalies. The comparison with the models suggests an age of 2.4 Gyr for the
system, and a metallicity [Fe/H] of approximately -0.3 that is consistent with
other indications, but requires confirmation.Comment: 14 pages, 13 figures. Accepted for publication in Ap
- …