Remnant radiation from the early universe, known as the Cosmic Microwave Background (CMB), has been redshifted and cooled, and today has a blackbody spectrum peaking at millimetre wavelengths. The QUBIC (Q&U Bolometric Interferometer for Cosmology) instrument is designed to map the very faint polaristion structure in the CMB. QUBIC is based on the novel concept of bolometric interferometry in conjunction with synthetic imaging. It will have a large array of input feedhorns, which creates a large number of interferometric baselines. <p> </p>The beam from each feedhorn is passed through an optical combiner, with an off-axis compensated Gregorian design, to allow the generation of the synthetic image. The optical-combiner will operate in two frequency bands (150 and 220 GHz with 25% and 18.2 % bandwidth respectively) while cryogenically cooled TES bolometers provide the sensitivity required at the image plane. <p> </p>The QUBIC Technical Demonstrator (TD), a proof of technology instrument that contains 64 input feed-horns, is currently being built and will be installed in the Alto Chorrillos region of Argentina. The plan is then for the full QUBIC instrument (400 feed-horns) to be deployed in Argentina and obtain cosmologically significant results. <p> </p>In this paper we will examine the output of the manufactered feed-horns in comparison to the nominal design. We will show the results of optical modelling that has been performed in anticipation of alignment and calibration of the TD in Paris, in particular testing the validity of real laboratory environments. We show the output of large calibrator sources (50 ° full width haf max Gaussian beams) and the importance of accurate mirror definitions when modelling large beams. Finally we describe the tolerance on errors of the position and orientation of mirrors in the optical combiner.
Big Bang cosmologies predict that the cosmic microwave background (CMB) contains faint temperature and polarisation
anisotropies imprinted in the early universe. ESA's PLANCK satellite has already measured the temperature
anisotropies1 in exquisite detail; the next ambitious step is to map the primordial polarisation signatures which are
several orders of magnitude lower. Polarisation E-modes have been measured2 but the even-fainter primordial B-modes
have so far eluded detection. Their magnitude is unknown but it is clear that a sensitive telescope with exceptional
control over systematic errors will be required.
QUBIC3 is a ground-based European experiment that aims to exploit the novel concept of bolometric interferometry in
order to measure B-mode polarisation anisotropies in the CMB. Beams from an aperture array of corrugated horns will
be combined to form a synthesised image of the sky Stokes parameters on two focal planes: one at 150 GHz the other at
220 GHz. In this paper we describe recent optical modelling of the QUBIC beam combiner, concentrating on modelling
the instrument point-spread-function and its operation in the 220-GHz band. We show the effects of optical aberrations
and truncation as successive components are added to the beam path. In the case of QUBIC, the aberrations introduced
by off-axis mirrors are the dominant contributor. As the frequency of operation is increased, the aperture horns allow up to five hybrid modes to propagate and we illustrate how the beam pattern changes across the 25% bandwidth. Finally we
describe modifications to the QUBIC optical design to be used in a technical demonstrator, currently being manufactured
for testing in 2016.
Semiconductor nanowires are drawing more and more interest due to their numerous potential applications in
nanoelectronics devices [1,2], including interconnects, transistor channels, nanoelectrodes, or in the emerging application
areas of photonics , chemistry  and photovoltaics . In this context, optical tweezers appear like a pertinent tool
for the manipulation and assembly of nanowires into complex structures.
It was previously shown that the near-field existing at the surface of a waveguide allows the micromanipulation of
nanoparticles and biological objects [6,7]. In this article, we investigate for the first time to our knowledge the motion of
silicon nanowires above silicon nitride waveguides. The nanowires in aqueous solution are attracted toward the
waveguide by optical gradient forces. The nanowires align themselves according to the axis of the waveguide and get
propelled along the waveguide due to radiation pressure. Velocities are up to 40 μm/s.
For a better understanding of the experimental results, the distribution of the electromagnetic field in the nanowire is
calculated using the finite element method. Then, the resulting optical forces exerted on the nanowires are calculated,
thanks to the Maxwell stress tensor formalism.