27,486 research outputs found
Coherent optical wavelength conversion via cavity-optomechanics
We theoretically propose and experimentally demonstrate coherent wavelength
conversion of optical photons using photon-phonon translation in a
cavity-optomechanical system. For an engineered silicon optomechanical crystal
nanocavity supporting a 4 GHz localized phonon mode, optical signals in a 1.5
MHz bandwidth are coherently converted over a 11.2 THz frequency span between
one cavity mode at wavelength 1460 nm and a second cavity mode at 1545 nm with
a 93% internal (2% external) peak efficiency. The thermal and quantum limiting
noise involved in the conversion process is also analyzed, and in terms of an
equivalent photon number signal level are found to correspond to an internal
noise level of only 6 and 4x10-3 quanta, respectively.Comment: 11 pages, 7 figures, appendi
Erasing the orbital angular momentum information of a photon
Quantum erasers with paths in the form of physical slits have been studied
extensively and proven instrumental in probing wave-particle duality in quantum
mechanics. Here we replace physical paths (slits) with abstract paths of
orbital angular momentum (OAM). Using spin-orbit hybrid entanglement of photons
we show that the OAM content of a photon can be erased with a complimentary
polarization projection of one of the entangled pair. The result is the
(dis)appearance of azimuthal fringes based on whether the \which-OAM"
information was erased. We extend this concept to a delayed measurement scheme
and show that the OAM information and fringe visibility are complimentary
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Understanding macroscale functionality of metal halide perovskites in terms of nanoscale heterogeneities
Hybrid metal halide perovskites have shown an unprecedented rise as semiconductor building blocks for solar energy conversion and light-emitting applications. Currently, the field moves empirically towards more and more complex chemical compositions, including mixed halide quadruple cation compounds that allow optical properties to be tuned and show promise for better stability. Despite tremendous progress in the field, there is a need for better understanding of mechanisms of efficiency loss and instabilities to facilitate rational optimization of composition. Starting from the device level and then diving into nanoscale properties, we highlight how structural and compositional heterogeneities affect macroscopic optoelectronic characteristics. Furthermore, we provide an overview of some of the advanced spectroscopy and imaging methods that are used to probe disorder and non-uniformities. A unique feature of hybrid halide perovskite compounds is the propensity for these heterogeneities to evolve in space and time under relatively mild illumination and applied electric fields, such as those found within active devices. This introduces an additional challenge for characterization and calls for application of complimentary probes that can aid in correlating the properties of local disorder with macroscopic function, with the ultimate goal of rationally tailoring synthesis towards optimal structures and compositions
The Planck-LFI instrument: analysis of the 1/f noise and implications for the scanning strategy
We study the impact of the 1/f noise on the PLANCK Low Frequency Instrument
(LFI) osbervations (Mandolesi et al 1998) and describe a simple method for
removing striping effects from the maps for a number of different scanning
stategies. A configuration with an angle between telescope optical axis and
spin-axis just less than 90 degrees (namely 85 degress) shows good destriping
efficiency for all receivers in the focal plane, with residual noise
degradation < 1-2 %. In this configuration, the full sky coverage can be
achieved for each channel separately with a 5 degrees spin-axis precession to
maintain a constant solar aspect angle.Comment: submitted to Astronomy and Astrophysics, 12 pages, 15 PostSript
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Charmonium Decays of $Y(4260), psi(4160), and psi(4040)
Using data collected with the CLEO detector operating at the CESR e+e-
collider at sqrt s = 3.97-4.26 GeV, we investigate 15 charmonium decay modes of
the psi(4040), psi(4160), and Y(4260) resonances. We confirm, at 11
significance, the BaBar Y(4260) --> pi+ pi- J/psi discovery, make the first
observation of Y(4260) --> pi0 pi0 J/psi (5.1 sigma), and find the first
evidence for Y(4260) --> K+ K- J/psi (3.7 sigma). We measure e+e-
cross-sections at sqrt s = 4.26 GeV as sigma(pi+ pi- J/psi) = 58 +12-10 +- 4
pb, sigma(pi0 pi0 J/psi) = 23 +12 -8 +- 1 pb, and sigma(K+ K- J/psi) = 9 +9 -5
+- 1 pb, in which the uncertainties are statistical and systematic,
respectively. Upper limits are placed on other decay rates from all three
resonances.Comment: 11 pages postscript,also available through
http://www.lns.cornell.edu/public/CLNS/2006/, Submitted to PR
Quantitative magneto-optical investigation of superconductor/ferromagnet hybrid structures
We present a detailed quantitative magneto-optical imaging study of several
superconductor/ferromagnet hybrid structures, including Nb deposited on top of
thermomagnetically patterned NdFeB, and permalloy/niobium with erasable and
tailored magnetic landscapes imprinted in the permalloy layer. The
magneto-optical imaging data is complemented with and compared to scanning Hall
probe microscopy measurements. Comprehensive protocols have been developed for
calibrating, testing, and converting Faraday rotation data to magnetic field
maps. Applied to the acquired data, they reveal the comparatively weaker
magnetic response of the superconductor from the background of larger fields
and field gradients generated by the magnetic layer.Comment: 21 pages, including 2 pages of supplementary materia
A bright nanowire single photon source based on SiV centers in diamond
The practical implementation of many quantum technologies relies on the
development of robust and bright single photon sources that operate at room
temperature. The negatively charged silicon-vacancy (SiV-) color center in
diamond is a possible candidate for such a single photon source. However, due
to the high refraction index mismatch to air, color centers in diamond
typically exhibit low photon out-coupling. An additional shortcoming is due to
the random localization of native defects in the diamond sample. Here we
demonstrate deterministic implantation of Si ions with high conversion
efficiency to single SiV- centers, targeted to fabricated nanowires. The
co-localization of single SiV- centers with the nanostructures yields a ten
times higher light coupling efficiency than for single SiV- centers in bulk
diamond. This enhanced photon out-coupling, together with the intrinsic
scalability of the SiV- creation method, enables a new class of devices for
integrated photonics and quantum science.Comment: 15 pages, 5 figure
Enhanced relativistic-electron beam collimation using two consecutive laser pulses
The double laser pulse approach to relativistic electron beam (REB)
collimation has been investigated at the LULI-ELFIE facility. In this scheme,
the magnetic field generated by the first laser-driven REB is used to guide a
second delayed REB. We show how electron beam collimation can be controlled by
properly adjusting laser parameters. By changing the ratio of focus size and
the delay time between the two pulses we found a maximum of electron beam
collimation clearly dependent on the focal spot size ratio of the two laser
pulses and related to the magnetic field dynamics. Cu-K alpha and CTR imaging
diagnostics were implemented to evaluate the collimation effects on the
respectively low energy ( MeV) components of the
REB
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