54 research outputs found
Cladding mode coupling in highly localized fiber Bragg gratings: modal properties and transmission spectra
The spectral characteristics of a fiber Bragg grating (FBG) with a
transversely inhomogeneous refractive index profile, differs con- siderably
from that of a transversely uniform one. Transmission spectra of inhomogeneous
and asymmetric FBGs that have been inscribed with focused ultrashort pulses
with the so-called point-by-point technique are investigated. The cladding mode
resonances of such FBGs can span a full octave in the spectrum and are very
pronounced (deeper than 20dB). Using a coupled-mode approach, we compute the
strength of resonant coupling and find that coupling into cladding modes of
higher azimuthal order is very sensitive to the position of the modification in
the core. Exploiting these properties allows precise control of such
reflections and may lead to many new sensing applications.Comment: Submission to OE, 16 pages, 6 figure
Modulation Instability of Ultrashort Pulses in Quadratic Nonlinear Media beyond the Slowly Varying Envelope Approximation
We report a modulational instability (MI) analysis of a mathematical model
appropriate for ultrashort pulses in cascaded quadratic-cubic nonlinear media
beyond the so-called slowly varying envelope approximation. Theoretically
predicted MI properties are found to be in good agreement with numerical
simulation. The study shows the possibility of controlling the generation of MI
and formation of solitons in a cascaded quadratic-cubic media in the few cycle
regimes. We also find that stable propagation of soliton-like few-cycle pulses
in the medium is subject to the fulfilment of the modulation instability
criteria
Integrated photonic quantum gates for polarization qubits
Integrated photonic circuits have a strong potential to perform quantum
information processing. Indeed, the ability to manipulate quantum states of
light by integrated devices may open new perspectives both for fundamental
tests of quantum mechanics and for novel technological applications. However,
the technology for handling polarization encoded qubits, the most commonly
adopted approach, is still missing in quantum optical circuits. Here we
demonstrate the first integrated photonic Controlled-NOT (CNOT) gate for
polarization encoded qubits. This result has been enabled by the integration,
based on femtosecond laser waveguide writing, of partially polarizing beam
splitters on a glass chip. We characterize the logical truth table of the
quantum gate demonstrating its high fidelity to the expected one. In addition,
we show the ability of this gate to transform separable states into entangled
ones and vice versa. Finally, the full accessibility of our device is exploited
to carry out a complete characterization of the CNOT gate through a quantum
process tomography.Comment: 6 pages, 4 figure
Search for the Decay
We have searched for the decay of the tau lepton into seven charged particles
and zero or one pi0. The data used in the search were collected with the CLEO
II detector at the Cornell Electron Storage Ring (CESR) and correspond to an
integrated luminosity of 4.61 fb^(-1). No evidence for a signal is found.
Assuming all the charged particles are pions, we set an upper limit on the
branching fraction, B(tau- -> 4pi- 3pi+ (pi0) nu_tau) < 2.4 x 10^(-6) at the
90% confidence level. This limit represents a significant improvement over the
previous limit.Comment: 9 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
A compact UV timing fiducial system for use with x-ray streak cameras at NIF
Abstract not provide
Study of the Decay tau^- \to 2pi^- pi^+ 3pi^0 nu_{tau}$
The decay tau- -> 2pi- pi+ 3pi0 nu_tau has been studied with the CLEO II
detector at the Cornell Electron Storage Ring (CESR). The branching fraction is
measured to be (2.85 +/- 0.56 +/- 0.51) x 10^(-4). The result is in good
agreement with the isospin expectation but somewhat below the
Conserved-Vector-Current (CVC) prediction. We have searched for resonance
substructure in the decay. Within the statistical precision, the decay is
saturated by the channels tau- -> pi- 2pi0 omega nu_tau, 2pi- pi+ eta nu_tau,
and pi- 2pi0 eta nu_tau. This is the first observation of this omega decay mode
and the branching fraction is measured to be (1.89 +0.74/-0.67 +/- 0.40) x
10^(-4).Comment: 10 pages, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
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Phasing beams with different dispersions and application to the Petawatt-class beamline at the National Ignition Facility
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