880 research outputs found
Coupled-mode analysis of light propagation in optically active crystals
A new mathematical formalism, based on a coupled-mode approach, is presented to describe light propagation in birefringent optically active crystals. An arbitrary light wave in the medium is represented as an expansion in terms of linearly polarized eigenmodes; explicit solutions of the equations for the coupled-wave amplitudes show how power is transferred between the principal components in the presence of optical activity. The (generally elliptically polarized) eigenmodes of the optically active crystal are also derived by a diagonalization of the coupled-mode equations. The analysis is extended to include electro-optic crystals, yielding a more general, complex coupling parameter. The predictions of the theory are in excellent agreement with spectral-transmission measurements in AgGaS2 near its isoindex point at 497 nm
Guided Wave Optics
Phenomena associated with the propagation and manipulation of light in thin-film dielectric waveguides are presently the object of considerable research effort, directed toward possible applications in communications and information processing. The theory of dielectric waveguide modes is reviewed, and the topics of directional coupling, input-output coupling, modulation, and distributed feedback laser sources are treated on the basis of coupled-mode theory. A summary of experimental results for each of the guided-wave optical phenomena covered by the theory is also presented
A Parallel Analog CCD/CMOS Signal Processor
A CCO based signal processing IC that computes a fully parallel single
quadrant vector-matrix multiplication has been designed and fabricated with a
2μm CCO/CMOS process. The device incorporates an array of Charge
Coupled Devices (CCO) which hold an analog matrix of charge encoding the
matrix elements. Input vectors are digital with 1 - 8 bit accuracy
Spatial Light Modulators As Parallel Memories For Optoelectronic Neural Networks
A generic architecture for realizing neural networks is presented in which the synaptic interaction matrix is loaded in parallel into an electronic integrated circuit from a SLM. Three types of the electronic processors are described using CCD, CID and CMOS technologies respectively. The pros and cons of currently existing SLMs for this architecture are pointed out
Spatial Light Modulators As Parallel Memories For Optoelectronic Neural Networks
A generic architecture for realizing neural networks is presented in which the synaptic interaction matrix is loaded in parallel into an electronic integrated circuit from a SLM. Three types of the electronic processors are described using CCD, CID and CMOS technologies respectively. The pros and cons of currently existing SLMs for this architecture are pointed out
The Sagnac effect in Coupled-Resonator Slow-Light Waveguide Structures
We study the effect of rotation on the propagation of electromagnetic waves
in slow-light waveguide structures consisting of coupled micro-ring resonators.
We show that such configurations exhibit new a type of the Sagnac effect which
can be used for the realization of highly-compact integrated rotation sensors
and gyroscopes
Magnetic anisotropies and general on--site Coulomb interactions in the cuprates
This paper derives the anisotropic superexchange interactions from a Hubbard
model for excitations within the copper 3d band and the oxygen 2p band of the
undoped insulating cuprates. We extend the recent calculation of Yildirim et
al. [Phys. Rev. B {\bf VV}, pp, 1995] in order to include the most general
on--site Coulomb interactions (including those which involve more than two
orbitals) when two holes occupy the same site. Our general results apply when
the oxygen ions surrounding the copper ions form an octahedron which has
tetragonal symmetry (but may be rotated as in lanthanum cuprate). For the
tetragonal cuprates we obtain an easy--plane anisotropy in good agreement with
experimental values. We predict the magnitude of the small in--plane anisoComment: 25 pages, revte
Long-term studies of hemoglobin-oxygen affinity in hypoxemic dogs with a right-to-left cardiac shunt
Long-standing hypoxemia was surgically created in dogs by inserting an aortic homograft between the inferior vena cava and right atrium. Ligation of the caval--atrial junction resulted in a right-to-left cardiac shunt. Arterial p O2 fell immediately and P50 increased within 20 min. The 2,3-diphosphoglycerate concentration rose in 4 hr following surgery, while hemoglobin concentration increased within 7 days. Alterations in hemoglobin--oxygen affinity can occur rapidly and may be beneficial compensatory responses to acute and chronic hypoxemia caused by a right-to-left cardiac shunt.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23370/1/0000314.pd
Quantized adiabatic charge pumping and resonant transmission
Adiabatically pumped charge, carried by non-interacting electrons through a
quantum dot in a turnstile geometry, is studied as function of the strength of
the two modulating potentials (related to the conductances of the two
point-contacts to the leads) and of the phase shift between them. It is shown
that the magnitude and sign of the pumped charge are determined by the relative
position and orientation of the closed contour traversed by the system in the
parameter plane, and the transmission peaks (or resonances) in that plane.
Integer values (in units of the electronic charge ) of the pumped charge
(per modulation period) are achieved when a transmission peak falls inside the
pumping contour. The integer value is given by the winding number of the
pumping contour: double winding in the same direction gives a charge of 2,
while winding around two opposite branches of the transmission peaks or winding
in opposite directions can give a charge close to zero.Comment: 7 pages, 12 figure
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