10,506 research outputs found
Wireless interrogation of an optically modulated resonant tunnelling diode oscillator
n this work, a resonant tunnelling diode-photo-detector based microwave oscillator is amplitude modulated using an optical signal. The modulated free running oscillator is coupled to an antenna and phase locked by a wireless carrier that allows remote extraction of the information contained in the modulation. An off-the-shelf demodulator has been used to recover the envelope of the baseband data originally contained in the optical signal. Data were successfully transmitted at a rate of 1 MSym/s with a bit error rate below 10â6
MKID development for SuperSpec: an on-chip, mm-wave, filter-bank spectrometer
SuperSpec is an ultra-compact spectrometer-on-a-chip for millimeter and
submillimeter wavelength astronomy. Its very small size, wide spectral
bandwidth, and highly multiplexed readout will enable construction of powerful
multibeam spectrometers for high-redshift observations. The spectrometer
consists of a horn-coupled microstrip feedline, a bank of narrow-band
superconducting resonator filters that provide spectral selectivity, and
Kinetic Inductance Detectors (KIDs) that detect the power admitted by each
filter resonator. The design is realized using thin-film lithographic
structures on a silicon wafer. The mm-wave microstrip feedline and spectral
filters of the first prototype are designed to operate in the band from 195-310
GHz and are fabricated from niobium with at Tc of 9.2K. The KIDs are designed
to operate at hundreds of MHz and are fabricated from titanium nitride with a
Tc of 2K. Radiation incident on the horn travels along the mm-wave microstrip,
passes through the frequency-selective filter, and is finally absorbed by the
corresponding KID where it causes a measurable shift in the resonant frequency.
In this proceedings, we present the design of the KIDs employed in SuperSpec
and the results of initial laboratory testing of a prototype device. We will
also briefly describe the ongoing development of a demonstration instrument
that will consist of two 500-channel, R=700 spectrometers, one operating in the
1-mm atmospheric window and the other covering the 650 and 850 micron bands.Comment: As submitted, except that "in prep" references have been update
GaAs optoelectronic neuron arrays
A simple optoelectronic circuit integrated monolithically in GaAs to implement sigmoidal neuron responses is presented. The circuit integrates a light-emitting diode with one or two transistors and one or two photodetectors. The design considerations for building arrays with densities of up to 10^4 cm^-2 are discussed
Toward an optimal foundation architecture for optoelectronic computing .1. Regularly interconnected device planes
Cataloged from PDF version of article.By systematically examining the tree of possibilities for optoelectronic computing architectures and
offering arguments that allow one to prune suboptimal branches of this tree, I come to the conclusion that
electronic circuit planes interconnected optically according to regular connection patterns represent an
alternative that is reasonably close to the best possible, as defined by physical limitations. Thus I
propose that this foundation architecture should provide a basis for future research and development in
this area. © 1997 Optical Society of Americ
Large atom number dual-species magneto-optical trap for fermionic 6Li and 40K atoms
We present the design, implementation and characterization of a dual-species
magneto-optical trap (MOT) for fermionic 6Li and 40K atoms with large atom
numbers. The MOT simultaneously contains 5.2x10^9 6Li-atoms and 8.0x10^9
40K-atoms, which are continuously loaded by a Zeeman slower for 6Li and a
2D-MOT for 40K. The atom sources induce capture rates of 1.2x10^9 6Li-atoms/s
and 1.4x10^9 40K-atoms/s. Trap losses due to light-induced interspecies
collisions of ~65% were observed and could be minimized to ~10% by using low
magnetic field gradients and low light powers in the repumping light of both
atomic species. The described system represents the starting point for the
production of a large-atom number quantum degenerate Fermi-Fermi mixture
A Breakdown Voltage Multiplier for High Voltage Swing Drivers
A novel breakdown voltage (BV) multiplier is introduced that makes it possible to generate high output voltage swings using transistors with low breakdown voltages. The timing analysis of the stage is used to optimize its dynamic response. A 10 Gb/s optical modulator driver with a differential output voltage swing of 8 V on a 50 Ω load was implemented in a SiGe BiCMOS process. It uses the BV-Doubler topology to achieve output swings twice the collectorâemitter breakdown voltage without stressing any single transistor
Optically interconnected phased arrays
Phased-array antennas are required for many future NASA missions. They will provide agile electronic beam forming for communications and tracking in the range of 1 to 100 GHz. Such phased arrays are expected to use several hundred GaAs monolithic integrated circuits (MMICs) as transmitting and receiving elements. However, the interconnections of these elements by conventional coaxial cables and waveguides add weight, reduce flexibility, and increase electrical interference. Alternative interconnections based on optical fibers, optical processing, and holography are under evaluation as possible solutions. In this paper, the current status of these techniques is described. Since high-frequency optical components such as photodetectors, lasers, and modulators are key elements in these interconnections, their performance and limitations are discussed
Real-time optical manipulation of cardiac conduction in intact hearts
Optogenetics has provided new insights in cardiovascular research, leading to new methods for cardiac pacing, resynchronization therapy and cardioversion. Although these interventions have clearly demonstrated the feasibility of cardiac manipulation, current optical stimulation strategies do not take into account cardiac wave dynamics in real time. Here, we developed an allâoptical platform complemented by integrated, newly developed software to monitor and control electrical activity in intact mouse hearts. The system combined a wideâfield mesoscope with a digital projector for optogenetic activation. Cardiac functionality could be manipulated either in freeârun mode with submillisecond temporal resolution or in a closedâloop fashion: a tailored hardware and software platform allowed realâtime intervention capable of reacting within 2 ms. The methodology was applied to restore normal electrical activity after atrioventricular block, by triggering the ventricle in response to optically mapped atrial activity with appropriate timing. Realâtime intraventricular manipulation of the propagating electrical wavefront was also demonstrated, opening the prospect for realâtime resynchronization therapy and cardiac defibrillation. Furthermore, the closedâloop approach was applied to simulate a reâentrant circuit across the ventricle demonstrating the capability of our system to manipulate heart conduction with high versatility even in arrhythmogenic conditions. The development of this innovative optical methodology provides the first proofâofâconcept that a realâtime optically based stimulation can control cardiac rhythm in normal and abnormal conditions, promising a new approach for the investigation of the (patho)physiology of the heart
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