651 research outputs found
Micromechanical resonator driven by radiation pressure force
Radiation pressure exerted by light on any surface is the pressure generated by the momentum of impinging photons. The associated force - fundamentally, a quantum mechanical aspect of light - is usually too small to be useful, except in large-scale problems in astronomy and astrodynamics. In atomic and molecular optics, radiation pressure can be used to trap or cool atoms and ions. Use of radiation pressure on larger objects such as micromechanical resonators has been so far limited to its coupling to an acoustic mode, sideband cooling, or levitation of microscopic objects. In this Letter, we demonstrate direct actuation of a radio-frequency micromechanical plate-type resonator by the radiation pressure force generated by a standard laser diode at room temperature. Using two independent methods, the magnitude of the resonator's response to forcing by radiation pressure is found to be proportional to the intensity of the incident light.https://www.nature.com/articles/s41598-017-16063-4.epdfPublished versio
Optical Wireless Information Transfer with Nonlinear Micromechanical Resonators
Wireless transfer of information is the basis of modern communication. It
includes cellular, WiFi, Bluetooth and GPS systems, all of which use
electromagnetic radio waves with frequencies ranging from typically 100 MHz to
a few GHz. However, several long-standing challenges with standard radio-wave
wireless transmission still exist, including keeping secure transmission of
data from potential compromise. Here, we demonstrate wireless information
transfer using a line-of-sight optical architecture with a micromechanical
element. In this fundamentally new approach, a laser beam encoded with
information impinges on a nonlinear micromechanical resonator located a
distance from the laser. The force generated by the radiation pressure of the
laser light on the nonlinear micromechanical resonator produces a sideband
modulation signal, which carries the precise information encoded in the subtle
changes in the radiation pressure. Using this, we demonstrate data and image
transfer with one hundred percent fidelity with a single 96 micron by 270
micron silicon resonator element in an optical frequency band. This mechanical
approach relies only on the momentum of the incident photons and is therefore
able to use any portion of the optical frequency banda band that is 10,000
times wider than the radio frequency band. Our line-of-sight architecture using
highly scalable micromechanical resonators offers new possibilities in wireless
communication. Due to their small size, these resonators can be easily arrayed
while maintaining a small form factor to provide redundancy and parallelism.Comment: 6 pages, 4 figure
Micromechanical microphone using sideband modulation of nonlinear resonators
We report the successful detection of an audio signal via sideband modulation
of a nonlinear piezoelectric micromechanical resonator. The
27096-m resonator was shown to be reliable in audio detection for
sound intensity levels as low as ambient room noise and to have an unamplified
sensitivity of 23.9 V/Pa. Such an approach may be adapted in acoustic
sensors and microphones for consumer electronics or medical equipment such as
hearing aids.Comment: 5 pages, 3 figure
Development of a global model for atmospheric backscatter at CO2 wavelengths
The effect of aerosol microphysical processes on the backscatter from an aerosol plume undergoing long-range atmospheric transport was studied. A numerical model which examines the effects of coagulation and sedimentation on an aerosol size distribution is under development and the initial results for a single homogeneous layer were obtained. Use was made of the SAGE/SAM II data set to study the global variation of aerosol concentration and, hence, to predict the variation of Beta sub CO2. Computer programs were written to determine the mean, median, and the probability distribution of the measured aerosol extinction as a function of altitude, latitude and geographical conditions. The first data sets analyzed in this way are under study. Data was used to study aerosol behavior over the U.S.A. and the Pacific Ocean
SAGE 1 and SAM 2 measurements of 1 micron aerosol extinction in the free troposphere
The SAGE 1 and SAM 2 satellite sensors were designed to measure, with global coverage, the 1 micron extinction produced by the stratospheric aerosol. In the absence of high altitude cloud, similar measurements may be made for the free tropospheric aerosol. Median extinction values in the Northern Hemisphere, for altitudes between 5 and 10 km, are found to be one-half to one order of magnitude greater than values at corresponding latitudes in the Southern Hemisphere. In addition, a seasonal increase by a factor of 1.5 yields 2 is observed in both hemispheres in local spring and summer. Following major volcanic eruptions, a long-lived enhancement of the aerosol extinction is observed for altitudes above 5 km
International medical graduates from India and Pakistan: an analysis of specialty areas on the UK medical register
Development of a global model for atmospheric backscatter at CO2 wavelengths
The variation of the aerosol backscattering at 10.6 micrometers within the free troposphere was investigated and a model to describe this variation was developed. The analysis combines theoretical modeling with the results contained within three independent data sets. The data sets used were obtained by the SAGE I/SAM II satellite experiments, the GAMETAG flight series, and by direct backscatter measurements. The theoretical work includes use of a bimodal, two component aerosol model, and the study of the microphysical and associated optical changes occurring within an aerosol plume. A consistent picture is obtained that describes the variation of the aerosol backscattering function in the free troposphere with altitude, latitude, and season
Development of global model for atmospheric backscatter at CO2 wavelengths
The improvement of an understanding of the variation of the aerosol backscattering at 10.6 micron within the free troposphere and the development model to describe this was undertaken. The analysis combines theoretical modeling with the results contained within three independent data sets. The data sets are obtained by the SAGE I/SAM II satellite experiments, the GAMETAG flight series and by direct backscatter measurements. The theoretical work includes use of a bimodal, two component aerosol model, and the study of the microphysical and associated optical changes occurring within an aerosol plume. A consistent picture is obtained, which describes the variation of the aerosol backscattering function in the free troposphere with altitude, latitude, and season. Most data are available and greatest consistency is found inside the Northern Hemisphere
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