Electronics Spectra - SMS Lucknow

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SMS Institute of Technology, L ucknow Department of Electronics & Co mmunication Plasmonics PLASMONICS is thought to repre sent the strongest points of both optical and electronic data tr ansfer. Optical data transfer, as in f iber optics, allows high bandwidth, b ut requires bulky "wires," or tubes with reflective interiors. Electron ic data transfer operates at frequencies inferior to fiber optics, but only requires tiny wires. Plasmonics, someti mes called "light on a wire," would allow the transmission of data at optical frequencies along the surface of a tiny metal wire, despite the fact that the data travels in the form of el ectron density distributions rather than photons. It is the fact that plasmonics have a great role in the green energy market economy by integrating with the existing PN junction solar cell by making it more absorbent of heat in all range of the frequency that co mes from the sunlight. Plasmonic, Nano particles of gold or silver. The main limitation to plasmonics today is that plasmon tends to dissipate after only a few millimeters, making them too short-lived to serve as a basis for computer chips, which are a few centimeters across. For se nding data even longer distances, th e key is using a material with a low refractive index, ideally negative, such that the incoming electromagnetic energy is reflected parallel to the surface of the material and transmitted along its length as far as possible. There exists no natural material with a neg ative refractive index, so nano stru ctured materials must be used to fabr icate effective plasmonic devices. For this reason, plasmonics is frequently associated with nanotechnology. ABOUT "PLASMON" The name plasmon derived from the physical plasma as a state of matter in which the a t- oms are ionized. At the lowest densities this means an ionize d gas, or classical plasma; but densities are much higher in a metal, or quantum plasma. Plasmon consists of discrete units known as plasmagenes. The extrachromosomal gene in plants was first described in 1908 by the German botanist. The plasmon energy for most metals corresponds to that of an ultraviolet photon. However, for silver, gold, the alkali metals, and a few other materials, the plasmon energy is sufficiently low to correspond to that of a visible or near-ultraviolet photon. This means there is a possibility of exciting plasmons by light. If plasmons are confined upon a surface, optical effects can be easily observed. In this case, the quanta are called surface plasmons, and they have the bulk plasmon energy as an upper energy limit.Surface plasmons were first proposed to explain energy losses by electrons reflected from metal surfaces. The plasmon is a quasiparticle. Its energy is approximately equal to L , where Saurabh EC - II year is the angular plasma (Langmuir) frequency, e and m are the charge and mass of the particles. The energy of a plasmon is determined from the characteristic energy losses sustained by electrons in metals: electrons passing through the plate expend energy on the excitation of plasma oscillations, that is, on the "creation" of plasmons. Another method of determining the 38 Electronics Spectra, 2010
SMS Institute of Technology, L ucknow Department of Electronics & Co mmunication energy of a plasmon is analysis of the light spectrum emitted by plasmons. APPLICATIONS Plasmon waveguides, extraordinary transmission through aper ture arrays, sensing and surface enhanced Raman scattering, spectroscopy as well as meta-materials. Position and intensity of plasmon absorption and emission peaks are affected by molecular adsorption, which can be used in molecular sensors Potential applications extend to new light sources, solar cells, holography, raman spectroscopy, and microscopy applications of surface plasmon resonance spectroscopy was the measurement of the thickness of adsorbed self-assembled nanofilms on gold substrates. Most practical applications is SPR emission When the surface plas mon wave hits a local particle or irregularity-like on a rough surface GENERATION OF PLASMON Plasmons are generated when, under the right conditions, light strikes a metal. The electric field of the light jiggles the electrons in the m etal to the light's frequency, setting off density waves of electrons. The process is analogous to how the vibrations of the larynx jiggle molecules in the air into density waves experienced as sound. Metals provide the best evidence of plasmons, because they have a high density of electrons free to move. Plasmons are density waves of electrons, which are created w hen light hits the surface of a metal under precise circumstances. Because these density waves are generated at optical frequencies, very small and rapid waves. Hybrid computer Computers are devices that exhibit features of analog computers and digital computers. The digital component normally serves as the controller and provides logical operations, while the analog component normally serves as a solver of differential equations. In hybrid computer Signals pass across the synapses from one nerve cell to the next as discrete (digital) packets of chemicals, which are then summed within the nerve cell in an analog fashion by building an electrochemical potential until its threshold is re ached, whereupon it discharges and se nds out a series of digital packets to the next nerve cell. The advantage s are at least threefold: noise within the system is minimized (and tends no t to be additive), no common ground ing system is required, and there is minimal degradation of the signal even if there are substantial differen ces in activity of the cells along a path (only the signal delays tend to vary ). The individual nerve cells are analogous to analog computers; the synapses are analogous to digital computers. Note that hybrid computers should be distinguished from hybrid systems. The latter may be no more than a digital computer equipped with an analog-to-digital converter at the input and/or a digital-to-analog converter at the output, to convert analog signals for ordinary digital signal processing, and conversely, e.g., for driving physical control systems, such as servomechanisms. Gaurav Mishra EC - III year 39 Electronics Spectra, 2010
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