In optics, if a beam of light hits a boundary at a certain critical angle, all the light will be reflected back. In classical physics none of the light crosses the boundary, but is instead reflected back perfectly. If the light is viewed as a potential wave, however, the probability of the particle's location decays inside the second material. This means there is a chance the photon exists within the restricted area, but it does not propagate there. The distance that the decaying, or evanescent, wave travels into the second medium is determined by the change in refractive index at the boundary. The evanescent wave will be changed if it interacts with a particle after crossing the boundary. This change in the wave can be observed by a change in the amount of light reflected back on the side of the first material.
Extending this idea from photons into electrons, we can create a field of plasma osc...
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...esonant frequency so that it is only periodically in contact with the material. This allows for a physical feedback of the height of the object but avoids scraping the tip across the material. The final method of imaging with the AFM is non-contact mode. This method is performed by oscillating the cantilever above its resonate frequency so that is is vibrating with an amplitude of 1-10nm. When placed near the surface of an object, the attractive van der Waals forces affect the probe's oscillations. This data is extrapolated and the location of the object is determined. The information is then fed back into the AFM so that the probe can be adjusted to maintain a constant, non-contact distance from the object. The most difficult problem with this method is that moisture between the object and the tip can create unwanted forces and bonds that produce erroneous results.
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- Carl Poltras talked to us about Nanophotonics. Photonics is the science based on the controlled flow of light, light is used in circuitry to do work; this is analogous to electricity in electronics. Photonics is carried out by carefully constructed waveguides made out of silicon and an etching method that boxes Si inside some other material, light is the coupled to optical fibers where it can then be transmitted. Successfully coupling light poses a significant challenge due to the size difference in the wave guide and fiber.... [tags: Venture capital, Private equity]
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