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Unformatted text preview: absorption line Most pronounced in the region of gain Can become negative “Pulse appears behind the medium before it arrived at it ?????” Subluminal light No absorption at v o but strong dispersion Group velocity as low as 0.44m/s I can ran faster than that In a dense medium: B ose E instein C condensate Anharmonic periodic waves • Fourier Series Every period signal can be expressed as a Fourier series Example: Square wave "#$ Nonperiodic waves • Fourier Integrals Pulses and Wave Packets • Fourier integrals give as a way to describe pulses • Case 1 (square pulse) Case 2: Monochromatic wave with beginning and end falls off fast The same for time and frequency " k " x " k = 2 # L " x = 2 L • For our pulse from before " x " k = 4 similarly "#" t = 4 $ A short pulse has a wide spectrum Uncertainty principle Coherence Length " v # 1 " t " t c # 1 " v Coherence time " l c = c " t c # c " v Coherence length...
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This note was uploaded on 08/06/2008 for the course PHYS 352 taught by Professor Dierolf during the Fall '04 term at Lehigh University .
 Fall '04
 DIEROLF

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