fc23abf0   
   XPost: alt.lasers   
   From: jappel@linux01.gwdg.de   
      
   Helpful person wrote:   
      
   > As one with no knowledge of the conditions to slow light down I have a   
   > question.   
      
   As already mentioned for slow light no Bose-Einstein-Condensate is needed.   
   All you need is a spectrally narrow transparency window (or gain) in your   
   medium, then the Kramers-Kronig relations which relate Dispersion and   
   absorpton to each other lead to a group velocity < c.   
      
   The effect is first described already in   
   Sommerfeld, A. Über die Fortpflanzung des Lichtes in dispergierenden Medien   
   Annalen Der Physik, 1914, 349, 177-202   
      
   and more specifically in   
      
   Garrett, C. G. B. & McCumber, D. E. Propagation of a Gaussian Light Pulse   
   through an Anomalous Dispersion Medium Physical Review A, 1970, 1, 305-313   
      
      
   [Bose-Einstein-Condensates]   
   > Presumably the materials have a very high refractive   
   > index.  Can conditions exist to create a lens?   
      
   Yes. That's actually one of the main problems when one wants to couple them   
   to optics: Huge optical densities in the center and strong density gradients   
   together with a size that is not much bigger than an optical wavelength make   
   BECs more often than not behave more than a scatterer than a nice optical   
   element.   
      
   Cheers   
   	Jürgen   
      
   --- SoupGate-Win32 v1.05   
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