XPost: sci.electronics.design   
   From: tmoranwms@charter.net   
      
   "Jan Panteltje"  wrote in message   
   news:l0kpna$r0e$1@news.albasani.net...   
   > How do you 'chirp' (that is frequency modulate no?) an optical pulse?   
      
   Send it through something dispersive (i.e., different index of refraction   
   vs. frequency).  Some examples include: non-ideal (physical) transmission   
   lines, waveguides, and gravity waves (ripples on a pond).   
      
   What they usually do is point the beam at a diffraction grating, which   
   reflects different frequencies at different angles (within an octave; of   
   course, it wraps around after that, because the grating is periodic, which   
   wouldn't be normal for dispersion), then collect the different angles with   
   a mirror so they become a beam again, but displaced in position and   
   therefore time.  This beam can be amplified (preserving the frequency and   
   phase) and sent back through a diffraction grating and focus mirror to   
   restore the original pulse.  This is how world record power levels are   
   achieved, because the single pulse cannot be amplified as-is (it would   
   burn a hole through the amplifying medium).   
      
   Tim   
      
   --   
   Deep Friar: a very philosophical monk.   
   Website: http://seventransistorlabs.com   
      
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