From: pcdhSpamMeSenseless@electrooptical.net   
      
   On 2023-03-21 18:46, RichD wrote:   
   > Say you want to generate a very narrow light   
   > band in the UV,  with precise desired frequency.   
   > Is it feasible to do so, by starting with a reference   
   > microwave signal, then heterodyning up and up,   
   > doubling in successive stages?   
   >   
   > What is the limit on this process?  Assume each   
   > stage utilizes a technology appropriate for that wavelength.   
   >   
   > --   
   > Rich   
   >   
      
   You actually go the other way, starting with a femtosecond Ti:sapphire   
   laser, pushing it through a holey fiber to broaden the spectrum by self   
   phase modulation, and then lock a line at the blue end to the second   
   harmonic of the red end.   
      
     It's a 1:1 lock, so there's no phase ambiguity.  You can lock the beat   
   frequency to an RF signal, and get e.g. x10**6 frequency multiplication   
   without the accompanying 120 dB phase noise penalty.   
      
   Jan Hall and Ted Haensch got the Nobel prize in physics for that bit of   
   extreme cleverness.   
      
   Cheers   
      
   Phil Hobbs   
      
   --   
   Dr Philip C D Hobbs   
   Principal Consultant   
   ElectroOptical Innovations LLC / Hobbs ElectroOptics   
   Optics, Electro-optics, Photonics, Analog Electronics   
   Briarcliff Manor NY 10510   
      
   http://electrooptical.net   
   http://hobbs-eo.com   
      
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