From: pcdhSpamMeSenseless@electrooptical.net   
      
   Lucile wrote:   
   > Hello,   
   >   
   > I am currently a PhD student at PROMES-CNRS and in the framework of   
   > my thesis I am working on small solar concentrators, to concentrate   
   > light up to 10 000 times in an optical fibre. To carry out the   
   > planned experiments we would need flashing illumination with the   
   > whole solar spectrum (wavelength from 350nm to 2500nm). So, we’re   
   > looking for a shutter capable of performing this task, ideally with   
   > shutter opening times ranging from the ns to the ms timescale. The   
   > shutter could be placed either on top of the concentrator (option 1),   
   > either between the secondary mirror and the optical fibre (option 2),   
   > please refer to the following figure. Please note that in position 2   
   > the shutter would be stressed, part of it would be exposed to very   
   > high illumination levels, which may raise additional mechanical   
   > issues.   
   >   
   > The parabolic concentrator's diameter is approximatively 10 cm and   
   > the distance between the optical fibre and the secondary mirror is   
   > approximatively 5 mm.   
   >   
   >   
   > Do you have any ideas where I could find this kind of products? Thank   
   > you in advance.   
   >   
   > Sincerely,   
   >   
   > Lucile Marechal   
   >   
      
   For milliseconds, an LCD would probably get my vote, because of its   
   extremely high damage threshold.  Being a polarization device, it'll   
   lose half your light, but large apertures are available at fairly low   
   cost, so it wouldn't have to go right at the fiber.  That'll help with   
   the damage issue as well.   
      
   I'd probably want to use a walkoff-plate polarizer at the fiber end, so   
   that the light can be dumped into something nice and durable.   
      
   Since at 10,000x the NA of sunlight is about 0.44, I gather that you're   
   using a high-NA multimode fiber.   
      
   Unless the fiber is really big, you surely aren't talking about that big   
   a concentrator--with a 100/125 um fiber, 10,000x only needs an input   
   area of 10 mm diameter.   
      
   Cheers   
      
   Phil Hobbs   
      
      
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   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   
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