From: greif1-nospamhere@rochester.rr.com   
      
   On 7/23/2013 2:48 AM, Ian Mackay wrote:   
   > Sam   
   >   
   > I'm working with Cavity Enhanced Spectroscopy but with a fairly low   
   > intensity,  non-coherent source so the normal approach of coupling light   
   > into the system through one of the mirrors doesn't really work so well. This   
   > hole-in-the-mirror approach is based on an old'ish paper dealing with   
   > stretching the optical path of an FTIR spectrometer.   
   >   
   > I had a local glazier do a couple of succesful dry runs drilling small holes   
   > on old mirrors but when I gave him the 'good' mirrors he managed to drill   
   > the holes off-centre and the wrong diameter. (other than that they were   
   > perfect).   
   >   
   > I'd also  prefer to isolate the gas sample cavity from the system   
   > electronics, hence removing some coating is more attractive, rather than   
   > drilling more holes.   
   >   
   > I hadn't thought about the possibility of 'spoiling' the current coating  -   
   > would you not need to know some details about the current coating's   
   > construction? Other than  the graphs Thorlabs publish on their website, I   
   > really don't know anything about their recipe.   
   >   
   > Ian   
   >   
   Coating with wax or thick photoresist, then boiling sulpheric acid might   
   make the coating give up and not hurt the glass much.   
      
   Or send it out to a glass machine shop which can precisely center the   
   hole. Grayglass might be a good choice.   
   http://www.grayglass.net/glass.cfm/Precision-Machining/Precision   
   Drilling/catid/46/conid/84   
      
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