On Tuesday, January 14, 2014 7:43:40 PM UTC-5, gghe...@gmail.com wrote:   
   > On Monday, January 13, 2014 12:02:06 PM UTC-5, haitic...@gmail.com wrote:   
   >    
   > > As a thought experiment, consider that an average Si PD detector is   
   somewhere around 2mmx2mm, as I remember. So the question arises in my mind,   
   has anyone cut the rather expensive filters into sizes needed for the   
   detectors? I looked around, and    
   Tungsten carbide scribe goes for $8 (seems to work better than the diamond   
   variety.)    
   >    
   > >    
   >    
   > > This could be done by hand, but a "scribing engine" worth consideration.   
   I'm still thinking about it, but ideal is to have tensioner spring, guide for   
   sliding, and way to immobilize the filter.    
   >    
   > >    
   >    
   > > What is needed for immobilization is a glue to temporarily fix the filter.   
   The dopping wax used by diamond polishers, the old standby Duco cement, or   
   Sodium Silicate, a water soluble glue. You probably dont want to melt wax, or   
   expose filter to water,   
    so that leaves Duco released with acetone. I'm even nervous with acetone,   
   since it has a hydrophilic double nature capable of penetrating inorganic   
   films. I'd feel better with a strictly hydrophobic solvent like toluene,   
   methylene chloride, or hexane.    
   >    
   > >    
   >    
   > > Possibly someone will post that the filter manufacturers like OCLI are   
   doing this already, but given that detectors are generally small area, it's a   
   bit surprising to me that the filters are so large.    
   >    
   > >    
   >    
   > > JB   
   >    
   >    
   >    
   > I think this is a bad idea,  Interference filters (IF) typically have   
   internal layers that don't like water, and hence a coating around the   
   perimeter.     
   >    
   > So it depends on the IF, only my supplier knows for sure.       
   >    
   >    
   >    
   > George H.   
      
   I used to make these professionally, if that matters. There are several   
   designs - many layer dielectrics and metal layers with a gap between. These   
   were made by magnetron sputtering, which produces a fairly hard coating,   
   depending on the material. They    
   are generally up to being cut. You understand, this is for prototype work, and   
   production would be different. Materials vary, but high index is often TiO2   
   and low can be MgF2. These are robust materials, as evidenced by some camera   
   filters directly    
   exposed to the ambient. In production, you might set the computer program   
   boundary conditions to index of refraction 1.33 to embed in Silicone. These   
   multilayer dielectrics are designed in computer programs, and the thicknesses   
   monitored by quartz    
   crystal oscillators inside the vacuum chamber.    
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)