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Entry  Fri Nov 9 18:56:49 2012, tara, HowTo, RefCav, Howto optically contact mirrors IMG_1964.jpgIMG_1955.jpgfixture_assem.PDF
    Reply  Wed Nov 28 20:37:57 2012, tara, HowTo, RefCav, assembling short ref cav IMG_2029.jpgIMG_2034.jpg
       Reply  Wed Apr 13 16:45:18 2016, tara, HowTo, RefCav, Optical Contact Tutorial IMG_2705.JPG
Message ID: 1631     Entry time: Wed Apr 13 16:45:18 2016     In reply to: 1085
Author: tara 
Type: HowTo 
Category: RefCav 
Subject: Optical Contact Tutorial 

I showed Antonio how to do optical contact (refcav-mirror setup).  The videos and pictures are posted on Google photo

 I used a blank plane mirror (from coastline optics, intended for AlGaAs coating) and bonded it on the spare 1.45" refcav. It took me 4-5 tries and I scratched one mirror (I put it back and marked the box) before I could get a reliable bond. In the videos, I added comments for each failure. Mostly I think the problem is only cleanliness of the tools and the solvent. 

 

After that I removed the mirror from the refcav. First I tried to use a setup to push the mirror along the mirror surface. To my surprise, the mirror did not pop out, but just slid off of center and still stuck on the surface of the refcav. 

So I used a razor blade to wedge in between the mirro and the refcav, add some isopropanol. With little effort, the mirror popped out nice and easy. The edge of the HR surface of the mirror is beveled, so it is easy to wedge in a razor blade without scratching the refcav or mirror's surfaces.

To sum up, before trying to do the optical bond we should

  • Prepare enough gloves, lens cleaning paper
  • Use spectochromatography grade isopropanol, or other solvents
  • Clean the area carefully.
  • Have a bright light source to inspect the surface and the bond. 

To do the bond

  • clean the surfaces, make sure there is no dust
  • Put the two surfaces together, give them a little push.
  • Observe the fringe to disappear as the two surfaces get together ( if your objects are transparent), So if you bond silicon cavity, you can't see it, but you should be able to tell if the bond is good or not by just try to pull them apart.
  • NOTE: I have done only dry bonding. The two surfaces are dry when I put them together.

Trouble shooting: If you can't form the bond

  • If you see the fringe, there are dust, debris on the surface, clean the surface again.
  • If you don't see the fringe. The two surfaces seem to have a contact, but still pop out with little force. You might want to push the mirror and the spacer together and see if the "color" of the bonding area changes or not. To have a good bond the contact surface should be completely transparent, not cloudy. You can tell by adding more pressure and see the cloudy area becomes more transparent, then there is some thing on the surface. It is most likely that the solvent has gone bad, or there is contamination in the solvent you use to clean the surface.
  • For a good bond, ususlly you cannot pull the mirror/rafcav off by your hands.
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