Hi!
I am planning on building a green DPSS laser and have been thinking about crystal mounting over the past few weeks.
The only information I've read with regards to mounting vanadate comes from Sam's Laser FAQ:
If I understand correctly, this mounting setup has copper plates lined with indium foil making contact with the front face (laser entry) and back face (laser exit), with a small aperature for the beam.The following suggestion would provide good thermal contact between a vanadate crystal and copper plates. At least one of these (the plate in contact with the pump-side of the vanadate is most important) could be attached to a heatsink or TEC.(From: Christoph Bollig (laserpower@gmx.net).)
- Take two copper plates, 3 to 5 mm thick. Screw them tightly together.
- Drill a 1 mm (0.04 inch) hole threw them, best if countersunk on the pump side to avoid clipping the pump beam.
- Take apart, put indium foil on both sides, put paper in between and screw together again (not too tight).
- Use the back of the 1 mm drill bit to push through. This will make a hole in the indium foil.
- Separate again. In theory, one piece of indium foil should stick to each metal piece. Take the paper off.
- Put the crystal in between and screw together again. Make sure, it is not skewed. Don't overtighten - vanadate isn't very strong!
This makes sense, as most of the heat produced comes from the first atoms struck by the 808nm pump beam.
However, I have major reservations when it comes to touching indium foil to the delicate optical coating of the crystal.
Anyway, the questions:
- Are the dichroic optical coatings resilient enough to survive indium foil being pressed against them?
- Is this a one shot deal? i.e., can the crystal be removed from its enclosure and still be in usable condition?
- How necessary is thermal contact with the front face if I'm using a ~2 watt pump? Is thermal lensing inevitable otherwise?
I've also got a question about mounting the KTP crystal:
- Since there is a correlation between KTP temperature and its theta, can I mount the crystal at a fixed 45 degree angle and just use a TEC to keep it at the whatever temperature produces a theta of 45 degrees in the KTP?
- I mocked up a possible KTP mount:
The inner cylinder would be machined a little bit too small to allow the application of thermal paste. Once the optimal angle is found, it is kept in place by a set screw (ultimately probably three set screws).
I know I'm asking to be spoon fed here, but these crystals (especially the vanadate) are ridiculously expensive... I really don't want to make a $400 mistake.
Thanks!