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Attempting harmonic generation.
Crystal number one: Beat up, unidentified, old piece of crap from eBay
Appearance
The shape is wedge-like, with what may be electrodes on one face.
Composition
Refractive index measurement: Not easy to do, but I came up with 2.83 at 632.8 nm. LiNbO3 has the highest of common crystals at 2.2864, so maybe that's what it is.
Phase matching
As far as I've been able to find, there is no angle where the ordinary polarized fundamental and the extraordinary polarized second harmonic have the same refractive index, at least at room temperature. Apparently, people stick with periodically poled LiNbO3 for efficient SHG.
Home-grown ADP
A crystal-growing set for kids produced a few of these. I can see 532 nm, but the flashlamp and maybe the 1064 nm overwhelms the green in the camera.
It doesn't generate a lot of green, at least not while it's just laying at a random angle to the pump, but on a target the 532 nm beam is slightly to the left of the pump beam, so it shows up a little.
Profiling the spot:
Conclusion: I haven't found a way to cut, let alone polish it, but I did find a schematic:
(Credit: http://www.nature.com/srep/2013/130403/srep01605/full/srep01605.html)
KDP
Two cells made by Cleveland Crystals circa the Jurassic.
Cell number 1: Model XF 1925, Type II.
Left: Using a pyroelectric detector to measure the energy, the max I've seen so far is 14.8% efficiency. The optic in the middle is an infrared filter, so this is solely 532 nm second harmonic being measured.
Right: The second harmonic pumping Rhodamine 6G in a dye laser (on the right).
The fundamental here and with the ADP above, is 1064 nm from an Nd:YAG laser.
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