Generation of polarization entangled photons

[AlexHT]

Hi,

What crystal do I need to generate polarization entangled photons? I read BBO (beta-BaB2O4) crystal are needed but when I call the engineers at commercial companies and mention the term "entangled photons" it goes way over their heads and they just say they don't make this crystal.

I am trying to use a laser diode at 856nm (give or take) and send it trough a second harmonic generator (now at 428nm) to hit the BBO crystal with. Much like it is described in the paper : http://xqp.physik.uni-muenchen.de/publ/apl_79_869_2001.pdf

Anyone has any suggestions - for a good company or share their experience with this field?

Thanks in advance!

[DrChinese]

Try this:

Downconversion Crystal: Cleveland Crystals, http://www.clevelandcrystals.com. Beta-barium borate ~BBO!
crystal, 3 mm long, for converting a cw 405-nm input to an
810-nm output, 3° cone angle on signal and idler, XH0503
housing with a 5-mm aperture, Humidity-barrier antireflective
coatings on the crystal faces, nitrogen purge connections,
and no windows; $2,160.