Quantum Entanglement, Dark Counts, Coincidence Detection

[caraher]

56. You should talk to their sales engineer

I'm not sure if there's more than one; every time I talk to them it's Jean. If you give the wavelength and tell them you want collinear Type II they'll know what you're talking about. It will take probably 7 weeks or so for them to make it for you (Incidentally, it's worth getting a coated crystal if only because BBO absorbs moisture and turns cloudy, and the coating helps protect against that! Their "p-coating" does that; I usually also get antireflection coatings, but you might actually want reflections to help you align it. In any event, you should store BBO in a sealed container with dessicant when not in use...)

I think the real issue with estimating brightness is that the full calculation is cumbersome and depends on knowing more details about your laser than most people have readily available.

Chapter 4 of this dissertation illustrates the effects of crystal tilt. The cones shrink as you tilt the BBO until they meet along a line, and if you keep tilting they eventually turn into non-overlapping cones and ultimately two beams. The 5-degree opening angle BBO cut for Type II can almost certainly be tilted to give collinear downconversion; on the other hand, a crystal made for collinear downconversion can surely be tilted to give rings with a few-degree opening angle.

(Incidentally, a beautifully-written dissertation on a topic similar to yours is David Branning's "Optical Tests of Complementarity and Nonlocality." Well worth reading... you probably won't follow all of it, but there are many passages accessible to the non-specialist reader.