Doubt it, but getting a pencil beam is nigh impossible with radio, there's going to be leakage somewhere. Also, you'd have a bunch of physicists asking about how you got a beam that thin.
I haven't actually done the math, but for a parabolic dish which is much larger than the waveguide diameter, shouldn't you get a very narrow beam? Isn't that how microwave uplinks like the Ubiquiti airFibre5 can give you wireless networks at gigabit speeds over hundreds of kilometers?
