But...On the topic of an orbiting shade...
Instead of a reflector could, you could use prisms?
I think they might do the same thing, except that one only slows the photons while the other would reflect them...
It might make some difference on your ability to keep the shade stationary in space...
Could the photon deflection be syncronized in a way that would keep the shade at the focal point between Venus and the Sun?
Need laserboy input...