Is it possible to create a holographic lighting in cycles? This is possible In the Blender Internal render engine, but I'm not going for linking lamps. Here is what I mean (the light that is holding the sphere inside it) -
Yes, this is possible using volumetrics:
Using a cube to scatter light emitted from a spot lamp.
Create a cube and give it a volume scatter material:
Add a spot lamp:
You could also fake this by modeling the cone, then using a volumetric gradient for the falloff:
It won't be as physically accurate or as flexible, but it will be less noisy:
Example .blend (for both methods)