After seeing the results obtained with LuxRender on this page, I was curious to try and reproduce beautiful caustics in Cycles such as these:
I created a scene and added some lights, following the advice given in this video to create the materials, and also trying out other materials.
I find it hard to find much documentation on caustics within Cycles; some people advise to use Sun Lamps, some other recommend emitter planes. Sometimes large emitter planes seem to work, sometimes people recommend smaller emitter planes. Besides from this confusion, in my various tests, the light that goes through the objects and hits the ground plane is usually very diffuse, of an evenly brightness, and doesn't have many sharp areas.
Here's an example of what I get the closest I get being the shape on the left):
Moreover, in the example given above, caustics appear on two sides of the object, probably due to the light bouncing inside the object and being projected out on both sides.
How should I set up materials and lights for sharp and realistic caustics, in Cycles?