Manifold Next Event Estimation Sampling Technique implemented in cycles.
https://developer.blender.org/D13533
Here in action...
https://www.youtube.com/watch?v=UbWWhPmqV5E
Caustics implemented in Cycles Blender 3.1
Caustics implemented in Cycles Blender 3.1
WIndows 11 Pro Ryzen 7 5700x RTX 3090 32 GB RAM