This was the answer:
Good question! We consulted Neil Davison, Project Coordinator of the Non-Lethal Weapons Research Project, at the Centre for Conflict Resolution (University of Bradford). He tells us: "I think this is a sci-fi cliché that will remain sci-fi. However, weapons that can be set to 'pain' instead of 'kill' are on the way. One US military prototype, the Active Denial System, projects a beam of energy that heats up the skin of the victim, causing a painful burning sensation. Another development project aims to use lasers to stimulate pain receptors in the skin. Either way it would be a far cry from the sort of harmless "stun" seen in Star Trek. Being on the receiving end would be very painful and could leave lasting damage."