Spark Plugs? Pfftt. Lasers, Man. LASERS!

The internal combustion engine has been around for quite a while, and yet we still find ways to tweak and cajole it into better performance and efficiently. The spark plugs in a gasoline engine do just that - provide a spark at the correct time to cause the fuel/air mixture to combust, expand the gas rapidly and drive the piston, which rotates the camshaft. 

But suppose you used a laser instead of a spark plug? It should be more controllable, more precise, etc. This is not strictly a new concept, but it's the first it's been shown to work in a real engine, thanks to Princeton Optronics.
The problem is that spark plugs can only ignite the fuel at one end of the chamber, says Chuni Ghosh, CEO of New Jersey-based Princeton Optronics, the firm that developed the new ignition system.

In Ghosh's engine, a laser ignites the fuel in the middle of the chamber instead, burning more of the fuel and improving combustion efficiency by 27 per cent. Laser ignition could boost the fuel efficiency of a car from 40 kilometres per litre up to around 50, for example. The more complete burn also emits fewer polluting by-products such as nitrogen dioxide