Image caption Two or three lasers are focused to ignite fuel in more than one place

Car engines could soon be fired by lasers instead of spark plugs, researchers say.

A team at the Conference on Lasers and Electro-Optics will report on 1 May that they have designed lasers that could ignite the fuel/air mixture in combustion engines.

The approach would increase efficiency of engines, and reduce their pollution, by igniting more of the mixture.

The team is in discussions with a spark plug manufacturer.

The idea of replacing spark plugs - a technology that has changed little since their invention 150 years ago - with lasers is not a new one.

Spark plugs only ignite the fuel mixture near the spark gap, reducing the combustion efficiency, and the metal that makes them up is slowly eroded as they age.

In the past, lasers that could meet those requirements were... big, inefficient, and unstable Takunori Taira, National Institutes of Natural Sciences, Okazaki

But only with the advent of smaller lasers has the idea of laser-based combustion become a practical one.

Ceramic powders

A team from Romania and Japan has now demonstrated a system that can focus two or three laser beams into an engine's cylinders at variable depths.

That increases the completeness of combustion and neatly avoids the issue of degradation with time.

However, it requires that lasers of high pulse energies are used; just as with spark plugs, a great deal of energy is needed to cause ignition of the fuel.

"In the past, lasers that could meet those requirements were limited to basic research because they were big, inefficient, and unstable," said Takunori Taira of the National Institutes of Natural Sciences in Okazaki, Japan.

Image caption Spark plugs only ignite the fuel mixture very near the spark gap

"Nor could they be located away from the engine, because their powerful beams would destroy any optical fibres that delivered light to the cylinders."

The team has been developing a new approach to the problem: lasers made of ceramic powders that are pressed into spark-plug sized cylinders.

These ceramic devices are lasers in their own right, gathering energy from compact, lower-power lasers that are sent in via optical fibre and releasing it in pulses just 800 trillionths of a second long.

Unlike the delicate crystals typically used in high-power lasers, the ceramics are more robust and can better handle the heat within combustion engines.

The team is in discussions to commercialise the technology with Denso, a major automobile component manufacturer.