You may have other plans for Sunday than attending the Conference on Lasers and Electro-Optics in Baltimore.

But if you were to sit in, you would hear a paper by a research team in Japan and Romania that offers a fascinating new avenue for increasing engine efficiency and reducing gas consumption: Ditch the spark plugs, and use lasers to ignite the fuel-air mixture.

Previously, lasers that could deliver sufficient power to ignite a fuel-air mixture were so large as to be impractical for use in an automotive engine--and also relatively fragile.

The team will report that it has developed new, smaller, tougher lasers made not of crystalline materials but ceramics, which are far more durable and resistant to the very high temperatures of a modern engine.

In effect, the team's ceramic laser cylinders (shaped roughly like spark plugs) accumulate energy sent via fiber optic cable from lower-power lasers. They then release the energy into the cylinder in pulses just 800 trillionths of a second long.

If they can be made sufficiently tough to withstand automotive use, lasers won't need to be replaced as spark plugs do when their metal tips erode.

But most importantly, the new lasers presented at the conference have a huge advantage over spark plugs: They can be focused to emit pulses at different depths within the cylinder cavity.

This permits much greater control over the process of combustion.

If engine-control software could simultaneously or sequentially ignite the fuel-air mixture at different spots throughout the combustion chamber, more complete combustion could be obtained and the energy contained in each hydrocarbon molecule more fully exploited--lowering consumption and raising gas mileage.

It's long been the goal of engine designers to use the minimum amount of fuel necessary to generate power.

Gasoline direct injection permits precisely metered volumes of fuel to be injected into the cylinder, varying with each successive combustion cycle if necessary.

If you can vary the fuel each time, why not vary the spark as well? But despite enormous refinements in engine design, the basic concept of a spark plug hasn't changed in more than a century. The conventional plug can only generate one type of spark, defined by the fixed length of its gap.

The new lasers offer the tantalizing promise of abolishing that limitation.In an era where modern vehicle and engine controllers allow precise control over a car's various systems and processes--including sensors and feedback loops so rapid that they can vary each individual combustion cycle--the spark plug seems increasingly anachronistic.

The Japanese-Romanian team is now in talks with auto-parts maker Denso--which does a large business in conventional spark plugs--to commercialize its new design.

[BBC, University of Liverpool via Jalopnik; spark plug photo, Wikimedia Commons; laser photo, Wikimedia Commons]

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