Roland Piquepaille writes "Laser lights can be used for optical sensing applications, for example to identify unknown gases emitted by an engine. And as these unknown substances react differently to different wavelengths, researchers at the University of Wisconsin at Madison have developed unique wavelength-agile lasers. And I'm amazed by the beauty and the simplicity of their idea. They're using white lasers which produce all colors simultaneously — but with a twist. The white laser light goes through a 20-kilometers long optical fiber before reaching its target. And because different colors 'travel' at different speeds, this produces independent results for the different wavelengths. The researchers are using spectral resolutions smaller than a thousandth of a nanometer and they are able to get all the results within a millionth of a second. This method could be used to design cleaner engines or data storage applications in a few years. Read more for other details, pictures and references."