A worldwide team of researchers has used an unusual imaging technique known as ghost imaging to make spectroscopic measurements of a gas molecule. The new approach by scientists at Tampere University of Technology in Finland, the University of Eastern Finland and the University of Burgundy Franche-Comté in France, works over a wide range of wavelengths and could advance measurements of atmospheric greenhouse gases, such as methane.
The researchers report their method to expand ghost imaging techniques to produce very efficient spectral measurements that divulge information about the chemical makeup of a gas molecule. They accomplish this by using ghost imaging with a supercontinuum light source, to capture the wavelength-dependent light transmitted through samples and prove that the technique can measure the spectral signature of the greenhouse gas methane with sub-nanometer resolution.
Ghost imaging produces images by connecting the intensity of two light beams that, taken separately, do not carry any significant information on the shape of the object, but instead allow ancillary inferences about its properties. This approach can remove some of the alterations linked with usual imaging systems in harsh environments, and has been used to create high-resolution images of physical objects.
Gas molecules are often scarce and thus only change the total light transmission by a small amount. This means that powerful light sources or exceptionally sensitive detectors are usually needed to detect them.