I still remember when I was a kid the wonder of seeing a beam of sunlight split into the rainbow colours by a prism. That was possible to artificially create the rainbow seemed like magic. Later on I appreciated that different molecules when hit by an electromagnetic field (and light is an electromagnetic field) distort the field in ways that are specific to those molecules (specific radiation emission).
This property has been used for decades to identify molecules by hitting them with an electromagnetic field and measuring the radiated one. This, in a nutshell, is spectroscopy. It provides a veery useful tool to scientist and has many practical applications including in detecting explosives.
The problem with spectroscopy is the bulkiness of the equipment involved and the time it takes to perform the analyses.
This is where this news gets interesting.
Researchers at the University of Michigan have found a way to use three laser beams to perform multidimensional coherent spectrography, a complex name to mean that the detection is performed using several layers of an electromagnetic field (each laser generates a layer). Two beams are combined, see the schematics, pass through the gas needing identification (molecules float in the gas) and merge with the third beam. The resulting beam is intercepted by the detector that analyses the spectrum and singles out the various molecules.
The whole set could be packaged into a 10x4x2 inches assemble that although not micro is way smaller than current spectrographic equipment. The pulses emitted by the lasers can be controlled in software, thus making it possible to detect a wide range of molecules in a fraction of a second.