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Tri-comb Spectroscopy

Three laser beams cooperating in detecting specific molecules. The detection can be as fast as half a second. Image credit: Bachana Lomsadze, Brad C. Smith & Steven T. Cundiff

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.

About Roberto Saracco

Roberto Saracco fell in love with technology and its implications long time ago. His background is in math and computer science. Until April 2017 he led the EIT Digital Italian Node and then was head of the Industrial Doctoral School of EIT Digital up to September 2018. Previously, up to December 2011 he was the Director of the Telecom Italia Future Centre in Venice, looking at the interplay of technology evolution, economics and society. At the turn of the century he led a World Bank-Infodev project to stimulate entrepreneurship in Latin America. He is a senior member of IEEE where he leads the New Initiative Committee and co-chairs the Digital Reality Initiative. He is a member of the IEEE in 2050 Ad Hoc Committee. He teaches a Master course on Technology Forecasting and Market impact at the University of Trento. He has published over 100 papers in journals and magazines and 14 books.