It’s a very useful instrument for chemical analysis, but Fourier transform infrared (FTIR) spectrometers are too bulky for field use. Efforts to downsize these tools for portability have proven cost-intensive to date.
This spectroscopy method identifies chemicals using an infrared light source to measure absorption. As a sample is exposed to different wavelengths of infrared light, the spectrometer measures which wavelengths are 
Schematic of the silicon chip platform. Source: University of Campinasabsorbed. The computer then conducts a mathematical process known as the Fourier transform to generate an absorbance pattern or spectrum, which is compared to a library of spectra for chemical compounds to find a match.
Researchers recently turned to silicon photonics for the successful and cost-effective miniaturization of FTIR units. These components are currently used to manufacture chips for smartphones and other electronic devices. A challenge encountered was the highly dispersive profile of silicon waveguides, meaning that each wavelength travels at a different speed in this material and hence has a different refractive index.
A laser calibration method was developed to quantify and correct the distortions caused by silicon waveguide dispersion and non-linearity. The 1 mm² proof of concept FTIR spectrometer chip is based on standard silicon photonics fabrication procedures. Laboratory tests yielded a broadband spectrum with a resolution of 0.38 terahertz (THz), which is comparable to the resolution of commercially available portable spectrometers that operate in the same wavelength range.
Scientists from the University of Campinas, Brazil and the University of California San Diego participated in this research, which is published in Nature Communications.
