Mass productionResearchers from the Massachusetts Institute of Technology (MIT) have, however, found a method to produce tiny spectrometers that are just as powerful and accurate, but that can be mass produced using existing chip manufacturing processes. This would enable new applications for spectroscopy that up to now were physically or financially impossible. The discovery has been published in Nature Communications.
ChallengeThe biggest challenge when building chip-size spectrometers is the size: the ability of an instrument to split light into its constituent wavelengths with the aid of conventional optics is strongly dependant on the dimensions: when these diminish, so does the performance.
Fourier transformationAnother type of spectrometer makes use of a mathematical approximation; Fourier transformation. However, the problem of the dimensions remains: for good performance a large optical path is required.
Optical switchThe system that has been been developed at MIT is based on optical switches that can direct the light beam through different optical paths with different lengths. These entirely electronic switches eliminate the need for the movable mirrors that are necessary in existing implementations. Additionally, these switches can be produced cheaply.
Powers of twoBy using path lengths that differ by ratios of 2 from each other, and by combining them in various ways and exponential number of discrete path lengths can be obtained; this finally leads to a spectral resolution that increases exponentially with the number of optical switches on the chip.