Alongside its compact size, the ETH physicists' innovation offers two other advantages: the "spectrometer on a chip" has to be calibrated only once, compared to conventional devices that needs recalibration over and over again; and because it contains no moving parts, it requires less maintenance.
For their spectrometer, the ETH researchers employed a material that is also used as a modulator in the telecommunications industry. This material has many positive properties, but as a waveguide, it confines the light to the inside. This is less than ideal, as a measurement is possible only if some of the guided light can get out. For this reason, the scientists attached delicate metal structures to the waveguides that scatter the light to the outside of the device. "It required a lot of work in the clean room until we could structure the material the way we wanted," Grange explains.
Until the current mini-spectrometer can actually be integrated into a mobile or other electronic device, however, there is still some technological progress to be made. "At the moment we're measuring the signal with an external camera," Grange says, "so if we want to have a compact device, we have to integrate this as well."
Originally the physicists were not aiming at chemical analyses, but at a completely different application: in astronomy, infrared spectrometers provide valuable information about distant celestial objects. Because the earth's atmosphere absorbs a high amount of infrared light, it would be ideal to station these instruments on satellites or telescope in space. A compact, lightweight and stable measurement device that can be launched into space relatively inexpensively would naturally offer a substantial benefit. Their findings were published in the Nature Photonics journal under the title “An integrated broadband spectrometer on thin-film lithium niobate”
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