ETH Researchers Create Tiny Infrared Spectrometer

Researchers at ETH have developed a very compact infrared spectrometer that is small enough to fit on a computer chip and still provides "interesting possibilities." The researchers say that the chip would be usable in space and everyday life. One example is integration into mobile phones.

With the small infrared spectrometer embedded into a smartphone, the team says that the device could do things like determining the alcohol content in beer or how ripe a piece of fruit is. What makes the chip such a breakthrough is that infrared spectrometers used for those types of analysis today are large devices that typically weigh several kilograms and are difficult to integrate into a handheld device.

A conventional spectrometer splits incident light into two paths before reflecting it off mirrors. The reflected light beams are recombined and measured with a photodetector. When one mirror is moved, the interference pattern can be used to determine the proportion of different wavelengths in an incoming signal.

ETH uses the same principle to develop the mini-spectrometer, but in their device, the incident light isn't measured by movable mirrors. ETH's device uses special waveguides with an optical refractive index that is adjusted externally via an electric field. Varying that refractive index has an effect similar to moving mirrors.

Changes in waveguide configuration allow the researchers to examine different parts of the light spectrum. The new spectrometer has other significant benefits, including that it only needs to be calibrated once compared to multiple calibrations for normal spectrometers. It also has no moving parts and requires less maintenance. The device has some progress to be made before it could be used in a mobile device.