Miniaturi­zation of infrared spectro­meters will lead to their wider use in consumer electronics, such as smartphones enabling food control, the detection of hazardous chemicals, air pollution monitoring and wearable elec­tronics. They can be used for the quick and easy detection of certain chemicals without using labora­tory equipment. Moreover, they can be useful for the detection of counterfeit medical drugs as well as of greenhouse gases such as methane and CO₂.

A Team of scientists at Empa, ETH Zurich, EPFL, the University of Salamanca, Spain, the European Space Agency (ESA) and the Univer­sity of Basel now built a proof-of-concept minia­turized Fourier-transform waveguide spectrometer that incorporates a subwavelength photo­detector as a light sensor, consisting of colloidal mercury telluride quantum dot and compatible with complementary metal-oxide-semi­conductor (CMOS) technology.

The resulting spectro­meter exhibits a large spectral bandwidth and moderate spectral resolution of 50 cm⁻¹ at a total active spectrometer volume below 100 μm × 100 μm × 100 μm. This ultra-compact spectro­meter design allows the inte­gration of optical-analytical measurement instruments into consumer electronics and space devices. “The monolithic integration of subwavelength IR photo­detectors has a tremendous effect on the scaling of Fourier-transform waveguide spectrometers”, says Empa researcher Ivan Shorubalko. “But this may also be of great interest for miniaturized Raman spectro­meters, biosensors and lab-on-a-chip devices as well as the development of high-resolution snapshot hyper­spectral cameras.” (Source: Empa)

Reference: M. J. Grotevent et al.: Integrated photodetectors for compact Fourier-transform waveguide spectrometers, Nat. Phot., online 24. Oktober 2022; DOI: 10.1038/s41566-022-01088-7

Link: Transport at Nanoscale Interfaces, Empa, Dübendorf, Switzerland