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Published January 19, 2022 | Supplemental Material
Journal Article Open

Development of a Compact and Robust Mid-Infrared Spectrometer by Using a Silicon/Air Hyperspectral Filter


The molecular absorption spectrum in the mid-infrared (mid-IR) region is typically measured by Fourier-transform infrared spectroscopy (FTIR). Such spectrometers require complex and delicately aligned interferometers, which increases their size and cost. Here, we present an alternative compact mid-IR spectrometer, which uses a variable mid-IR filter with a gradual change of cavity length between two silicon/air dielectric mirrors. When combined with a modern uncooled thermal imaging camera, hyperspectral filtering can provide a powerful solution for the miniaturization of mid-IR spectrometers. By using the hyperspectral filter, light from a broadband light source can be dispersed and assigned to individual pixels of a microbolometer array of the thermal imaging camera. This technology offers an inexpensive and compact mid-IR spectrometer design with no moving parts and rapid acquisition time.

Additional Information

© 2021 American Chemical Society. Received 15 November 2021. Published online 30 December 2021. This work was supported by Kairos Ventures. We thank Dr. Nina Hong for IR ellipsometry measurement. The device nanofabrication was performed at the Kavli Nanoscience Institute at Caltech. Author Contributions. T.J. and A.S. conceived the project. T.J. made the filter with help of W.M.J. T.J. performed the optical design of the spectrometer with the help of A.N. and J.P.C. Software development for the detector was done by A.N., C.C., and C.R. T.J. and A.S. wrote the manuscript with input from all authors. The authors declare no competing financial interest.

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September 22, 2023
March 5, 2024