Wisconsin Alumni Research Foundation


UW–Madison researchers, led by Professor Mikhail Kats, have developed a new device – the Planck spectrometer – that can measure the spectral characteristics of an object based on thermal emission at different temperatures. This highly innovative approach (inspired by Planck’s law of thermal radiation) eliminates the need for wavelength-selective optical components, such as gratings, prisms, or interferometers with moving mirrors.


Optical spectrometers are common analytical instruments used to measure light frequency (a spectrum) emitted or reflected from, or transmitted through, an object to reveal its properties. In one simple spectrometer design, different frequency components of the light from the object being studied are spatially dispersed by a prism, grating, or other component. Broadband detectors are then spatially arrayed in the dispersion to separately measure each frequency component of a spectrum.

Across the different classes of spectrometers there are significant drawbacks, notably, the reliance on costly and complex components such as narrowband filters, narrowband light sources, dispersive elements, and/or precise mechanical positioning of optical elements.


The Kats team’s robust, low-res solution replaces complex spectroscopy mechanisms with a simple, electrically controllable heater. It can also integrate as an add-on to existing spectroscopy systems. Extremely well adapted for mid-infrared or near-infrared imaging, the Planck spectrometer detects light emitted from an object as its temperature is changed. The measurement of the time varying (and temperature varying) ‘blackbody’ radiation from the object can then be processed to reveal the underlying spectral characteristics of the object being studied. Alternatively, thermal radiation from a known reference emitter may be used to illuminate a separate sample to similar effect.


As a new spectroscopic technique, this innovation can be expected to take a share of a very large global market, worth more than $38 billion in 2021. Its reliance on thermal information and the absence of complex components make it possible to adapt it to smart phones and other consumer products, expanding the use of spectroscopy to new areas, for example measuring the sugar content of the fruit one is buying. The market for smartphone apps is expected to reach almost half a trillion dollars by 2024.

Principal Investigator

Learn more about Mikhail Kats, a 2021 WARF Innovation Award nominee. The annual prize recognizes outstanding disclosures with potential high impact and broad benefit to humankind.


Xiao, Yuzhe, et al. “Planck spectroscopy.” Laser & Photonics Reviews 15.10 (2021): 2100121. https://doi.org/10.1364/CLEO_AT.2021.JW2G.4

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