A KAIST team led by Professor Mooseok Jang has developed an ultra-compact, high-resolution spectrometer using 'double-layer disordered metasurfaces' that generate unique random patterns depending on the color of light. This new concept spectrometer technology achieves 1-nm-level high resolutions in a device smaller than 1 cm, making it suitable for integration into smartphones and wearable devices. Furthermore, the precise prediction and utilization of the random patterns from the double-layer disordered metasurface enable expansion into advanced optical technologies such as hyperspectral imaging and ultrafast imaging.

Color, referring to how the wavelength of light is perceived by the human eye, goes beyond a simple aesthetic element, containing important scientific information related to a substance's composition or state. Spectrometers are optical devices that analyze material properties by decomposing light into its constituent wavelengths, and they are widely used in various scientific and industrial fields, including material analysis, chemical component detection, and life science research. Current high-resolution spectrometers are large and complex, making them difficult to apply to widespread daily use. However, due to the ultra-compact, high-resolution spectrometer developed by KAIST researchers, it is now expected that the color information of light can be utilized even within smartphones or wearable devices.

KAIST (President Kwang Hyung Lee) announced that Professor Mooseok Jang's research team at the Department of Bio and Brain Engineering has successfully developed a reconstruction-based spectrometer technology using double-layer disordered metasurfaces*.

*Double-layer disordered metasurface: An innovative optical device that complexly scatters light through two layers of disordered nanostructures, creating unique and predictable speckle patterns for each wavelength.

Existing high-resolution spectrometers have a large form factor, on the order of tens of centimeters, and require complex calibration processes to maintain a high level of accuracy. This stems fundamentally from the operating principle of traditional dispersive elements, such as gratings and prisms, which separate light wavelengths along the propagation direction, akin to how a rainbow separates colors. Consequently, despite the potential for the color information of light to be widely useful in daily life, spectroscopic technology has been limited to laboratory or industrial manufacturing environments.

The research team devised a method that departs from the conventional spectroscopic paradigm of using diffraction gratings or prisms, which establish a one-to-one correspondence between light's color information and its propagation direction, by utilizing designed disordered structures as optical components. To realize this, they employed metasurfaces, which can freely control the light propagation process using structures tens to hundreds of nanometers in size, to implement 'complex random patterns (speckle*)' accurately.

*Speckle: An irregular pattern of light intensity created by the interference of multiple wavefronts of light.

Specifically, they developed a method that involves implementing a double-layer disordered metasurface to generate wavelength-specific speckle patterns and then reconstructing precise color information (wavelength) of the light from random patterns measured by a camera.

As a result, they successfully developed a new concept of spectrometer technology that can accurately measure light across a broad visible to infrared range (440-1300 nm) with a high resolution of 1 nm in a device smaller than a fingernail (less than 1 cm) using only a single captured image.

Dong-Gu Lee, a lead author of this study, says, "This technology is implemented in a way that is directly integrated with commercial image sensors, and we expect that it will enable easy acquisition and utilization of light's wavelength information in daily life when built into mobile devices in the future."

Professor Mooseok Jang said, "This technology overcomes the limitations of existing RGB three-color based machine vision fields, which only distinguish and recognize three color components (red, green, blue), and has diverse applications. We anticipate various applied research for this technology, which expands the horizon of laboratory-level technology to daily-level machine vision technology for applications such as food component analysis, crop health diagnosis, skin health measurements, environmental pollution detection, and bio/medical diagnostics." He added, "Furthermore, it can be extended to various advanced optical technologies such as hyperspectral imaging, which records wavelength and spatial information simultaneously with a high resolution, 3D optical focusing technology, which precisely combines light of multiple wavelengths into desired forms, and ultrafast imaging technology, which captures phenomena occurring in very short periods."

This research was collaboratively led by Dong-Gu Lee (Ph.D. candidate) and Gookho Song (Ph.D. candidate) from the KAIST Department of Bio and Brain Engineering as co-first authors, with Professor Mooseok Jang as the corresponding author. The findings were published under the title “Reconstructive spectrometer using double-layer disordered metasurfaces” in the international journal Science Advances on May 28, 2025.

* DOI: 10.1126/sciadv.adv2376