KAIST announced on June 13 that a research team led by Professor Jang Museok from the Department of Bio and Brain Engineering has succeeded in developing a reconstruction-based spectrometer technology using a bilayer disordered metasurface?an optical device that creates unique and predictable speckle patterns for each wavelength by intricately scattering light through two layers of disordered nanostructures.
(From left) Professor Jang Museok, Doctoral Candidate Lee Donggu, Doctoral Candidate Song Gukho. Provided by KAIST
A spectrometer is an optical instrument that analyzes the physical properties of light by separating it into its component wavelengths. It is widely used in scientific and industrial fields, including material analysis, chemical component detection, and life science research.
However, conventional high-resolution spectrometers are large and complex, which has limited their use in everyday applications. This limitation fundamentally arises from the operating principle of traditional dispersive elements, which separate light into its component wavelengths along the direction of propagation, similar to how a rainbow separates colors.
As a result, spectroscopic technology has primarily been used in laboratories or industrial manufacturing sites, with limited applicability in daily life.
However, the ultra-compact, high-resolution spectrometer developed by the research team is expected to enable the use of color information from light in smartphones and wearable devices in the future.
The research team devised an approach that departs from the conventional spectroscopic paradigm of using diffraction gratings or prisms?which map color information to the direction of light propagation on a one-to-one basis?and instead utilizes a designed disordered structure as an optical component.
To accurately generate the "complex random pattern" (an irregular light pattern of varying brightness created by the interference of multiple light wavefronts, known as a "speckle"), the team employed metasurfaces composed of structures tens to hundreds of nanometers in size, allowing them to freely control the propagation of light.
By implementing a bilayer disordered metasurface, they generated speckle patterns in a wavelength-specific manner, and then reconstructed precise color (wavelength) information from the light based on the random patterns measured by a camera.
According to the research team, this enabled the development of a novel spectrometer technology capable of accurately measuring broadband visible-to-infrared light (440?1300 nm) at a high resolution of around 1 nm, using a device smaller than a fingernail (less than 1 cm) and requiring only a single captured image.
Lee Donggu, a researcher who participated as the first author, said, "This technology is implemented in a way that can be directly integrated into commercial image sensors, so in the future, it will enable people to easily acquire and utilize wavelength information from light in their daily lives through mobile devices."
Professor Jang Museok stated, "The technology developed by our team surpasses the limitations of conventional RGB tricolor-based machine vision, which recognizes only three color components: red, green, and blue. Its significance lies in extending laboratory-level technologies to everyday machine vision, enabling applications such as food composition analysis, crop condition diagnosis, skin health measurement, environmental pollution detection, and bio-medical diagnostics."
This research was supported by the Samsung Science & Technology Foundation, as well as the Excellent Young Researcher Program, Leading Research Center Support Program, and Bio-Medical Technology Development Program, all administered by the National Research Foundation of Korea under the Ministry of Science and ICT.
The study was carried out with Lee Donggu and Song Gukho, both doctoral candidates in the Department of Bio and Brain Engineering, as co-first authors, and Professor Jang Museok as the corresponding author. The research results (paper) were published online in the international journal "Science Advances" on May 28.
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