A next-generation optical sensor technology capable of precisely detecting not only the intensity and wavelength of light but also its rotational direction has been developed in South Korea.
On Monday, a research team led by Professor Yang Ji-woong of the Department of Energy Engineering at DGIST (Daegu Gyeongbuk Institute of Science and Technology) announced it has built a quantum dot-based optical sensor that detects circularly polarized light across an ultra-broadband spectrum ranging from ultraviolet to shortwave infrared. The device demonstrated outstanding photodetection performance comparable to that of commercial silicon optical sensors.
Circularly polarized light (CPL) is light whose electric field rotates in a helical pattern as it propagates, and is directly linked to the spin information of photons, the particles of light.
Polarization information serves as a critical signal in next-generation security and communication technologies such as quantum communication, quantum cryptography and light-based quantum information processing, drawing global attention to related optical sensor technologies.
Conventional CPL optical sensors required the light-absorbing material itself to possess a "chiral structure" — a specific helical directionality. This approach limited the range of usable materials and confined the detectable wavelength to ultraviolet and visible light ranges, creating a bottleneck in extending the technology to the infrared spectrum essential for quantum communication and optical sensing.
Professor Yang's team broke through this limitation with a counterintuitive design strategy: instead of engineering chirality into the light-absorbing material, the researchers introduced a chiral structure into the charge transport pathway — the route electrons travel.
The team developed a zinc oxide (ZnO) electron transport layer bonded with chiral molecules and applied it to a quantum dot photodiode, successfully achieving the selective transmission of electrons with a specific spin orientation. Electrons generated by circularly polarized light pass through this specialized layer, producing current differences based on their spin states, which enables direct reading of the light's rotational direction.
The quantum dot optical sensor developed in this study can detect circularly polarized light across an ultra-broadband wavelength range encompassing ultraviolet, visible, near-infrared and shortwave infrared regions. Achieving detection of polarization information across such a wide wavelength range with a single device is considered an exceptionally rare and unparalleled accomplishment.
The sensor also recorded high performance reaching 10¹² Jones (a unit measuring photodetection capability), indicating very strong potential for commercialization.
"This research carries great significance in presenting an optical sensor based on a new principle for detecting the spin information of photons," Professor Yang said. "It has strong potential to serve as a core sensor technology driving various quantum optoelectronic fields including quantum communication, quantum sensing, next-generation image sensors and secure optical communications."
The research was conducted with support from the Ministry of Science and ICT (MSIT) and the National Research Foundation of Korea's Nano and Materials Technology Development Program, as well as the Ministry of Trade, Industry and Energy (MOTIE) and the Korea Institute for Advancement of Technology's International Joint Technology Development Program. The findings were published in *Advanced Materials*, a top-tier international journal in materials science.