From hospitals to manufacturing facilities, ultraviolet light is widely used as a powerful disinfectant. Beyond sterilisation, the higher-energy, invisible form known as deep ultraviolet (DUV) light plays an important role in enabling next-generation optical devices such as ultrasensitive photodetectors and sensors. Manipulating this light and harnessing this energy effectively remains a challenge, however, as it tends to leak into the surrounding materials when used with semiconductor, resulting in low-quality resonance.
“We want to control DUV light at the nanoscale using materials already present in today’s computer chips. This could open the possibility of making optical devices that are smaller, more cost-effective and easier to integrate with existing technologies,” said Zhaogang Dong, a Principal Scientist at the A*STAR Institute of Materials and Research Engineering (A*STAR IMRE) and A*STAR Quantum Innovation Centre (A*STAR Q.InC).
To achieve this, Dong and colleagues have been working on interband plasmonics, which use the interaction of light with bound electrons in semiconductor materials like silicon, aiming to enhance the confinement and resonance of DUV light. They collaborated with students and researchers at A*STAR IMRE; A*STAR Q.InC; A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE2); the University of Sheffield in the UK; the Singapore University of Technology and Design; and the National University of Singapore.
The team set out to design a new nanophotonic platform that would hybridise a plasmonic mode and a cavity mode, leading to better light confinement and reduced energy loss. An antenna made of silicon nanodisks, supporting plasmonic resonances, was stacked on top of a thin dielectric layer as the cavity.
“The antenna traps and concentrates the light, while the cavity makes the light bounce back and forth between two mirror-like surfaces like an echo,” Dong explained. “When these two effects are matched correctly, the light becomes much stronger than either effect alone.” By carefully tuning the cavity thickness and nanodisk size, the researchers ensured that both modes resonated at the same energy.
Their hybrid nanoantenna platform enhanced the quality factor by more than 10-fold compared to conventional interband plasmonic structures, indicating that the light stayed resonating for longer. “This opens a new semiconductor-based route for ultraviolet nanophotonics,” said Yan Liu, a Senior Scientist at A*STAR Q.InC.
The enhanced resonance also led to improved absorption of DUV light in experimental tests. Building on this, the researchers plan to apply the same hybridisation strategy to develop more efficient silicon-based DUV photodetectors. Through these efforts, they aim to create compact, multifunctional optical components for next generation of photonic devices.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Materials and Research Engineering (A*STAR IMRE), the A*STAR Quantum Innovation Centre (A*STAR Q.InC) and the A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE2).
