Ultraviolet light has several uses in the medical and healthcare fields, including treatment, sterilization, and disinfection. Microcircuits and patterns are also made with them in the semiconductor sector. Control of the optical characteristics of these UV rays is made possible by a metalens manufacturing technique devised by a group of researchers at Pohang University of Science and Technology (POSTECH). This idea has received substantial attention across sectors, piquing interest in prospective developments.
(Left) Mass-produced UV metalenses. (Right) Atomic layer deposition of high-refractive-index films to enhance efficiency. Image Credit: Pohang University of Science and Technology
This collaborative research group, which includes Ph.D. candidates Joohoon Kim and Yeseul Kim from the Department of Mechanical Engineering at POSTECH, Professor Junsuk Rho from the Department of Mechanical Engineering and the Department of Chemical Engineering, and Professor Heon Lee and Wonjoong Kim from the Department of Materials Science and Engineering at Korea University, has developed a method for producing large-area metalenses in large quantities that are specifically designed for use in the ultraviolet spectrum. Materials Today published the research findings.
Metalenses affect light characteristics by forming nanometer-scale patterns or structures on lens surfaces. With the capacity to lower the thickness of standard lenses by a factor of 10,000, they offer great promise for medical devices injected into the body and wearable devices. Ongoing research seeks to develop mass production and commercialization of metalenses.
However, ultraviolet light provides challenges since it is absorbed by most materials due to its tremendous energy. The shorter wavelength of UV light necessitates more structures for the same area.
Furthermore, unlike visible and infrared light, the restricted availability of materials transparent to ultraviolet light hampers the fabrication of large-area metalens. Due to limitations in nanoprocessing technology, most reported metalenses for UV light are smaller than 500 μm.
Prior research projects involved the team working with Dr. Gyoseon Jeon’s group at the Research Institute of Industrial Science and Technology (RIST) to successfully produce metalenses for both visible and infrared light, as reported in recent journals Laser and Photonics Reviews and Nature Materials.
By adding a zirconium oxide (ZrO2) material, which is transparent in the UV spectrum, the researchers were able to expand their method and produce a metalense in large quantities that measured one centimeter (cm) on a wafer. Utilizing a nano-imprinting technique that imprints the design like a stamp, the group produced metalenses twenty thousand times larger than conventional ones in a timely and cost-effective manner.
This marks the first instance of implementing a metalens with exceptional light-modulation capabilities over a large area in the ultraviolet region. We are committed to continually improving the technology for potential applications in industrial sectors such as semiconductor inspection equipment through further research efforts.
Junsuk Rho, Mu-Eun-Jae Endowed Chair Associate Professor, Pohang University of Science and Technology
The N.EX.T Impact Project of POSCO Holdings, the Future Material Discovery Program of the Ministry of Science and ICT, the RLRC Program, the Nanomaterial Technology Development Program, and the STEAM Research Program provided funding for the study.
Journal Reference:
Kim, J., et. al. (2024) 8” wafer-scale, centimeter-sized, high-efficiency metalenses in the ultraviolet. Materials Today. doi:10.1016/j.mattod.2024.01.010.