Sustainable Manufacturing of optical metasurfaces for imaging, sensing and display

Metamaterials and metasurfaces are novel optical components composed of nanostructure arrays. They offer the advantage of an ultracompact form factor and can image submicron objects with resolution approaching the diffraction limit of light. The scope of this imaging extends from simple microscopes to more advanced light imaging applications such as 3D sensors, LiDAR, bio-imaging, and cameras. The wavelength range of imaging is also diversifying to support various imaging applications. Metalenses operating in the UV region enable high-resolution imaging due to the short wavelength of light. In the visible light spectrum, metalenses can be used for imaging in VR/AR displays. Near-infrared metalenses have potential applications in night vision devices and endoscopes. The wavelength range extends further to include the ultrasound region, where it can be used in photoacoustic microscopy. Additionally, elastic metalenses can be applied for energy harvesting, and acoustic metalenses can be used to focus sound waves. Furthermore, metalenses can perform imaging with various functionalities. They can tune their focal length, demonstrate trichannel imaging based on spin, and even image single photons emitted from a source. While metalenses operate across various wavelengths and offer diverse functionalities for numerous imaging applications, their design is currently not scalable, making large-area designs computationally heavy and expensive. To address this, efficient computational methods like RCWA and AI/DB-based design approaches have been developed. However, even with advances in large-area design capabilities, their commercialization has been hindered by manufacturing limitations such as high cost and low throughput. To reduce the production cost of metalenses, nanoimprint lithography has been employed. To address the low refractive index of conventional imprint resins, high-refractive-index particles are incorporated, creating a one-step printable platform On the other hand, ArF photolithography has been used to overcome low throughput and produce large-area metasurfaces at wafer scale. However, due to the high manufacturing costs associated with this method, research has been conducted on mass-producing metasurfaces by using wafer-scale nanoimprint technology to replicate metasurfaces initially created through photolithography. These scalable manufacturing approaches are expected to propel metalenses beyond the research level and into practical applications.