Collaborative Research: Three-Dimensional Laser Holographic Nanopatterning Using Metamaterial Phase Masks

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There is a strong need for nanomanufacturing technologies that are digitally controllable in space and in laser wavelength. These new technologies are desired to generate spatially varying nanostructures for a wide range of applications from electronics to photonics to energy storage. Examples include gradient multiple-symmetry nanostructures to improve light extraction efficiency of organic light emitting devices, light coupling efficiency in photovoltaic devices, and light absorption in photo-detectors. This award investigates nanostructure and process design principles involving laser beam steering through a metamaterial photomask and selective laser material removal, leading to the formation of complex functional nanosystems. Despite progress at single wavelengths, a photomask-based nanofabrication technology that can steer lasers at multiple wavelengths at high resolution is lacking. This project paves the way for future parallel, multi-wavelength, spatially varying three-dimensional nanopatterning that can significantly simplify the photolithography process used by the semiconductor industry. The project provides education opportunities in the fields of nanomanufacturing, optical design, simulation and characterization to students at both undergraduate and graduate levels. It also includes outreach activities engaging women and under-represented minorities in research and targeting the general public via the Fort Worth Museum of Science and History.This project investigates laser holographic nanofabrication of a new type of spatially-gradient nanostructure using new metamaterial phase masks designed and operated at multiple laser wavelengths. The current phase mask patterning technology controls light sequentially. For example, in traditional dielectric phase masks with gratings in two layers, the light modulated by the first layer grating is modulated again by the second layer grating. In order to realize selective laser modulation in space and in wavelength, the new phase mask concept consists of resonators distributed in one or two layers that can be used to realize desired phase and amplitude profiles at multiple wavelengths independently and simultaneously, namely, in parallel. Using the new plasmonic resonator-based metamaterial phase mask, the laser light is only modulated by resonators pre-determined by design, leading to the manufacturing of 3D nano-architectures with high spatial resolution and feature size reduction from microns to 100 nm in spatially-gradient photonic super-crystal structures. Overall, the single plasmonic element and single exposure-based nanofabrication process provides a highly efficient approach with a simple optical setup for realizing spatially-gradient nanostructures for many applications.