Micro-3D sculptured metastructures

Abstract

Today three-dimensional (3D) printers are highly popular and find use in a vast range of applications thanks to their capability to construct complex 3D structures. However, 3D-printing vertical structures with a high aspect ratio of height to width remains a pending challenge especially when a high lateral resolution is required in large footprints. In this thesis, we propose and demonstrate micro-3D sculptured metastructures using the idea of constructing deep trenches to erect their high aspect ratio metal lines along long strips. To generate such deep-trenched 3D-patterns, our construction relies on nonlinear absorption process, enabling the two-photon polymerization (2PP). In our fabrication, the 2PP process requires optical trajectory optimization, followed by electroplating thick metal film and dry etching seed layer. To test the developed process flow of 2PP, we built three-dimensional RF metastructures showcasing the depth effect as a third dimension. Based on our systematic numerical and experimental studies, our designed metastructure resonators are found to fall within a targeted specific operating resonance frequency range, with their resonance frequency being con-trolled and shifted and their quality factor (Q-factor) tuned as a function of their cross-sectional aspect ratio. In the thesis, with these proof-of-concept demonstrations, we show that such 2PP-defined high aspect ratio RF resonators highly benefit in terms of tunability of their resonance frequencies, along with increased Q-factor and reduced footprint. The findings of this thesis indicate that the pro-posed fabrication method of producing deep trenches via 3D-printing provides rich opportunities to implement high aspect ratio, complex structures that are highly miniaturized.