Multiphoton polymerization (MPP) as one of the direct laser writing techniques is capable of manufacturing three-dimensional (3D) micro-structures with complex shapes and novel functionalities. However, current MPP methods rely on point-by-point or layer-by-layer scanning and therefore are time-consuming. The low fabrication throughput of conventional MPP is the key factor that limits its wider adoption for industrial manufacturing over large surface area. One way to increase the fabrication speed is to turn layer-by-layer process into a volumetric process. An ideal volumetric printing method can fabricate structures with complex 3D geometry by single exposure and should be easy to implement. As a step towards this goal, this dissertation discusses a volumetric fabrication method based on 3D structured light fields. I will discuss the application of zero-order Bessel beams for rapid fabrication of various high-aspect-ratio structures such as polymer fibers and scaffolds. Next, I demonstrate the generation of superposed high-order Bessel beams using a spatial light modulator (SLM). Such beams have multiple foci with long depth of focus and are suitable for parallel fabrication of high-aspect-ratio structures. Furthermore, I investigate optical aberration observed when Bessel beams propagate through tilted interfaces. A method is introduced in which a single phase map on an SLM is used to generate an "elliptical axicon" that compensates for such aberration. Finally, I develop the theory of "helical beams", whose transverse intensity distribution rotates while propagating along the optical axis. Both transverse and longitudinal shape of such beams are tunable. These beams are generated as a superposition of high-order Bessel modes and have a closed-form expression relating the design of the phase mask to the rotation rate of the beam. I demonstrate rapid fabrication of helical microstructures with tunable shape in polymer by single exposure using these beams. This volumetric fabrication technique increases the throughput by orders of magnitude compared to conventional MPP, paving the way for adopting MPP in many industrial applications. The presented technique should have potential applications in other fields such as laser processing of bulk semiconductor/dielectric with increased throughput.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:etd2020-2462 |
| Date | 01 January 2022 |
| Creators | Cheng, He |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Electronic Theses and Dissertations, 2020- |
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