Böhringer, Karl FHan, Zheyi2023-04-172023-04-172023-04-172023Han_washington_0250E_25137.pdfhttp://hdl.handle.net/1773/49898Thesis (Ph.D.)--University of Washington, 2023Meta-optics – ultrathin and subwavelength-patterned diffractive optics – are novel replacements for bulky freeform optical elements showing high potential with their greatly reduced volume and high compatibility with modern microfabrication processes. Miniature lenses with tunable focus are essential components for many modern applications involving compact optical systems. While several tunable lenses have been reported with various tuning mechanisms, they often face challenges in power consumption, tuning speed, fabrication cost, or production scalability. In the first part of this thesis, we have adapted the mechanism of an Alvarez lens – a varifocal composite lens in which lateral shifts of two optical elements with cubic phase surfaces give rise to a change in optical power – to construct a miniature, MEMS-actuated meta-optic Alvarez lens. The implementation based on electrostatic microelectromechanical systems (MEMS) generates fast and controllable actuation with low power consumption. The utilization of meta-optics as the optical elements greatly reduces the device volume compared to systems using conventional freeform lenses. The entire MEMS Alvarez metalens is fully compatible with modern semiconductor fabrication technologies, granting it the potential to be mass-produced at a low unit cost. In our latest prototype operating at 1550 nm wavelength, a total uniaxial displacement of 19 µm is achieved in the Alvarez metalens with direct-current (DC) voltage application up to 40 V, modulating the focal position within a total tuning range of 3.1 mm, producing more than two orders of magnitude change in focal length and 200 diopters change in optical power. The MEMS Alvarez metalens has a robust design that can potentially generate a much larger tuning range without substantially increasing device volume or energy consumption, making it desirable for a wide range of imaging and display applications. With some crucial modifications in materials selection and fabrication process design, we also demonstrate the potential to adapt the same design principle to fabricate miniature tunable Alvarez metalenses for the visible spectrum. Rising interest in compact optics with large apertures calls for the development of large-area meta-optics. In the second part of the thesis, we explain the fabrication challenges and demonstrate the process development to manufacture large-area meta-optics, focusing on processes compatible with fast prototyping and affordable mass-production. As examples, we present several application cases of fabricated large-area meta-optics operating in the spectra from long-wave infrared to visible frequencies.application/pdfen-USCC BY-NC-NDMEMSMeta-opticsMetasurfaceMicro-electro-mechanical systemsMicrofabricationTunable metalensesElectrical engineeringElectrical and computer engineeringThesis