Optical metasurfaces are a class of ultra-thin diffractive optical elements, which can control different properties of light such as amplitude, phase, polarization and direction at various wavelengths. The compatibility of optical metasurfaces with standard micro- and nano-fabrication processes makes them highly-suitable for realization of compact and planar form optical devices and systems. In addition, optical metasurfaces have achieved unique and unprecedented functionalities not possible by conventional diffractive or refractive optical elements. In this thesis, after a short review on the history and state of the art optical metasurfaces, I will discuss the systems consisting of optical metasurfaces, called optical meta-systems, which allow for implementations of complicated optical functions, such as wide field of view imaging and projection, tunable cameras, retro-reflection, phase-imaging, multi-color imaging, etc. Thereafter, the concept of folded metasurface optics is introduced and a compact folded metasurface spectrometer is showcased to demonstrate how the folded meta-systems can be designed, fabricated and practically utilized for real-life applications. Furthermore, different approaches for implementation of miniaturized hyperspectral imagers are investigated, among which the folded metasurface optics and a computational scheme using a random metasurface mask will be highlighted. Other potentials of optical metasurfaces achieved by the employment of optimization techniques to improve their multi-functional performances, as well as example applications in realizing optical vortex cornographs are studied. Finally, I will conclude the dissertation with an outlook on further applications of optical metasurfaces, where they can surpass the performance of current optical devices and systems and what limitations are still to be overcome before we can expect their wide-spread applications in our daily life.</p
