Design, Fabrication, and Characterization of Micro/Nano Photonic Structures for Light Control and Computational Multimodal Sensing

Abstract: Light waves can carry information in the form of amplitude, phase, spectrum, polarization, and propagation direction. Manipulating the light propagation and detecting the carried information are of fundamental importance, as they enable broad applications in optical communication, sensing, spectroscopy, and imaging. With the increasing demand for portable and integrated devices, wave interactions with various miniature optical structures have been extensively investigated. Particularly, whispering gallery mode (WGM) resonators have emerged as great candidates for studying light-matter interactions and controlling light transport due to their high quality factor, tight mode volume, and flexible tunability of operation conditions. In addition, flat optical structures with material properties controllable at the wavelength scale allow for the effective engineering of light transmission in free space. By integrating these planar structures with detector arrays and computational methods enhanced by machine learning, we could capture multiple types of optical information simultaneously at an unprecedent level of compactness. This is in contrast to traditional bulky systems and may open up new avenues for portable healthcare and consumer electronics.

In this dissertation, we first demonstrate the control of light transport using a WGM microresonator. We provide theoretical and experimental evidence for nonreciprocal light transmission by leveraging the asymmetric mode coupling and optical nonlinearity. Second, we introduce optically functionalized image sensors designed for computational multimodal sensing, including the retrieval of spectrum, polarization, and angle information from incident light. We present the single-shot spectral sensing using photonic crystal slabs and computational reconstruction and explore the capability to further obtain the polarization information of the input light. The practical application of the polarization-sensitive spectrometer is also investigated. Lastly, we demonstrate an angle-sensitive image sensor by integrating a layer of metal apertures on top and showcase its potential for wavefront imaging.