Multilayer Meta-Optics for Next-Generation Multifunctional Photonics

Author: Baspinar, Ayse Bilgehan

Year: 2026

Degree: Dissertation (Ph.D.)

Advisor: Faraon, Andrei

Committee Members: Vahala, Kerry J.; Atwater, Harry Albert; Scherer, Axel; Faraon, Andrei

Option: Applied Physics

Abstract

Optical metasurfaces, planar arrays of subwavelength scatterers that precisely manipulate the amplitude, phase, and polarization of light, have emerged as a compelling platform for next-generation photonic systems. While single-layer passive metasurfaces have demonstrated remarkable optical functionalities, practical applications increasingly demand devices that are dynamically reconfigurable, spectrally multifunctional, and compatible with scalable nanofabrication. This thesis addresses these challenges through the design, fabrication, and characterization of active and multilayer metasurfaces across a diverse set of photonic applications. Active functionality is realized through a nanoelectromechanically tunable architecture based on slot-mode resonances at telecom wavelengths, where an on-substrate design of high-aspect-ratio doped silicon slabs overcomes the fragility of prior suspended structures to achieve low-voltage amplitude and phase modulation and efficient beam steering. A central enabling contribution is a high-throughput direct-write electron-beam lithography platform, in which an antimony precursor decomposes in situ into high-index Sb₂S₃, eliminating deposition and etching steps and unlocking efficient multilayer fabrication. This platform underpins several advances: three-layer quasi-bound-state-in-the-continuum metasurfaces forming decorrelated filter arrays for compressive hyperspectral imaging that surpass prior implementations; an inverse-designed vertical fiber-to-chip coupler reaching high simulated coupling efficiency without modifying the underlying photonic circuit; and, to our knowledge, the first free-form multilayer meta-optic Bayer color router in the visible spectrum, demonstrating the highest layer count achieved with this platform to date. The work further extends to system-level applications, presenting geometric-phase metasurfaces that serve as phase aberration correctors for optical vortex coronagraphs, validated by Mueller-matrix polarimetry across centimeter-scale apertures, and a planar metamirror that stabilizes a cavity for microwave-to-optical quantum transduction. Together, this thesis establishes a unified framework spanning material and fabrication innovation, dispersion engineering, and inverse design, advancing meta-optics toward scalable, multifunctional photonic systems for real-world applications.