| Author: | Wang, Yue |
| Title: | Multifunctional fiber devices enabled by metasurface and graphene |
| Advisors: | Yu, Changyuan (EEE) |
| Degree: | Ph.D. |
| Year: | 2025 |
| Department: | Department of Electrical and Electronic Engineering |
| Pages: | xvii, 123 pages : color illustrations |
| Language: | English |
| Abstract: | Optical fibers, serving as the backbone of modern telecommunication and sensing systems, have long been constrained by their intrinsic functional limitations. Conventional optical fibers relying on total internal reflection mechanisms fundamentally lack dynamic light-field manipulation capabilities at subwavelength scales, restricting their applications to passive light-guiding roles. This functional limitation seriously contrasts with the growing demand for integrated optical systems in emerging fields such as smart optical networks, miniaturized biosensors, and quantum photonic circuits. Emerging nanophotonic platforms, particularly metasurface and two-dimensional (2D) materials, offer transformative solutions to these challenges. Metasurface, comprising subwavelength nanostructured arrays, enable unprecedented control over electromagnetic wavefronts through localized phase engineering. Meanwhile, 2D materials like graphene exhibit exceptional optoelectronic tunability from strong light-matter interactions and gate-voltage-dependent optical responses. By synergistically integrating these nanotechnologies with optical fibers, we propose a new meta-fiber platform toward multifunctional fiber devices for compact and active communication and sensing systems. This dissertation establishes the feasibility of the meta-fiber platform through the development of three functional fiber devices: two fiber-tip-integrated metasurface devices and one tunable D-shaped fiber polarizer exploiting graphene-light interactions. Chapter 3 introduces a complete fabrication framework for metasurface integration on optical fiber tips, demonstrating a flat-band plasmonic quasi-BIC metasurface that couples efficiently with fiber propagation modes. By precisely controlling symmetry-breaking parameters, we achieve a high-Q and ultra-sensitive fiber sensor with real-time refractive index resolution of 1.7 x 10⁻⁴ RIU. Chapter 4 implements the established framework to fabricate a fiber-integrated metalens exhibiting exceptional circular dichroism, experimentally enabling polarization-modulated all-optical switching in 2 Gbps PAM4 systems with >20 dB extinction ratio. Chapter 5 is a proof-of-concept electro-optically tunable D-shaped fiber polarization filter exploiting hybrid graphene-gold plasmonic interactions. The phase-matching condition between the fiber's fundamental mode and gold grating-induced surface plasmon resonance (SPR) can be tuned via graphene chemical potential modulation, achieving continuous spectral tuning across C-band (1530-1565 nm) and O-band (1260-1360 nm) with ~30 dB extinction. Collectively, these advances bridge nanophotonic functionalities with fiber-optic architectures, presenting their scalable applications in optical sensing, high-speed communications, and tunable optical systems. |
| Rights: | All rights reserved |
| Access: | open access |
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