Optical nonlinearity in graphene coated hollow-core fibers

• Main Author: Goh, Zhi Ping
• Other Authors: Wonkeun Chang
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering
• Online Access: https://hdl.handle.net/10356/176975
• Institution: Nanyang Technological University

In recent years, hollow-core optical fiber technology has made significant advances in attenuation, bringing them down to a transmission loss of no more than 0.11 dB/km, comparable to any solid-core fiber of the same type [1]. This rapid progress has reignited interest in achieving the most transparent air/vacuum-core waveguides across all optical spectral regions. which offers numerous solutions for laser-matter interactions, including atoms, molecules, liquids, solids, and plasmas, among others. One notable example is gas-molecule-filled hollow-core fibers, which have demonstrated remarkable optical nonlinearities for applications such as supercontinuum generation, pulse compression, and UV/MIR generation, etc. However, those gas molecules constrain thermal dynamics, ionization, pressure maintaining as well as lacking of optical nonlinear susceptibility χ(2). In this project, we will explore optical nonlinearities for both χ(2) and χ(3) in hollow-core fibers coated with Graphene on their inner walls. Uniform Graphene can be coated onto the inner wall surface of hollow-core fibers by using a liquid phase chemical synthesis method. We will systematically study the optical properties of monolayer/multilayer graphene within hollow-core fibers. Although graphene is centrosymmetric, χ(2) can be experimentally observed due to defects and bended graphene coatings. Additionally, the final year project aims to review various physical mechanisms in hollow-core optical fibers. For these technologies to propagate light to the core, different guidance mechanisms are employed, and the attenuation of the light is controlled by physical processes different from conventional solid-core fibers. To understand electron-photon interaction, such as nonlinear interactions between graphene and ultrashort pulses and the universal absorption law, a comprehensive overview of its optical response will be provided in both linear and nonlinear regimes. Finally, the nonlinear response of graphene will be explained using a state-of-the-art model, particularly focusing on scenarios where bending is essential, and the output spectra are severely affected.