ORCID

0000-0002-1744-8907

Keywords

Hollow core fiber, mode field adapters, motheye surface treatment, fusion splicing

Subject Categories

Electrical and Computer Engineering | Optics | Physics

Abstract

Optical fiber systems based on solid-core silica waveguides underpin modern telecommunications, high-power laser delivery, precision sensing, and coherent optical systems. However, nonlinear effects, material absorption, and thermal limitations within silica increasingly constrain further scaling in both optical power and transmission performance. Antiresonant hollow-core fibers provide a promising alternative by guiding light predominantly in air, substantially reducing nonlinear interactions, latency, and optical damage while enabling transmission regimes inaccessible to conventional solid-core fibers. Despite rapid advances in antiresonant hollow-core fiber attenuation and power handling, one of the largest remaining barriers to widespread adoption is reliable integration with the existing solid-core fiber ecosystem.

This dissertation investigates several approaches for improving the compatibility of antiresonant hollow-core fibers with modern optical architectures through polarization-selective hollow-core fiber design, high-power fusion splicing, and advanced mode-field adaptation. First, a single-polarization antiresonant hollow-core fiber design based on resonator asymmetry is investigated numerically, demonstrating polarization-selective confinement loss through engineered antiresonant behavior. The influence of resonator geometry, wall thickness, and capillary configuration on polarization extinction ratio, confinement loss, and modal purity is analyzed.

Second, a high-power fusion splice between a large-mode-area ytterbium-doped fiber and a nested antiresonant nodeless fiber is experimentally demonstrated using thermally robust moth-eye anti-reflective surface structures. The splice achieved insertion losses below 0.3~dB with back reflections below -32~dB while delivering optical powers approaching 800 W. Thermal imaging and microscopic analysis demonstrated that the nanostructured anti-reflective surfaces remained intact through the fusion-splicing process and under high optical loading.

Finally, a novel multi-stage mode field adapter architecture is proposed and analyzed for low-loss coupling between conventional single-mode fibers and antiresonant hollow-core fibers. Using split-step beam propagation simulations and Monte Carlo tolerance analysis, the design demonstrates substantially relaxed fabrication tolerances relative to conventional GRIN-only adapters while enabling reduced reflected-light coupling through controlled beam offset and angled interfaces. Experimental validation demonstrated fusion spliced insertion losses as low as 0.227 dB per connection with back reflections below -38~dB without anti-reflective surface treatment or coating.

Collectively, this work addresses several critical challenges preventing large-scale deployment of hollow-core fiber systems and provides practical pathways for integrating antiresonant hollow-core fiber technology into next-generation high-power laser and telecommunications architectures.

Completion Date

2026

Semester

Summer

Committee Chair

Amezcua Correa, Rodrigo

Degree

Doctor of Philosophy (Ph.D.)

College

College of Optics and Photonics

Department

CREOL

Format

PDF

Document Type

Dissertation

Language

English

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