Integrated optical devices in side-polished fibres

Abstract

Fibre side-polishing technology was explored to meet the need for miniature, multifunctional, and low-loss device platforms for optical applications. Different polishing techniques were investigated to achieve side-polished fibres with low transmission loss, high polished surface quality and long interaction lengths. This side-polished fibre platform was combined with some of the most popular two-dimensional materials, including graphene and molybdenum disulfide, to fabricate integrated optical fibre devices. A high refractive index polyvinyl butyral layer was coated on top of graphene and molybdenum disulfide to enhance the light-matter interaction between the evanescent field of the core guided mode and the two-dimensional materials. By using the excellent photonic properties of graphene, a broadband graphene-based fibre polariser was proposed and fabricated using the low-loss side-polished optical fibre platform. Characterisation of the optical properties revealed that the graphene-based polariser retains low transmission losses and high extinction ratios across an extended telecoms band. The graphene-based fibre device was also utilized to demonstrate a high-speed, in-fibre optical modulator, which realised fast modulation speed and high modulation depth. By using the same design, a low-loss molybdenum disulfide-based all-optical modulator was also demonstrated with a even higher modulation depth. Wavelength-dependent interaction and spectral broadening was observed in the molybdenum disulfide sheet, suggesting that the higher modulation depth was from a resonance-enhanced interaction. To extend the application scenarios of the side-polishing technique, a low loss, wideband multi-core to single-mode fibre coupler was also demonstrated. The coupler was designed to access light from a single core of the multi-core fibre without disrupting the signal propagation in the remaining cores. The coupling ratio between the two fibres could be continuously tuned over the entire spectral band via a simple mechanical displacement method.

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Identifiers

ORCID for Haojie Zhang: orcid.org/0000-0002-4577-3600

ORCID for Anna Peacock: orcid.org/0000-0002-1940-7172

ORCID for Daniel Hewak: orcid.org/0000-0002-2093-5773

ORCID for Chung-Che Huang: orcid.org/0000-0003-3471-2463

ORCID for David Richardson: orcid.org/0000-0002-7751-1058

ORCID for Marco Petrovich: orcid.org/0000-0002-3905-5901

ORCID for Nikolai Zheludev: orcid.org/0000-0002-1013-6636

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