title: Enhanced all-optical modulation in a graphene-coated fibre with low insertion loss.
abstract: Graphene is a highly versatile two-dimensional material platform that offers exceptional optical and electrical properties. Of these, its dynamic conductivity and low effective carrier mass are of particular interest for optoelectronic applications as they underpin the material's broadband nonlinear optical absorption and ultra-fast carrier mobility, respectively. In this paper, we utilize these phenomena to demonstrate a high-speed, in-fibre optical modulator developed on a side-polished optical fibre platform. An especially low insertion loss (<1 dB) was achieved by polishing the fibre to a near atomically smooth surface (<1 nm RMS), which minimized scattering and ensured excellent contact between the graphene film and the fibre. In order to enhance the light-matter interaction, the graphene film is coated with a high index polyvinyl butyral layer, which has the added advantage of acting as a barrier to the surrounding environment. Using this innovative approach, we have fabricated a robust and stable all-fibre device with an extinction ratio as high as 9 dB and operation bandwidth of 0.5 THz. These results represent a key step towards the integration of low-dimensional materials within standard telecoms networks.
authors.affiliation: Optoelectronics Research Centre, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
authors.forename: Haojie
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Optoelectronics Research Centre, University of Southampton, Highfield, Southampton SO17 1BJ, UK.|Emerging Technology and Materials Group, School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Noel
authors.initials: N
authors.lastname: Healy
authors.affiliation: Optoelectronics Research Centre, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
authors.forename: Li
authors.initials: L
authors.lastname: Shen
authors.affiliation: Optoelectronics Research Centre, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
authors.forename: Chung Che
authors.initials: CC
authors.lastname: Huang
authors.affiliation: Optoelectronics Research Centre, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Hewak
authors.affiliation: Optoelectronics Research Centre, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
authors.forename: Anna C
authors.initials: AC
authors.lastname: Peacock