title: Graphene-based D-shaped fiber multicore mode interferometer for chemical gas sensing.
abstract: In this Letter, a graphene-coated D-shaped fiber (GDF) chemical gas sensor is proposed and demonstrated. Taking advantage of both the graphene-induced evanescent field enhancement and the in-fiber multimode interferometer, the GDF shows very high sensitivity for polar gas molecule adsorptions. An extinction ratio of up to 28 dB within the free spectrum range of ~30  nm in the transmission spectrum is achieved. The maximum sensitivities for NH₃ and H₂O gas detections are ~0.04 and ~0.1  ppm, respectively. A hybrid sensing scheme with such compactness, high sensitivity, and online monitoring capabilities may pave the way for others to explore a series of graphene-based lab-on-fiber devices for biochemical sensing.
authors.forename: Y
authors.initials: Y
authors.lastname: Wu
authors.forename: B C
authors.initials: BC
authors.lastname: Yao
authors.forename: A Q
authors.initials: AQ
authors.lastname: Zhang
authors.forename: X L
authors.initials: XL
authors.lastname: Cao
authors.forename: Z G
authors.initials: ZG
authors.lastname: Wang
authors.forename: Y J
authors.initials: YJ
authors.lastname: Rao
authors.forename: Y
authors.initials: Y
authors.lastname: Gong
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: Y F
authors.initials: YF
authors.lastname: Chen
authors.forename: K S
authors.initials: KS
authors.lastname: Chiang