title: In-line microfluidic integration of photonic crystal fibres as a highly sensitive refractometer.
abstract: Photonic crystal fibres appear to be an ideal platform for the realisation of novel optofluidic devices and sensors due to their waveguide nature and microstructured architecture. In this paper, we present the fabrication and characterisation of an in-line photonic crystal fibre microfluidic refractometer enabled by a C-shaped fibre. The C-shaped fibre spliced in-between the photonic crystal fibre and the single-mode fibre allows simultaneous in-line optical signal delivery and analyte fluid feeding. Through an arc discharge pre-treatment technique, we successfully achieve selective exploitation of only the central two channels of the photonic crystal fibre for microfluidic sensing. After constructing a Sagnac interferometer, a highly sensitive refractometer with a sensitivity of 8699 nm per RIU was achieved experimentally; this agrees very well with the theoretical value of 8675 nm per RIU. As a demonstration for label-free optical sensing application, the refractometer was used to measure the concentration of NaCl solution with a sensitivity of 15.08 nm/(1 wt%) and a detection limit of 2.3 × 10(-3) wt% (23 ppm).
authors.affiliation: Institute of Photonics Technology, Jinan University, Guangzhou 510632, China. tguanbo@jnu.edu.cn.
authors.forename: Chuang
authors.initials: C
authors.lastname: Wu
authors.forename: Ming-Leung Vincent
authors.initials: ML
authors.lastname: Tse
authors.forename: Zhengyong
authors.initials: Z
authors.lastname: Liu
authors.forename: Bai-Ou
authors.initials: BO
authors.lastname: Guan
authors.forename: A Ping
authors.initials: AP
authors.lastname: Zhang
authors.forename: Chao
authors.initials: C
authors.lastname: Lu
authors.forename: Hwa-Yaw
authors.initials: HY
authors.lastname: Tam
mesh_terms: D003460:Crystallization; D057230:Limit of Detection; D044085:Microfluidics / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D017785:Photons; D012031:Refractometry / Q000295:instrumentation*