Photonic sensor of liquids based on suspended-core fibres Barbara Wajnchold* a , Michał Grabka a , Szymon Pustelny a , Wojciech Gawlik a , Paweł Mergo b a Marian Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Cracow, Poland; b Faculty of Chemistry, Marie Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 3, 20-031 Lublin, Poland ABSTRACT The small size of the core (about 1 μm) of the suspended-core optical fibres gives rise to evanescent wave in the surrounding channels. That process allows efficient coupling between light and liquid introduced into the channels and application of the fibre for analytic purposes. In the presented work, the channels of a suspended-core fibre were filled with water and aqueous solutions of oxazine 725 perchlorate and their absorption spectra were measured. While the spectra of the water-filled fibre were consistent with the Lambert-Beer law, the absorptivity of the fibre filled with oxazine 725 perchlorate solution demonstrated an increased sensitivity caused by aggregation of the oxazine molecules, independent on the fibre length. Keywords: suspended-core fibre, chemical sensing 1. INTRODUCTION A photonic-crystal fibre (PCF) is a special microstructure optical waveguide made by stacking capillaries and rods. Such fibres have unique optical properties important for various applications. Particularly, the fibres with suspended core offer a possibility to use evanescent waves for coupling light to matter in a controlled way [1, 2], to observe surface plasmon effects [3], perform absorption and/or fluorescence measurements [4], and produce such nonlinear effects as supercontinuum generation [5]. The suspended-core fibres possess large channels which can be filled with gas or liquid. This offers a possibility of exerting extra control over the light propagation which is desired from a point of spectroscopy and sensing applications. Many groups presented various approaches to filling microstructured fibres with foreign media. Some of them achieved a lateral access to the channels by using a laser [6], an ion beam [7], a fusion splicer [8] or by drilling [9]. All these methods, however, are challenging and require special equipment. The simplest method of filling the fibres is to dip a fibre tip in a medium and use either capillary forces for liquid filling or diffusion for gas filling. Despite its simplicity, this method allows also a selective fibre filling [10]. The suspended-core PCFs were used for measuring numerous physical quantities. Important examples include studies of absorption spectra of acetylene [11] and aqueous nickel (II) chloride solution [12]. Also fluorescence of organic dyes [13], semiconductor quantum dots [14], and fluorophore labelled antibodies [15] were investigated with the suspended- core fibres. *baska.baran@uj.edu.pl, www.if.uj.edu.pl/pl/ZF/ Microstructured and Specialty Optical Fibres, edited by Kyriacos Kalli, Alexis Mendez, Proc. of SPIE Vol. 8426, 84261M · © 2012 SPIE · CCC code: 0277-786X/12/$18 · doi: 10.1117/12.924061 Proc. of SPIE Vol. 8426 84261M-1 Downloaded from SPIE Digital Library on 07 May 2012 to 149.156.168.108. Terms of Use: http://spiedl.org/terms