OSA/ANIC/IPR/Sensors/SL/SOF/SPPCom/2011
SWC5.pdf
High refractive-index-contrast polymer waveguide platform for excitation and sensing in aqueous environments Bjorn Agnarsson, Hamid Keshmiri, Jennifer Halldorson and Kristjan Leosson Department of Physics, Science Institute, University of Iceland, Dunhagi 3, 107 Reykavik, Iceland
[email protected]
Abstract: A high-refractive-index-contrast polymer waveguide platform is presented. The platform is applicable to a wide range of biophotonic applications which rely on evanescentwave sensing or excitation in aqueous solutions and offers a high level of integration and functionality. © 2011 Optical Society of America OCIS codes: 230.3120, 230.7400, 230.7390, 240.6680, 280.1415
Optical biosensors have been gaining increasing interest over last years mainly due to the high sensitivity and functional diversity that such devices provide. Here we describe a novel waveguide platform that can be used for various types of applications, but is especially suited for excitation and sensing of biological samples in aqueous solutions [1]. A special fluorinated polymer, Cytop (Asahi Glass Co.), with refractive index n=1.34, closely matching that of water (n=1.33), is used as bottom and (partially) as upper cladding material. An optical polymer of choice can be used as core material. In our studies we used mainly polymethyl methacrylate (PMMA, MicroChem Corp.) or Ormoclear (micro resist technology GmbH), with refractive indices n=1.49 and n=1.54 respectively. A water droplet (n=1.33) containing the specimen to be optically sensed or excited, then forms a part of the upper cladding layer of the waveguide structure. As an alternative to using dielectric waveguides, we will also present work on plasmonic waveguides consisting of thin metal films. The rather unique refractive index of the Cytop cladding material ensures a near-to-symmetric single-mode profile of the guided light, giving the structure some interesting properties. Light can be efficiently coupled into the waveguide structure by end-fire coupling and the evanescent tail of the propagating mode is then used to either excite or sense a specimen found in the water droplet. The penetration depth of the evanescent field can be tailored over a wide range, and the simple end-fire coupling allows for multiple-wavelength excitation through the same optical path. The relatively high refractive index contrast of the core and cladding polymer materials ensures high mode confinement, making the structure well suitable for high-density integration of optical components for lab-on-a-chip type of applications. Evanescent-wave excitation has been demonstrated for fluorescence microscopy [2] and various optical components have been integrated into the platform and tested [3]. Ongoing studies include fabrication of a hybrid dielectricplasmonic structure for utilizing the special properties of plasmonic waveguides. References 1. Agnarsson B., Halldorsson J., Arnfinnsdottir N., Ingthorsson S., Gudjonsson T. and Leosson K., Fabrication of planar polymer waveguides for evanescent-wave sensing in aqueous environments, Microelectronic Engineering 87, 56–61 (2010) 2. Agnarsson B., Ingthorsson S., Gudjonsson T. and Leosson K., Evanescent-wave fluorescence microscopy using symmetric planar waveguides, Optics Express 17, 5075–5082 (2009) 3. Halldorsson J. and Arnfinnsdottir N.B. and Jonsdottir A.B. and Agnarsson B. and Leosson, K., High index contrast polymer waveguide platform for integrated biophotonics, Optics Express 18, 16217–16226 (2010)
