title: Fibre coupled micro-light emitting diode array light source with integrated band-pass filter for fluorescence detection in miniaturised analytical systems.
abstract: In this work, a new type of miniaturized fibre-coupled solid-state light source is demonstrated as an excitation source for fluorescence detection in capillary electrophoresis. It is based on a parabolically shaped micro-light emitting diode (μ-LED) array with a custom band-pass optical interference filter (IF) deposited at the back of the LED substrate. The GaN μ-LED array consisted of 270 individual μ-LED elements with a peak emission at 470 nm, each about 14 μm in diameter and operated as a single unit. Light was extracted through the transparent substrate material, and coupled to an optical fibre (OF, 400 μm in diameter, numerical aperture NA=0.37), to form an integrated μ-LED-IF-OF light source component. This packaged μ-LED-IF-OF light source emitted approximately 225 μW of optical power at a bias current of 20 mA. The bandpass IF filter was designed to reduce undesirable LED light emissions in the wavelength range above 490 nm. Devices with and without IF were compared in terms of the optical power output, spectral characteristics as well as LOD values. While the IF consisted of only 7.5 pairs (15 layers) of SiO2/HfO2 layers, it resulted in an improvement of the baseline noise as well as the detection limit measured using fluorescein as test analyte, both by approximately one order of magnitude, with a LOD of 1×10(-8) mol L(-1) obtained under optimised conditions. The μ-LED-IF-OF light source was then demonstrated for use in capillary electrophoresis with fluorimetric detection. The limits of detection obtained by this device were compared to those obtained with a commercial fibre coupled LED device.
authors.affiliation: Irish Separation Science Cluster, National Centre for Sensor Research and School of Chemical Sciences, Dublin City University, Dublin 9, Ireland; Australian Centre for Research on Separation Science and School of Chemistry, University of Tasmania, Private Bag 75, Hobart 7001, Australia; Central European Institute of Technology, Brno University of Technology, Technicka 3058/10, CZ-616 00 Brno, Czech Republic.
authors.forename: Markéta
authors.initials: M
authors.lastname: Vaculovičová
authors.affiliation: Tyndall National Institute, Dyke Parade, University College Cork, Cork, Ireland.
authors.forename: Mahbub
authors.initials: M
authors.lastname: Akther
authors.affiliation: Tyndall National Institute, Dyke Parade, University College Cork, Cork, Ireland.
authors.forename: Pleun
authors.initials: P
authors.lastname: Maaskant
authors.affiliation: Irish Separation Science Cluster, National Centre for Sensor Research and School of Chemical Sciences, Dublin City University, Dublin 9, Ireland; Advanced Processing Technology Research Centre, School of Mechanical & Manufacturing Engineering, Dublin City University, Dublin 9, Ireland.
authors.forename: Dermot
authors.initials: D
authors.lastname: Brabazon
authors.affiliation: Australian Centre for Research on Separation Science and School of Chemistry, University of Tasmania, Private Bag 75, Hobart 7001, Australia. Electronic address: mirek.macka@utas.edu.au.
authors.forename: Mirek
authors.initials: M
authors.lastname: Macka
keywords: Capillary electrophoresis; Fluorescence detection; Light source; Micro-light emitting diode array; Optical fibre; Separations