title: Fiber-free coupling between bulk laser beams and on-chip polymer-based multimode waveguides.
abstract: In this paper, we demonstrate the design of a virtually alignment-free optical setup for use with microfluidic applications involving a layered glass/SU-8/PDMS (polydimethylsiloxane) chip. We show how inexpensive external lenses combined with carefully designed on-chip lenses can be used to couple light from a bulk beam to on-chip waveguides and back into a bulk beam again. Using this setup, as much as 20% of the light coming from the source can be retrieved after passing through the on-chip waveguides. The proposed setup is based on a pin-aided alignment system that makes it possible to change chips in the optical train in only a few seconds with a standard deviation of about 2% in the transmitted power. Furthermore, we demonstrate how these optical setups can be combined with microfluidics to create an on-chip flow cytometer enabling detection and counting of polystyrene particles down to 1 μm at a rate of 100 Hz.
authors.affiliation: DTU Nanotech, Department of Micro and Nanotechnology, Technical University of Denmark (DTU), Lyngby, Denmark.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Jensen
authors.forename: Lars B
authors.initials: LB
authors.lastname: Nielsen
authors.forename: Jörg P
authors.initials: JP
authors.lastname: Kutter
mesh_terms: D004129:Dimethylpolysiloxanes / Q000737:chemistry; D004852:Epoxy Compounds / Q000737:chemistry; D004867:Equipment Design; D005434:Flow Cytometry / Q000295:instrumentation*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D011108:Polymers / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry
chemical_list: D004129:Dimethylpolysiloxanes; D004852:Epoxy Compounds; D011108:Polymers; C520895:SU-8 compound; C013830:baysilon; D019904:Polymethyl Methacrylate