title: Diffusion driven optofluidic dye lasers encapsulated into polymer chips.
abstract: Lab-on-a-chip systems made of polymers are promising for the integration of active optical elements, enabling e.g. on-chip excitation of fluorescent markers or spectroscopy. In this work we present diffusion operation of tunable optofluidic dye lasers in a polymer foil. We demonstrate that these first order distributed feedback lasers can be operated for more than 90 min at a pulse repetition rate of 2 Hz without fluidic pumping. Ultra-high output pulse energies of more than 10 μJ and laser thresholds of 2 μJ are achieved for resonator lengths of 3 mm. By introducing comparatively large on-chip dye solution reservoirs, the required exchange of dye molecules is accomplished solely by diffusion. Polymer chips the size of a microscope cover slip (18 × 18 mm(2)) were fabricated in batches on a wafer using a commercially available polymer (TOPAS(®) Cyclic Olefin Copolymer). Thermal imprinting of micro- and nanoscale structures into 100 μm foils simultaneously defines photonic resonators, liquid-core waveguides, and fluidic reservoirs. Subsequently, the fluidic structures are sealed with another 220 μm foil by thermal bonding. Tunability of laser output wavelengths over a spectral range of 24 nm on a single chip is accomplished by varying the laser grating period in steps of 2 nm. Low-cost manufacturing suitable for mass production, wide laser tunability, ultra-high output pulse energies, and long operation times without external fluidic pumping make these on-chip lasers suitable for a wide range of lab-on-a-chip applications, e.g. on-chip spectroscopy, biosensing, excitation of fluorescent markers, or surface enhanced Raman spectroscopy (SERS).
authors: Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT), 76128, Karlsruhe, Germany. tobias.wienhold@kit.edu
authors: Tobias
authors: T
authors: Wienhold
authors: Felix
authors: F
authors: Breithaupt
authors: Christoph
authors: C
authors: Vannahme
authors: Mads Brøkner
authors: MB
authors: Christiansen
authors: Willy
authors: W
authors: Dörfler
authors: Anders
authors: A
authors: Kristensen
authors: Timo
authors: T
authors: Mappes