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Author: Schmidt, Markus A. × Has files: Yes × Type: Text × Subject: Hollow-core × WGL Institute: IPHT ×

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    On-chip fluorescence detection using photonic bandgap guiding optofluidic hollow-core light cage
    (Melville, NY : AIP Publishing, 2022) Kim, Jisoo; Jang, Bumjoon; Wieduwilt, Torsten; Warren-Smith, Stephen C.; Bürger, Johannes; Maier, Stefan A.; Schmidt, Markus A.
    The on-chip detection of fluorescent light is essential for many bioanalytical and life-science related applications. Here, the optofluidic light cage consisting of a sparse array of micrometer encircling a hollow core represents an innovative concept, particularly for on-chip waveguide-based spectroscopy. In the present work, we demonstrate the potential of the optofluidic light cage concept in the context of integrated on-chip fluorescence spectroscopy. Specifically, we show that fluorescent light from a dye-doped aqueous solution generated in the core of a nanoprinted dual-ring light cage can be efficiently captured and guided to the waveguide ports. Notably, the fluorescence collection occurs predominantly in the fundamental mode, a property that distinguishes it from evanescent field-based waveguide detection schemes that favor collection in higher-order modes. Through exploiting the flexibility of waveguide design and 3D nanoprinting, both excitation and emission have been localized in the high transmission domains of the fundamental core mode. Fast diffusion, detection limits comparable to bulk measurements, and the potential of this approach in terms of device integration were demonstrated. Together with previous results on absorption spectroscopy, the achievements presented here suggest that the optofluidic light cage concept defines a novel photonic platform for integrated on-chip spectroscopic devices and real-time sensors compatible with both the fiber circuitry and microfluidics. Applications in areas such as bioanalytics and environmental sciences are conceivable, while more sophisticated applications such as nanoparticle tracking analysis and integrated Raman spectroscopy could be envisioned,
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    3D-nanoprinted on-chip antiresonant waveguide with hollow core and microgaps for integrated optofluidic spectroscopy
    (Washington, DC : Optica, 2023) Kim, Jisoo; Bürger, Johannes; Jang, Bumjoon; Zeisberger, Matthias; Gargiulo, Julian; Menezes, Leonardo de S.; Maier, Stefan A.; Schmidt, Markus A.
    Here, we unlock the properties of the recently introduced on-chip hollow-core microgap waveguide in the context of optofluidics which allows for intense light-water interaction over long lengths with fast response times. The nanoprinted waveguide operates by the antiresonance effect in the visible and near-infrared domain and includes a hollow core with defined gaps every 176 µm. The spectroscopic capabilities are demonstrated by various absorption-related experiments, showing that the Beer-Lambert law can be applied without any modification. In addition to revealing key performance parameters, time-resolved experiments showed a decisive improvement in diffusion times resulting from the lateral access provided by the microgaps. Overall, the microgap waveguide represents a pathway for on-chip spectroscopy in aqueous environments.