Optofluidic, lab-on-a-chip fluorescence sensors were fabricated using buried anti-resonant reflecting optical waveguides (bARROWs). The bARROWs are impervious to the negative water absorption effects that typically occur in waveguides made using hygroscopic, plasma-enhanced chemical vapor deposition (PECVD) oxides. These sensors were used to detect fluorescent microbeads and had an average signal-to-noise ratio (SNR) that was 81.3% higher than that of single-oxide ARROW fluorescence sensors. While the single-oxide ARROW sensors were annealed at 300 °C to drive moisture out of the waveguides, the bARROW sensors required no annealing process to obtain a high SNR.

Multimode interference (MMI) waveguides can be used for multiplexing and de-multiplexing optical signals. High fidelity, wavelength dependent multi-spot patterns from MMI waveguides are useful for sensitive and simultaneous identification of multiple targets in multiplexed fluorescence optofluidic biosensors. Through experiments and simulation, this paper explores design parameters for an MMI rib anti-resonant reflecting optical waveguide (ARROW) in order to produce high fidelity spot patterns at the liquid core biomarker excitation region. Width and etch depth of the single excitation rib waveguide used to excite the MMI waveguide are especially critical because they determine the size of the input optical mode which is imaged at the MMI waveguide's output. To increase optical throughput into the MMI waveguide when light is coupled in from an optical fiber, tapers in the waveguide width can be used for better mode matching.

Multimode interference (MMI) waveguides can be used to create wavelength-dependent spot patterns which enables simultaneous analyte detection on a single optofluidic chip, useful for disease diagnostics. The fidelity of such multi-spot patterns is important for high sensitivity and accurate target identification. Buried rib structures have been incorporated into these SiO2-based waveguides to improve environmental stability. Through experiments and simulation, this letter explores design parameters for a buried MMI rib waveguide based on anti-resonant reflecting optical waveguides in order to produce high-fidelity spot patterns. Optimal rib heights and widths are reported in the context of available microfabrication etch technology and performance for an optimized biosensor is shown.

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