A compact opto-fluidic platform for chemical sensing with photonic crystal fibers

We report a compact opto-fluidic platform capable of continuous analyte loading and unloading with a 3 dB optical insertion loss. The customized opto-fluidic manipulator enabled infiltration of photonic crystal fibers (PCFs) at ten times the rate achievable by capillary action. Additionally, it is to our knowledge, the first demonstration of complete and rapid evacuation performed with a syringe pump for extended lengths (>100 mm) of PCF. These properties render the device highly promising for continuous real-time sensing applications. Study was conducted on a PCF under macro-bending, taking advantage of its wavelength-dependent bending losses that red-shifted with the increasing refractive indices of the infiltrated analytes. The flexibility of the platform also facilitated the selection of an optimal bending radius (12.5 mm) for the analysis, based on sensitivity (Δλ/Δn) and signal to noise ratio (Q-factor). The subsequent comparison of experiment with simulation results was noted to show good coherence. Moreover, experimental results showed repeatability throughout the multiple cycles of infiltration and evacuation executed. The further employment of the device in the chemical sensing of ethanol solutions exhibited good consistency with calibrated data for concentrations up to 50% by weight.