Abstract
A refractive index sensor has been fabricated in silicon oxynitride by standard UV lithography and dry etching processes. The refractive index sensor consists of a 1D photonic crystal (PhC) embedded in a microfluidic channel addressed by fiber-terminated planar waveguides. Experimental demonstrations performed with several ethanol solutions ranging from a purity of 96.00% (n = 1.36356) to 95.04% (n = 1.36377) yielded a sensitivity (Δλ/Δn) of 836 nm/RIU and a limit of detection (LOD) of 6 × 10−5 RIU, which is, however, still one order of magnitude higher than the theoretical lower limit of the limit of detection 1.3 × 10−6 RIU.
Highlights
A lot of work has been done on the miniaturization of chemical analysis systems in order to benefit from faster analysis times, reduced reagent consumption and possibly to realize cheaper portable systems
We have developed a waveguide-based refractive index sensor that relies on a 1D photonic resonator for label-free detection in miniaturized separation systems
A refractive index sensor has been integrated in a microfluidic channel to probe the bulk of the analyte
Summary
A lot of work has been done on the miniaturization of chemical analysis systems in order to benefit from faster analysis times, reduced reagent consumption and possibly to realize cheaper portable systems. We have developed a waveguide-based refractive index sensor that relies on a 1D photonic resonator for label-free detection in miniaturized separation systems. This sensor differs from the vast majority of waveguide-based evanescent wave sensors, because it utilizes a free-space configuration in order to probe the bulk and not the surface of the solution. The pillar array that constitutes such a separation column is used as a resonator for on-column label-free detection, where integrated waveguides couple infrared light into/out of the detection site, Figure 1 The advantage of this approach lies in the fact that the detection system imparts no changes to the fluidics, thereby reducing the distortion of the analyte bands in the chemical separation process, and achieving a high resolution in the chemical analysis. Improvements in the optics and fluidics are reported, resulting in two orders of magnitude better detection limit
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