Planar antiresonant reflecting optical waveguides as sensors for liquid substances

In this paper, we present the use of planar antiresonant reflecting optical waveguide (ARROW) as sensor for liquid substances. With a suitable design, a strong variation of the waveguide attenuation can be obtained by simply varying the refractive index of the cover cladding. In this configuration the waveguide acts like a vertical interferometer and can be used as an integrated refractometer. Fabrication of the device is accomplished using a silicon substrate and a process technology (PECVD) that is fully compatible with bipolar and CMOS IC processes. Preliminary measurements, performed using a flow cell clamped onto the surface of the sensor and filled with the analyte, show the validity of the approach.