Planar antiresonant reflecting optical waveguides as integrated optical refractometer

This paper reports on an integrated refractometer sensor, useful for measuring chemical quantities, based on antiresonant reflecting optical waveguides (ARROWs). We show that, by a suitable design, the attenuation in ARROW waveguides can strongly depend on the refractive index of the superstrate layer. We use this property to design and realize an integrated refractometer. The proposed sensor structure is unique in that it consists in the ARROW waveguide itself acting like a vertical interferometer. The device is fabricated using standard silicon technology fully compatible with bipolar and CMOS integrated circuit process. The measurement results show a sensing resolution of Δn = 6e - 4 when used in a solution with a refractive index of 1.4600.