Integrated refractive index sensor using silicon slot waveguides.

We propose an integrated refractive index (RI) sensor based on evanescent field absorption (EFA) within a silicon slot waveguide, where the RI variation is translated into a varied attenuation coefficient and eventually the output power at the end of the waveguide. To demonstrate the operating principle of such a RI-EFA sensor, a specific structure is designed and discussed with numerical simulations. The calculated results indicate that the detection limit of our proposed RI-EFA sensor could be as good as ∼10^-8  RIU for homogeneous sensing and ∼10^-7  RIU for surface sensing with optimized structural parameters at a wavelength of 1064 nm. Since only a straight slot waveguide and optical power detection are required for our proposed sensor, we believe that it is promising to achieve an integrated and portable sensor on a single chip.