Ultrasensitive refractive index sensor based on the resonant scattering effect between double air circular-holes on silicon waveguides.

Recently, we have proposed a sensitive refractive index sensor design by integrating a circular-hole defect with an etched diffraction grating (EDG) spectrometer based on amorphous silicon photonic platforms. In the present paper, we will show that a much better sensitivity (~17422 nm/RIU) can be obtained by using double circular-holes with an appropriate interval. The influence of the double-hole interval on the performance of sensing applications is also characterized. A sinusoidal pattern of the sensitivity can be found as the interval increases. However, the intensity of the resonant peak (i.e., the detectability for sensing applications) significantly oscillates as the interval varies.