Design and analysis of refractive index sensors based on slotted photonic crystal nanobeam cavities with sidewall gratings

We propose and numerically investigate a refractive index sensor based on a one-dimensional slotted photonic crystal nanobeam cavity with sidewall gratings for refractive index sensing in a gaseous environment. By using the three-dimensional finite-difference time-domain method, we demonstrate that our proposed sensor simultaneously possesses a high quality factor of 3.71 x 10(6) and a high sensitivity of 508 nm/RIU (refractive index unit) at the resonant wavelength near 1583 nm, yielding a detection limit as low as 1.97 x 10(-6) RIU. Moreover, the mode volume of the cavity's fundamental resonant mode is found to be as small as 0.022(lambda/n)(3), resulting in a very compact effective sensing area. We finally study and assess the effect of fabrication disorder on the performances of our proposed sensor. We believe our proposed sensor will be a promising candidate for applications not only in multiplexed biochemical sensing and multielement mixture detection, but also in optical trapping of single biomolecules or nanoparticles. (C) 2020 Optical Society of America