Refractive index sensing with an air-slot photonic crystal nanocavity

We investigate an air-slot photonic crystal cavity for high-precision refractive index sensing. The high quality factor similar to 2.6 x 10(4) of the cavity, along with a strong overlap between the resonant mode and the hollow core region, allows us to achieve an experimental sensitivity of 510 nm per refractive index unit (RUI) and a detection limit below 1 x 10(-5) RUI. The device has a remarkably low sensing volume of 40 aliters, holding less than 1 x 10(6) molecules. (C) 2010 Optical Society of America