High-sensitive refractive index sensor based on slow light engineered photonic crystal cavity

A high-sensitive refractive index sensor was theoretically demonstrated in a slow light engineered photonic crystal (PhC) cavity. In the proposed device configuration, one pair of two air holes was inserted into a line defected PhC waveguide as two reflectors, and a point defect was defined between the two reflectors to form a cavity. Then to improve the system sensitivity, slow light was introduced in the PhC waveguide by infiltrating fluid into the first two rows of air holes, without any structural variations. Finally, combined with a simple, high-precision, and low-cost Mach-Zehnder interferometer (MZI) for wavelength demodulation, the detection limit of this miniaturized and simple device could reach to 3.4×10^-6 RIU. This is an encouraged result for the use of refractive index sensor in applications such as biochemical and biomedical sensing and diagnosis.