High-sensitivity silicon-based photonic crystal refractive index biosensor based on defect-mode coupling

A high-sensitivity, high-resolution, multi-working-channel and real-time-detection typed one-dimensional photonic crystal biosensor is proposed in this paper. Through changing the slit's width between two adjacent silicon layers, multiple defects with different resonant wavelengths are designed. Based on the air-typed defect mode whose light energy is greatly localized in the lower refractive index region and the coupling interaction between different defects, a subtle alteration of the liquid's refractive index can make the resonant wavelength and light transmittance change significantly. Different liquid samples can flow freely within respective channels, and they can be measured in real time and at the same time. Through analyzing the alteration of the wavelengths and transmittances, the concentration information of a variety of liquid samples can be measured through a wide transmission spectrum measurement. When the working wavelength λres is about 1559.0 nm, the bulk refractive index sensitivity as high as ∼810 nm/RIU is obtained with the quality factor of ∼9679 and the detection limit of ∼4.18×10−6.