Slow light-based refractive index sensor in single mode photonic crystal waveguide

Abstract

Here, a slow light-based refractive index sensor has been presented in a hole-type 2D hexagonal lattice photonic crystal waveguide by insertion of only four defect holes inside the channel. The width of the channel has been optimized to provide single mode operation and large free spectral range. Also, the performance of the sensor with and without introducing the central cavity inside the channel have been regarded for different radii of defects. The proposed sensor presents the highest sensitivity and detection range of 126 nm/RIU and 1–2.2, respectively for the detection based on band edge shift. The defects inside the channel have been introduced to obtain high Q-factor by defect radii tailoring. The highest average Q-factor and sensitivity of 1570 and 249.5 have been obtained for defect hole with radius of rc = 0.34a. The study has been carried out by plane wave expansion and finite difference time domain analysis. There is a good agreement between the results and the study proves the effect of slow light on the enhancement of light-matter interaction and sensitivity. The proposed structures can find potential applications in gas or liquid detection in medical and biochemical fields.