Design on-chip width-modulated line-defect cavity array structure for multiplexing complex refractive index sensing

• Published in: Sensors and actuators. A. Physical. Vol. 257; pp. 8 - 14
• Main Authors: Sun, Fujun, Zhou, Jian, Huang, Lijun, Fu, Zhongyuan, Ding, Zhaoxiang, Tian, Huiping
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.04.2017; Elsevier BV
• Subjects: Arrays; Complex refractive index sensing; Crystal defects; Crystals; Design defects; Detection; Finite difference method; Finite difference time domain method; Holes; Multiplexing; Photonic crystal; Photonic crystals; Refractivity; Sensitivity; Sensor array; Sensors; Simulation; Time domain analysis; Width-modulated line-defect micro-cavity; Width-modulated line-defect micro-cavity; Sensor array; Photonic crystal; Complex refractive index sensing
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2017.01.024

•Sensor array based on photonic crystal width-modulated line-defect micro-cavity.•The first geometry to realize multiplexing complex refractive index sensing.•Two cascaded micro-cavities with Q-factor over 15,000.•The sensitivity of the real part over 167.6nm/RIU.•The sensitivity of the imaginary part over 200nm/RIU. We propose an integrated sensor array based on photonic crystal width-modulated line-defect micro-cavity for complex refractive index sensing. The width-modulated line-defect cavity is formed by decreasing the width of W1 waveguide with several holes in the first row shifted towards the line defect. By applying the three-dimensional finite-difference time-domain (3D-FDTD) simulation method, we demonstrate that simply shifting eight holes on each side by a distance of 100nm is sufficient to achieve a high quality (Q) factor over 2×104. The proposed device consists of two cascaded micro-cavities with Q-factor over 1.5×104. The sensitivities of the real part (n) for cavity-1 and cavity-2 are 174.1nm/RIU (refractive index unit) and 167.6nm/RIU, respectively. The sensitivities of the imaginary part (k) are 230nm/RIU and 200nm/RIU for cavity-1 and cavity-2, respectively. In addition, a phenomenon that the sensitivity of imaginary part is much higher for smaller k values is described and explained. To the best of our knowledge, this is the first geometry to realize high-sensitivity multiplexing complex refractive index sensing.