Photonic crystal elliptical-hole tapered low-index-mode nanobeam cavities for sensing

• Published in: Applied optics (2004) 2018-11, Vol.57 (33), p.9822
• Main Authors: Huang, Lijun, He, Dajiang, Mi, Xianwu, Ding, Jianqun, Chen, Shenghai, Peng, Xiaoliang
• Format: Article
• Language: English
• Subjects: Environmental impact; Finite difference time domain method; Holes; Photonic band gaps; Photonic crystals; Q factors; Refractivity; Segments
• ISSN: 1559-128X; 2155-3165
• DOI: 10.1364/AO.57.009822

A one-dimensional photonic crystal elliptical-hole tapered low-index-mode nanobeam cavity sensor fully encapsulated in a water environment is proposed. In the proposed structure, to confine the light in the low-index region and enhance the light-matter interaction, a tapered major axis of the elliptical hole away from the nanobeam cavities center is optimized. Through a three-dimensional finite-difference time-domain simulation, the results show that the low-index-mode of the middle geometry cell is confined in the photonic bandgap of two-sided cells. The highest quality factor of 6.04×10 is achieved when 13 tapered segments and 5 mirror segments are placed at both sides of the host waveguide. The proposed nanobeam structure theoretically possesses a sensitivity of 244.7 nm/RIU (refractive index unit) in a water environment. Moreover, an ultra-compact footprint of 6.4  μm×0.85  μm is achieved, which is only half of the size compared to the best value reported for the nanobeam structure. The results indicate that it is a promising sensor for excellent on-chip sensing with respect to the very small footprint.