High figure of merit ultra-compact 3-channel parallel-connected photonic crystal mini-hexagonal-H1 defect microcavity sensor array

Abstract In this paper, a photonic crystal (PhC) butt-coupled mini-hexagonal-H1 defect (MHHD) microcavity sensor is proposed. The MHHD microcavity is designed by introducing six mini-holes into the initial H1 defect region. Further, based on a well-designed 1 ×3 PhC Beam Splitter and three optimal MHHD microcavity sensors with different lattice constants ( a ), a 3-channel parallel-connected PhC sensor array on monolithic silicon on insulator (SOI) is proposed. Finite-difference time-domain (FDTD) simulations method is performed to demonstrate the high performance of our structures. As statistics show, the quality factor ( Q ) of our optimal MHHD microcavity attains higher than 7×10 4 , while the sensitivity ( S ) reaches up to 233 nm/RIU(RIU = refractive index unit). Thus, the figure of merit ( FOM ) >10 4 of the sensor is obtained, which is enhanced by two orders of magnitude compared to the previous butt-coupled sensors [1] , [2] , [3] , [4] . As for the 3-channel parallel-connected PhC MHHD microcavity sensor array, the FOM s of three independent MHHD microcavity sensors are 8071, 8250 and 8250, respectively. In addition, the total footprint of the proposed 3-channel parallel-connected PhC sensor array is ultra-compactness of 12.5 µm ×31 µm (width × length). Therefore, the proposed high FOM sensor array is an ideal platform for realizing ultra-compact highly parallel refractive index (RI) sensing.