Design of a highly sensitive blood sensor based on a 2D photonic crystal L3 cavity

In this paper, a 2D photonic crystal (PC) biosensor is proposed. The basic PC structure consists of 17 × 15 holes in <i>X</i> and <i>Z</i> direction over a silicon slab of refractive index (RI) equal to 3.46. The sensor structure consists of two L3 cavities created on the either side of a defect waveguide. The band diagram of the proposed structure is analyzed using plane wave expansion method (PWEM) and simulations of light propagation through the biosensor are carried out using 2D finite difference time domain method (2D-FDTDM). The parameters are optimized to obtain the best possible performance. The sensitivity of the proposed biosensor is determined by the shift in the wavelength of transmission deep as a function of RI of sensing holes. The proposed biosensor exhibits a high-quality factor (Q-factor) of 2587, with a spectral width of 0.6 nm (at the wavelength of 1552 nm) of the transmission deep. The biosensor has ultra-compact footprint of 29 µm<sup>2</sup>. Further, it shows a high figure of merit (666 RIU<sup>–1</sup>), a low detection limit (1.49 × 10<sup>–4</sup> RIU), and a maximum sensitivity of 400 nm/RIU. The proposed biosensor might have potential applications in detection of many blood related diseases.