Proposal of a high-Q biosensor using a triangular photonic crystal filter

The present paper examines a photonic crystal-based ring resonator created using a triangular lattice to design a biosensor with a sensing cavity based on an optical filter. Using this structure, the central wavelength of 1547 nm can be filtered with a transmission coefficient of 95%. Additionally, the maximum value of ultra-high-quality factor (Q) in the proposed structure is about 3740 at 1496 nm wavelengths. Moreover, the minimum detection limit and maximum sensitivity for the proposed structure are calculated to be 7.15 × 10–8 RIU (refractive index unit) and 561 nm/RIU, respectively. In this paper, the effects of structural parameters, including refractive index, lattice constant, and the radius of the rods in the resonator core on the central wavelength of the filter, transmission coefficient, and quality factor have been investigated. The plane wave expansion (PWE) method has been used to extract the photonic bandgap and the finite-difference time-domain (FDTD) method has been used to study the optical behavior of the photonic crystal structure.