A High Quality Factor and Wide Measurement Range Biosensor Based on Photonic Crystal Nanocavity Resonator

In this paper, we describe a compact biosensor based on two-dimensional photonic crystal with hexagonal lattice of air holes in a silicon slab. This biosensor is constructed by introducing waveguides and nanocavity into the periodic photonic crystal structure. The waveguides are obtained by eliminating two groups of air holes and nanocavity is formed by changing the dimension of air holes. The simulation results show that resonant wavelength of nanocavity shifts to longer wavelengths with trapping chemicals and biomaterial like, DNA molecule, protein and so on. The biosensor is designed for wavelength range of 1.5744-1.7006 mu m with optimized Q-value which is one of the important parameters to obtain high-resolution sensor. The sensitivity of sensor equals to 63.1 nm per refractive index unit (nm/RIU), and a change in refractive index of Delta n = 0.006 can be apparent. This small size photonic crystal biosensor can be utilized to measure diversity of analytes in a wide measurement range of refractive index due to their PBG with optimized quality factor and reasonable efficiency which affect the resolution of biosensor and make the detection of bio-materials possible and easy. Two-dimensional finite-difference time-domain (FDTD) method is chosen for simulation of the proposed structure. The band diagram obtained by plane-wave expansion (PWE) method shows that solely TE mode can emit through the structure.