Computational study of a label-free biosensor based on a photonic crystal nanocavity resonator

In this paper, we demonstrate and theoretically investigate a compact two-dimensional (2D) photonic crystal biosensor implemented by a waveguide and cavity. Biomaterials such as DNA molecules and proteins trapped inside a hole cause resonant wavelength shifting at the output terminal. The quality factor and sensitivity were obtained at about 4000 and 1.63  nm/fg, respectively. Also, we investigated this structure as a bulk refractive index sensor with a sensitivity of about 165.45  nm/RIU (refractive index units). Then, we modified the structure as a multichannel biosensor. This biosensor has the capability of highly parallel operation because of special architecture that was obtained by lattice shifting of a single hole around the cavity. Each channel had a different resonant cavity wavelength and the filling of analyte in selected holes caused resonant wavelength shifting, independently. Plane wave expansion (PWE) and finite difference time domain (FDTD) methods were used to analyze and compute the sensor characteristics.