Integration of high transmittance photonic crystal H2 nanocavity and broadband W1 waveguide for biosensing applications based on Silicon-on-Insulator substrate

In this paper, we exhibit an integration of simultaneously high transmittance and high extinction ratio H2-type photonic crystal (PhC) nanocavitiy and broadband W1 waveguide above Silicon-on-Insulator (SOI) substrate. The integrated structure can be used as an opto-fluidic architecture for label-free biochemical detection with high resolution and large sensing range. With the plane-wave expansion (PWE) method, the results show a single resonant mode operation at normalized frequency between 0.2213 (2πc/a) and 0.2917 (2πc/a), which correspond to wide resonant wavelength ranges from 1440 to 1898 nm. By applying three-dimensional finite-difference time-domain (3D-FDTD) technique, we simulate the change of optical properties caused by the H2 structural variation. Through modifying the number and sizes of the air-holes near to the defect cavity, over 95% transmission efficiency is achieved, accompanied with an improved extinction ratio of 25 dB. Combined broadband W1 waveguide with high transmittance H2 nanocavity well meets the demand of extensive biosensing. In addition, a high resolution that we show to be Ο(10−6) refractive index units (RIU) under optimal conditions.