Study of photonic crystal microcavities coupled with waveguide for biosensing applications

Abstract

In this paper, we propose a two-dimensional photonic crystal biosensor implemented by waveguide and microcavity. The optical sensing characteristics of the structure are analyzed by using two-dimensional finite difference time domain method. Biomolecules, e.g., DNAs, trapped in selected holes cause resonant wavelength shifting at the output terminal. The quality factor and the sensitivity of the proposed structure are about 6776 and 3.4 nm/fg, respectively, with a minimum detectable biomolecule weight in a sensing hole of 0.029 fg. We have also investigated the structure for use in bulk refractive index sensing. A sensitivity and detection limit of 210 nm/RIU and 8.92 × 10−5 were obtained respectively. Furthermore, to overcome the single purpose capacity of the sensor, a multichannel optofluidic sensor has been designed. The structure is made up of three microcavities connected in series and coupled to a waveguide. Simulation results indicate that the response of each detection unit to the refractive index variation (from 1.330 to 1.371) was completely independent. These features make the designed device a promising element for performing label-free multiplexed detection in monolithic substrate for medical diagnostics and environmental monitoring.