LAUSR

A 3 × 3 linearly distributed optical coupler was used in a Vernier -based SOI microring resonator in order to design a label-free biosensor takes advantage of low loss and fully isolated reference unit from the measurand. The coupled mode theory was used to drive the optical transfer function of the system. The electric field propagation through the sensor’s waveguides and the normalized light transmission versus the wavelength spectrum were studied using variational finite-difference time domain (varFDTD) method. The sensor performance was characterized based on the refractive index variation of the optical waveguide superstrate by applying different concentrations of glucose and NaCl solutions. Then, three types of cancer cells, including MCF7, MDA-MB-231 and Hella cell line, were detected based on the antibody–antigen reaction. The sensitivity and the detection limit of the proposed sensor were measured to be 578 nm/RIU and 2.8 × 10−5 RIU, respectively. Results show the capability of the proposed sensor as a high-performance device for label-free sensing. The proposed sensor can potentially be used for measuring the sucrose concentration in food industries and accurate determination of seawater salinity.