Reflectivity difference biosensor based on dual polarization detection

In order to further improve the detection sensitivity, simplify the optical system structure and reduce the manufacturing difficulty of sensing unit, the method using dual polarization to achieve differential detection is adopted on the basis of the existing theory. With the incidence of different polarization onto the sensing unit, reflectivity difference is obtained, and the thickness of biomolecule can be calculated by the reflectivity difference. According to the simulation results, when the thickness of silicon dioxide increases 1 nm, the reflectivity difference obtained by dual polarization detection method is 0.7988%. By changing the incidence angle of different polarization, the maximum of reflectivity difference is 0.9143%. When the incidence wavelength has an excursion for 1 nm, the reflectivity difference changes 0.23% compared with the initial condition. Compared with the sensing unit using periodic structure, the method has higher sensitivity and dull reaction to wavelength excursion and machining error.