Characterization of Cascaded Porous Silicon Microcavity Biosensor

This paper proposes a cascaded optical system composed of two identical porous silicon microcavity structures, and investigates its sensing characteristics for DNA detection. In the cascaded optical system, functionalization treatment is performed on only one of the microcavity structures, and then this microcavity structure is enabled to be contacted with the analyte, while the other microcavity structure is kept not contact with the analyte, so as to achieve the purpose of changing the light path, i.e., changing the incident angle of light onto the microcavity which is contacted with the analyte. Sensor's response can be obtained by measuring changes of the defect peak varying with the incident angle. Results of numerical simulations and experiments show that the cascade structure can effectively reduce the full width at half maxima (FWHM) of the defect peak. By utilizing the change of angular position of the defect peak, detection on an 8-base pair DNA is achieved with a detection limit of 77 nM.