Sensing Applications on Refractive Index Based on Metal Gratings

Sensing applications on refractive index based on metal gratings are investigated. The excitation of surface plasmon on a metal grating placed in planer or conical mounting is examined. Numerical results are compared with experimental data. When a TM wave illuminates a metal grating, total or partial absorption of incident light occurs at angles of incidence at which the surface plasmon waves are excited. A conical mounting is introduced in the sensing application in which an enhancement of TM-TE mode conversion is observed in close vicinity to the resonance angle at which almost of the reflected light is in TE polarization. This, hence, makes the reciprocal of the TM-wave efficiency a good measure in finding the angles of incidence at which the surface waves are excited, which leads to a precise measurement. Yasuura's modal-expansion method is introduced in the numerical simulation. The setup for sensing application is represented in details.