Novel Slab Waveguide Optical Sensors

Abstract

An optical slab waveguide sensor is proposed. The structure of the proposed sensor consists of three-layer dielectric slab waveguide with conducting layers at the interfaces. The dispersion relation, sensitivity, and power flow are derived for transverse electric (TE) and transverse magnetic (TM) polarizations. Positive and negative surface conductivities are considered at the substrate/film and film/cladding interfaces. The enhancement of the sensing sensitivity of the effective refractive index to any variation in the index of an analyte is shown for a wide range of the surface conductivity. A sensitivity improvement of more than 150% is found compared to the conventional slab waveguide sensor. Compared to other waveguide sensors, the proposed sensor differs in that the sensitivity can be controlled or adjusted without changing the waveguide structure. It is resembles using the focusing in the microscope to get clearer image of the specimen using the coarse and fine focus adjustment. Adjusting the sensor's sensitivity can be done by changing the surface conductivity using a transverse voltage.