Slab waveguide sensor based on amplified phase change due to multiple total internal reflections

We present theoretically an optical slab waveguide sensor based on amplified phase change due to multiple total internal reflections (TIRs). Compared with the conventional waveguide sensors, the proposed approach provides higher sensitivity. In this sensor, we adopt the change in the ellipsometric total phase change Δ as the measuring probe of changes in the refractive index (RI) of the cladding. The change in Δ is calculated for large number of alternating total reflections. Numerical calculations show that Δ is strongly dependent on the RI variations of the cladding. Moreover, theoretical simulations show that the resolution of this sensor is predicted to be ≈ 10^−8 refractive index units (RIU). The proposed sensor could be used as a RI and a pressure sensor.