SPR phase sensitivity enhancement in common-path polarization heterodyne interferometer by polarization tuning

In this work, we have theoretically investigated three designs of common-path polarization heterodyne interferometry (CPHI) with the possibility of to enhance the phase sensitivity and sensitivity-tunable ability. The schemes are established by utilizing some quarter wave plates (QWP) to control the ellipticity of polarization of light, and adjusting the azimuthal angle to achieve adequate phase sensitivity. The theoretical analysis has been done by Jones calculus and the results will be compared with conventional polarization heterodyne interferometry. The proposed designs have high phase sensitivity and sensitivity-tunable ability. Additionally it causes to shift the point of the extreme slope to the smaller incidence angle which usually is more convenient for SPR measurement. By the simulation, the phase sensitivity and resolving power of refractive index measurement has been estimated 5.5 × 105 °/RIU and 1.8 × 10−8 RIU, respectively.