SPR sensor based on phase modulation and polarization interferometry

In this paper, a new Surface Plasmon Resonance (SPR) sensor for refractive index (RI) based on polarization interferometry and phase modulation is presented. Its sensitivity is not a direct function on intensity variations (∂r ∂n ), nor on phase variations(∂φ)/ ∂n), but on ((∂r/∂n)Δφ +r(∂φ/∂n)) (here r andφ represent the amplitude and the phase of reflectivity; n represents the refractive index). According to our theoretical calculation, the dynamic range of this kind of SPR sensor is much wider than that of sensors based on either variations of intensity or variations of phase. This sensor can also provide very high resolution comparable with SPR sensors base on phase variations which has the highest sensitivities till now.