Comparison between sensitivities of phase and intensity detection in surface plasmon resonance

We have experimentally and theoretically compared intensity and phase measurements of surface plasmon resonance, in order to check the widely claimed superiority of the phase method. Both experiment and theory show a slightly higher sensitivity for intensity detection. Simulations confirm that this result is generally true for a wide range of resonance conditions. The basic reason is that phase measurements must be performed by measuring light intensities in some way, and therefore both modes of operation are limited in similar ways by photon statistics. Sensitivity can only be improved by using larger light intensities.