Effect of finite aperture on Interferometric Surface Plasmon microscopic sensing performance

Interferometric Surface Plasmons (SPs) microscopic sensing can be used to measure the thickness or refractive index variation of nanomaterial within the order of diffraction limit in the lateral directions. However experimental results in literatures have shown the technique suffers from severely low signal to noise ratio (SNR) which limits its practical resolution and may cause failure of the technique in some hostile environment. In this paper, we study the effect of finite numerical aperture (NA) on the interferometric SPs sensing performance and explore the possibility of imposing proper pupil apodization functions to suppress the effect. We also propose a TM-only mode apodization filter to further improve the sensing performance of the interferometric SPs microscopy.