Dual-channel illumination surface plasmon resonance holographic microscopy for resolution improvement.

Surface plasmon resonance holographic microscopy (SPRHM), combining digital holographic microscopy with surface plasmon resonance (SPR), can simultaneously obtain the amplitude and phase distributions of the reflected beam carrying specimen information in SPR. Due to the decaying length of the surface plasmon wave as large as tens of micrometers, the spatial resolution of SPRHM is lower than that of ordinary optical microscopes. In this work, we propose a scheme to improve the spatial resolution of SPRHM by applying dual-channel SPR excitations. Through the polarization multiplexing technique, two holograms carrying the information of SPR excited in orthogonal directions are simultaneously acquired. Via a numerical reconstruction and filtering algorithm for holograms, the lateral spatial resolution of SPRHM can be effectively enhanced to reach nearly 1 µm at a wavelength of 632.8 nm. This is comparable to the resolution of traditional optical microscopes, while possessing the advantages of wide-field imaging and high measurement sensitivity of SPR.