<title>SNOM investigation of the electromagnetic field intensity and polarization distribution in the vicinity of subwavelength structures</title>

Abstract

Experimental and calculated results of the investigation of electromagnetic field distribution including its polarization characteristics in the vicinity of the structures with subwavelength sizes are presented. The experimental investigation was realized by aperture type scanning near field optical microscope, which operated in collection mode and provided both high spatial resolution and large scanning range. Shear force detection was used for the control of aperture to surface gap. Normal resolution, which allows us to image down to 0.3 nm height surface steps, was demonstrated for this gap control system. Theoretical computation of electromagnetic field distribution was realized by finite-difference time-domain (FDTD) method. Experimental three-dimensional maps of intensity and polarization distribution as a result of light diffraction at subwavelength aperture in metal screen, dielectric and metallized subwavelength cylinders were obtained. The qualitative difference between the orthogonal polarized component distributions near subwavelength aperture in aluminium screen was experimentally shown. The electromagnetic field concentration in the proximity of the dielectric nanocylinders was observed. This observation gives good fit with the results of FDTD computations. A spiral type electromagnetic field distribution pattern was experimentally observed in the proximity of metallized subwavelength cylinders, which is unexpected from both experimental and theoretical points of view.