Localized surface plasmon microscope employing a beam scanning method

We propose a localized surface plasmon microscope that uses a zeroth-order Bessel beam for the illumination to employ a beam scanning method. The microscope visualizes the refractive index distribution in the optical near-field from a substrate surface by measuring the coupling strength between illumination light and surface plasmons from the light absorption. The beam scanning method utilizing a galvano mirror for the fast scanning axis increases the repetition rate up to 2 kHz. In order to confirm imaging properties of the developed microscope, we observe the point spread function by using a latex particle with the diameter of 175nm. It is revealed that the properties of the observed point spread function coincide with that of the calculated intensity distribution of the electric field.