Near-Field Scanning Optical Microscope with a Laser Trapped Probe

Abstract

We made an experiment of near-field microscopic imaging using a laser-beam trapped probe. Differently from a conventional near-field (and/or photon-tunneling) scanning optical microscope, the probe is physically isolated from the scanning microscope system; it is trapped and scanned on the sample surface by the radiation force of near-infrared laser beam. The distance between the probe and the sample surface is maintained to be constant (zero) during scanning. Another laser beam for microscopic imaging is incident on the sample surface in the condition of total internal reflection; the probe on the sample couples with the photons localized near the sample surface as the evanescent filed and scatters out. The scattered photons are collected through an microscope objective lens, which is the same lens as the one used for focusing the infrared laser beam on the probe. A near-field image of the sample surface is formed, as the probe is laterally scanned on the sample. The experimental setup of the proposed microscope is described and the image data obtained with the developed microscope are shown for refractive samples and fluorescent samples with sub micrometer structure.