Optics of nano-objects

Conventional optics is diffraction limited to about half of the effective optical wavelength. However the current trend towards miniaturization of optical elements and devices requires methods of observation with high spatial resolutions adapted to the micrometer and submicrometer optical regime. More specifically, the use of Scanning near-field optical microscope (SNOM or NSOM) in various domains is overviewed. Basically an optical tip with a subwavelength aperture at its apex scans over a surface with a spatial resolution, which is not limited by light diffraction. This characteristic makes SNOM a valuable tool to perform various optical or spectroscopic studies on nanoobjects, such as semiconductor quantum dots (QDs), or to address them optically. The paper reviews different methods of far-field and near-field approach to visualize nano-size objects.