Near Field Probes: From Optical Fibers to Optical Nanoantennas

This chapter reports a broad overview of near-field optical probes. They represent the key components for the performance of the scanning near field optical microscope (SNOM). In this frame, we consider the two main classes of sensors: aperture and apertureless probes. In particular, attention is focused on optical fiber probes and on nanoantenna probes. Recent developments in the improvement of optical throughput and in the control of the near field polarization state are reported. The electromagnetic field distributions of the nanometric optical source, as well as the fabrication methods are dealt with. In order to provide a clear, complete and comprehensive description of the technique, brief explanations of the working principles of the SNOM and conventional microscopy are given. Finally, this chapter is tale about recent SNOM applications that have been widened thanks to the improved features of the probes.