Coaxial scanning near-field optical microscope tips: an alternative for conventional tips with high transmission...

Since the development of the first scanning near-field optical microscope, great effort has been put into the development of near-field optical probe tips with a good lateral resolution of the order of several tens of nanometres and a high power throughput. Several groups have proposed the use of scanning near-field optical tips with a coaxial structure. From electromagnetic theory, it is known that such structures have no cut-off frequency and a power transmission close to unity. In this paper we discuss some topics concerning the stimulation of optical coaxial waves and their propagation behaviour.