Description of near- and far-field light emitted from a metal-coated tapered fiber tip

We present an analytical calculation of near-and far-field radiation emitted from a metal -coated tapered fiber probe. From FDTD simulations made in Cartesian coordinates we find that charge distribution on a tip is rim localized and its density is a bipolar periodic and continuous function. Similar angular charge density distributions may result from random irregularities of tip surfaces created in the fabrication process. Thus forward emission from a tip can be described as emission of quasi -dipoles and multi -quasi -dipoles. Analytically calculated characteristics are in agreement with our FDTD simulations and previous measurements of Obermuller and Karrai. (c) 2007 Optical Society of America.