Terahertz near-field measurements of field enhancement near metal objects

We present THz near-field measurements and calculations of the electric field around metal objects with sizes comparable to the wavelength. Several examples are presented, such as the fields of one metal sphere, and of several spheres. We show how the near-field depends on the THz polarization and frequency and on the distance between the spheres. Our results are compared with Mie theory describing the scattering of light by particles. The enhancements of the field due to a sphere are compared with those generated by a metal tip used for near-field imaging.