LIGHT CONFINEMENT IN SCANNING NEAR-FIELD OPTICAL MICROSCOPY

Light propagation and light confinement in scanning near-field optical microscopy (SNOM) are studied by means of the multiple multipole meth od (MMP). Helmholtz' vector wave equation is solved in three dimension s for four different near-field optical probes: a bare glass tip, a me tal-clad aperture probe, an ''entirely coated'' tip and a novel plasmo n probe. The latter two are capable of producing a near-field light sp ot of less than 20 nm (FWHM) extension. The spots have a single intens ity peak at the centre, in contrast to the field distribution behind a n aperture, which is doubly peaked. The effect of various parameters o n light throughput and confinement is investigated for these probes.