Tunnel near-field optical microscopy (TNOM-2)

Light emitted from the aperture of a near-field optical probe in the close vicinity of a dielectric object propagates in classically `forbidden' as well as `allowed' directions; the two zones are separated by the critical angle for total internal reflection. The new `tunnel' near-field optical microscopy (TNOM) technique makes use of forbidden and allowed radiation, in contrast to standard scanning near-field optical microscopy (SNOM or NSOM), which records only the allowed light. Scan images obtained with allowed and forbidden light are complementary to some extent; the latter, however, provide high contrast and resolution even in situations in which standard SNOM/NSOM shows little or no contrast. The influence of topography on image formation is analyzed and discussed.