REFLECTION-MODE SCANNING NEAR-FIELD OPTICAL MICROSCOPY USING AN APERTURELESS METALLIC TIP

Recently, a reflection-mode near-field optical microscope with an aper tureless tungsten tip has been introduced and 100-nm resolution has be en achieved [R. Bachelot, P. Gleyzes, and A. C. Boccara, Microsc. Micr oanal. Microstruc. 5, 389-397 (1994)]. The optical signal is recorded in parallel with a tapping-mode atomic force microscope signal. By sho wing several images here, we confirm the capabilities of this device a nd clearly demonstrate a 20-nm (similar to gamma/35) resolution that h as been achieved with smaller tips. A study of these images shows that both the topography and the near electromagnetic field of the sample can be independently probed by this device. Additionally, we discuss t he principle of our approach, notably on the basis of interference phe nomena between a Rayleigh scatterer and its image through the reflecti ng surface, and some of the setup's experimental characteristics are p resented. (C) 1997 Optical Society of America.