Abstract

A real-time near-field optical microscope (RNOM) has been developed that is capable of 80 nm resolution with visible light. Previous near-field optical microscopes imaged through a tiny pinhole placed very close to the sample and used mechanical scanning. The RNOM operates in real time, has a good light budget, and can be added to a standard or real-time confocal microscope. The principle of the RNOM is similar to that of an oil-immersion microscope, in which the transverse resolution is improved by a factor of n, the refractive index of the oil. The RNOM uses a solid immersion lens (SIL) placed between a long-working-distance objective and the sample to achieve a corresponding improvement. Because good optical materials can be found with indices as great as 3.4, the RNOM achieves better resolutions than a liquid-immersion system and can be used to image inside solid materials with refractive indices close to that of the SIL. We have used the RNOM with an n = 2 SIL to image 160 nm lines and spaces. The experimental edge response of the system is twice that of the confocal microscope.

© 1990 Optical Society of America