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168 5 Near Field
(a) (b) (c)
Low refractive
index
High refractive
index
q
d<<l
Incident angle q > d<<l
total reflection angle
Fig. 5.1. Methods how to produce near field at object surface

Electric flux

Low refractive index
- - - - - - - - -
+ + + + + + + + + + + + + +
+
+
+
+
High refractive index
_
_
_
_
_
_
_
_
_
Incident light Dipole
Reflective light
Fig. 5.2. Sketch of the near field produced at the low-refraction medium surface as
the electric flux generated by dipoles due to the attenuated total reflection of light
3. An apertureless scatteringprobe: a metallic needle [5.5, 5.6] and a
nanometer-size metallic sphere [5.7, 5.8] are used for strongenhance-
ment of the near field.
The idea of usinga small aperture for high-resolution microscopy was re-
ported a long time ago. Pohl et al. [5.9] showed a high-resolution capability
(20 nm) by line scanningwith a transparent probe coated with metal and hav-
inga small aperture at the apex in 1884. Imagingin reflection by a scanning
near-field microscopy (SNOM) was demonstrated with an aperture probe by
Fischer et al. in 1888 [5.10]. In the 1990s, Betzigat Bell Labs. invented a
pulled-fiber probe with a metal coating. He and his coworkers demonstrated
various applications in superresolution microscopy [5.11]. Ohtsu et al. fabri-
cated many sophisticated sharpened structured fiber probes and they are also
developingatom-manipulation techniques usingnear-field light [5.3]. Kawata
et al. developed a new concept of physics and instrumentation by combining
near-field and surface plasmon polaritons [5.4].
Driven by great expectations, various studies of microscopy were carried
out. However, success in practical use was delayed by problems of probe