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Forbidden light scanning near‐field optical microscopy
Author(s) -
HEINZELMANN H.,
HECHT B.,
NOVOTNY L.,
POHL D. W.
Publication year - 1995
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1995.tb03541.x
Subject(s) - near field scanning optical microscope , optics , microscopy , optical microscope , total internal reflection , aperture (computer memory) , near and far field , numerical aperture , multipole expansion , near field optics , fresnel equations , refractive index , physics , scanning electron microscope , acoustics , wavelength , quantum mechanics
SUMMARY Near‐field optics (NFO) opens the door to light microscopy techniques with resolutions well beyond the diffraction limit. The richness of optical investigations is now applicable on a near‐molecular level. Among the novel scanning near‐field optical microscopy (SNOM) schemes, the most prominent representatives are aperture SNOM and scanning tunnelling optical microscopy (STOM or PSTM). New experimental and theoretical work has to be performed to study the phenomena specific to NFO. One such example is the angular dependence of light emission in aperture SNOM. The detection of radiation at angles greater than the critical angle of total internal reflection α c = arcsin( n −1 ), where n is the sample refractive index, can represent a microscopy scheme that combines the respective advantages of both aperture SNOM and STOM. Recent experiments have demonstrated the expected exponential dependence of light intensity on gap width (for fixed emission angle α > α c ). The decay length as a function of α is in agreement with the Fresnel description of the evanescent field when total reflection occurs at an interface. These investigations were additionally motivated by calculations based on the multiple multipole method.