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Fighting against diffraction: apodization and near field diffraction structures
Author(s) -
Wang H.,
Sheppard C.J.R.,
Ravi K.,
Ho S.T.,
Vienne G.
Publication year - 2012
Publication title -
laser and photonics reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.778
H-Index - 116
eISSN - 1863-8899
pISSN - 1863-8880
DOI - 10.1002/lpor.201100009
Subject(s) - diffraction , optics , apodization , fresnel diffraction , beam (structure) , beam divergence , physics , sted microscopy , biophotonics , near and far field , materials science , laser beam quality , laser , stimulated emission , laser beams
Diffraction is a natural phenomenon, which occurs when waves propagate or encounter an obstacle. Diffraction is also a fundamental aspect of modern optics: all imaging systems are diffraction systems. However, like a coin has two sides, diffraction also leads to some unfavorable effects, such as an increase in the size of a beam during propagation, and a limited minimal beam size after focusing. To overcome these disadvantages set by diffraction, many techniques have been developed by various groups, including apodization techniques to reduce the divergence of a laser beam and increase the resolution, and time reversal, STED microscopy, super lenses and optical antennas to obtain resolution down to nano‐scale. This review concentrates on the diffraction of electromagnetic waves, and the ways to overcome beam divergence and the diffraction limit.