Electromagnetic field in the focal region of wide-angular annular lens and mirror systems
作者:
C.J.R.Sheppard,
期刊:
IEE Journal on Microwaves, Optics and Acoustics
(IET Available online 1978)
卷期:
Volume 2,
issue 5
页码: 163-166
年代: 1978
DOI:10.1049/ij-moa.1978.0035
出版商: IEE
数据来源: IET
摘要:
The time-averaged electric energy density near the focus of a lens or mirror system with annular aperture is calculated. The distribution shows greater difference from the paraxial approximation than for the full circular aperture. The vector distribution of the polarisation after focusing greatly affects the field near the focus. In particular, a mirror with annular aperture which deflects a plane-polarised wave through a small angle gives a distribution in the focal plane which exhibits bright rings around a dark centre. The field distribution of an annular system is found to consist of just two modes of free space.
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