Focusing of the plane wave with radially polarized electric field by an arbitrary opening paraboloid mirror is analyzed using a rigorous vectorial diffraction theory, i.e., Stratton-Chu integral. In the vicinity of the focus, far-field approximation conditions are used to simplify the derived integrals with sufficiently high accuracy. It is found that a noticeable deviation of the approximate integral, as characterized by a phenomenon of focal shift, from the exact integral can be observed when the maximum focusing semi-angle α below π/9. For α=π/2, the radial spot size reduces to below 0.40λ if cutting off the central segment, larger than π/4, of the paraboloid mirror. The sharp focusing property of the paraboloid mirror has the potential application in super-resolution confocal scanning microscopy. Specific confocal scanning arrangements are provided and remarked.

Date Published: 31 January 2013
PDF: 6 pages
Proc. SPIE 8759, Eighth International Symposium on Precision Engineering Measurement and Instrumentation, 87591Z (31 January 2013); doi: 10.1117/12.2014045

Published in SPIE Proceedings Vol. 8759:
Eighth International Symposium on Precision Engineering Measurement and Instrumentation
Jie Lin, Editor(s)