Title

Generation of a Spherical Focal Spot in a 4Pi Focusing System through Reversing the Radiation of Infinite Biconical Antenna

Document Type

Article

Publication Date

9-2015

Publication Source

Optics Communications

Abstract

A method of generating spherical focal spot is demonstrated through reversely propagating and tightly focusing the electric field at the pupil plane radiated from an infinite biconical antenna centered at the foci of two confocal high numerical aperture aplanatic objective lenses. The required incident field distribution at the pupil plane is found by solving the inverse problem of radiation from an infinite biconical antenna using the Richards–Wolf vectorial diffraction theory. Numerical simulations show that a focal spot of excellent spherical symmetry along with extremely low sidelobe (~4.72% of the peak) and diffraction limited spot size of 0.432λ can be obtained in a 4Pi focusing system.

It is also shown that the generated focal spot can be shifted along the optical axis while still maintaining its spherical shape and diffraction limited size through introducing a phase difference between the pupil illumination fields of the two objective lenses used in the 4Pi focusing system.

Inclusive pages

217–221

ISBN/ISSN

0030-4018

Comments

Permission documentation is on file.

Publisher

Elsevier

Volume

350

Peer Reviewed

yes