In this paper, we demonstrate a time-reversal methodology to create diffraction-limited optical focal spot with arbitrarily oriented magnetic dipolar field component using a 4pi microscopic configuration. Through combining the magnetic dipole radiation pattern and the Richards–Wolf vectorial diffraction method, the required illuminations at the pupil plane of a 4pi focusing configuration for the reconstruction of magnetic dipole focal field are found analytically. In general, the calculated pupil field is a complex optical field with amplitude, phase and polarization variations within the cross section. Such required pupil fields can be experimentally generated with the recently develop Vectorial Optical Field Generator. Furthermore, the orientation of the magnetic field component within the doughnut shape focal field can be rotated arbitrarily by modulating the pupil field distribution carefully while maintaining the diffraction-limited focal spot size. These unique focal field distributions are expected to exhibit novel phenomena when interact with various type of structured-materials. These interactions may find important applications in super-resolution microscopy, particle trapping and manipulation, materials characterization, as well as three-dimensional high-density optical storage.
Sichao Zhou, Guanghao Rui, Hongwei Chen, and Qiwen Zhan, "Creation of diffraction-limited optical focal spot with arbitrarily oriented magnetic dipolar field (Conference Presentation)," Proc. SPIE 10732, Spintronics XI, 107321D (Presented at SPIE Nanoscience + Engineering: August 21, 2018; Published: 18 September 2018); https://doi.org/10.1117/12.2319852.5836443470001.
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