Optical magnetism has long been the elusive, missing component in light-matter interaction. Interesting applications may emerge if optical magnetism is effectively harnessed and exploited. Of particular interest is the possible manipulation of the optical magnetic force, in the form of photo-induced magnetic force microscopy. We propose an optical system for inducing magnetic forces in an axis-aligned Si disk under azimuthally polarized beam illumination. The designed Si disk can support a magnetic resonance in the visible range under azimuthal polarization by interacting with the longitudinal magnetic field at the overlapping axis. Such structure can serve as the unique magnetic probe to “feel” the magnetic force of light. In our current step, we use photo-induced force microscopy to characterize the near-field electric field distribution of this system. Measurements show a stronger electric field enhancement near the edge of the Si disk which indicates a longitudinal magnetic field enhancement at the overlapping axis. This measurement is in accordance with theoretical modeling, confirming the observed magnetic enhancement. This indirect measurement on the magnetic response of the Si disk defines an important step towards our final goal of achieving direct mapping of the local magnetic field with photo-induced magnetic force microscopy. Also, our methodology can be extended to the characterization of arbitrary nanostructures, including metamaterials and metasurfaces, under structured light illumination.
Jinwei Zeng, Mahsa Darvishzadeh-Varcheie, Mohsen Rajaei, Mohammad Albooyeh, Eric Potma, Filippo Capolino, and H. Kumar Wickramasinghe, "Probing magnetic nanoprobe in structured light by a subtle soft touch (Conference Presentation)," Proc. SPIE 10549, Complex Light and Optical Forces XII, 1054919 (Presented at SPIE OPTO: February 01, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2289527.5751542812001.
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