ABSTRACT
Near-fields are wave fields (across all wave types such as light or acoustic waves) that only exist in very close proximity to a source or material boundary. The wave-equation imbues near-fields with unique properties at the expense of being trapped deep below the wavelength scale. The properties and behaviour of near-fields is a fascinating topic and recently become a fertile ground for novel applications such as near-field directionality, which can be exploited for nanorouting, quantum readout of spin states, non-reciprocal guiding, and optical force manipulation.
In this talk we will start with a brief review of the polarization properties of near-fields across several wave-field types: electromagnetic, acoustic and linearised gravitational waves. The polarization properties include the existence of transverse spin as well as more complex relations between field components. We will overview the application for near-field directionality [1], and describe the existence of a family of near-field directional sources: circular dipoles, Huygens and Janus dipoles [2], which exist not only in electromagnetism but also in acoustics [3]. We will discuss implication for near-field optical forces. We will also move beyond these sources to consider more complex directionalities combining higher order multipoles.
[1] Rodríguez-Fortuño, F. J. et al. Near-Field Interference for the Unidirectional Excitation of Electromagnetic Guided Modes. Science 340, 328–330 (2013).
[2] Picardi, M. F., Zayats, A. V. & Rodríguez-Fortuño, F. J. Janus and Huygens Dipoles: Near-Field Directionality Beyond Spin-Momentum Locking. Phys. Rev. Lett. 120, 117402 (2018).
[3] Wei, L. & Rodríguez-Fortuño, F. J. Far-field and near-field directionality in acoustic scattering. New J. Phys. 22, 083016 (2020).
BIOGRAPHY
Francisco J. Rodríguez-Fortuño is Reader at King's College London Physics Department, researching on nanophotonics, spin-orbit interactions of light and new electromagnetic phenomena, with a focus on near-field effects. Francisco earned his Telecommunications Engineering BSc, MSc and PhD at Universitat Politecnica de Valencia, Spain, with long research stays at University of Pennsylvania and King's College London, where he became a postdoc and later obtained a permanent academic position in 2015, starting his own research team. Francisco is author of 56 research papers on international journals, 11 invited presentations at conferences, h-index 26 (Google Scholar), and is PI on European Research Council Starting Grant PSINFONI.
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