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Far-field directional scattering and near-field directional coupling from simple sources have recently received great attention in photonics: beyond circularly-polarized dipoles, whose directional coupling to evanescent waves was recently applied to acoustics, the near-field directionality of modes in optics includes phased combinations of electric and magnetic dipoles, such as the Janus dipole and the Huygens dipole, both of which have been experimentally implemented using high refractive index nanoparticles. In this work we extend this to acoustics: we propose the use of high acoustic index scatterers exhibiting phased combinations of acoustic monopoles and dipoles with far-field and near-field directionality. All solutions stem from the elegant acoustic angular spectrum of the acoustic source, in close analogy to electromagnetism. A Huygens acoustic source with zero backward scattering is proposed and numerically demonstrated, as well as a Janus source achieving face-selective and position-dependent evanescent coupling to nearby acoustic waveguides.
We construct a novel Lagrangian representation of acoustic field theory that describes the local vector properties of longitudinal (curl-free) acoustic fields. In particular, this approach accounts for the recently-discovered nonzero spin angular mom
Micro-nanoparticle systems have wide applications in thermal science and technology. In dense particulate system, the particle separation distance may be less than the characteristic thermal wavelength and near field effect will be significant and be
Directional excitation of guidance modes is central to many applications ranging from light harvesting, optical information processing to quantum optical technology. Of paramount interest, especially, the active control of near-field directionality p
We examine the non-equilibrium radiative heat transfer between a plate and finite cylinders and cones, making the first accurate theoretical predictions for the total heat transfer and the spatial heat flux profile for three-dimensional compact objec
Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the aco