Abstract
The future of ultra-fast optical communication systems is inevitably connected with progress in optical circuits and nanoantennas. One of the key points of this progress is the creation of elementary components of optical devices with scattering diagrams tailored for redirecting the incident light in a desired manner. Here we demonstrate theoretically and experimentally that a small, simple, spatially homogeneous dielectric subwavelength sphere with a high refractive index and low losses (as some semiconductors in the visible or near infrared region) exhibits properties allowing to utilize it as a new multifunctional element for the mentioned devices. This can be achieved by taking advantage of the coherent effects between dipolar and multipolar modes, which produce anomalous scattering effects. The effects open a new way to control the directionality of the scattered light. The directional tuning can be obtained in a practical way just by a change in the frequency of the incident wave, and/or by a well-chosen diameter of the sphere. Dielectric nanoparticles with the required optical properties in the VIS-NIR may be now readily fabricated. These particles could be an efficient alternative to the widely discussed scattering units with a more complicated design.
Highlights
The recent extensive research of light scattering by various plasmonic nanostructures[1,2,3,4,5,6,7,8,9,10,11,12] is explained by the hope of numerous future applications of these structures, especially in ultra-fast optical communication systems and nanoantennas
It is characterized by the inverted hierarchy of resonances, when the quadrupole plasmon resonance is more pronounced than the dipole, octupole is more pronounced than the quadrupole, etc.[13]
A natural question arises: “May an analog of the anomalous scattering be observed in light scattering by a dielectric particle?”
Summary
The recent extensive research of light scattering by various plasmonic nanostructures[1,2,3,4,5,6,7,8,9,10,11,12] is explained by the hope of numerous future applications of these structures, especially in ultra-fast optical communication systems and nanoantennas. The final goal of this research is to create physical grounds for the design and fabrication of optical scattering elements capable to control the intensity, polarization, phase and directionality of the scattered radiation in rather wide limits In principle, this can be achieved by selective excitation of different plasmonic eigenmodes and their controlled interference. Despite the smallness of the particles, the anomalous scattering has nothing in common with the conventional Rayleigh scattering, being in seeming violent contradiction with what is written in any textbook of optics, see, for instance, Ref. 16 It is characterized by the inverted hierarchy of resonances, when the quadrupole plasmon resonance is more pronounced than the dipole, octupole is more pronounced than the quadrupole, etc.[13]. A natural question arises: “May an analog of the anomalous scattering be observed in light scattering by a dielectric particle?”
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