Browsing by Author "Kivshar, Yuri S."

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All-dielectric reciprocal bianisotropic nanoparticles
(2015) Alaee, Rasoul; Albooyeh, Mohammad; Rahimzadegan, Aso; Mirmoosa, Mohammad S.; Kivshar, Yuri S.; Rockstuhl, Carsten
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The study of high-index dielectric nanoparticles currently attracts a lot of attention. They do not suffer from absorption but promise to provide control of the properties of light comparable to plasmonic nanoparticles. To further advance the field, it is important to identify versatile dielectric nanoparticles with unconventional properties. Here, we show that breaking the symmetry of an all-dielectric nanoparticle leads to a geometrically tunable magnetoelectric coupling, i.e., an omega-type bianisotropy. The suggested nanoparticle exhibits different backscatterings and, as an interesting consequence, different optical scattering forces for opposite illumination directions. An array of such nanoparticles provides different reflection phases when illuminated from opposite directions. With a proper geometrical tuning, this bianisotropic nanoparticle is capable of providing a 2π phase change in the reflection spectrum while possessing a rather large and constant amplitude. This allows the creation of reflectarrays with near-perfect transmission out of the resonance band due to the absence of a usually employed metallic screen.
An antenna model for the Purcell effect
(2015) Krasnok, Alexander E.; Slobozhanyuk, Alexey P.; Simovski, Constantin R.; Tretyakov, Sergei A.; Poddubny, Alexander N.; Miroshnichenko, Andrey E.; Kivshar, Yuri S.; Belov, Pavel A.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The Purcell effect is defined as a modification of the spontaneous emission rate of a quantum emitter at the presence of a resonant cavity. However, a change of the emission rate of an emitter caused by an environment has a classical counterpart. Any small antenna tuned to a resonance can be described as an oscillator with radiative losses, and the effect of the environment on its radiation can be modeled and measured in terms of the antenna radiation resistance, similar to a quantum emitter. We exploit this analogue behavior to develop a general approach for calculating the Purcell factors of different systems and various frequency ranges including both electric and magnetic Purcell factors. Our approach is illustrated by a general equivalent scheme, and it allows resenting the Purcell factor through the continuous radiation of a small antenna at the presence of an electromagnetic environment.
Resonant metasurfaces at oblique incidence: interplay of order and disorder
(2014) Albooyeh, Mohammad; Kruk, Sergey; Menzel, Christoph; Helgert, Christian; Kroll, Matthias; Krysinski, Adam; Decker, Manuel; Neshev, Dragomir N.; Pertsch, Thomas; Etrich, Christoph; Rockstuhl, Carsten; Tretyakov, Sergei A.; Simovski, Constantin R.; Kivshar, Yuri S.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Understanding the impact of order and disorder is of fundamental importance to perceive and to appreciate the functionality of modern photonic metasurfaces. Metasurfaces with disordered and amorphous inner arrangements promise to mitigate problems that arise for their counterparts with strictly periodic lattices of elementary unit cells such as, e.g., spatial dispersion, and allows the use of fabrication techniques that are suitable for large scale and cheap fabrication of metasurfaces. In this study, we analytically, numerically and experimentally investigate metasurfaces with different lattice arrangements and uncover the influence of lattice disorder on their electromagnetic properties. The considered metasurfaces are composed of metal-dielectric-metal elements that sustain both electric and magnetic resonances. Emphasis is placed on understanding the effect of the transition of the lattice symmetry from a periodic to an amorphous state and on studying oblique illumination. For this scenario, we develop a powerful analytical model that yields, for the first time, an adequate description of the scattering properties of amorphous metasurfaces, paving the way for their integration into future applications.