Alexander Poshakinskiy
Ioffe Institute
Alexander Poshakinskiy graduated from St. Petersburg Academic University in 2014. He performed his PhD studies at the Ioffe Institute (St. Petersburg, Russia) and received the PhD degree in 2017. Now he continues his work as a researcher in the Sector of theory of quantum coherent phenomena in solids at the Ioffe Institute. The research interests lie in the fields of spin physics, excitonic effects in semiconductor nanostructures, and resonant optomechanics.
The ability to control the direction, frequency, and polarization of the scattered light is essential for operation of antennas, routing of light, and design of topologically protected optical states. For visible light... [ view full abstract ]
The ability to control the direction, frequency, and polarization of the scattered light is essential for operation of antennas, routing of light, and design of topologically protected optical states. For visible light scattered on a particle, the directionality can be provided by the Kerker effect, exploiting the interference of electric and magnetic dipole emission patterns. However, magnetic optical resonances in the particles smaller than the light wavelength in the medium are relativistically weak.
Here, we put forward an optomechanical Kerker effect, where the tunable directional forward or backward inelastic scattering is achieved for a particle lacking magnetic resonances that trembles in space, see panel (a) of the Figure. Our concept is sketched in panel (b). The incident wave excites electric dipole polarization of the particle that oscillates in time. Trembling of the electric dipole in the direction transverse to its polarization induces the loop electric current with non-zero magnetic momentum as well as the electric quadrupole momentum. To describe this multipole conversion, we have developed a novel theoretical framework that incorporates rigorously the effect of the resonant dispersion of the moving medium on the multipolar emission and goes beyond previous approaches restricted to dielectric scatterers with non-resonant permittivity.
We found that the phase difference between electric and magnetic dipoles induced it the trembling particle is governed by the frequency dependence of the particle permittivity. For a particle with resonant permittivity, this enables control of the scattering direction via the detuning of light frequency from resonance. Panel (c) shows by color the forward directivity of the scattered light. The directivity can reach the values up to 5.25 that surpasses the limiting value of 3 for the classical Kerker effect, because the motion-induced electric quadrupole is additionally involved.
Our results apply to a variety of optomechanical systems based on the objects with resonant response, such as quantum dots, two-dimensional semiconductors, cold atoms, or superconducting qubits. We also put forward an optomechanical spin Hall effect, i.e., directional inelastic scattering of light depending on its circular polarization.
