Nanostratification of optical excitation in self-interacting 1D arrays

The major assumption of the Lorentz-Lorenz theory about uniformity of local fields and atomic polarization in dense material does not hold in finite groups of atoms, as we reported earlier [A. E. Kaplan and S. N. Volkov, Phys. Rev. Lett., v. 101, 133902 (2008)]. The uniformity is broken at sub-wavelength scale, where the system may exhibit strong stratification of local field and dipole polarization, with the strata period being much shorter than the incident wavelength. In this paper, we further develop and advance that theory for the most fundamental case of one-dimensional arrays, and study nanoscale excitation of so called "locsitons" and their standing waves (strata) that result in size-related resonances and related large field enhancement in finite arrays of atoms. The locsitons may have a whole spectrum of spatial frequencies, ranging from long waves, to an extent reminiscent of ferromagnetic domains, -- to super-short waves, with neighboring atoms alternating their polarizations, which are reminiscent of antiferromagnetic spin patterns. Of great interest is the new kind of "hybrid" modes of excitation, greatly departing from any magnetic analogies. We also study differences between Ising-like near-neighbor approximation and the case where each atom interacts with all other atoms in the array. We find an infinite number of "exponential eigenmodes" in the lossless system in the latter case. At certain "magic" numbers of atoms in the array, the system may exhibit self-induced (but linear in the field) cancellation of resonant local-field suppression. We also studied nonlinear modes of locsitons and found optical bistability and hysteresis in an infinite array for the simplest modes.Comment: 39 pages, 5 figures; v2: Added the Conclusions section, corrected a typo in Eq. (5.3), corrected minor stylistic and grammatical imperfection

Scattering of slow-light gap solitons with charges in a two-level medium

The Maxwell-Bloch system describes a quantum two-level medium interacting with a classical electromagnetic field by mediation of the the population density. This population density variation is a purely quantum effect which is actually at the very origin of nonlinearity. The resulting nonlinear coupling possesses particularly interesting consequences at the resonance (when the frequency of the excitation is close to the transition frequency of the two-level medium) as e.g. slow-light gap solitons that result from the nonlinear instability of the evanescent wave at the boundary. As nonlinearity couples the different polarizations of the electromagnetic field, the slow-light gap soliton is shown to experience effective scattering whith charges in the medium, allowing it for instance to be trapped or reflected. This scattering process is understood qualitatively as being governed by a nonlinear Schroedinger model in an external potential related to the charges (the electrostatic permanent background component of the field).Comment: RevTex, 14 pages with 5 figures, to appear in J. Phys. A: Math. Theo

Nonreciprocal amplitude-frequency resonant response of metasandwiches “ferrite plate-grating of resonant elements”

New microwave nonreciprocal properties are investigated in “ferrite plate – grating of resonant elements” metasandwiches arranged along the axis of a rectangular waveguide in a transverse constant magnetic field. Giant nonreciprocity in the transmission is observed at the ferromagnetic resonance frequencies at certain values of the magnetic field under conditions of a mutual influence between the ferromagnetic and the grating resonances. In addition, nonreciprocal splitting of the resonance in grating elements is observed under small magnetic field, which is much less than the field necessary to the ferromagnetic resonance excitation. The nonreciprocal transmission does not take place in the case of free ferrite in the absence of a grating. Sign reversal of the nonreciprocity is observed, when ferrite transfers to the opposite side of a grating as well as under certain values of the constant magnetic field, when the sign reversal of difference between frequencies of the ferromagnetic resonance and the grating resonance takes place. Nonreciprocal effects are explained by the interaction between precessing spins in ferrite and a magnetic field of the surface wave, formed by a grating, and by coupling between the resonances of grating elements. It has been shown theoretically that microwaves in waveguide with bianisotropic layer, simulating a grating of resonant elements, are elliptically or circularly polarized with frequency and spatially – dependent rotating sense of the microwave magnetic field. The nonreciprocal effects have been observed for different grating elements: for both electric dipoles and chiral elements