Modes of coupled photonic crystal waveguides

We consider the modes of coupled photonic crystal waveguides. We find that the fundamental modes of these structures can be either even or odd, in contrast with the behavior in coupled conventional waveguides, in which the fundamental mode is always even. We explain this finding using an asymptotic model that is valid for long wavelengths.     

Optical polarization driven giant relief modulation in amorphous chalcogenide glasses

We report on the observation of giant relief modulation in amorphous chalcogenide As2S3 glass under polarization modulated near band gap light illumination. We show that these periodic modulations are created as a result of the photoinduced mass transport despite the very low and uniform intensity light illumination. A phenomenological model, based on a photoinduced alignment of anisotropic microvolumes within the glass, is proposed to explain the phenomenon.     

Magnetic resonance in Pb<Subscript>x</Subscript>Nb<Subscript>y</Subscript>O<Subscript>z</Subscript> ceramics as a system containing chemical fluctuation regions

Simulation of the chemical fluctuation regions in PMN-like relaxors through growth of the Pb_xNb_yO_z eramics was performed. Different Pb_xNb_yO_z clusters (chemically and structurally) coexist in such ceramics. Hole polaron and bipolaron (Cr³⁺-two polaronic-hole) paramagnetic complexes were considered for explanation of the EPR spectra in Pb_xNb_yO_z ceramics. Dynamical averaging, light-induced effects, and significant effects of reduction treatment giving the coexistence of Nb⁵⁺ and Nb³⁺ ions, as well as of a strong internal magnetic field, were discovered in this ceramics. The latter could be related to antiferromagnetic phase realization in Pb_xNb_yO_z clusters containing a sufficiently high concentration of magnetic Nb³⁺ host lattice ions. Such a situation leads to antiferromagnetic resonance on Nb³⁺ ions, as well as to EPR of Cr³⁺-related paramagnetic complexes in a Nb³⁺-induced internal magnetic field. Charge transfer vibronic excitons (CTVE) in free and in CTVE phase states were detected in Pb_xNb_yO_z ceramics by photoluminescence studies.     

Family of paramagnetic centers of Ce3+ ions in yttrium aluminum garnet

The electron paramagnetic resonance (EPR) spectra of Ce³⁺ ions in single crystals of yttrium aluminum garnet have been investigated. It has been found that, in addition to the usually observed EPR signals of Ce³⁺ ions located in the regular environment at dodecahedral sites of the crystal lattice, the spectra contain a group of less intense anisotropic lines with g-factors close to the corresponding parameters of Ce³⁺ ions in the regular environment. It has been concluded that the observed satellite lines belong to the family of Ce³⁺ ions in the immediate vicinity of which there are permutation defects that lead to a change in the strength and symmetry of the crystal field in the vicinity of the paramagnetic center.