We have observed laserlike emission of surface plasmon polaritons (SPPs) decoupled to the glass prism in an attenuated total reflection setup. SPPs were excited by optically pumped molecules in a polymeric film deposited on the top of a silver film. Stimulated emission was characterized by a distinct threshold in the input-output dependence and narrowing of the emission spectrum. The observed stimulated emission and corresponding compensation of the metallic absorption loss by gain enables many applications of metamaterials and nanoplasmonic devices.

Optical properties of manganese-doped yttrium orthoaluminate crystals (Mn:YAlO 3 ), grown by the Czochralski technique, are reported. Luminescence and absorption spectra indicate the presence of Mn 4ϩ ions in as-grown crystals, and Mn 3ϩ , Mn 4ϩ , and Mn 5ϩ ions simultaneously in photoexcited crystals. A permanent diffraction grating, erasable by heating, was obtained in the crystals with diffraction efficiency of more than 50% at 514.5 nm reading wavelength and 1-2 % in 632-930 nm wavelength range. Reading at wavelengths longer than 630 nm did not damage the recorded grating. The electro-optical effect observed in the photoexcited crystals implies that manganese ions disturb the YAlO 3 crystal structure so that it becomes noncentrosymmetric.

Magnetic nanoparticles of γ-Fe 2 O 3 coated by organic molecules and suspended in liquid and solid matrices, as well as a non-diluted magnetic fluid have been studied by electron magnetic resonance (EMR) at 77-380 K. Slightly asymmetric spectra observed at room temperature become much broader, symmetric, and shift to lower fields upon cooling. An The shift and broadening of the spectrum upon cooling are ascribed to the role of the surface layer, which is considered with taking into account the strong surface-related anisotropy. To describe the overall spectrum shape, a "quantization" model is used which includes summation of the resonances corresponding to various orientations of the particle's magnetic moment at a given temperature. This approach, supplemented with some phenomenological assumptions, provides satisfactory agreement with the experimental data.

Mie-resonant high-index dielectric nanoparticles and metasurfaces have been suggested as a viable platform for enhancing both electric and magnetic dipole transitions of fluorescent emitters. While the enhancement of the electric dipole transitions by such dielectric nanoparticles has been demonstrated experimentally, the case of magneticdipole transitions remains largely unexplored. Here, we study the enhancement of spontaneous emission of Eu 3+ ions, featuring both electric and magnetic-dominated dipole transitions, by dielectric metasurfaces composed of Mie-resonant silicon nanocylinders.By coating the metasurfaces with a layer of an Eu 3+ doped polymer, we observe an enhancement of the Eu 3+ emission associated with the electric (at 610 nm) and magneticdominated (at 590 nm) dipole transitions. The enhancement factor depends systematically on the spectral proximity of the atomic transitions to the Mie resonances as well as their multipolar order, which is controlled by the nanocylinder radius. Importantly, the branching ratio of emission via the electric or magnetic transition channel can be modified by carefully designing the metasurface, where the magnetic dipole transition is enhanced more than the electric transition for cylinders with radii of about 130 nm.We confirm our observations by numerical simulations based on the reciprocity principle. Our results open new opportunities for bright nanoscale light sources based on magnetic transitions.

Absorption at multiple resonance frequencies is observed in magnetic nanoparticles in strong similarity with forbidden multiple quantum transitions known for paramagnetic ions. Temperature and concentration dependences have been studied to reveal the origin of the signals. The results are discussed using a "quantization" approach, considering resonance transitions between energy levels of a giant spin corresponding to the total magnetic moment of a nanoparticle. The multiple quantum transitions are ascribed to both the effects of anisotropy and dipole-dipole interactions between nanoparticles.