Peculiarities of two-colour optical superradiance in the LaF 3:Pr3+ crystal

We report the results of detailed investigation of optical superradiance (SR) in LaF3:Pr3+ crystal resonantly excited on 3P0-3H4(0) transition by laser pulse. When the power of the pumping pulse was higher than a certain threshold, the resonant medium emitted an optical SR pulse on 3P 0-3H4(0) transition in the direction of the pumping pulse (as well as in the opposite direction) delayed in time with respect to the pumping pulse. Further increasing of the peak power of the pumping pulse led to the observation of SR on the 3P 0-3H6(1) transition also. Thus, the two-color SR in the employed crystal was observed

Specific features of local data erasure and laser cooling in van vleck paramagnetics

Nonequilibrium population of hyperfine sublevels of the ground electronic state of rare-earth ions is theoretically investigated for Van Vleck paramagnetic crystals subject to optical excitation with laser pulses. We discuss the possibility of using the predicted specific features of the phenomenon under study for the development of methods for the laser cooling of the nuclear spin system and methods of local data erasure in the regime of long-lived photon echo. Copyright © 1997 by MAHK Hayka/Interperiodica Publishing

Multipole claster superfluorescence: The generalized Dicke model

The peculiarities of superfluorescence in systems consisting of a few neighbor particles (clusters), when exchange or/and electrostatic multipole interactions between particles become significant, are investigated theoretically. It is shown that interaction between particles in the cluster leads to superpuassonian statistics of emitted photons and the intensity 1 of quadrupole superfluorescence on the double frequency depends on the number N of active centers as 1-Nα, where α > 2. In particular, α = 3, when N ≫ 1. Possible schemes of cluster construction in nuclei systems are considered and prospects of observation of multipole gamma superfluorescence are discussed

The peculiarities of accumulated long-lived photon echo in van vleck paramagnetics

Theory of accumulated long-lived photon echo in Van Vleck paramagnetics is developed. From comparison with experimental data obtained in LaF 3 : Pr 3+ (the 3H 4- 3P 0 transition) the relaxation rates of population of the 3H 4(0) level hyperfine transitions are estimated. Copyright © 1996 by MAHK Hayka/Interperiodica Publishing

Stimulated photon echo with temporal data coding in the Hopfield-Little regime

A model of an optical neural network with associative memory using stimulated photon echo (SPE) with temporal data coding is presented. The electrical field's calculation of the SPE signals is carried out for case of multiple influences on the resonant medium by optical pulses. A computer model of an optical echo processor with associative retrieval of information is elaborated. © 2009 Allerton Press, Inc

New possibilities of photon echo: Determination of ground and excited states g-factors applying a weak magnetic field pulse

© Published under licence by IOP Publishing Ltd. We have measured the magnetic parameters of a paramagnetic ion in the ground and excited states by controlling the relative phases of excited dipoles with pulse of a weak magnetic field. Er3+ in two crystals LuLiF4 and YLiF4 has been used as a paramagnetic ion. The second matrix was used for control. Optical transition is 4I15/2 → 4F9/2

Suppression of spin-state transition in epitaxially strained LaCoO_{3}

Epitaxial thin films of LaCoO_{3} (E-LCO) exhibit ferromagnetic order with a transition temperature T_c = 85 K, while polycrystalline thin LaCoO_{3} films (P-LCO) remain paramagnetic. The temperature-dependent spin-state structure for both E-LCO and P-LCO was studied by x-ray absorption spectroscopy at the Co L_{2,3} and O K edges. Considerable spectral redistributions over temperature are observed for P-LCO. The spectra for E-LCO, on the other hand, do not show any significant changes for temperatures between 30 K and 450 K at both edges, indicating that the spin state remains constant and that the epitaxial strain inhibits any population of the low-spin (S = 0) state with decreasing temperature. This observation identifies an important prerequisite for ferromagnetism in E-LCO thin films.Comment: 5 pages, 5 figures, submitted to Physical Review