The light tracks in an anisotropic optical fiber are studied by the optical metric model. The ordinary and extraordinary light tracks are determined by solving the null geodesic equation. In the paraxial approximation the birefringence of the fiber is analyzed. The focusing and defocusing characte ristics of a light beam are described via the geodesic deviation equation

A scheme of quantum nondemolition measurement is proposed for probing the phonon inside a crystal by using the Raman-induced Kerr effect. The results of calculation show that under certain conditions either a backaction evading measurement or a quantum state preparation can be performed.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

The destabilization of the poloidal rotation for the species of ions with the poloidally inhomogeneous sources or sinks is studied in multiple ion species tokamak plasmas. Based on the fluid equations, the evolution equation of the poloidal ion rotation speed is derived analytically. The magnitude of the inhomogeneous sources or sinks needed to destabilize the rotation is shown to be proportional to the ion density. It is suggested that the poloidal plasma rotation can be generated by destabilizing the rotation of the minority ions.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

We have proposed the Hamiltonian of a polaron bound to a donor impurity in semiconductor quantum wells (QWs) in the presence of an electric field. The couplings of an electron with the confined bulk like longitudinal optical (L_{0}) phonons, halfspace L_{0} phonons and interface phonons are considered. In particular, the interaction of the impurity with the various phonon modes is also included. We have calculated the ionization energy of a bound polaron in Al_{xl} Ga_{1-xl} As/GaAs/Al_{xr} Ga_{1-xr} As asymmetric and symmetric QWs. Results are obtained as a function of the barrier height (or equivalently of Al concentration x),the well width, the electric field intensities and the position of impurity in the QWs. Our numerical calculations show clearly that the interaction between the impurity and the phonon field plays an important role in screening the Coulomb interaction. It is shown that for at hin well (＜12nm), the cumulative effects of the electronphonon coupling and the impurityphonon coupling can contribute appreciably to the donor ionization energy and polarizability.

A systematic investigation of nitrides R_{3}Fe_{29-x}Cr_{x}N_{4}(R=Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed. The nitrogen concentration in the nitride R_{3}Fe_{29-x}Cr_{x}N_{y} was determined to be y=4. Nitrogenation leads to a relative volume expansion of about 5.3%. The lattice constants and unit cell volume decrease with in creasing rare earth atomic number from Nd to Dy, reflecting the lanthanide contraction. In average, the increase of Curie temperature upon nitrogenation is about 200 K, compared with its parent compound. The nitrogenation also results in a remarkable improvement in the saturation magnetization and anisotropy fields for R_{3}Fe_{29-x}Cr_{x}N_{4} at 4.2 K and room temperature, comp ared with their parent compounds. A spin reorientation of Nd_{3}Fe_{24.5} Cr_{4.5}N_{4} occurs at around 368 K, which is 138 K higher than that of Nd_{3}Fe_{24.5}Cr_{4.5}.Magnetohistory effects of R_{3}Fe_{29-x}Cr_{x}N_{4}(R=Nd and Sm) are observed in a low field of 0.04 T. First order magneti zation process occurs in Sm_{3}Fe_{24.0}Cr_{5.0}N_{4} in magnetic fields of around 3.0 T at 4.2 K. After nitrogenation the easy magnetization direction of Sm_{3}Fe_{24.0}Cr_{5.0} is changed from the easy cone structure to the uniaxial. The excellent intrinsic magnetic properties of Sm_{3}Fe_{24.0}Cr_{5.0}N_{4} make this compound a hopeful candidate for new high performance permanent magnets.

The possibilities of the generation of secondorder dc and secondharmonic magnetic fields excited by the magnetostatic surface wave (M SSW) and backward volume wave (MSBVW) in ferromagnetic films have been analyzed and discussed through the calculations of source terms in the equations satisfying the magnetostatic potentials. The results show that the nonlinear magnetization responses of the film to the MSSW can generate neither dc nor the secondhar monic magnetic fields. And the responses to the MSBVW will not induce the dc field, but can excite secondharmonics under some conditions. The general expressions of third order nonlinear magnetization are also derived and discussed.

8000 CROSSDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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