Fixed Photorefractive Holograms With Maximum Index-of-refraction Modulation In Linbo3:fe

We report the recording of a fixed good quality transmission hologram in LiNbO3:Fe with maximum index-of-refraction modulation using the simultaneous recording/compensation process at 120 °C in a specially designed setup with λ=514.5 nm. This process was shown to be reproducible and in good agreement with an already reported theoretical model. The analysis of this recording process showed that material saturation was reached so that the maximum possible fixed index-of-refraction modulation was achieved. From the comparison of theoretical and experimental recording/compensation process data some material parameters (dielectric relaxation time τMe ≈15 min, saturation space-charge field Eq =18.8 kV/cm, and photovoltaic-to-saturation field ratio Eph / Eq =0.80) were determined. The diffraction efficiency of this grating was measured using a λ=633 nm probe laser beam in an independent setup and its actual value computed, taking into account the angular divergence of the probe beam. The good grating performance as an optical Bragg filter was experimentally characterized by independently measuring its angular (approximately 1.2 mrad) and spectral (approximately 0.1 nm) selectivities, both at the probe beam wavelength of 633 nm. © 2009 American Institute of Physics.1066Müller, R., Santos, M.T., Arizmendi, L., Cabrera, J.M., (1994) J. Phys. D: Appl. Phys., 27, p. 241. , 0022-3727,. 10.1088/0022-3727/27/2/010Buse, K., Adibi, A., Psaltis, D., Non-volatile hologrphic storage in doubly doped lithium niobate crystals (1998) Nature, 393 (6686), pp. 665-668. , DOI 10.1038/31429Amodei, J., Staebler, D., (1971) Appl. Phys. Lett., 18, p. 540. , 0003-6951,. 10.1063/1.1653530Arizmendi, L., (1989) J. Appl. Phys., 65, p. 423. , 0021-8979,. 10.1063/1.343122Breer, S., Buse, K., Peithmann, K., Vogt, H., Krätzig, E., (1998) Rev. Sci. Instrum., 69, p. 1591. , 0034-6748,. 10.1063/1.1148814Korneev, N., Veenhuis, H., Buse, K., Krätzig, E., (2001) J. Opt. Soc. Am. B, 18, p. 1570. , 0740-3224,. 10.1364/JOSAB.18.001570McCahon, S.W., Rytz, D., Valley, G.C., Klein, M.B., Wechsler, B.A., (1989) Appl. Opt., 28, p. 1967. , 0003-6935,. 10.1364/AO.28.001967Yariv, A., Orlov, S., Rakuljik, G., Leyva, V., (1995) Opt. Lett., 20, p. 1334. , 0146-9592,. 10.1364/OL.20.001334Freschi, A.A., Frejlich, J., (1994) J. Opt. Soc. Am. B, 11, p. 1837. , 0740-3224,. 10.1364/JOSAB.11.001837De Oliveira, I., Frejlich, J., Arizmendi, L., Carrascosa, M., (2004) Opt. Commun., 229, p. 371. , 0030-4018,. 10.1016/j.optcom.2003.10.027De Oliveira, I., Frejlich, J., Arizmendi, L., Carrascosa, M., Nearly 100% diffraction efficiency fixed holograms in oxidized iron-doped LiNbO3 crystals using self-stabilized recording technique (2005) Optics Communications, 247 (1-3), pp. 39-48. , DOI 10.1016/j.optcom.2004.11.046, PII S0030401804011745Garcia, P.M., Buse, K., Kip, D., Frejlich, J., (1995) Opt. Commun., 117, p. 235. , 0030-4018,. 10.1016/0030-4018(95)00157-4Rakuljic, G.A., (1997) Opt. Lett., 22, p. 825. , 0146-9592,. 10.1364/OL.22.000825Breer, S., Buse, K., Rickermann, F., (1998) Opt. Lett., 23, p. 73. , 0146-9592,. 10.1364/OL.23.000073Frejlich, J., De Oliveira, I., Arizmendi, L., Carrascosa, M., (2007) Appl. Opt., 46, p. 227. , 0003-6935,. 10.1364/AO.46.000227Ḿndez, A., Arizmendi, L., (1998) Opt. Mater. (Amsterdam, Neth.), 10, p. 55. , 0925-3467,. 10.1016/S0925-3467(97)00056-6Von Bassewitz, J., De Oliveira, I., Frejlich, J., (2008) Appl. Opt., 47, p. 5315. , 0003-6935,. 10.1364/AO.47.005315Sturman, B.I., Carrascosa, M., Agullo-Lopez, F., Limeres, J., (1998) Phys. Rev. B, 57, p. 12792. , 0163-1829,. 10.1103/PhysRevB.57.12792De Oliveira, I., Frejlich, J., Arizmendi, L., Carrascosa, M., (2003) Opt. Lett., 28, p. 1040. , 0146-9592,. 10.1364/OL.28.001040Frejlich, J., (2006) Photorefractive Materials: Fundamental Concepts, Holographic Recording, and Materials Characterization, , (Wiley-Interscience, New York)De Oliveira, I., Frejlich, J., (2003) J. Opt. A, Pure Appl. Opt., 5, p. 428. , 1464-4258,. 10.1088/1464-4258/5/6/005Kogelnik, H., (1969) Bell Syst. Tech. J., 48, p. 2909. , 0005-858

Affleck-Dine dynamics and the dark sector of pangenesis

Pangenesis is the mechanism for jointly producing the visible and dark matter asymmetries via Affleck-Dine dynamics in a baryon-symmetric universe. The baryon-symmetric feature means that the dark asymmetry cancels the visible baryon asymmetry and thus enforces a tight relationship between the visible and dark matter number densities. The purpose of this paper is to analyse the general dynamics of this scenario in more detail and to construct specific models. After reviewing the simple symmetry structure that underpins all baryon-symmetric models, we turn to a detailed analysis of the required Affleck-Dine dynamics. Both gravity-mediated and gauge-mediated supersymmetry breaking are considered, with the messenger scale left arbitrary in the latter, and the viable regions of parameter space are determined. In the gauge-mediated case where gravitinos are light and stable, the regime where they constitute a small fraction of the dark matter density is identified. We discuss the formation of Q-balls, and delineate various regimes in the parameter space of the Affleck-Dine potential with respect to their stability or lifetime and their decay modes. We outline the regions in which Q-ball formation and decay is consistent with successful pangenesis. Examples of viable dark sectors are presented, and constraints are derived from big bang nucleosynthesis, large scale structure formation and the Bullet cluster. Collider signatures and implications for direct dark matter detection experiments are briefly discussed. The following would constitute evidence for pangenesis: supersymmetry, GeV-scale dark matter mass(es) and a Z' boson with a significant invisible width into the dark sector.Comment: 51 pages, 7 figures; v2: minor modifications, comments and references added; v3: minor changes, matches published versio

Bounds on the mass of the b' quark, revisited

Recent results from the DELPHI collaboration led us to review the present bounds on the b' quark mass. We use all available experimental data for m_b' > 96 GeV to constrain the b' quark mass as a function of the Cabibbo-Kobayashi-Maskawa elements in a sequential four generations model. We find that there is still room for a b' with a mass larger than 96 GeV.Comment: 9 pages and 7 figures. REVTEX

Influence Of Spin Reorientation On Magnetocaloric Effect In Nd Al2: A Microscopic Model

We report a theoretical investigation about the influence of the spin reorientation from easy magnetic direction 001 to the applied magnetic field direction 111 on the magnetocaloric properties of Nd Al2. This compound was fully investigated using a model Hamiltonian which includes the Zeeman-exchange interactions and the crystalline electrical field, which are responsible for the magnetic anisotropy. All theoretical results were obtained using the proper model parameters for Nd Al2, found in the literature. The existence of a minimum in magnetic entropy change below the phase transition was predicted and ascribed to the strong jump on the spin reorientation. © 2006 The American Physical Society.745Tishin, A.M., Spichkin, Y.I., (2003) The Magnetocaloric Effect and Its Applications, , Institute of Physics, BristolPecharsky, V.K., Gschneidner Jr., K.A., (1997) Phys. Rev. Lett., 78, p. 4494. , PRLTAO 0031-9007 10.1103/PhysRevLett.78.4494Tegus, O., Brück, E., Buschow, K.H.J., De Boer, F.R., (2002) Nature, 415, p. 150. , NATUAS 0028-0836 10.1038/415150AWada, H., Tanabe, Y., (2001) Appl. Phys. Lett., 79, p. 3302. , APPLAB 0003-6951Wada, H., Morikawa, T., Taniguchi, K., Shibata, T., Yamada, Y., Akishige, Y., (2003) Physica B, 328, p. 114. , PHYBE3 0921-4526 10.1016/S0921-4526(02)01822-7Hu, F., Shen, B., Sun, J., Cheng, Z., Rao, G., Zhang, X., (2001) Appl. Phys. Lett., 78, p. 3675. , APPLAB 0003-6951Fujita, A., Fujieda, S., Hasegawa, Y., Fukamichi, K., (2003) Phys. Rev. B, 67, p. 104416. , PRBMDO 0163-1829 10.1103/PhysRevB.67.104416Brown, G.V., (1976) J. Appl. Phys., 47, p. 3673. , JAPIAU 0021-8979 10.1063/1.323176Von Ranke, P.J., De Oliveira, N.A., Gama, S., (2004) J. Magn. Magn. Mater., 277, p. 78. , JMMMDC 0304-8853 10.1016/j.jmmm.2003.10.013Von Ranke, P.J., De Oliveira, N.A., Gama, S., (2004) Phys. Lett. a, 320, p. 302. , PYLAAG 0375-9601 10.1016/j.physleta.2003.10.067Von Ranke, P.J., De Campos, A., Caron, L., Coelho, A.A., Gama, S., De Oliveira, N.A., (2004) Phys. Rev. B, 70, p. 094410. , PRBMDO 0163-1829 10.1103/PhysRevB.70.094410Gama, S., Coelho, A.A., De Campos, A., Carvalho, A.M., Gandra, F.C.G., Von Ranke, P., De Oliveira, N.A., (2004) Phys. Rev. Lett., 93, p. 237202. , PRLTAO 0031-9007 10.1103/PhysRevLett.93.237202Von Ranke, P.J., De Oliveira, N.A., Mello, C., Carvalho, A.M., Gama, S., (2005) Phys. Rev. B, 71, p. 054410. , PRBMDO 0163-1829 10.1103/PhysRevB.71.054410Von Ranke, P.J., Gama, S., Coelho, A.A., De Campos, A., Carvalho, A.M., Gandra, F.C.G., De Oliveira, N.A., (2006) Phys. Rev. B, 73, p. 014415. , PRBMDO 0163-1829 10.1103/PhysRevB.73.014415Von Ranke, P.J., Pecharsky, V.K., Gschneidner, K.A., Korte, B.J., (1998) Phys. Rev. B, 58, p. 14436. , PRBMDO 0163-1829 10.1103/PhysRevB.58.14436Von Ranke, P.J., Mota, M.A., Grangeia, D.F., Carvalho, A.M., Gandra, F.C.G., Coelho, A.A., Caldas, A., Gama, S., (2004) Phys. Rev. B, 70, p. 134428. , PRBMDO 0163-1829 10.1103/PhysRevB.70.134428Lima, A.L., Tsokol, A.O., Gschneidner Jr., K.A., Pecharsky, V.K., Lograsso, T.A., Schlagel, D.L., (2005) Phys. Rev. B, 72, p. 024403. , PRBMDO 0163-1829 10.1103/PhysRevB.72.024403Von Ranke, P.J., De Oliveira, I.G., Guimaraes, A.P., Da Silva, X.A., (2000) Phys. Rev. B, 61, p. 447. , PRBMDO 0163-1829 10.1103/PhysRevB.61.447Lea, K.R., Leask, M.J.M., Wolf, W.P., (1962) J. Phys. Chem. Solids, 33, p. 1381. , JPCSAW 0022-3697Stevens, K.W.H., (1952) Proc. Phys. Soc., London, Sect. a, 65, p. 209. , PPSAAM 0370-1298 10.1088/0370-1298/65/3/308Purwins, H.G., Leson, A., (1990) Adv. Phys., 39, p. 309. , ADPHAH 0001-8732 10.1080/00018739000101511Bak, P., (1974) J. Phys. C, 7, p. 4097. , JPSOAW 0022-3719 10.1088/0022-3719/7/22/014Nereson, N., Olsen, C., Arnold, G., (1996) J. Appl. Phys., 37, p. 4575. , JAPIAU 0021-8979 10.1063/1.1708083Deenadas, C., Thompson, A.W., Graig, R.S., Wallace, W.E., (1971) J. Phys. Chem. Solids, 32, p. 1843. , JPCSAW 0022-3697Inoue, T., Sankar, S.G., Graig, R.S., Wallace, W.E., Gschneidner Jr., K.A., (1997) J. Phys. Chem. Solids, 38, p. 487. , JPCSAW 0022-3697Barbara, B., Boucherle, J.X., Michelutti, B., Rossignol, M.F., (1979) Solid State Commun., 31, p. 477. , SSCOA4 0038-1098Barbara, B., Rossignol, M.F., Boucherle, J.X., (1975) Phys. Lett., 55, p. 321. , PYLAAG 0375-9601 10.1016/0375-9601(75)90489-

Structural And Magnetic Characterization Of Eute/snte Superlattices Grown By Molecular Beam Epitaxy

Here we investigate the structural and magnetic properties of 24 repetitions EuTe/SnTe superlattices (SLs), with 3 monolayers (ML) EuTe films and SnTe thicknesses between 13 and 36 ML. The SLs were grown by molecular beam epitaxy on 3 μm SnTe buffer layers, grown on top of (111)BaF2 substrates. High resolution x-ray diffraction measurements indicated that the SLs with thicker SnTe layers have higher structural quality. This is due to the SnTe growth mode on EuTe, which starts in islands and evolves to layer-by-layer. The magnetic diffraction peak observed for the higher quality SLs proved the existence of antiferromagnetic order within the individual EuTe layers. Decreasing the width of the non-magnetic SnTe layers resulted in rougher interfaces, and the fading of the magnetic peak signal. The magnetization versus applied field curves indicated that the magnetic moments of SLs with thinner SnTe layers were also harder to align along the field direction. We interpret our results considering the loss of Eu neighbors, related with the increasing roughness of the SL interfaces. © 2009 American Institute of Physics.1199157158Kepa, H., (2003) Phys. Rev. B, 68, p. 024419Blinowski, J., Kacman, P., (2001) Phys. Rev. B, 64, p. 045302Oliveira, N.F., Foner, S., Shapira, Y., Reed, T.B., (1972) Phys. Rev. B, 5, p. 2634Díaz, B., (2008) Appl. Phys. Lett, 92, p. 242511Díaz, B., Rappl, P.H.O., Abramof, E., (2007) J. Cryst. Growth, 308, p. 218Holý, V., Kubena, J., Ploog, K., (1990) Phys. Status Solidi B, 162, p. 347Giles, C., (2003) J. Synchrotron Rad, 10, p. 43

D-braneworld cosmology

We discuss D-braneworld cosmology, that is, the brane is described by the Born-Infeld action. Compared with the usual Randall-Sundrum braneworld cosmology where the brane action is the Nambu-Goto one, we can see some drastic changes at the very early universe: (i)universe may experience the rapid accelerating phase (ii)the closed universe may avoid the initial singularity. We also briefly address the dynamics of the cosmology in the open string metric, which might be favorer than the induced metric from the view point of the D-brane.Comment: 6 pages, 3 figures, minor corrections, accepted for publication in Phys. Rev.

The Consistent Result of Cosmological Constant From Quantum Cosmology and Inflation with Born-Infeld Scalar Field

The Quantum cosmology with Born-Infeld(B-I) type scalar field is considered. In the extreme limits of small cosmological scale factor the wave function of the universe can also be obtained by applying the methods developed by Hartle-Hawking(H-H) and Vilenkin. H-H wave function predicts that most Probable cosmological constant $\Lambda$ equals to $\frac{1}{\eta}$($\frac{1}{2\eta}$ equals to the maximum of the kinetic energy of scalar field). It is different from the original results($\Lambda=0$) in cosmological constant obtained by Hartle-Hawking. The Vilenkin wave function predicts a nucleating unverse with largest possible cosmological constant and it is larger than $1/\eta$. The conclusions have been nicely to reconcile with cosmic inflation. We investigate the inflation model with B-I type scalar field, and find that $\eta$ depends on the amplitude of tensor perturbation $\delta_h$, with the form $\frac{1}{\eta}\simeq \frac{m^2}{12\pi[(\frac{9\delta_{\Phi}^2}{N \delta_h^2})^2-1]}.$ The vacuum energy in inflation epoch depends on the tensor-to-scalar ratio $\frac{\delta_h}{\delta_{\Phi}}$. The amplitude of the tensor perturbation ${\delta_{h}}$ can, in principle, be large enough to be discovered. However, it is only on the border of detectability in future experiments. If it has been observed in future, this is very interesting to determine the vacuum energy in inflation epoch.Comment: 12 pages, one figure, references added, accepted by European Physical Journal

Inducing the cosmological constant from five-dimensional Weyl space

We investigate the possibility of inducing the cosmological constant from extra dimensions by embedding our four-dimensional Riemannian space-time into a five-dimensional Weyl integrable space. Following approach of the induced matter theory we show that when we go down from five to four dimensions, the Weyl field may contribute both to the induced energy-tensor as well as to the cosmological constant, or more generally, it may generate a time-dependent cosmological parameter. As an application, we construct a simple cosmological model which has some interesting properties.Comment: 7 page