Effect of vacuum-induced coherence on lasing without inversion in an equispaced three-level ladder system

The effects of vacuum-induced coherence (VIC) on the properties of the absorption and gain of the probe field in an equispaced three-level ladder atomic system are investigated. It is found that lasing without inversion (LWI) is remarkably enhanced due to the effect of VIC in the case of the small incoherent pump rate.

Duration-dependent asymmetry in photoionization of H atoms in few-cycle laser pulses

The photoionization of H atoms irradiated by few-cycle laser pulses is studied numerically. The variations of the total ionization, the partial ionizations in opposite directions, and the corresponding asymmetry with the carrier-envelope phase in several pulse durations are obtained. We find that besides a stronger modulation on the partial ionizations, the change of pulse duration leads to a shift along carrier-envelope (CE) phase in the calculated signals. The phase shift arises from the nonlinear property of ionization and relates closely to the Coulomb attraction of the parent ion to the ionized electron. Our calculations show good agreement with the experimental observation under similar conditions.

Measurement of the neutron beta decay asymmetry using ultracold neutrons

The free neutron beta decay correlation A₀ between neutron polarization and electron emission direction provides the strongest constraint on the ratio λ = g_A/g_V of the Axial-vector to Vector coupling constants in Weak decay. In conjunction with the CKM Matrix element V_ud and the neutron lifetime τ_n, λ provides a test of Standard Model assumptions for the Weak interaction. Leading high-precision measurements of A₀ and τ_n in the 1995-2005 time period showed discrepancies with prior measurements and Standard Model predictions for the relationship between λ, τ_n, and V_ud. The UCNA experiment was developed to measure A₀ from decay of polarized ultracold neutrons (UCN), providing a complementary determination of λ with different systematic uncertainties from prior cold neutron beam experiments. This dissertation describes analysis of the dataset collected by UCNA in 2010, with emphasis on detector response calibrations and systematics. The UCNA measurement is placed in the context of the most recent τ_n results and cold neutron A₀ experiments.

Electrochromic effect in domain-inversion process LiNbO3 : Ru : Fe crystals

A reversible electrochromic effect accompanying domain-inversion during the electrical poling process in LiNbO3: Ru: Fe crystals at room temperature has been observed. In electrode area, both electrochromism and domain-inversion occur alternately, and electrochromism is also reversible during back-switch poling, which is experimentally verified and whose mechanism is briefly explained using a microstructure ferroelectric model. In addition, because of the enhancing elcctrochromic effect, different from the undoped LiNbO3 crystals, the coercive riled (21.0 kV/mm or so) measured in LiNbO3: Ru: Fe is lower than its breakdown field, thus providing a possible new technique for realizing the domain-inversion by constant electric field rather than a pulsed one.

Electrochromism accompanying ferroelectric domain inversion in congruent RuO2 : LiNbO3 crystal

Electrochromic phenomena accompanying the ferroelectric domain inversion in congruent RuO2-doped z-cut LiNbO3 crystals at room temperature are observed in experiments. During the electric poling process, the electrochromism accompanies the ferroelectric domain inversion simultaneously in the same poled area. The electrochromism is completely reversible when the domain is inverted from the reverse direction. The influences of electric field and annealing conditions on domain inversion and electrochromism are also discussed. We propose the reasonable assumption that charge redistribution within the crystal structure caused by domain inversion is the source for electrochemically oxidation and reduction of Ru ion to produce the electrochromic effect. (c) 2005 Optical Society of America.

Reversible electrochromic effect accompanying domain-inversion in LiNbO3 : Ru : Fe crystals

A reversible electrochromic effect during the electrical poling process in LiNbO3:Ru:Fe crystals at room temperature is observed. In electrode area, both electrochromism and domain-inversion occur mutually and electrochromism is reversible during back-switch poling, which are experimentally verified, and a microstructure model to explain the mechanism is proposed. In addition, different from the undoped LiNbO3 crystals, the breakdown field (> 25.0 kV/mm) is higher than the coercive (21.0 kV/mm) measured in LiNbO3:Ru:Fe, which proves a possible new technique to realize domain-inversion by constant electric field rather than pulsed one. (c) 2005 American Institute of Physics.

Quantitative measurement of domain inversion in RuO2 : LiNbO3 crystal by digital holographic interferometry

We quantitatively study the domain inversion in a RuO2:LiNbO3 crystal wafer by the digital holographic interferometry. The crystal wafer is placed into one arm of a Mach-Zehnder-type interferometer to record a series of holograms. Making use of the angular spectrum backward propagation algorithm, we reconstruct the optical wave field in the crystal plane. The extracted phase difference from the reconstructed optical wave field is a well linear function of the applied external voltage. We deduce that the linear electro-optic coefficient of the detected RuO2:LiNbO3 crystal sample is 9.1x10(-12) m/V. An unexpected phase contrast at the antiparallel domain wall is observed and the influence of the applied external voltage on it is studied in detail. Also the built-in internal field is quantitatively measured as 0.72 kV/mm. (c) 2006 American Institute of Physics.

Red laser-induced domain inversion in MgO-doped lithium niobate crystals

A laser beam at wavelength 647 nm is focused on a sample of 5 mol% MgO-doped lithium niobate crystal for domain inversion by a conventional external electric field. In this case, a reduction of 36% in the electric field required for domain nucleation (nucleation field) is observed. To the best of our knowledge, it is the longest wavelength reported for laser-induced domain inversion. This extends the spectrum of laser inducing, and the experimental results are helpful to understand the nucleation dynamics under laser illumination. The dependence of nucleation fields on intensities of laser beams is analysed in experiments.

Digital holographic interferometry and the angular spectrum method applied to measuring the domain inversion in ferroelectric crystal

The application of digital holographic interferometry on the quantitative measurement of the domain inversion in a RuO2: LiNbO3 crystal wafer is presented. The recorded holograms are reconstructed by the angular spectrum method. From the reconstructed phase distribution we can clearly observe the boundary between the inverted and un-inverted domain regions. Comparisons with the results reconstructed by use of the Fresnel transform method are given. Factors that influence the measurement include the spectrum filter size and the spectrum movement are discussed. The spectrum filter size has an effect on the measurement of the details. Although the spectrum movement affects every single reconstructed image, it has no influence on the final measurement.

Inversion extranjera directa en America Latina y el Caribe: el caso de Brasil

[ES] Evolución de la inversión extranjera directa en América Latina y el Caribe, con especial interés en el caso de Brasil

Transverse target single-spin asymmetry in inclusive electroproduction of charged pions and kaons

Single-spin asymmetries were investigated in inclusive electroproduction of charged pions and kaons from transversely polarized protons at the HERMES experiment. The asymmetries were studied as a function of the azimuthal angle psi about the beam direction between the target-spin direction and the hadron production plane, the transverse hadron momentum P-T relative to the direction of the incident beam, and the Feynman variable x(F). The sin psi* amplitudes are positive for pi(+) and K+ slightly negative for pi(-) and consistent with zero for K-, with particular P-T but weak x(F) dependences. Especially large asymmetries are observed for two small subsamples of events, where also the scattered electron was recorded by the spectrometer. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.