The analysis of negative birefringence optically induced in major air components [Loriot et al., Opt. Express 17, 13429 (2009); Loriot et al., Opt. Express 18, 3011 (2010)] is revisited in light of the recently reported plasma grating-induced phase-shift effect predicted for strong-field pump-probe experiments [Wahlstrand and Milchberg, Opt. Lett. 36, 3822 (2011)]. The nonlinear birefringence induced by a short and intense laser pulse in argon is measured by femtosecond time-resolved polarimetry. The experiments are performed with degenerate colors, where the pump and probe beam share the same spectrum, or with two different colors and nonoverlapping spectra. The interpretation of the experimental results is substantiated using a numerical 3D+1 model accounting for nonlinear propagation effects, cross-beam geometry of the interacting laser pulses, and detection technique. The model also includes the ionization rate of argon and high-order Kerr indices introduced by Loriot et al., enabling one to assess the contribution of both terms to the observed effect. The results show that the ionization-induced phase shift has a minor contribution compared to the high-order Kerr effect formerly introduced, the latter allowing a reasonably good reproduction of the experimental data for the present conditions.

Relative partial cross sections have been measured following photoexcitation of atomic chlorine near the Cl 2$p$ and Cl 1$s$ ionization thresholds. In addition, Breit-Pauli $R$-matrix calculations have been carried out in the region of the 2$p$ thresholds, and the results are compared with experiment. Owing to angular-momentum considerations, it was found that the resonances associated with the higher $2p^{-1}$ thresholds should be significantly wider than the lower ones, and this is borne out in both the experimental and the theoretical results. It is shown that a large number of resonance series contribute to the cross section, which make it difficult to untangle, and suggestions for further work to better understand the spectra are presented.

We propose a generalized Floquet Hamiltonian method that is applicable to laser-induced molecular dynamics including nonperiodicity arising from time dependence of laser parameters and nuclear kinematic effects. Effects from these two types of nonperiodicity are formulated as generalized nonadiabatic transitions and treated in a unified manner. In this unified treatment, the field-induced dynamics of a molecule is mapped onto an effective nonadiabatic dynamics. An analog of the gradient approximation to the field-free nonadiabatic dynamics thus naturally follows and the relevant validity conditions are also formulated. Full-quantum-type numerical implementation of this method is applied first to the field-induced dynamics of H${}_2{}^{+}$/D${}_2{}^{+}$ within a two-state model and second to that of LiF based on the ab initio potential-energy surfaces. With the H${}_2{}^{+}$/D${}_2{}^{+}$ calculations, we confirm the validity of our formalism by reproducing the previously reported dissociation probabilities, which represent the phenomena of bond softening and bond hardening, including the “inverse bond-hardening effect” that has been identified in the present study. In the calculations of LiF, we realize full generalized ab initio Floquet analysis including the intrinsic nuclear derivative coupling. The effects of nuclear derivative couplings are assessed by directly comparing the calculations with and without the couplings. The present method, giving a simple and clear view of field-induced and kinematically induced nonadiabatic transitions, appears to be promising for the study of ab initio laser-induced dynamics of a system with nuclear derivative couplings.

We consider a matter-wave bright soliton interferometer composed of a harmonic potential trap with a Rosen-Morse barrier at its center on which an incident soliton collides and splits into two solitons. These two solitons recombine after a dipole oscillation in the trap at the position of the barrier. We focus on the characterization of the splitting process in the case in which the reflected and transmitted solitons have the same number of atoms. We obtain that the velocity of the split solitons strongly depends on the nonlinearity and on the width of the barrier and that the reflected soliton is in general slower than the transmitted one. Also, we study the phase difference acquired between the two solitons during the splitting and we fit semianalytically the main dependences with the velocity of the incident soliton, the nonlinearity, and the width of the barrier. The implementation of the full interferometer sequence is tested by means of the phase imprinting method.

We have performed a principle-proof experiment of a magneto-optical diffraction (MOD) technique that requires no energy level splitting by a homogeneous magnetic field and a circularly polarized optical lattice, avoiding system errors in an interferometer based on the MOD. The principle for this MOD is that asynchronized switching of the quadrupole trap and the Ioffe trap in a quadrupole-Ioffe-configuration trap can generate a residual magnetic force to drive a Bose-Einstein condensate (BEC) to move. We have observed asymmetric atomic diffraction resulting from the asymmetric distribution of the Bloch eigenstates involved in the diffraction process when the condensate is driven by such a force, and matter-wave self-imaging due to coherent population oscillation of the dominantly occupied Bloch eigenstates. We have classified the mechanisms that lead to symmetric or asymmetric diffraction and found that our experiment presents a magnetic alternative to a moving optical lattice, with a great potential to achieve a very large momentum transfer ($>110\hslash k$) to a BEC using well-developed magnetic trapping techniques.

We demonstrate the existence of one- and two-dimensional (1D and 2D, respectively) bright solitons in the Bose-Einstein condensate with repulsive dipole-dipole interactions induced by a combination of dc and ac polarizing fields, oriented perpendicular to the plane in which the BEC is trapped, assuming that the strength of the fields grows in the radial ($r$) direction faster than $r^3$. Stable tightly confined 1D and 2D fundamental solitons, twisted solitons in 1D, and solitary vortices in 2D are found in a numerical form. The fundamental solitons remain robust under the action of an expulsive potential, which is induced by the interaction of the dipoles with the polarizing field. The confinement and scaling properties of the soliton families are explained analytically. The Thomas-Fermi approximation is elaborated for fundamental solitons. The mobility of the fundamental solitons is limited to the central area. Stable 1D even and odd solitons are also found in the setting with a double-well modulation function, along with a regime of Josephson oscillations.

We study the ground-state topology and quasiparticle properties in bosonic Mott insulators with two-dimensional spin-orbit couplings in cold atomic optical lattices. We show that the many-body Chern and spin-Chern number can be expressed as an integral of the quasihole Berry curvatures over the Brillouin zone. Using a strong-coupling perturbation theory, for an experimentally feasible spin-orbit coupling, we compute the Berry curvature and the spin Chern number and find that these quantities can be generated purely by interactions. We also compute the quasiparticle dispersions, spectral weights, and the quasimomentum space distribution of particle and spin density, which can be accessed in cold-atom experiments and used to deduce the Berry curvature and Chern numbers.

We analyze an intensity interferometry measurement carried out with two pointlike detectors facing a distant source (e.g., a star) that may be partially occluded by an absorptive object (e.g., a planet). Such a measurement, based on the perturbation of the observed covariance function due to the object's presence, can provide information of the object complementary to a direct optical intensity measurement. In particular, one can infer the orientation of the object's transient trajectory. We identify the key parameters that impact this perturbation and show that its magnitude is equal to the magnitude of the intensity variation caused by the same object. In astronomy applications, this value may be very small, so a differential measurement may be necessary. Finally, we discuss the signal-to-noise ratio that may be expected in this type of measurement.

We develop a rigorous and physically transparent theory of enhancement of third-order nonlinear optical processes achievable in plasmonic structures. The results show that the effective nonlinear index can be enhanced by many orders of magnitude, but, due to high metal losses the most relevant figure of merit, the amount of phase shift per one absorption length, remains very low. This makes nonlinear plasmonic materials a poor match for applications requiring high efficiency, such as all-optical switching and wavelength conversion, but does not preclude the applications where overall high efficiency is not required, such as sensing.

We set forth a method to analyze the orbital angular momentum of a light field. Instead of using the canonical formalism for the conjugate pair angle-angular momentum, we model this latter variable by the superposition of two independent harmonic oscillators along two orthogonal axes. By describing each oscillator by a standard Wigner function, we derive, via a consistent change of variables, a comprehensive picture of the orbital angular momentum. We compare this with previous approaches and show how this method works in some relevant examples.

In this paper we theoretically investigate the photonic spin Hall effect (SHE) of a Gaussian beam reflected from the interface between air and topological insulators (TIs). The photonic SHE is attributed to spin-orbit coupling and manifests itself as in-plane and transverse spin-dependent splitting. We reveal that the spin-orbit coupling effect in TIs can be routed by adjusting the axion angle variations. We find that, unlike the transverse spin-dependent splitting, the in-plane one is sensitive to the axion angle. It is shown that the polarization structure in the magneto-optical Kerr effect is significantly altered due to the spin-dependent splitting in the photonic SHE. We theoretically propose a weak measurement method to determine the strength of axion coupling by probing the in-plane splitting of the photonic SHE.

In this work, we investigated the temporal dynamics of the optical Tamm state (OTS) that arises at the interface between a one-dimensional photonic crystal and a gold nanofilm. The temporal dynamics was measured by two methods: (1) the spectral method, which is based on the analysis of the spectral composition of reflected light, and (2) the probe method, i.e., by embedding an inertialess probe into the OTS mode. It was found that the temporal dynamics of OTS formation is determined by the quality factor of the photonic-crystal/nanofilm microcavity with a characteristic time of OTS formation in the range of 100 to 300 fs.

In this paper, we analyze the multiwavelength thermal ghost imaging with the spatial light modulating system (SLMS) and rotating ground glass plate (RGGP), respectively. We find that the multiwavelength ghost imaging dramatically enhances the signal-to-noise ratio (SNR) of ghost imaging for all types of objects. The $N$-wavelength ghost imaging with SLMS produces $N^2$ ghost images incoherently added together to form one ghost image whose SNR is $N^2$ times the one of single-wavelength ghost imaging. The $N$-wavelength ghost imaging with RGGP produces $N$ ghost images incoherently added together to form one ghost image whose SNR is $N$ times the one of single-wavelength ghost imaging. We find that a quantum effect is involved in the thermal light, although in a specific scenario at present. Moreover, the color ghost image obtained by the multiwavelength ghost imaging is better than the monochromatic ghost image in our observation.

We investigate time-dependent stochastic disorder in the one-dimensional Jaynes-Cummings-Hubbard model and show that it gives rise to diffusive behavior. We find that disorder correlation frequency is effective in controlling the level of diffusivity. In the defectless system the mean squared displacement (MSD), which is a measure of the diffusivity, increases with increasing disorder frequency. Contrastingly, when static defects are present, the MSD increases with disorder frequency only at lower frequencies; at higher frequencies, increasing disorder frequency actually reduces the MSD.

The issue of the ab initio evaluation of the first-order nonadiabatic couplings (NAC's) is re-examined. In particular, a recent derivation in Phys. Rev. A 82, 062508 (2010) of the NAC's is corrected by performing an extension of the derivation to the case of arbitrary values of the Kohn-Sham (KS) occupation factors. A single expression for the nonadiabatic couplings, valid both for integer and fractional values of the KS occupation factors, is provided.

We reply to the Comment by Proetto on our paper [Phys. Rev. A 82, 062508 (2010)] describing correction and extension of our formula. We appreciate the author for correcting a typing mistake in the derivation of our formula, but we also point out that the use of fractional occupation, while being a natural extension for getting the ground-state total energies or excitation energies, is not so straightforward for getting nonadiabatic couplings.

Production of electron-positron pairs by a high-energy probe photon propagating through a high-intensity laser field is considered in the nonperturbative interaction regime. The laser field consists of a strong low-frequency and a weak high-frequency component. While for each component alone photoproduction of pairs is strongly suppressed, we show that their combination can largely amplify the pair production probability by facilitating to bridge the energetic barrier of the process. Our predictions can be tested by utilizing presently available high-intensity laser devices.

We study Faraday rotation in the quantum relativistic limit. Starting from the photon self-energy in the presence of a constant magnetic field the rotation of the polarization vector of a plane electromagnetic wave which travel along the fermion-antifermion gas is studied. The connection between Faraday effect and quantum Hall effect (QHE) is discussed. The Faraday effect is also investigated for a massless relativistic (2+1)-dimensional fermion system which is derived by using the compactification along the dimension parallel to the magnetic field. The Faraday angle shows a quantized behavior as Hall conductivity in two and three dimensions.

We construct nonlinear multiparty entanglement measures for distinguishable particles, bosons, and fermions. In each case properties of an entanglement measure are related to the decomposition of the suitably chosen representation of the relevant symmetry group onto irreducible components. In the case of distinguishable particles considered entanglement measure reduces to the well-known many-particle concurrence. We prove that our entanglement criterion is sufficient and necessary for pure states living in both finite and infinite dimensional spaces. We generalize our entanglement measures to mixed states by the convex roof extension and give a nontrivial lower bound of thus obtained generalized concurrence.