High-frequency transport in perfect periodic dielectric cylinder arrays is studied. We analytically calculate the diffusive-ballistic transport crossover, which displays the competition between weak localization and ballistic transport.

The anisotropic diamagnetic Kepler problem (ADKP) is realized experimentally by the orbital electrons of a P donor in Si under magnetic fields. The interference of electron wave packets which leads to quasi-Landau resonances (QLR) were observed. Applying the closed-orbit theory to an anisotropic solid state environment, we have identified orbits responsible for the QLR manifesting the quantum chaotic behavior in Rydberg atoms. The excellent consistency between the measured spectra and theoretical calculation provides unambiguous evidence of quantum chaotic dynamics of electrons in the ADKP.

Dynamical relaxation of a pure electron plasma in a Malmberg-Penning trap is studied, comparing experiments, numerical simulations and statistical theories of weakly dissipative two-dimensional (2D) turbulence. Simulations confirm that the dynamics are approximated well by a 2D hydrodynamic model. Statistical analysis favors a theoretical picture of relaxation to a near-maximum entropy state with constrained energy, circulation, and angular momentum. This provides evidence that 2D electron fluid relaxation in a turbulent regime is governed by principles of maximum entropy.

We introduce the three-mode optoacoustic parametric amplifier (OAPA), a close analog of the optical parametric amplifier, for macroscopic quantum mechanics experiments. The radiation pressure reaction of light on the reflective surface of an acoustic resonator provides a nonlinearity similar to the Kerr effect in the optical parametric amplifier. The OAPA can be tuned to operate in a positive gain regime where acoustic signals are amplified or in a negative gain regime where acoustic modes are cooled. Compared with conventional optoacoustic devices, (i) the OAPA incorporates two transverse cavity modes such that the carrier and sideband fields simultaneously resonate, and (ii) it is less susceptible to the laser phase and amplitude noise. These two features significantly ease the experimental requirements for cooling of acoustic modes to their quantum-ground state and creating entangled pairs of phonons and photons.

The Floquet spectrum of a class of driven SU(2) systems is shown to display a butterfly pattern with multifractal properties. The level crossing between Floquet states of the same parity or different parities is studied. The results are relevant to studies of fractal statistics, quantum chaos, coherent destruction of tunneling, and the validity of mean-field descriptions of Bose-Einstein condensates.

A closed-form analytic formula for high-order harmonic generation (HHG) rates for atoms (that generalizes an HHG formula for negative ions [M. V. Frolov et al., J. Phys. B 42, 035601 (2009)]) is used to study laser wavelength scaling of the HHG yield for harmonic energies in the cutoff region of the HHG plateau. We predict increases of the harmonic power for HHG by Ar, Kr, and Xe with increasing wavelength $\lambda$ over atom-specific intervals of $\lambda$ in the infrared region, $\lambda \sim (0.8-2.0)\mu \mathrm{m}$.

Three-dimensional spiral waves in the Belousov-Zhabotinsky reaction are pinned to unexcitable heterogeneities. This pinning can prevent the collapse of scroll rings even if the heterogeneity does not extend along the entire wave filament. In the latter case, frequency differences create stationary gradients in the rotation phase. These twist patterns and their frequencies agree with algebraic solutions of the forced Burgers equation revealing insights into the phase coupling of scroll waves.

When a periodic 1D system described by a tight-binding model is uniformly initialized with equal amplitudes at all sites, yet with completely random phases, it evolves into a thermal distribution with no spatial correlations. However, when the system is nonlinear, correlations are spontaneously formed. We find that for strong nonlinearities, the intensity histograms approach a narrow Gaussian distributed around their mean and phase correlations are formed between neighboring sites. Sites tend to be out of phase for a positive nonlinearity and in phase for a negative one. Most impressively, the field correlation takes a universal shape independent of parameters. These results are relevant to bosonic gas in 1D optical lattices as well as to nonlinear optical waveguide arrays, which are used to demonstrate experimentally some of the features of this equilibrium state.

We introduce spatiotemporally expanding self-similar light bullets and vortex torus solutions to the $(3+1)\mathrm{D}$ nonlinear Schrödinger equation with gain. In the absence of an initial vorticity, we demonstrate an expanding solution with a parabolic intensity profile and linear spatiotemporal chirp. With a nonzero initial vorticity, expanding vortex torus solutions with a centrally embedded phase singularity are found. Such expanding self-similar structures suggest a route towards a new regime of collapse-free spatiotemporal nonlinear optics.

By applying the femtosecond laser blackening technique directly to a tungsten incandescent lamp filament, we dramatically brighten the tungsten lamp and enhance its emission efficiency to approach 100%. A comparison study of emission and absorption for the structured metal surfaces shows that Kirchhoff’s law is applicable for the black metal. Furthermore, we demonstrate that we can even obtain partially polarized light as well as control the spectral range of the optimal light emission from the laser-blackened tungsten lamp.

We use a simple method to generate toroidal droplets and study how they transform into spherical droplets. The method relies on the viscous forces exerted by a rotating continuous phase over a liquid which is extruded from an injection needle; the resultant jet is forced to close into a torus due to the imposed rotation. Once formed, the torus transforms into single or multiple spheres. Interestingly, we find there are two routes for this process depending on the aspect ratio of the torus. For thin tori, classical hydrodynamic instabilities induce its breakup into a precise number of droplets. By contrast, for sufficiently fat tori, unstable modes are unable to grow, and the torus evolves through a different route; it shrinks towards its center to coalesce onto itself, to finally form a single spherical droplet.

We propose to exploit a self-focusing effect in the atmosphere to assist delivering powerful laser beams from orbit to the ground. We demonstrate through numerical modeling that when the self-focusing length is comparable with the atmosphere height the spot size on the ground can be reduced well below the diffraction limits without beam quality degradation. The density variation suppresses beam filamentation and provides the self-focusing of the beam as a whole. The use of light self-focusing in the atmosphere can greatly relax the requirements for the orbital optics and ground receivers.

We propose the general concept of cloaking a sensor without affecting its capability to receive, measure, and observe an incoming signal. This may be obtained by using a plasmonic sensor, based on cloaking, made of materials available in nature at infrared and optical frequencies, or realizable as a metamaterial at lower frequencies. The result is a sensing system that may receive and transmit information, while its presence is not perceived by the surrounding, which may be of fundamental importance in a wide range of biological, optics, physics, and engineering applications.

Direct frequency comb spectroscopy of trapped ions is demonstrated for the first time. It is shown that the $4s{}^{2}S_{1/2}–4p{}^{2}P_{3/2}$ transition in calcium ions can be excited directly with a frequency comb laser that is up-converted to 393 nm. Detection of the transition is performed using a shelving scheme to suppress the background signal from nonresonant comb modes. The measured transition frequency of $f=761905012.7(0.5)\mathrm{MHz}$ presents an improvement in accuracy of more than 2 orders of magnitude.

We theoretically investigate the motion of collective excitations in the two-dimensional nonlinear Schrödinger equation with cubic nonlinearity. The form of these excitations for a broad range of parameters is derived. Their evolution and interaction is numerically studied and the modulation instability is discussed. The case of saturable nonlinearity is revisited.

The dynamics of spectral transport in two-dimensional turbulent convection of electrically conducting fluids is studied by means of direct numerical simulations in the frame of the magnetohydrodynamic Boussinesq approximation. The system performs quasioscillations between two different regimes of small-scale turbulence: one dominated by nonlinear magnetohydrodynamic interactions; the other governed by buoyancy forces. The self-excited change of turbulent states is reported here for the first time. The process is controlled by the ideal invariant cross helicity, $H^C={\int }_{S}dS\mathbf{v}·\mathbf{b}$. The observations are explained by the interplay of convective driving with the nonlinear spectral transfer of total magnetohydrodynamic energy and cross helicity.

In this work, we present a mechanical example of an experimental realization of a stability reversal between on-site and intersite centered localized modes. A corresponding realization of a vanishing of the Peierls-Nabarro barrier allows for an experimentally observed enhanced mobility of the localized modes near the reversal point. These features are supported by detailed numerical computations of the stability and mobility of the discrete breathers in this system of forced and damped coupled pendula. Furthermore, additional exotic features of the relevant model, such as dark breathers are briefly discussed.

We demonstrate that optomechanical devices can exhibit nonreciprocal behavior when the dominant light-matter interaction takes place via a linear momentum exchange between light and the mechanical structure. As an example, we propose a microscale optomechanical device that can exhibit a nonreciprocal behavior in a microphotonic platform operating at room temperature. We show that, depending on the direction of the incident light, the device switches between a high and low transparency state with more than a 20 dB extinction ratio.

The temporal coherence of an attosecond optical field in the extreme ultraviolet wavelength region can be defined in terms of the extent of interference in time domain. We successfully measured this phenomenon both with and without spectral decomposition. We also report the results of using this approach to directly observe both symmetry and symmetry breaking of interference fringes in an attosecond pulse train.

Optical diffraction tomography (ODT) is a recent imaging technique that combines the experimental methods of phase microscopy and synthetic aperture with the mathematical tools of inverse scattering theory. We show experimentally that this approach permits us to obtain the map of permittivity of highly scattering samples with axial and transverse resolutions that are much better than that of a microscope with the same numerical aperture.