We study experimentally the case of steady-state simultaneous two-phase flow in a quasi-two-dimensional porous media. The dynamics is dominated by the interplay between a viscous pressure field from the wetting fluid and bubble transport of a less viscous, nonwetting phase. In contrast with more studied displacement front systems, steady-state flow is in equilibrium, statistically speaking. The corresponding theoretical simplicity allows us to explain a data collapse in the cluster size distribution as well as the relation $|\nabla P|\propto \sqrt{\mathrm{Ca}}$ between the pressure gradient in the system and the capillary number.

It has recently been shown that the structured surface of a perfect conductor can support surface-plasmon-like modes [Pendry et al., Science 305, 847 (2004)]. Such structures have a thickness of at least the order of the wavelength. Here, using microwave wavelength radiation incident beyond the critical angle of a wax prism, we quantify the surface-plasmon-like dispersion for a metamaterial surface with a thickness very much smaller than the incident wavelength.

We reveal and observe experimentally significant modifications undertaken by discrete solitons in waveguide lattices upon the continuous transformation of the lattice structure from one-dimensional to two-dimensional. Light evolution and soliton excitation in arrays with a gradually increasing number of rows are investigated, yielding solitons with an effective reduced dimensionality residing at the edge and in the bulk of the lattice.

Hamiltonian mixed systems with unbounded phase space are typically characterized by two asymptotic algebraic laws: decay of recurrence time statistics ($\gamma$) and superdiffusion ($\beta$). We conjecture the universal exponents $\gamma =\beta =3/2$ for trapping of trajectories to regular islands based on our analytical results for a wide class of area-preserving maps. For Hamiltonian mixed systems with a bounded phase space the interval $3/2\le {\gamma }_b\le 3$ is obtained, given that trapping takes place. A number of simulations and experiments by other authors give additional support to our claims.

We report the results of high-resolution direct numerical simulations of two-dimensional Rayleigh-Bénard convection for Rayleigh numbers up to $\mathrm{Ra}={10}^{10}$ in order to study the influence of temperature boundary conditions on turbulent heat transport. Specifically, we considered the extreme cases of fixed heat flux (where the top and bottom boundaries are poor thermal conductors) and fixed temperature (perfectly conducting boundaries). Both cases display identical heat transport at high Rayleigh numbers fitting a power law $\mathrm{Nu}\approx 0.138\times {\mathrm{Ra}}^{0.285}$ with a scaling exponent indistinguishable from $2/7=0.2857\dots$ above $\mathrm{Ra}={10}^7$. The overall flow dynamics for both scenarios, in particular, the time averaged temperature profiles, are also indistinguishable at the highest Rayleigh numbers.

We have demonstrated slow propagation of surface plasmons on metallic Moiré surfaces. The phase shift at the node of the Moiré surface localizes the propagating surface plasmons and adjacent nodes form weakly coupled plasmonic cavities. Group velocities around $v_g=0.44c$ at the center of the coupled cavity band and almost a zero group velocity at the band edges are observed. A tight binding model is used to understand the coupling behavior. Furthermore, the sinusoidally modified amplitude about the node suppresses the radiation losses and reveals a relatively high quality factor ($Q=103$).

The dominant role of quantum fluctuations in determining the steady-state and transient response of a laser is demonstrated when there is a small number of particles in the system. In this regime, quantum fluctuations are found to suppress the lasing threshold and create a non-Poisson probability distribution for $n$ discrete excited electronic states and $s$ discrete photons. The correlation between $n$ and $s$ damps the averaged dynamic response of laser emission. Random walk calculations verify the master equation predictions and are used to connect to systems containing larger numbers of particles.

We demonstrate theoretically that electromagnetically induced transparency can be achieved in metamaterials, in which electromagnetic radiation is interacting resonantly with mesoscopic oscillators rather than with atoms. We describe novel metamaterial designs that can support a full dark resonant state upon interaction with an electromagnetic beam and we present results of its frequency-dependent effective permeability and permittivity. These results, showing a transparency window with extremely low absorption and strong dispersion, are confirmed by accurate simulations of the electromagnetic field propagation in the metamaterial.

Statistical properties of a laser based on a one-dimensional disordered superlattice open at one side are studied numerically. The passive normal modes of the system are determined using the Feshbach projection technique. It is found that the mode competition due to the spacial hole burning leads to a saturation of the number of lasing modes with increasing pump rate. It is also responsible for nonmonotonic dependence of intensities of lasing modes as functions of pumping. Computed distributions of spectral spacing and intensity statistics are in qualitative agreement with experimental results.

Adiabatic frequency shifting is demonstrated by tuning an ultrahigh-$Q$ photonic crystal nanocavity dynamically. By resolving the output temporally and spectrally, we showed that the frequency of the light in the cavity follows the cavity resonance shift and remains in a single mode throughout the process. This confirmed unambiguously that the frequency shift results from the adiabatic tuning. We have employed this process to achieve the dynamic release of a trapped light from an ultrahigh-$Q$ cavity and thus generate a short pulse. This approach provides a simple way of tuning $Q$ dynamically.

The transient dynamics of the eigenstates and coherent states released from a square quantum billiard is analytically and numerically investigated. It is experimentally verified that this transient dynamic can be analogously observed with the free-space propagation of the lasing modes emitted from the laterally confined, vertically emitted cavities. Furthermore, we exploit a chaotically shaped cavity to originally demonstrate the diffraction-in-time characteristics of the chaotic wave functions. It is found that the transient patterns of chaotic wave functions exhibit a striking feature of random branching behavior with the appearance of intricate interference fringes.

We report an experimental study of the three-dimensional spatial structure of the low-frequency temperature oscillations in a cylindrical Rayleigh-Bénard convection cell. Through simultaneous multipoint temperature measurements it is found that, contrary to the popular scenario, thermal plumes are emitted neither periodically nor alternately, but randomly and continuously, from the top and bottom plates. We further identify a new flow mode—the sloshing mode of the large-scale circulation (LSC). This sloshing mode, together with the torsional mode of the LSC, are found to be the origin of the oscillation of the temperature field.

We analyze the beating between intrinsic frequencies that are simultaneously generated by a modulation (Turing) instability in a nonlinear extended system. The model studied is that of a coherently driven photonic crystal fiber cavity. Beating in the form of a slow modulation of fast intensity oscillations is found to be stable for a wide range of parameters. We find that such beating can also be localized and contain only a finite number of slow modulations. These structures consist of dips in the amplitude of the fast intensity oscillations, which can either be isolated or regularly spaced. An asymptotic analysis close to the modulation instability threshold allows us to explain this phenomenon as a manifestation of homoclinic snaking for dissipative localized structures.

By incorporating a large-scale shear flow into turbulent rotating convection, we show that a sufficiently strong shear can promote dynamo action in flows that are otherwise nondynamos. Our results are consistent with a dynamo driven either by the shear-current effect or by a fluctuating $\alpha$ effect interacting with the shear, but not with either a classical ${\alpha }^2$ or $\alpha \omega$ dynamo.

Experimental and numerical data for the heat transfer as a function of the Rayleigh, Prandtl, and Rossby numbers in turbulent rotating Rayleigh-Bénard convection are presented. For relatively small $\mathrm{Ra}\approx {10}^8$ and large Pr modest rotation can enhance the heat transfer by up to 30%. At larger Ra there is less heat-transfer enhancement, and at small $\mathrm{Pr}\lesssim 0.7$ there is no heat-transfer enhancement at all. We suggest that the small-Pr behavior is due to the breakdown of the heat-transfer-enhancing Ekman pumping because of larger thermal diffusion.

Stimulated Brillouin scattering with both pump and Stokes beams in resonance with whispering gallery modes of an ultrahigh $Q$ calcium fluoride resonator is demonstrated for the first time. The resonator is pumped with 1064 nm light and has $3\mu \mathrm{W}$ Brillouin lasing threshold. The scattering is observed due to the unique morphology of the resonator reducing the phase mismatch between the optical modes and the hypersound wave.

We report the first experimental observation of Dyakonov surface waves existing at the interface of transparent anisotropic crystals. A Otto-Kretchmann configuration was used to excite the surface waves at the interface between a potassium titanyl phosphate biaxial crystal and an index-matching liquid fulfilling the conditions at which the waves exist. The signature of surface wave excitation was obtained by using enhanced polarization-conversion reflectance phenomena. We measured the cutoff propagation angles for different index-matching liquids, confirming the high sensitivity of the propagation conditions with the properties of the supporting interface.

We propose a novel subwavelength terahertz (THz) waveguide based on the magnetic plasmon polariton mode guided by a narrow gap in a negative permeability metamaterial. Deep subwavelength waveguiding ($<\lambda /10$) with group velocities down to $c/21.8$ is demonstrated in a straight waveguide, a 90° bend, and a splitter. The proposed waveguiding system inherently has no cutoff for any core width and height, paving the way toward the deep subwavelength transport of THz waves for integrated THz device applications.

A massively parallel deterministic method is described for reconstructing shift-invariant complex Green’s functions. As a first experimental implementation, we use a single phase contrast x-ray image to reconstruct the complex Green’s function associated with Bragg reflection from a thick perfect crystal. The reconstruction is in excellent agreement with a classic prediction of dynamical diffraction theory.

With a phase-sensitive near-field microscope we measure independently the two in-plane electric field components of light propagating through a 2D photonic crystal waveguide and the phase difference between them. Consequently, we are able to reconstruct the electric vector field distribution with subwavelength resolution. In the complex field distribution we observe both time-dependent and time-independent polarization singularities and determine the topology of the surrounding electric field.