We show experimentally that parametric interaction can induce a cooperative oscillation of nonsimultaneously resonant transverse modes in an optical parametric oscillator. More generally, this effect is expected to occur in any spatially extended system subjected to boundary conditions where nonlinear wave mixing of two nonresonant spatial modes can generate a resonant oscillation.

We report a phenomenon of focusing a radially polarized beam from the visible range by a silver film with no hole on the optical axis and double-sided concentric corrugations. The axes of symmetry of grooves and the illuminating beam coincide. An Ag lens of 100 nm thickness, five grooves, of which the outermost has $5\mu \mathrm{m}$ diameter, at $\lambda =400\mathrm{nm}$ transmits 22% of electric energy and focuses light into a $0.2{\lambda }^2$ spot area at a focal length close to $2\lambda$, while at $\lambda =500\mathrm{nm}$ the results are 11%, $0.16{\lambda }^2$ and $\lambda$, respectively. This Ag lens focuses without contribution of evanescent waves a far-field source into a far-field spot. The nanolens acts like a refractive optical system of high numerical aperture close to unity.

We designed a metamaterial field rotator that can rotate electromagnetic wave fronts. Our starting point was the transformation-media concept. Effective medium theories and full simulations facilitated the actual design process. We created at a very simple structure comprising of an array of identical aluminum metal plates. We made and measured a sample and we experimentally demonstrated the field rotation effect as well as the broadband functionality at microwave frequencies.

The structure and flow of water inside 75 and 150 nm-long carbon nanotubes with diameters ranging from 0.83 to 1.66 nm are examined using molecular dynamics simulation. The flow rate enhancement, defined as the ratio of the observed flow rate to that predicted from the no-slip Poiseuille relation, is calculated for each tube and the liquid structure is examined using an axial distribution function. The relationship between the intermolecular water structure and water flow is quantified and differences between continuum and subcontinuum flow are discussed.

In both experiment and molecular simulation, it is found that a higher pressure is required to sustain the infiltration of smaller ions in a molecular-sized nanochannel. Simulations indicate that the effective ion solubility of the infiltrated liquid is reduced to nearly zero. Because of the strong interactions between the ion couples and the solid or liquid phases, an external force is required to continuously advance the confined liquid segment. The competition between the probability of ion entry and ion-couple formation causes the observed ion-size-dependent characteristics.

The study of chaos in relativistic systems has been hampered by the observer dependence of Lyapunov exponents (LEs) and of conditions, such as orbit boundedness, invoked in the interpretation of LEs as indicators of chaos. Here we establish a general framework that overcomes both difficulties and apply the resulting approach to address three fundamental questions: how LEs transform under Lorentz and Rindler transformations and under transformations to uniformly rotating frames. The answers to the first and third questions show that inertial and uniformly rotating observers agree on a characterization of chaos based on LEs. The second question, on the other hand, is an ill-posed problem due to the event horizons inherent to uniformly accelerated observers.

We address the problem of achieving an optical random laser with a cloud of cold atoms, in which gain and scattering are provided by the same atoms. The lasing threshold can be defined using the on-resonance optical thickness $b_0$ as a single critical parameter. We predict the threshold quantitatively, as well as power and frequency of the emitted light, using two different light transport models and the atomic polarizability of a strongly pumped two-level atom. We find a critical $b_0$ on the order of 300, which is within reach of state-of-the-art cold-atom experiments. Interestingly, we find that random lasing can already occur in a regime of relatively low scattering.

We report first observations of deterministic phase- and resonance-controlled all-optical electromagnetically induced transparency in multiple coupled photonic crystal cavities. The full-range tuning of coherently coupled cavity-cavity phase and resonances allow observations of transparency resonance in dark states with lifetimes longer than incoherently summed individual cavities. Supported by theoretical analyses, our multipump beam approach allows arbitrary control in two and three coupled cavities, while the standing-wave wavelength-scale photon localization allows direct scalability for chip-scale optical pulse trapping and coupled-cavity QED.

We study numerically and experimentally the dynamics and control of viscous fingering patterns in a circular Hele-Shaw cell. The nonlocality and nonlinearity of the system, especially interactions among developing fingers, make the emergent pattern difficult to predict and control. By controlling the injection rate of the less viscous fluid, we can precisely suppress the evolving interfacial instabilities. There exist denumerable attractive, self-similarly evolving symmetric, universal shapes. Experiments confirm the feasibility of the control strategy, which is summarized in a morphology diagram.

Here we demonstrate that, paradoxically, subwavelength imaging can be produced by purely resistive means. Space acts like a low pass filter for highly evanescent field components, and if a sheet or thin layer of imperfectly conducting material is placed adjacent to a source, such that the layer overcomes the larger impedance of the spatial low pass filter, no relative attenuation of evanescent components is experienced at the location of the sheet. This results in near-field subwavelength imaging, which also holds for reactive sheets. The conducting layer enables us to trade definition for amplitude. Impedance sheets are commonplace in radio frequencies or microwaves, hence the phenomenon identified here is widespread, and can be extended into the IR or optical region, as well as to other areas of physics where wave motion exists.

We propose and realize a novel concept of a self-organized three-dimensional metamaterial with a plasma frequency in the visible regime. We utilize the concept of self-rolling strained layers to roll up $\mathrm{InGaAs}/\mathrm{GaAs}/\mathrm{Ag}$ multilayers with multiple rotations. The walls of the resulting tubes represent a radial superlattice with a tunable layer thickness ratio and lattice constant. We show that the plasma frequency of the radial superlattice can be tuned over a broad range in the visible and near infrared by changing the layer thickness ratio in good agreement with an effective metamaterial description. Finite difference time domain simulations reveal that the rolled-up radial superlattices can be used as hyperlenses in the visible.

Droplet deposition onto a hydrophobic surface is studied experimentally and numerically. A wide range of droplet sizes can result from the same syringe, depending strongly on the needle retraction speed. Three regimes are identified according to the motion of the contact line. In region I, at slow retraction speeds, the contact line expands and large droplets can be achieved. In region II, at moderate needle speeds, a quasicylindrical liquid bridge forms resulting in drops approximately the size of the needle. Finally, at high speeds (region III), the contact line retracts and droplets much smaller than the syringe diameter are observed. Scaling arguments are presented identifying the dominant mechanisms in each regime. Results from nonlinear numerical simulations agree well with the experiments, although the accuracy of the predictions is limited by inadequate models for the behavior of the dynamic contact angle.

We formulate wave propagation in arrays of subwavelength waveguides with sharp index contrasts and demonstrate the collapse of bands into evanescent modes and lattice solitons with superluminal phase velocity. We find a self-reviving soliton (“phoenix soliton”) comprised of coupled forward- and backward-propagating light, originating solely from evanescent bands. In the linear regime, all Bloch waves comprising this beam decay, whereas a proper nonlinearity assembles them into a propagating self-trapped beam. Finally, we simulate the dynamics of such a beam and observe breakup into temporal pulses, indicating a new kind of slow-light gap solitons, trapped in time and in one transverse dimension.

Cavity solitons (CS) are localized structures appearing as single intensity peaks in the homogeneous background of the field emitted by a nonlinear (micro)resonator. In real devices, their position is strongly influenced by the presence of defects in the device structure. In this Letter we show that the interplay between these defects and a phase gradient in the driving field induces the spontaneous formation of a regular sequence of CSs moving in the gradient direction. Hence, defects behave as a device built-in CS source, where the CS generation rate can be set by controlling the system parameters.

Evolution of ultrathin bilayer films under the joint action of van der Waals forces and Marangoni stresses in the presence of an inclined temperature gradient, is investigated. The problem is solved by means of a linear stability theory and nonlinear simulations. Two novel effects are found. First, linear analysis leads to the discovery of the phenomenon of “isotropization.” Second, the formation of ordered structures that consist of equally sized droplets moving with equal velocities and located at equal distances from each other, is revealed.

We show experimentally and theoretically that super resolution can be achieved while imaging with a flat lens consisting of a phononic crystal exhibiting negative refraction. This phenomenon is related to the coupling between the incident evanescent waves and a bound slab mode of the phononic crystal lens, leading to amplification of evanescent waves by the slab mode. Super resolution is only observed when the source is located very near to the lens, and is very sensitive to the location of the source parallel to the lens surface as well as to site disorder in the phononic crystal lattice.

The optical properties of textured metallic surfaces are governed by the scattering of surface plasmon polaritons (SPPs) and of quasicylindrical waves (CWs), which are both excited by the nano-objects located on the surface. We study here a fundamental scattering process of these fields, namely, the cross conversion of a CW into a SPP. We first show that this inelastic process is inevitable in multi-nano-object ensembles and then propose a procedure enabling a rigorous calculation of the cross conversion scattering coefficients. Additionally, by mapping this intricate process to a much simpler one, we derive general and simple expressions for the cross conversion efficiency. All predictions are carefully supported by fully vectorial computational results.

The lower branch of the dispersion relation of exciton polaritons in semiconductor microcavities, operating in the strong-coupling regime, contains sections of both positive and negative curvature along one spatial direction. We show that this leads to the existence of stable one-dimensional bright microcavity solitons supported by the repulsive polariton nonlinearity. To achieve localization along the second transverse direction we propose to create a special soliton waveguide by changing the cavity detuning and hence the boundary of the soliton existence in such a way that the solitons are allowed only within the stripe of the desired width.

We show by experimental measurements and theoretical analyses that there exists a pattern transition from optical modulation instability to transverse instability in nonlinear media. An input coherent beam propagating in the photorefractive crystals is observed to break up into stripe filaments at a first threshold voltage. By modeling the periodic strip filaments as cnoidal waves, we demonstrate that a second threshold voltage for forming dot filaments comes from the transverse instability, resulting in a good agreement with the experimental data.

We report the observation of almost perfect light tunneling inhibition at the edge and inside laser-written waveguide arrays due to band collapse. When the refractive index of the guiding channels is harmonically modulated along the propagation direction and out-of-phase in adjacent guides, light is trapped in the excited waveguide over a long distance due to resonances. The phenomenon can be used for tuning the localization threshold power.