We report the first experimental observation of noise-free stochastic resonance by utilizing the intrinsic chaotic dynamics of the system. To this end we have investigated the effect of an external periodic modulation on intermittent signals observed by high power ferromagnetic resonance in yttrium iron garnet spheres. Both the signal-to-noise ratio and the residence time distributions show the characteristic features of stochastic resonance. The phenomena can be explained by means of a one-dimensional intermittent map. We present analytical results as well as computer simulations.

Amplitude-squeezed light from a quantum-well semiconductor laser with weak optical feedback from a highly dispersive grating is employed for laser Doppler anemometry. Up to 2 dB noise reduction below the shot-noise level is observed with a feedback factor of $1.5\times {10}^{-4\mathrm{}}$. Enhanced sensitivity is demonstrated in the Doppler measurement of a gas flow velocity with an improvement in the signal to noise ratio of 1.0 dB above the shot-noise limit.

We address the interplay among the intrinsic dynamic structure of chaos, external weak periodic perturbation, and noise. The periodicity and the stability condition of the chaos controlled by a weak periodic perturbation are determined. The results explain why controlling chaos works in the Braiman and Goldhirsch method, and the conditions for the targeted state to be successfully created are presented. The stochastic response of the system when contaminated with a dynamic noise is also derived.

We use a thin dielectric-loaded microwave cavity to identify experimentally the signature of non-Newtonian periodic orbits caused by ray splitting at sharp, dielectric interfaces. In our experiments non-Newtonian orbits manifest themselves as distinctive peaks in the Fourier transform of the frequency spectrum, which cannot be assigned to any Newtonian periodic orbits. Because the electromagnetic Helmholtz and quantal Schrödinger equations are equivalent in two dimensions, our results are directly relevant to quantum chaos studies.

We have demonstrated nonvolatile holographic storage with two-photon, two-step recording in nominally pure lithium niobate. An energy level slightly below the conduction band with lifetime 10–100 ms was found to be the intermediate state in the two-step electron ionization. The long lifetime allowed the use of cw lasers with moderate intensity at near infrared wavelengths. Nonvolatile readout of volume holographic images stored at near infrared wavelength was demonstrated.

We report the first observation of self-trapping of an optical vortex due to the bulk photovoltaic effect. A singly charged vortex nested on a broad cw laser beam is trapped in both transverse dimensions in a lithium niobate crystal. Although the optically induced photovoltaic current is inherently polar, the space charge field gives rise to two-dimensional self-defocusing effects. We observe both circular and elliptical self-trapped vortices, as well as beam deformation due to modulation instability.

We present experimental and theoretical results for the angular dependence of third harmonic generation of water droplets in the micrometer range (size parameter $62<\mathrm{ka}<\mathrm{}248\mathrm{}$). The third harmonic generation signal in $p$ and $s$ polarization obtained with ultrashort laser pulses is compared with a recently developed nonlinear extension of classical Mie theory including multipoles of order $l\le 250$. Both theory and experiment yield over a wide range of size parameters remarkably stable intensity maxima close to the forward and backward direction at “magic angles.” In contrast to linear Mie scattering, both are of comparable intensity.

A strong electrostatic field applied to glass is spatially modulated by intense light at frequencies $\omega$ and $2\omega$. The phenomenon is explained in terms of photoconductivity being dependent on the relative phase of the light fields at different frequencies.

A significant enhancement in the diffraction efficiency of multiplexed holograms recorded in cerium-doped S${\mathrm{r}}_{0.75}$B${\mathrm{a}}_{0.25}$N${\mathrm{b}}_2$${\mathrm{O}}_6$ was achieved by applying a negative electrical pulse prior to recording and a positive electrical pulse after recording. The enhancement is characterized by the striking appearance of two distinct erasure time constants induced by the depoling effects of the negative electric field pulse. An exposure time schedule that takes into account the two erasure time constants was derived and applied to obtain uniform diffraction efficiency of multiplexed holograms.

We propose and verify a wave-vector-space version of generalized extended self-similarity [R. Benzi et al., Europhys. Lett. 32, 709 (1995)] and broaden its applicability to uncover intriguing, universal scaling in the far dissipation range by computing high-order ( $\le 20$) structure functions numerically for (1) the three-dimensional, incompressible Navier-Stokes equation (with and without hyperviscosity) and (2) the Gledzer-Ohkitani-Yamada shell model for turbulence. Also, in case (2), with Taylor-microscale Reynolds numbers $4\times {10}^4\le {\mathrm{Re}}_{\lambda }\le 3\times {10}^6$, we find that the inertial-range exponents ( ${\zeta }_p$) of the order- $p$ structure functions do not approach their Kolmogorov value $p/3$ as ${\mathrm{Re}}_{\lambda }$ increases.

In a multiattractor state of a globally coupled dynamical system, stability of the attractors is studied by recording the return rates to themselves after perturbations. Besides the basin volume, attractors are characterized by strength, defined as the threshold perturbation for the full return rate. It is observed that Milnor attractors with a vanishing strength are dominant in the partially ordered phase. Attractions to weak attractors are found to be often enhanced with the addition of a noise, selectively for its amplitude.

Using prebunched electrons of 35 MeV from a linear accelerator, we have constructed a new type of free electron laser (FEL) which has a quasicontinuous spectrum in the millimeter wave region. The FEL consists of an open resonator and a bending magnet. Wave packets of coherent radiation from electron bunches are stored in the resonator to stimulate the radiation from the following bunches. The accumulated radiation is composed of overtones of the radio frequency of the accelerator and is quasicontinuously distributed over a wide region. By tuning the resonator, either all overtones or a part of them are amplified.

Several important dynamical aspects of parametrically excited multisolitons are observed experimentally and further simulated with the parametrically driven, damped nonlinear Schrödinger equation. These aspects include the three basic modes of soliton-soliton interactions, the chaotic motions of the solitons, and transitions among different soliton states.

A novel two-step excitation scheme for an efficient table-top x-ray laser has been realized for the first time. A nanosecond pulse creates a plasma of neonlike ions of titanium, followed by a subpicosecond pulse which excites a nonstationary population inversion. With only a few joules of pump energy, a compact x-ray laser at 32.6 nm with a very high gain coefficient of $g=19\mathrm{}{\mathrm{cm}}^{-1\mathrm{}}$ and a gain-length product of $gL=9.5\mathrm{}$ was achieved.

We have designed and fabricated a novel nonlinear optical superlattice of LiTa${\mathrm{O}}_3$ in which two antiparallel 180° domains building blocks A and B were arranged as a Fibonacci sequence. We measured the quasi-phase-matched second-harmonic spectrum of the superlattice. The second-harmonic blue, green, red, and infrared light generation, with energy conversion efficiencies of $\sim 5\%–20\%$, was demonstrated experimentally, which efficiencies are comparable with those of a periodic superlattice. Destruction of self-similarity and extinction phenomenon have also been observed in the spectrum. The experiment results are in good agreement with theory.

A novel type of spatial modulational instability induced by the dynamical interaction of two strongly coupled fundamental and harmonic fields in a second-order nonlinear optical material is demonstrated experimentally. This phenomenon is explained theoretically on the basis of a one-dimensional Floquet theory. At high intensities, the formation of a 1D solitary wave lattice is superseded by the onset of 2D modulational instabilities.

An all-optical control of light-angular-momentum transfer to nematic-liquid-crystal molecules is carried out by two copropagating noncoherent waves of orthogonal circular polarization. This allows the continuous variation of the total angular momentum of the light while conserving its circular symmetry. The molecular precession frequency is thus effectively and thoroughly controlled. The light-induced molecular reorientation threshold is shown to depend significantly on the azimuthal symmetry of the excitation light, while remaining the same for different values of its total angular momentum.

We present a thermodynamic theory of weakly excited two-dimensional granular systems from the viewpoint of elementary excitations of spinless Fermions. We introduce a global temperature $T$ that is associated with the acceleration amplitude $\gamma$ in a vibrating bed. We show that the configurational statistics of weakly excited granular materials in a vibrating bed obey the Fermi statistics.

The expansion of the conductivity in $2$- $d$ quantum Lorentz models in terms of the scatterer density $n$ is considered. We show that nonanalyticities in the density expansion due to scattering processes with small and large momentum transfers, respectively, have different functional forms. Some of the latter are not logarithmic, but rather of power-law nature, in sharp contrast to the $3$- $d$ case. In a $2$- $d$ model with point-like scatterers we find that the leading nonanalytic correction to the Boltzmann conductivity, apart from the frequency dependent weak-localization term, is of order $n^{3/2}$.