Generation of single chaotic microwave pulses in a self-oscillating ring system with ferromagnetic film under the action of external noise

The generation of single chaotic microwave pulses in a self-oscillating ring system with ferromagnetic film under the action of external narrow-band noise microwave signal occurring outside the band of frequencies of the chaotic microwave signal was observed. Chaotic generation emerged due to the parametric instability of the magnetostatic surface wave in the ferromagnetic film, whereas formation of single chaotic microwave pulses was caused by the absence of complete suppression of chaos under the action of narrowband noise.     

Generation of chaotic microwave pulses in broadband self-oscillating ring system with ferromagnetic film under the action of external pulse-modulated microwave signal

We have experimentally studied specific features of the generation of chaotic microwave pulse trains in a self-oscillating ring system with nonlinear delay line on surface magnetostatic waves, bandpass filter, and power amplifier on GaAs field-effect transistors under the action of an external pulse-modulated microwave signal occurring outside the band of the generated chaotic signal. It is established that a decrease in the off/duty ratio in the external pulse-modulated microwave signal leads to an increase in this ratio for the chaotic microwave pulses. The integral power of the chaotic microwave signal generated under the pulsed external signal action is increased as compared to the power of signal generated in the autonomous regime.     

Self-deflection of dissipative holographic screening-photovoltaic solitons in a biased dissipative photovoltaic-photorefractive crystal

The self-deflection of dissipative holographic screening-photovoltaic (DHSP) solitons has been investigated in the dissipative system, which consists of a biased dissipative photovoltaic-photorefractive (PV-PR) crystal and two coherently coupled beams; the signal beam (self-trapping beam) gets the energy gain from the pump beam via the two-beam coupling process. The analytical results are in good agreement with the numerical ones. Both predict that the centre of the solitary beam moves on a parabolic trajectory. Moreover, the central spatial-frequency component shifts linearly with the propagation distance. The DHSP soliton has the fixed self-deflection that is completely determined by the system parameters, its self-deflection is slight under small-signal condition, which will bring little influence on the formation of DHSP solitons. Furthermore, the relevant properties on the behaviour of bright DHSP soliton are discussed in detail.     

Generation of dissipative structures in self-oscillating ring systems upon parametric interaction of spin waves

A quasi-periodic sequence of pulses in a self-oscillating ring system with a resonant amplifier and a ferromagnetic film has been generated upon three-wave parametric interaction of spin waves. It is established that the generated pulses are analogs of dissipative bright solitons, which are formed as a result of competition between amplification and loss, as well as between time dispersion and nonlinearity. To describe the mechanism of formation of these structures, we have proposed a model in the form of three parametrically coupled differential equations with amplification and a differential equation of linear oscillator. Under certain assumptions, this model has analytical solutions in time in the form of structures with a profile similar to that of bright solitons.     

Wideband chaotic microwave signal generation in a ring system with a nonlinear delay line on coupled ferromagnetic films

Various regimes of chaotic signal generation have been studied in an self-oscillating ring system with a wideband nonlinear delay line based on coupled ferromagnetic films, in which magnetostatic backward volume waves (MSBVWs) are excited. It is shown for the first time that the simultaneous excitation of two waves in the coupled films leads to the appearance of a falling part in the dynamic characteristic of the MSBVW delay line and the generation of a broadband chaotic signal with a continuous spectrum. Under certain conditions, the ring exhibits a regime of intermittency, in which broadband chaotic signals with both continuous and discrete spectra are generated.     

Surface gap solitons in one-dimensional dual-frequency lattices

We study the surface gap solitons in an interface between one-dimensional dual-frequency lattices and uniform media. We reveal that the property of these lattices features solitons with some unique properties. It is worth pointing out that the intensity peak position of a soliton moves away from the surface of the lattice as the soliton's power for large propagation constant increases, and at the critical value of propagation constant μ = 2.1 (corresponding to power P = 6.1), the soliton closest to the surface of the lattice is formed, which reveals that low power is enough to form a real surface dual-frequency lattice soliton. These properties are contrary to those of surface solitons formed with the aid of semi-infinite symmetrical lattices.     

Optical-axis perturbation in triaxial ring resonator

We report several findings on the optical-axis perturbation of monolithic triaxial ring resonator. A criterion, C, which represents the mismatching error of the monolithic triaxial ring resonator, has been found out and it cannot be decreased by modifying the angles of the terminal surfaces or the terminal mirrors of the resonator. When C not equal 0, an optimization method to share the mismatching error C in some specific directions equally and simultaneously has been proposed. The interesting findings are important to cavity design, cavity improvement, and alignment of the monolithic triaxial ring resonator.     

Surface modification of elongated one-dimensional titanium dioxide structures with ferromagnetic nanoparticles

Nanostructured TiO₂ in the form of elongated one-dimensional structures having a highly ordered layered morphology, with cobalt-containing agglomerates on their surface, has been prepared by hydrothermal treatment of CoTiO₃ powder in the presence of chitosan, a bioactive natural polymer. The synthesis products have been characterized by scanning electron microscopy, transmission electron microscopy, IR spectroscopy, X-ray diffraction, elemental analysis, and magnetic measurements. The structures have been shown to be up to several microns in length, and their typical width ranges from 100 to 400 nm. The one-dimensional structures retain high thermal stability at calcination temperatures of up to 800°C. After vacuum heat treatment at 600°C and above, the nanostructured material possesses anomalously high ferromagnetic characteristics.     

On vibrations of thin plates with one-dimensional periodic structure

A new approach to problems of thin plates with a periodic structure along one direction in the planes parallel to the plate midplane is proposed. The model is a certain generalisation of the length-scale models for periodic plates, which make it possible to take into account the effect of periodicity cell size on the dynamics of plates with two-dimensional periodic structure [J. J drysiak, C. Woźniak, J. Theoret. Appl. Mech. 33 (1995) 337–349; J. J drysiak, Eng. Trans. 46 (1998) 73–87]. In order to describe this effect in stationary processes, e.g., a plate stability, and non-stationary processes for one-dimensional periodic plates the generalised model is presented in this paper. In order to show differences between governing equations of the extended model and the model for plates with two-dimensional periodic structure or the homogenised model vibrations problems of one-dimensional periodic plates will be analysed.     

Generation of chaotic microwave pulses with the help of passive synchronization of spin wave self-modulation frequencies in self-oscillatory ring systems

Passive synchronization (PS) of spin wave self-modulation frequencies of a chaotic microwave signal has been observed for the first time in a self-oscillatory ring system involving a nonlinear passive element with saturable absorption. The development of PS led to the generation of a periodic train of chaotic microwave pulses with an off/duty ratio exceeding 20. It is established that the repetition period of chaotic microwave pulses can be controlled by changing gain in the ring system.     

Generation of radially polarized beams with an image-rotating resonator

We show how a passive image-rotating optical resonator can be used to convert a linearly polarised, lowest-order Gaussian beam into a radially polarized beam. The image and polarization rotation of the cavity removes the frequency degeneracy of the modes, making it possible to select the radially polarized mode by cavity tuning. With the addition of gain, the same cavity should operate as a radially polarized laser when injection seeded at the proper wavelength.     

Effect of system parameters on evolution and stability of dark dissipative holographic screening-photovoltaic solitons in a biased dissipative system

In a dissipative photovoltaic-photorefractive (PV-PR) system, the dynamical evolution and stability of dark dissipative holographic screening-photovoltaic (DHSP) solitons are numerically investigated in this paper. A DHSP soliton is supported and determined by the given dissipative system, its stability is impacted by the system parameters, such as the linear loss of the crystal, the biasing field, the photovoltaic field, the angle between two input beams, the angle of the polarized directions and the system temperature. Such DHSP solitons can be easily amplified or absorbed by adjusting the system parameters, moreover, they are stable against small perturbation of amplitude or width.     

Ringing phenomenon of the fiber ring resonator

A resonator fiber-optic gyro (R-FOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A fiber ring resonator is the core sensing element in the R-FOG. When the frequency of the fiber ring resonator input laser is swept linearly with time, ringing of the output resonance curve is observed. The output field of the fiber ring resonator is derived from the superposition of the light transmitted through the directional coupler directly and the multiple light components circulated in the fiber ring resonator when the frequency of the laser is swept. The amplitude and phase of the output field are analyzed, and it is found that the difference in time for different light components in the fiber ring resonator to reach a point of destructive interference causes the ringing phenomenon. Finally the ringing phenomenon is observed in experiments, and the experimental results agree with the theoretical analysis well.     

Broadband absorbance in a liquid-core optical ring resonator

We have demonstrated the application of broadband absorption spectroscopy in a liquid-core optical ring resonator. An initial proof of concept of the broadband liquid-core optical ring resonator (BLCORR) was constructed using a thinned-wall, 250-μm-inner-diameter fused silica capillary, tapered multimode optical fibers for input and output coupling, and a light-emitting diode (LED) source. When compared with standard cuvette measurements, an apparent path length as high as 5 cm was observed for methylene blue (MB). MB is a cationic dye that exhibits strong surface interaction with bare silica. Bromothymol blue (BTB), on the other hand, has a similar absorbance spectrum but does not share this same surface activity. On comparing these two dyes, the apparent path length for MB was found to reach more than 50 times that of BTB, confirming the expectation that the sensing region being probed is largely within the evanescent field at the inner surface of the capillary. The BLCORR may also inherit, from attenuated total reflection (ATR) spectroscopy, the ability to analyze highly concentrated chromophores. Concentrations of BTB as high as 10(-2) and 10(-3) M were easily distinguished from each other at the λ(max) in the BLCORR, whereas this was not the case in a 4-mm cuvette cell. Our presented device employs commercially available materials and could incorporate well into microfluidic systems. These benefits, along with the demonstrated ability to take enhanced surface absorbance measurements in a capillary, give the BLCORR potential in a variety of applications.     

Dynamic evolution of dissipative holographic solitons in photorefractive materials via two-wave mixing with a moving grating

The dynamic evolution and stability of bright dissipative holographic solitons supported by photorefractive materials via two-wave mixing with a moving grating are investigated numerically. Results show that these solitons are stable relative to small perturbations. The state of such solitons can be easily controlled by adjusting some system parameters, such as the linear loss of the crystal and the frequency detuning between the pump beam and the self-trapping beam. Potential amplification in optical switches, repeaters or splitters is discussed.     

Coexisting chaotic and periodic dynamics in clock escapements

This paper addresses the nature of noise in machines. As a concrete example, we examine the dynamics of clock escapements from experimental, historical and analytical points of view. Experiments on two escapement mechanisms from the Reuleaux kinematic collection at Cornell University are used to illustrate chaotic-like noise in clocks. These vibrations coexist with the periodic dynamics of the balance wheel or pendulum. A mathematical model is presented that shows how self-generated chaos in clocks can break the dry friction in the gear train. This model is shown to exhibit a strange attractor in the structural vibration of the clock. The internal feedback between the oscillator and the escapement structure is similar to anti-control of chaos models.