Influence of the amplitude and phase nonlinearity of a spin-wave delay line on the wideband chaotic microwave generation

Regimes of wideband chaotic microwave generation have been studied in a self-oscillating ring system with a nonlinear delay line, in which magnetostatic backward volume waves (MSBVWs) are excited. It is established that a change in length of the delay line influences on its amplitude and phase nonlineartity, thus making it possible to control the characteristics of the chaotic microwave signal generated in the ring. It is demonstrated for the first time that a wideband chaotic microwave signal with a continuous spectrum and a nearly Gaussian probability density distribution can be generated by exciting MSBVWs in a self-oscillating ring system with a nonlinear delay line based on single ferromagnetic film.     

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.     

Generation of chaotic microwave pulses in a ring system based on a klystron power amplifier and a nonlinear delay line on magnetostatic waves

The autonomous generation of stationary chaotic microwave pulse trains in a self-oscillating ring system with a multicavity klystron power amplifier operating in a small-signal regime and a wideband non-linear delay line on surface magnetostatic waves has been experimentally studied. It is established that the characteristics of generated chaotic microwave pulses can be controlled by varying the electron beam current and accelerating voltage in the klystron.     

A microwave photonic generator of chaotic and noise signals

The transition to chaos in a microwave photonic generator has been experimentally studied for the first time, and the generated broadband chaotic microwave signal has been analyzed. The generator represented a ring circuit with the microwave tract containing a low-pass filter and a microwave amplifier. The optical tract comprised a fiber delay line. The possibility of generating chaotic oscillations with uniform spectral power density in a 3–8 GHz range is demonstrated.     

Controlled chaotic microwave generation under conditions of four-wave parametric interaction of surface spin waves

Controlled chaotic microwave generation under the conditions of four-wave parametric interaction of the surface spin waves has been experimentally studied in active resonance rings based on tangentially magnetized ferromagnetic films. It is shown that the chaotic microwave signal parameters can be effectively controlled.     

Experimental study of the effect of external signal on microwave oscillations in a nonrelativistic electron beam with virtual cathode

The effect of an external harmonic signal on the characteristics of microwave generation in a non-relativistic electron beam with virtual cathode (VC) formed in a static retarding electric field (low-voltage vircator system) has been experimentally studied. A significant increase in the vircator generation power is observed when the frequency of the external signal is close to the frequency of VC oscillations. At large detunings, a broadband chaotic generation is observed.     

Hyperbolic chaos generator based on coupled drift klystrons

A scheme of the generator of chaotic oscillations in the microwave band is proposed that is based on two drift klystrons coupled in a ring circuit. The first klystron doubles the frequency of the input signal and the second klystron mixes the second harmonic signal and the reference signal representing a periodic sequence of radio pulses filled with the third harmonic, followed by separation of the differential first harmonic signal. As a result, the transformation of the signal phase during the period of pulse repetition is described by a stretching map of the circle (Bernoulli map) and demonstrates chaotic behavior. Results of numerical calculations are presented that confirm the implementation of the proposed mechanism to ensure the generation of robust, structurally stable chaos in the system under consideration.     

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.     

Controlled stochastization of oscillations in a chaotic delayed-feedback system

A mathematical model of the ring autooscillatory system, which possesses chaotic dynamics and comprises a nonlinear amplifier with a differentiating element in the feedback chain, a nonlinear oscillatory circuit, and a delay line, is considered. Numerical analysis has been performed for irregularly varying initial conditions. These conditions were set by the solutions of equations describing chaos that simulated intrinsic noises of a real autooscillatory system. It is shown that the irregularly varying conditions of excitation can lead to stochastization of the chaotic oscillations, in which case the oscillatory process becomes irreproducible.     

Efficient generation of ultra broadband supercontinuum in a mid-infrared field

We theoretically investigate the generation of ultra broadband supercontinuum from helium atoms exposed to a linearly polarized mid-infrared field. By adopting a UV trigger pulse to the mid-infrared field, the continuous harmonic yields are significantly enhanced by 3.5 orders, and a supercontinuum with the width of 230?eV is observed. The spectrum can support a sub-20 as pulse, which is below one atomic unit of time (24 as). The short quantum path is selected by adjusting the time delay between the UV pulse and the mid-infrared pulse, then broadband single 70 as pulses with tunable central wavelengths are obtained, which can be extended to the ‘water window’ region (284–543?eV).     

Realization of a strange attractor of the Smale-Williams type in a radiotechnical delay-feedback oscillator

Based on a nonautonomous delay-feedback van der Pol oscillator, a radiotechnical circuit generating chaotic signals has been proposed and implemented, which alternatively occurs in the states of excitation and decay. This is ensured by the periodic variation of a parameter responsible for the bifurcation creating a limit cycle. The excitation of oscillations at every next activity stage is stimulated by a signal generated at the preceding stage and arriving via a delay line. Owing to a quadratic nonlinear transformation of the delayed feedback signal, the phase variable exhibits doubling at every excitation stage, which implies that the phase is subjected to circle-stretching mapping (Bernoulli mapping) with a chaotic dynamics.     

Parametric chaos in yttrium-iron garnet films grown from weakly dissociated solution melt

We present the results of a comparative study of the chaotic generation of parametric spin waves in yttrium-iron garnet (YIG) films grown from a standard solution melt and in the films grown from a weakly dissociated solution melt containing garnet ferrite and orthoferrite clusters. It is shown that the efficiency of magnetic chaos generation is significantly higher in the latter case.     

Chaotic microwave self-generation in active rings based on ferromagnetic films

The phenomenon of chaotic microwave self-generation under conditions of a four-wave parametric spin wave interaction in active resonance rings based on ferromagnetic films has been studied for the first time. It is shown that microwave signals of various types—in particular, monochromatic, stationary soliton-like pulse trains, and dynamic chaos—can be generated by controlling the gain level in the active ring. Parameters characterizing the chaotic signal generated in the ring are determined.     

Tunable generator of broadband chaotic microwave oscillations on turbulent electron beams

A new generator of broadband chaotic microwave oscillations of medium power on turbulent electron beams is proposed, in which it is possible to tune the generation regime. The characteristics of turbulent electron beams have been studied by experimental and theoretical methods. It is established that drag of the electron beam produces its turbulization, which leads to the generation of broadband chaotic microwave oscillations.     

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.     

Electronically controlled agile lens-based broadband variable photonic delay line for photonic and radio frequency signal processing

To the best of our knowledge, proposed for the first time is the design of an optically broadband variable photonic delay line (VPDL) using an electronically controlled variable focus lens (ECVFL), mirror motion, and beam-conditioned free-space laser beam propagation. This loss-minimized fiber-coupled VPDL design using micro-optic components has the ability to simultaneously provide optical attenuation controls and analog-mode high-resolution (subpicoseconds) continuous delays over a moderate (e.g., <5 ns) range of time delays. An example VPDL design using a liquid-based ECVFL demonstrates up to a 1 ns time-delay range with >10 dB optical attenuation controls. The proposed VPDL is deployed to demonstrate a two-tap RF notch filter with tuned notches at 854.04 and 855.19 MHz with 22.6 dB notch depth control via VPDL attenuation control operations. The proposed VPDL is useful in signal conditioning applications requiring fiber-coupled broadband light time delay and attenuation controls.     

Chaos generators based on yttrium-iron garnet films for communication systems with a chaotic synchronous response

This Letter reports the development of a directly chaotic communication system, in which chaos generators are used that are based on yttrium-iron garnet (YIG) films. YIG-based chaos generators provide a stable chaotic synchronous response and almost ideal masking of the signal with high communication reliability and quality. Characteristics of these generators are compared with conventional chaos generators.     

Spatiotemporal chaos synchronization in beam-plasma systems with supercritical current

It is established that coupled beam-plasma systems with supercritical current can feature the phenomenon of chaotic synchronization. As the coupling between subsystems increases, a distributed beam-plasma system exhibits the transition from asynchronous behavior via phase synchronization to the state of complete chaotic synchronization. The phenomenon of chaotic synchronization is studied using a method developed previously on the basis of the introduction of a continuous manifold of phases of the chaotic signal.     

Correlation effects of chaotic and phase-diffusion fields on polarization beats in a V-type three-level system

Abstract

The correlation effects of fourth-order on polarization beats in a V-type three-level system (PBVTS) are investigated using chaotic and phase-diffusion models. It has been found that the temporal behaviour of the beat signal depends on the stochastic properties of the lasers and transverse relaxation rate of the transitions, and the modulation terms of the beat signal depend on the second-order coherence function, which is determined by the laser line shape. Since different stochastic models of the laser field affect only the fourth-order coherence function, they have little influence on the general temporal modulation behaviour of the beat signal. The different roles of the phase fluctuation and amplitude fluctuation have been pointed out in the time domain. The fourth-order coherence function theory of chaotic field is of vital importance in PBVTS. The cases where the pump beams have either narrow band or broadband linewidth are considered and it has been found that for both cases a Doppler-free precision in the measurement of the energy-level splitting between two states can be achieved. Finally, the difference between the PBVTS and DeBeer's ultrafast modulation spectroscopy is discussed as well from a physical viewpoint.     

Chaotic scattering of waves from nonlinear scatterers

Summary Two examples of the effect of nonlinearities on the scattering of nondispersive waves are presented. It is shown that nonlinear boundary conditions can lead to broadband, chaotic scattered waves when the scatterer is excited by a single wavelength plane wave. One of the examples treats a spherical scatterer in a linear elastic medium. A number of modern techniques in nonlinear analysis is used to diagnose the chaotic dynamics including Poincaré maps, fractal dimensions and Lyapunov exponents.