Influence of high-frequency electromagnetic radiation on the de Haas–van Alphen effect in graphene

The differential magnetic susceptibility of graphene exposed to high-frequency electromagnetic radiation is calculated. The period of the quantum oscillations of magnetic susceptibility is determined for low temperatures. The period of such oscillations is shown to depend on the amplitude of the electromagnetic radiation.     

Direct Transformation of a Video Pulse into a Radio Pulse in Coupled Transmission Lines with Normal and Anomalous Dispersion

We consider generation of high-frequency oscillations by an electromagnetic shock wave propagating under synchronism with the backward wave in coupled transmission lines having normal and anomalous dispersion and ferrite-based nonlinear elements. It is shown that the amplitude attenuation of generated oscillations can be significantly reduced due to an increase in the fraction of high-frequency energy flux in the anomalous-dispersion transmission line in which high-frequency losses are relatively low.     

光受激发射的稳定性

本文推导出描述三能级Laser工作过程的准经典方程组,并分析了输出振动的稳定性。在阈值以上,当T₁?T₂,q^-1时,只在1/(qT₂)>1时,输出振幅是稳定的(其中T₁,T₂,q^-1分别是分子纵向、横向及谐振腔的弛豫时间)。在稳定区域,趋向平衡的时间与T₁成正比。当分子线宽小于谐振腔宽度时,输出是不稳定的,而在1/(qT₂)减小时,平衡点由稳定变到不稳定时产生一个稳定的极限环,即输出振幅逐渐开始振动。关于稳定性的结论在气体Laser中是可以检验的。本文指出,在红宝石Laser中看到的输出不稳定,可能就是谐振腔的q很大的结果。     

Influence of local dispersion on transient processes accompanying the generation of rf radiation by an electromagnetic shock wave

Transient processes accompanying the conversion of a video pulse into a radio pulse in a nonlinear transmission line having hysteretic properties are studied. It is established that the transition process leading to the establishment of “steady-state” (close in amplitude) oscillations has a minimum when the electromagnetic shock wave front is phase-matched with the wave excited by it at a frequency near the minimum local dispersion of the group velocity. Zh. Tekh. Fiz. 68, 89–95 (January 1998)     

Electromagnetic emission of a strongly charged oscillating droplet

Analytical expressions for electric field in the vicinity of an oscillating strongly charged droplet of nonviscous conducting liquid and intensity of electromagnetic radiation are derived in the linear approximation with respect to perturbation amplitude of the droplet surface. Order-of-magnitude estimations of the radiation intensity are presented. The intensity of electromagnetic radiation of a ball lightning that can be simulated using a charged droplet is not related to the surface oscillations.     

Resonant interaction of an electromagnetic wave with an inhomogeneous plasma slab

Resonant interaction at oblique incidence of an electromagnetic wave on an inhomogeneous plasma slab is studied. The time evolution of this interaction is solved numerically from two-fluid equations, adiabatic equation for electron pressure and from Maxwell equations. It is shown that the electromagnetic energy of an incident wave is transformed both into the heat energy and into the energy of plasma oscillations in the direction of density gradient. The distribution of the transformed energy between the heat energy and the energy of plasma oscillations is strongly dependent on the plasma temperature. The ratio of heat energy to the energy of plasma oscillations is growing with growing temperature. The plasma oscillations are generated by magnetic induction of the penetrating wave. In a cold plasma they are generated especially in the overdense region and their frequency is equal to local plasma frequency. The electric field in the direction of plasma gradient has a form of a wave packet whose envelope reaches a maximum at resonance. The characteristic wavelength in the wave packet decreases and the amplitude of the packet increases with the time.     

Nonlinear Theory of the Instability of a Modulated Electron Beam of Low Density in a Plasma. I. Conservation Laws of Energy and Momentum for Electromagnetic Waves in a Nonequilibrium Dispersive and Dissipative Medium in the Case of a Slow Change of Amplitude and Phase of the Wave

A formula is given for the energy and momentum conservation laws for a narrow spectrum of electromagnetic waves in an unstable dispersive and dissipative medium by any level of dissipation and on condition that the amplitude and phase change slowly in the time and space period of oscillations. It is shown that the density of energy and momentum of the motion of resonant particles, connected with the propagation of the electromagnetic wave, generally cannot be expressed by the dielectric function of the unstable system. For example it is demonstrated that the well known Landau formula for determining the density of the wave energy in a unstable monoenergetic beam-plasma system in general is not applicable as it is often done in literature.     

Terahertz electromagnetic radiation from quantum wells

The observation of terahertz electromagnetic dipole radiation from quantum well structures has finally proven the existence of charge oscillations in semiconductors associated with wave packet dynamics. This article closely examines the physics behind the emission of terahertz electromagnetic radiation from excitonic charge oscillations in such quantum well structures, points out similarities and differences between the various generation schemes, and discusses the various relaxation mechanisms involved. Finally, we show how both amplitude and phase of charge oscillations and the corresponding terahertz emission can be manipulated using phase-locked optical pulses.     

Quadrupole electromagnetic radiation of an oscillating charged droplet

Analytical calculations using the first order of smallness with respect to dimensionless amplitude of oscillations show that the intensity of electromagnetic radiation of a charged droplet is determined by time-dependent quadrupole moment.     

Coherent summation of power of nanosecond relativistic microwave oscillators

The possibility of developing a two-channel nanosecond relativistic microwave oscillator with a phase stability in each channel sufficient for coherent summation of their electromagnetic fields is demonstrated experimentally. In experiments, vacuum diodes of two independent superradiant backward wave oscillators operating in 10-GHz frequency range were connected to a common voltage source with a subnanosecond pulse rise time, which ensured the fixation of the initial phase of electromagnetic oscillations. The measured values of the phase difference jitter of the channel electromagnetic oscillations amount to several percent of the oscillation period.     

Excitation of the Morse oscillator by an ultrashort chirped pulse

The excitation of the classic Morse oscillator by an ultrashort electromagnetic pulse with a linear frequency chirp is studied theoretically. Formulas are derived for the oscillation amplitude and the radiation power averaged over a period as functions of the excitation energy for free oscillations of the Morse oscillator. Analytical expressions for describing the oscillator motion after the end of the pulse are obtained in the harmonic limit. In the general case of arbitrary parameters of the problem, the specific features of an excited Morse oscillator are analyzed numerically. Prominence is given to the effect of chirp on the excitation energy. The consideration is performed in terms of dimensionless variables, which makes it possible to apply the results obtained to a wide range of molecular systems and exciting-pulse parameters.     

Equivalent damping and frequency change for linear and nonlinear hybrid vibrational energy harvesting systems

A unified approximation method is derived to illustrate the effect of electro-mechanical coupling on vibration-based energy harvesting systems caused by variations in damping ratio and excitation frequency of the mechanical subsystem. Vibrational energy harvesters are electro-mechanical systems that generate power from the ambient oscillations. Typically vibration-based energy harvesters employ a mechanical subsystem tuned to resonate with ambient oscillations. The piezoelectric or electromagnetic coupling mechanisms utilized in energy harvesters, transfers some energy from the mechanical subsystem and converts it to an electric energy. Recently the focus of energy harvesting community has shifted toward nonlinear energy harvesters that are less sensitive to the frequency of ambient vibrations. We consider the general class of hybrid energy harvesters that use both piezoelectric and electromagnetic energy harvesting mechanisms. Through using perturbation methods for low amplitude oscillations and numerical integration for large amplitude vibrations we establish a unified approximation method for linear, softly nonlinear, and bi-stable nonlinear energy harvesters. The method quantifies equivalent changes in damping and excitation frequency of the mechanical subsystem that resembles the backward coupling from energy harvesting. We investigate a novel nonlinear hybrid energy harvester as a case study of the proposed method. The approximation method is accurate, provides an intuitive explanation for backward coupling effects and in some cases reduces the computational efforts by an order of magnitude.     

Complex mixed-mode periodic and chaotic oscillations in a simple three-variable model of nonlinear system

A detailed study of a generic model exhibiting new type of mixed-mode oscillations is presented. Period doubling and various period adding sequences of bifurcations are observed. New type of a family of 1D (one-dimensional) return maps is found. The maps are discontinuous at three points and consist of four branches. They are not invertible. The model describes in a qualitative way mixed-mode oscillations with two types of small amplitude oscillations at local maxima and local minima of large amplitude oscillations, which have been observed recently in the Belousov-Zhabotinsky system. (c) 2000 American Institute of Physics.     

Oscillations of a spin in a circular orbit in the schwarzschild and Lense-Thirring metrics

A gyroscope in motion along a circular geodesic line oscillates with respect to a reference body because of the variability of the inclination of its orbit. Due to precession of the spin vector, these oscillations have the appearance of beats whose frequency is close to that of the orbital motion, and whose amplitude changes with a large period, so that the amplitude increases linearly during a long time. This phenomenon can be detected using symmetrical oscillations of gyroscopes with opposite spin vectors in an orbit around the Earth, or by observing the evolution of a planet orbit in the solar system.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 68–70, November, 1982.The author is thankful to Yu. S. Vladimirov and N. V. Mitskevich for their discussion of the results.     

On the fictitious nonlinearity of the surface impedance of the Earth’s crust

The observations of Alfvén oscillations of the magnetosphere are used to study the Earth’s crust and upper mantle by the magnetotelluric sounding method. The sounding procedure involves the measurement of the horizontal components of the electromagnetic field at a given point on the ground, the calculation of the surface impedance, and the determination of the conductivity of rocks from these data. It has been shown that the anharmonicity of the oscillations of the magnetosphere in combination with the nonlocality of the boundary condition on the ground gives rise to the amplitude dependence of the impedance calculated using the classical magnetotelluric sounding method. This apparent nonlinearity of the impedance can be manifested in the sounding of the Earth’s interior with intense electromagnetic pulsations, which appear when the Earth’s magnetosphere is embedded in the highspeed solar wind flow.     

Effect of the Excitation Radiation Coherence on Oscillations of the Photon Echo Intensity

The physical reasons for observing the splitting of optical lines several orders of magnitude smaller than the spectral width of a laser pulse are investigated. A theory of coherent and incoherent photon echo (PE) in an external static magnetic field and in the presence of a pulsed magnetic field, which causes oscillations of the PE intensity, is elaborated. It is shown that the periods of oscillations in the echo intensity, the echo duration, and the dimensions of the regions in the inhomogeneous line, where the excited ions are coherent, do not depend on the degree of coherence of the laser pulse and on the external static magnetic field. As follows from the theory, in the case of the coherent excitation of the echo, the amplitude of the intensity oscillations is independent of the external static magnetic field if the inhomogeneous line is symmetric. It is shown that the amplitude of the oscillations at the incoherent excitation of the echo is equal to the autocorrelation function of the distribution function of the transition frequency along the inhomogeneous line with the argument equal to the Zeeman splitting of the optical line in the external magnetic field. In this case, the experimental values of the oscillation amplitude are in good agreement with the calculated values of the autocorrelation function for the total inhomogeneous line in LuLiF₄:Er³⁺ (⁴I_15/2?F_9/2 transition). In the same way, the autocorrelation function has been obtained for YLiF₄:Er³⁺ on the same transition.     

Nonlinear non-spherical oscillations of gas bubble under a periodic variation of ambient liquid pressure

A mathematical model is constructed for the bubble dynamics, in which the interphase surface variation is presented in the form of a series in spherical harmonics, and the equations are written with the accuracy up to the squared amplitude of the distortion of the spherical shape of the bubble. In the oscillation regimes close to periodic sonoluminescence of a single bubble in a standing acoustic wave, the character of air bubble oscillations in water was studied depending on the bubble initial radius and the amplitude of the liquid pressure variation. It was found that non-spherical oscillations of bounded amplitude can take place outside the region of linearly stable spherical oscillations. Both the oscillations with a period equal to one or several periods of the liquid pressure variation and aperiodic oscillations are observed. It is shown that neglecting the distortions in the form of spherical harmonics with large numbers (i > 3) may lead to a change of oscillation regimes. The influence of distortions on the bubble surface shape for the harmonics with i > 8 is insignificant.     

The Dynamics of a Field in a Cavity with a Slowly Oscillating Metal Mirror

We have examined analytically the behavior of an electromagnetic field in a cavity of one of two metal mirrors that is stationary, while the other mirror oscillates in the vicinity of its equilibrium position. The case in which the period of the mirror oscillations substantially exceeds the characteristic roundtrip time of the electromagnetic radiation in the cavity has been considered. To solve the problem, we have applied the method of two time scales. The method makes it possible to solve the problem by using the expansion with respect to a small parameter, for which the ratio of the cavity roundtrip time to the mirror-oscillation period is used. The solution to the problem in the zeroth-order approximation with respect to the small parameter has been obtained and examined. This solution has been shown to be correct up to the mirror-oscillation amplitude being on the order of the average cavity length. We have showed that this scheme can be used to gain and generate electromagnetic radiation. We have compared our results obtained for the oscillating mirror with the results of an exact solution of the problem when the mirror moves uniformly and rectilinearly. We have showed that, in these two cases, a change in the total field energy in the cavity is inversely proportional to the current value of the cavity length.     

Parametric resonance in neutrino oscillations in periodically varying electromagnetic fields

It is shown that a parametric resonance may arise in neutrino oscillations in varying electromagnetic fields. For two types of electromagnetic fields—an amplitude-modulated electromagnetic wave and a transverse magnetic field that is constant in time, but which has an amplitude periodically varying in space—the probabilities of the ν _i ? ν _j neutrino transitions are found, and it is shown that the probability amplitudes increase with time for a specific choice of the parameters of external electromagnetic fields.     

Interaction-enhanced double resonance in cold gases

A new type of double-resonance spectroscopy of a quantum gas based on interaction-induced frequency modulation of a probe transition has been considered. Interstate interaction of multilevel atoms causes a coherence-dependent collisional shift of the transition between the atomic states |1〉 and |2〉 due to a nonzero population of the state |3〉. Thus, the frequency of the probe transition |1〉?|2〉 experiences oscillations associated with the Rabi oscillations between the states |1〉 and |3〉 under continuous excitation of the drive resonance |1〉?|3〉. Such a dynamic frequency shift leads to a change in the electromagnetic absorption at the probe frequency and, consequently, greatly enhances the sensitivity of double-resonance spectroscopy as compared to traditional “hole burning”, which is solely due to a decrease in the population of the initial state |1〉. In particular, it has been shown that the resonance linewidth is determined by the magnitude of the contact shift and the amplitude of the drive field and does not depend on the static field gradient. The calculated line shape and width agree with the low-temperature electron-nuclear double-resonance spectra of two-dimensional atomic hydrogen.