Parametric Wave Interaction Research Articles

Topological edge solitons in χ(2) waveguide arrays.

We address the formation of χ(2) topological edge solitons emerging in a topologically nontrivial phase in Su-Schrieffer-Heeger (SSH) waveguide arrays. We consider edge solitons, whose fundamental frequency (FF) component belongs to the topological gap, while the phase mismatch determines whether the second harmonic (SH) component falls into topological or trivial forbidden gaps of the spectrum for the SH wave. Two representative types of edge solitons are found, one of which is thresholdless and bifurcates from the topological edge state in the FF component, while the other exists above a power threshold and emanates from the topological edge state in the SH wave. Both types of soliton can be stable. Their stability, localization degree, and internal structure strongly depend on the phase mismatch between the FF and SH waves. Our results open up new prospects for the control of topologically nontrivial states by parametric wave interactions.

Competing processes in generation of the third optical harmonic in air under femtosecond infrared repetitively pulsed excitation

Parametric interaction of electromagnetic and gravitational waves with the radiation generation at the third harmonic wavelength is one of the ways to detect gravitational interaction in a material medium. To implement the effect in question, superstrong fields must be used, but in this case competing nonlinear processes arise, leading to the generation of the third harmonic as a result of laser radiation filamentation. This paper investigates the characteristics of the radiation recorded for femtosecond (250 fs) laser pulses with a wavelength of λ = 1032 nm focused in air. The threshold pump power made it possible to observe the formation of a filament with concomitant generation of narrow-band radiation at the focus of the lens at the third harmonic wavelength λ = 344 nm. The research presents spectral and spatial dependences of ultraviolet radiation (λ = 344 nm) at pumping power of infrared radiation (λ = 1032 nm) of 500 mW. Energy dependences of the third harmonic generation efficiency in the power range from 150 to 1750 mW are obtained.

Generation of harmonics and degenerate parametric interaction of longitudinal acoustic waves in solids with quadratically-bimodular nonlinearity

The theoretical study by the perturbation method of the acoustic effects at the degenerate parametric interaction of a strong high-frequency and a weak low-frequency longitudinal elastic waves in microinhomogeneous solids with a quadratically-bimodular nonlinearity is presented. The amplitude dependences for the following nonlinear effects are revealed and analyzed: generation of second and fourth harmonics of the strong high-frequency wave and changes in the amplitude (amplification or weakening) of the weak low-frequency wave under the action of the strong high-frequency wave. It is noted that the experimental study of these effects can be used to determine nonlinear parameters of such solids.

Frequency transformation of ultrafast laser pulses in metamaterials

The nonstationary parametric interaction of waves in negative-index metamaterials is studied in the second-order dispersion theory. A nonlinear interaction between a long pulse of a strong pump wave and an ultrashort pulse with quadratic phase modulation is considered. The results of calculating the shape of the spectrum of an excited signal wave are presented. A comparison is made with the case of interaction in an ordinary medium. It is shown that the effects of group-velocity dispersion and dispersive spreading in such materials lead to a narrowing of the spectrum of the excited wave. The presence of phase modulation of the exciting idler pulse promotes broadening of the central maximum of the spectrum of the excited signal wave. As the modulation factor increases, the fragmentation of the excited pulse is observed.

Self-Generation of Chaotic Microwave Signal in Spin Wave Optoelectronic Generator

The self-generation of a chaotic microwave signal in a spin-wave optoelectronic generator has been experimentally investigated for the first time. The generator was a ring circuit, in the microwave path of which there was a spin-wave delay line on the film of an yttrium iron garnet (YIG) and a microwave amplifier. The optical path contained a fiber optic delay line. The nonlinear element of the generator was a film of YIG, which worked under the conditions of four-wave parametric interaction of spin waves. It has been shown that it is possible to generate monochromatic, periodic, quasi-periodic, and chaotic microwave signals by controlling the gain coefficient of the ring. The parameters characterizing the chaotic signal that are generated by the ring have been determined.

Explosive Instability of Gravity-Capillary Waves under Ultrasound Radiation Pressure

The parametric interaction of ultrasonic and gravity-capillary waves (GCWs) on a liquid surface has been investigated. Harmonic modulation of the intensity of a plane ultrasonic wave incident on the liquid surface from the depth provides nonlinear parametric coupling of GCW wave triads. We determined the resonance conditions, providing spatiotemporal synchronism of interacting waves, and the threshold ultrasound intensities, at which an explosive-type instability develops in the system of standing and traveling GCWs.

Difference frequency generation of narrow-band THz radiation on the basis of a parametric three-wave interaction in a ZnTe crystal

We consider theoretically difference frequency generation of terahertz (THz) radiation in a collinear one-chip scheme with distributed feedback realized by the parametric interaction of optical waves in a periodically inhomogeneous zinc telluride (ZnTe) crystal with a quadratic nonlinearity. In the approximation of inexhaustible optical pumping at a wavelength λ=0.77μm, the possibility of obtaining a parametric generation with high-efficiency optical-THz conversion (more than 10−2 at temperature 80 K) is shown with an extremely narrow generation line of less than 0.01 THz. The conversion efficiencies at temperatures 80, 200 and 295 K are studied. The obtained results can be used to construct narrow-band THz lasers with a power of about 105 W/cm2 in the quasi-continuous generation regime.

Parametric excitation of very low frequency (VLF) electromagnetic whistler waves and interaction with energetic electrons in radiation belt

The concept of a parametric antenna in ionospheric plasma is analyzed. Such antennas are capable of exciting electromagnetic radiation fields, specifically the creation of whistler waves generated at the very low frequency (VLF) range, which are also capable of propagating large distances away from the source region. The mechanism of whistler wave generation is considered a parametric interaction of quasi-electrostatic whistler waves (also known as low oblique resonance (LOR) oscillations) excited by a conventional loop antenna. The interaction of LOR waves with quasi-neutral density perturbations in the near field of an antenna gives rise to electromagnetic whistler waves on combination frequencies. It is shown in this work that the amplitude of these waves can considerably exceed the amplitude of whistler waves directly excited by a loop. Additionally, particle-in-cell simulations, which demonstrate the excitation and spatial structure of VLF waves excited by a loop antenna, are presented. Possible applications including the wave-particle interactions to mitigate performance anomalies of low Earth orbit satellites, active space experiments, communication via VLF waves, and modification experiments in the ionosphere will be discussed.

Автогенерация хаотического СВЧ-сигнала в спин-волновом оптоэлектронном генераторе

Abstract —The self-generation of a chaotic microwave signal in a spin-wave optoelectronic generator has been experimentally investigated for the first time. The generator was a ring circuit, in the microwave path of which there was a spin-wave delay line on the film of an yttrium iron garnet (YIG) and a microwave amplifier. The optical path contained a fiber optic delay line. The nonlinear element of the generator was a film of YIG, which worked under the conditions of four-wave parametric interaction of spin waves. It has been shown that it is possible to generate monochromatic, periodic, quasi-periodic, and chaotic microwave signals by controlling the gain coefficient of the ring. The parameters characterizing the chaotic signal that are generated by the ring have been determined.

Two-color walking Peregrine solitary waves.

We study the extreme localization of light, evolving upon a non-zero background, in two-color parametric wave interaction in nonlinear quadratic media. We report the existence of quadratic Peregrine solitary waves, in the presence of significant group-velocity mismatch between the waves (or Poynting vector beam walk-off), in the regime of cascading second-harmonic generation. This finding opens a novel path for the experimental demonstration of extreme rogue waves in ultrafast quadratic nonlinear optics.

Parametric interaction of optical waves in metamaterials under low-frequency pumping

The influence of phase effects under three-wave parametric interaction and low-frequency pumping in metamaterials is studied in the case of a negative refractive index at a signal-wave frequency. It is found that the efficiency of the backward signal-wave amplification is the higher, the greater the ratio of the intensities of the idler and signal waves at the input to the metamaterial. An increase in the idler wave intensity at the input by five times, as compared to the signal-wave intensity, leads to a nonlinear increase in the signal-wave amplification by almost 20 times. According to the analytic expressions obtained in the constant-intensity approximation, the choice of the optimal parameters for the pump intensity, total length of the metamaterial and phase detuning will facilitate the implementation of regimes of effective amplification and generation of the signal wave. A comparison is made with the results obtained in the constant-field approximation, and a numerical estimate of the expected efficiency of the frequency conversion is presented. Control of frequency and pump power is shown to make possible the smooth tuning of the parametric converter frequency. The developed method can be used to design frequency converters based on nonlinear metamaterials.

Transient processes in the parametric interaction of counter-propagating waves

We present a comparative analysis of transient processes in media with a negative refractive index for the parametric interaction of co- and counter-propagating waves. The transient time for the interaction of counter-propagating waves is shown to considerably exceed that for the interaction of co-propagating waves. In the case of counter-propagating waves, we present fitting results for the generated wave amplitude as a function of time and for the transient time vs. the amplitude of the pump wave and the length of the medium.

Nonlinear wave interactions in modern photonics

One of the main factors impeding further progress in the field of application of met materials is significant energy losses due to the physical nature of exploited plasmon resonance, and their compensation is the most urgent problem to be addressed by the modern science of met materials. That is why this paper studies the parametric interaction of electromagnetic waves and, in particular, the process of generation and amplification of the second harmonic generation in met materials with the negative refractive index. It is found that the fundamental waves in the process of the second harmonic generation cannot exchange energy through the second harmonic wave at the non-collinear phase matching, and, thus, further consideration is required of optical rectification of the field in the nonlinear met materials.

Parametric interaction of acoustic waves in a resonant nonlinear layer

The degenerate parametric interaction of acoustic waves in a nonlinear resonator (plane-parallel layer placed into an external linear medium and irradiated by primary harmonic waves with frequencies ω and 2ω incident along the normal) is investigated. The amplitudes of secondary waves at combination frequencies ω and 3ω in the external media are determined. The method for determining the nonlinearity parameter of the medium in the layer is considered; the method is based on measuring the amplitude of the secondary wave at frequency ω or 3ω, which is emitted by the layer into the external medium in the forward or reverse (relative to the direction of propagation of primary waves) direction.

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.

Parametric wave interaction in media exhibiting quadratic and cubic nonlinearities under high-frequency pumping conditions

Specific features of parametric interaction in media exhibiting quadratic and cubic nonlinearities under conditions of high-frequency pumping and nonzero detuning from the phase matching are analyzed. It is shown that the presence of two types of nonlinearities and frequency detuning broaden the possibilities of controlling the dynamics of the forming partial pulses by changing the pump power. The possibility of the signal and idler waves’ decay into four frequency-modulated partial wave packets with different values of chirp and velocities of their envelope maximum is established. The envelope maximum velocities of the partial pulses, as well as their walk-off velocities, can reach values exceeding the speed of light in vacuum.

Parametric interaction of acoustic waves in micro-inhomogeneous media with hysteretic nonlinearity and relaxation

A theoretical investigation of parametric processes that arise as a result of the interaction of powerful and weak longitudinal acoustic waves in micro-inhomogeneous media with hysteretic nonlinearity and relaxation was carried out. The case of degenerate interaction between a powerful high-frequency wave and a weak low-frequency one was considered. The nonlinear damping coefficient and the carrier frequency phase delay of the weak wave propagating under the action of the powerful wave were determined.

Parametric wave interaction in one-dimensional nonlinear photonic crystal with randomized distribution of second-order nonlinearity

We theoretically study the parametric wave interaction in nonlinear optical media with randomized distribution of the quadratic nonlinearity \(\chi ^{(2)}\). In particular, we discuss the properties of second and cascaded third harmonic generation. We derive analytical formulas describing emission properties of such harmonics in the presence of \(\chi ^{(2)}\) disorder and show that the latter process is governed by the characteristics of the constituent processes, i.e. second harmonic generation and sum frequency mixing. We demonstrate the role of randomness on various second and third harmonic generation regimes such as Raman–Nath and Cerenkov nonlinear diffraction. We show that the randomness-induced incoherence in the wave interaction leads to deterioration of conversion efficiency and angular spreading of harmonic generated in the processes relying on transverse phase matching such as Raman–Nath interaction. On the other hand, the Cerenkov frequency generation is basically insensitive to the domain randomness.

Broadband cascading of second-order nonlinearity in randomized nonlinear photonic crystal

We study both experimentally and theoretically optical parametric process in one-dimensional nonlinear photonic crystal with random variation to the sign of the second-order nonlinear coefficient. We demonstrate that the structure randomness enables broadband third-harmonic generation via cascading of two second-order nonlinear parametric wave interactions with the overall conversion efficiency higher than previously recorded in fully disordered media such as the as-grown strontium barium niobate crystal. Furthermore, thanks to the one-dimensional modulation of the second-order nonlinearity, the emitted broadband harmonics preserve well the spatial intensity profile of the incident fundamental light beam, a feature critical for applications of optical frequency conversion but unavailable in two-dimensional fully random media due to the beam divergence caused by the simultaneous emission of noncollinear harmonic.

Third harmonic generation in the field of a backward pump wave

Third harmonic generation in a nonlinear medium the refractive index of which is negative at the pump frequency and positive at the harmonic frequency with allowance for self-action effects is considered theoretically. An exact solution of equations that describe the parametric interaction of continuous waves has been obtained analytically. The behavior of the solution is analyzed depending on the degree of violation of the phase matching condition. It is shown that, in a definite domain of values of nonlinear susceptibilities of the third order, there exists a critical value of the phase detuning at which the monotonic transform of the pump into the harmonic is changed by a periodical one. This phenomenon does not occur when the third harmonic is generated in ordinary media with a positive refractive index.