Self-induced Transparency Effect Research Articles

Nonlinear-Optical Analogies in Nuclear-Like Soliton Reactions: Selection Rules, Nonlinear Tunneling and Sub-Barrier Fusion–Fission

Abstract The main goal of our study is to reveal unexpected but intriguing analogies arising between optical solitons and nuclear physics, which still remain hidden from us. We consider the main cornerstones of the concept of nonlinear optics of nuclear reactions and the well-dressed repulsive-core solitons. On the base of this model, we reveal the most intriguing properties of the nonlinear tunneling of nucleus-like solitons and the soliton self-induced sub-barrier transparency effect. We describe novel interesting and stimulating analogies between the interaction of nucleus-like solitons on the repulsive barrier and nuclear sub-barrier reactions. The main finding of this study concerns the conservation of total number of nucleons (or the baryon number) in nuclear-like soliton reactions. We show that inelastic interactions among well-dressed repulsive-core solitons arise only when a “cloud” of “dressing” spectral side-bands appears in the frequency spectra of the solitons. This property of nucleus-like solitons is directly related to the nuclear density distribution described by the dimensionless small shape-squareness parameter. Thus the Fourier spectra of nucleus-like solitons are similar to the nuclear form factors. We show that the nuclear-like reactions between well-dressed solitons are realized by “exchange” between “particle-like” side bands in their spectra.

Self-induced transparency in a perfectly absorbing chiral second-harmonic generator

Transparency and perfect absorption are two contradictory terms; a perfect absorber never permits waves to transmit through. However, this statement only remains true in the linear regime, where the nonlinearity has been omitted and the physical system like the perfect absorber is not affected by the incoming waves. Here we experimentally demonstrate an intriguing self-induced transparency effect in a perfectly absorbing optical microcavity, which perfectly absorbs any incoming waves at the low power level, but allows a portion of waves to be transmitted at the higher power due to the nonlinear coupling between the fundamental and its second harmonic modes. Moreover, the asymmetric scattering nature of the microcavity enables a chiral and unidirectional reflection in one of the input ports, this leads to asymmetric and chiral coherent control of the perfect absorption states through phase varying. More importantly, such chiral behaviors also empower the chiral emission of second-harmonic generation with a high distinct ratio in the transparency state. These results pave the way for controllable transparency in a wide range of fields in optics, microwaves, acoustics, mechanics, and matter waves.

Coherent brightening of a multilayer MQW− structure taking into account resonant tunneling for ultra-short IR pulses in a transverse electric field

The features of the effect of self-induced transparency (SIT) in a multi-well M Q W − structure with two working levels in quantum wells (QWs) in a transverse electric field are considered. The cycle of energy exchange between an ultrashort pulse and the resonant medium of two-level systems, which leads to coherent bleaching of the M Q W − structure, is complicated by resonant tunneling between the size-quantization levels of neighboring QWs. The behavior of a radiation pulse during the propagation of two-level QWs in a resonant medium in the self-transparency regime is analyzed. Analytical dependences of various branches of evolution and possible transition conditions between branches for propagating pulses are demonstrated. Practical possibilities are pointed out for deforming the envelope profile and the duration of the radiation pulse by varying the strength of the applied external electric field. The direct possibility for such controlled manifestations of the SIT effect as propagation without absorption, pulse delay, and variation of the observability threshold is emphasized. • The features of the self-induced transparency (SIT) effect in a multi-well MQW-structure with two working levels in quantum wells (QWs) are considered. • The structure is placed in a transverse electric field directed perpendicularly to the vertical walls of the QW, which ensures that the ground level of one well coincides with the energy of the excited level of the neighboring well. • The cycle of energy exchange between an ultra-short pulse and the resonant medium of two-level system is complicated by the processes of resonant tunneling between the quantum-confinement levels of neighboring QWs. • The behavior of a radiation pulse during propagation of two-level QWs in a resonant medium is analyzed taking into account resonant tunneling between neighboring QWs in the self-transparency mode.

Optical resonance in the inversion [formula omitted] channel of a silicon MOS structure

The features of the manifestation of the self-induced transparency (SIT) effect at intersubband resonance in the inversion n− layer of silicon semiconductor systems (in field-effect transistors (100)Si−MOSFET) are analyzed. The course of the interaction of ultrashort laser pulses with the quantum states of the inversion layer of the MOS structure varies, depending on the concentration of the induced charge, by changing the voltage across the metal gate. The evolution of a pulse in the transient stage of deformation as it propagates in a resonant medium of an inversion channel is discussed. Possible consequences for a non-degenerate one-photon resonance are considered, with controlled changes in the detuning between a fixed pulse frequency and the resonant energy of the intersubband transition, caused by changes in the charge density. The parametric dependence on the concentration of the induced charges in the “area theorem” for the propagation process in the inversion channel is revealed.

Entrainment, stopping, and transmission of microwave solitons of self-induced transparency in counter-propagating magnetized electron beam.

Based on numerical simulations of a boundary problem, we study various scenarios of microwave soliton formation in the process of cyclotron resonance interaction of a short electromagnetic pulse with a counter-propagating initially rectilinear electron beam taking into account the relativistic dependence of the cyclotron frequency on the electrons' energy. When a certain threshold in the pulse energy is exceeded, the incident pulse can propagate without damping in the absorbing beam, similar to the effect of self-induced transparency in optics. However, mutual motion of the wave and electrons can lead to some novel effects. For relatively small energy of the incident pulse, the microwave soliton is entrained by the electron beam opposite to the direction of the wave's group velocity. With an increase in the pulse energy, soliton stopping occurs. This regime is characterized by the close-to-zero pulse velocity and can be interpreted as a variety of the "light stopping." High-energy microwave solitons propagate in the direction of the unperturbed group velocity. Their amplitude may exceed the amplitude of the incident pulse, i.e., nonlinear self-compression takes place. A further increase in the incident energy leads to the formation of additional high-order solitons whose behavior is similar to that of the first-order ones. The characteristics of each soliton (its amplitude and duration) correspond to analytical two-parametric soliton solutions that are to be found from consideration of the unbounded problem.

Self-induced transparency in a system of resonant–quasiresonant transitions

The effect of self-induced transparency is investigated for a three-level system with a V-scheme of the allowed transitions in the case where one of the transitions is resonant while another one is quasiresonant. The generalized system of the wave and material equations for the resonant transition, taking into account the presence of a quasiresonant transition, is derived. This system is integrable, and its soliton solutions are investigated. It is shown that quasiresonant transition has an influence on the profile of the optical soliton and leads to its phase modulation. The conditions under which the propagation of the soliton is followed by the full inversion of the populations of quantum levels of the resonant transition are established.

Self-Induced Transparency of Few-Cycle Terahertz Pulses

A new integrable system of equations that describes the effect of self-induced transparency for few-cycle terahertz pulses propagating in a system of resonant tunnel transitions is obtained. This system is derived within an approach based on the concept of envelopes for the electric field of a pulse and dipole moments of resonant and nonresonant transitions involved in the interaction with it. This approach makes it possible to describe solitons, whose velocity can be much less than the linear group velocity of light in the medium. This distinguishes it favorably from the method in which the concept of envelopes is not used but the density of the medium is assumed to be low.

Effect of Self-Induced Transparency in a Massive of Spherical Quantum Dots Under the Conditions of Strong Dimensional Quantization

The influence of dimensional quantization on the process of self-induced transparency in the system of spherical quantum dots in the frames of the model of the simplest interband transition in the symmetrical spherical infinitely deep wall is considered. Expressions describing the evolution of the energy of ultraviolet pulses are obtained. The relative energy losses when it becomes the 2π-pulse during propagation in a nanoscale medium, and also the polarization of the medium of non-homogeneous broadening, caused by the dispersion of radius of spherical quantum dots are obtained. The case when the radial distribution is described by the Lifshitz-Slyozov formula is considered.

Mode Locking in a Ti:Sapphire Laser by Means of a Coherent Absorber

The regime of passive mode locking in a Ti:sapphire laser with a coherent absorber resulting in the emission of pulses with a duration considerably shorter than the absorber relaxation times is demonstrated experimentally. A cell filled with rubidium vapor placed in the laser cavity serves as a coherent absorber. Mode locking arises when the laser oscillation frequency is tuned to the resonance transitions in rubidium. In our opinion, 2π pulses of self-induced transparency appear in the cavity, and the reported results represent the first experimental demonstration of passive mode locking caused by the effect of self-induced transparency, which has previously been discussed only theoretically.

Explicitly covariant dispersion relations and self-induced transparency

Explicitly covariant dispersion relations for a variety of plasma waves in unmagnetized and magnetized plasmas are derived in a systematic manner from a fully covariant plasma formulation. One needs to invoke relatively little known invariant combinations constructed from the ambient electromagnetic fields and the wave vector to accomplish the program. The implication of this work applied to the self-induced transparency effect is discussed. Some problems arising from the inconsistent use of relativity are pointed out.

Self-induced transparency effect on the two-soliton interaction

We report on the numerical investigation of the interaction between two solitons in a doped nonlinear dispersive medium. The dopant is modeled as a two-level atomic system coherently driven to support simultaneous nonlinear Schrödinger equation and self-induced transparency solitons. We investigate the influence of the self-Induced transparency in the case where the two-solitons are in phase. It is found that the periodical soliton collision effect disappears due to the presence of the atomic system. This new phenomenon is understood considering the detuning parameter on the atomic system description. This result can be exploited in multiple pulse propagation where the soliton interactions play an important role.

SOLITON INTERACTIONS FOR A HIROTA–MAXWELL–BLOCH SYSTEM IN THE INHOMOGENEOUS ERBIUM-DOPED FIBER

In this paper, we consider a generalized Hirota–Maxwell–Bloch system with the higher-order dispersion and self-steepening effects, which describes the propagation of ultrashort optical pulse in the inhomogeneous erbium-doped fiber. Under certain coefficient constraints, N-soliton solutions are obtained through the Hirota method and symbolic computation. Soliton interactions are graphically presented and analyzed in the different fibers. Compared with the Hirota equation without the Maxwell–Bloch parts, the self-induced transparency effect caused by the doped erbium atoms is found to lead to the change of the soliton velocity and phase. In addition, the amplitudes and widths of solitons are respectively observed to decrease and increase in the dispersion-decreasing and dispersion-increasing fibers. Finally, we give the modulational instability condition through the linear stability analysis.

Self-induced transparency in diblock copolymer dispersions

We report on the versatile effect of weak red laser light impinging on diblock copolymer [poly(isoprene-b-styrene)] dispersions in two selective solvents for each block. In the strongly scattering but transparent micellar solutions in hexane (a good solvent for polyisoprene), higher refractive index copolymer-rich fibers were formed. In the turbid dispersions of the same copolymer in ethyl acetate (a good solvent for polystyrene), the effect of self-induced transparency was observed. A two-step patterning mechanism caused the generation of a transparent microchannel, increasing light transmission. The analogy between the current effect and that observed in homopolymer polyisoprene solutions in different solvents is discussed toward an understanding of the unanticipated light-soft-matter interaction.

The amplification, compression, and self-induced transparency effects for the ultrashort electromagnetic pulses propagating along quasi-stationary electron beams

By analogy with the coherent interaction of short (on the scale of relaxation times) light pulses with inverted, i.e., active, and non-inverted, i.e., passive, two-level quantum systems, we study the possibility of the nonstationary amplification, self-induced transparency, and compression effects for the microwave electromagnetic pulses propagating along quasi-stationary electron beams. The considered analogy is not of only general physical, but also practical significance since a number of practically interesting transformation modes of ultrashort pulses, including the microwave superradiance pulses, can be implemented on its basis. The first experiments, in which the nonstationary amplification during the pulse—electron-beam interaction in a waveguide with dielectric insert was observed and pulses with subgigawatt peak powers at a carrier wavelength of 8 mm and uniquely short durations less than 100 ps were obtained, are described.

Multi-Soliton Solutions for an Inhomogeneous Nonlinear Schrödinger– Maxwell–Bloch System in the Erbium-Doped Fiber

Under investigation in this paper is an inhomogeneous nonlinear Schrödinger-Maxwell-Bloch system with variable dispersion and nonlinear effects, which describes the propagation of optical pulses in an inhomogeneous erbium-doped fiber. Under certain coefficient constraints, multi-soliton solutions are obtained by the Hirota method and symbolic computation. Evolution and interaction of the solitons are plotted, and the self-induced transparency effect caused by the doped erbium atoms is found to lead to the change of the soliton velocity and phase. Overall phase shift can be observed when the parameter accounting for the interaction between the silica and doped erbium atoms is taken as a constant.

Self-induced transparency, compression, and stopping of electromagnetic pulses interacting with beams of unexcited classical oscillators

The self-induced transparency effects that emerge when short (on the relaxation time scale) light pulses propagate in a two-level noninverted medium are well known in optics. The interaction of microwave pulses with an initially rectilinear electron beam under cyclotron resonance conditions can serve as a classical analog of the described effects. In this case, at a certain intensity of the input signal, the cyclotron absorption is replaced by self-induced transparency when the input pulse propagates almost without any change of its profile, forming a soliton whose amplitude and duration are rigidly related to its velocity. In a certain domain of parameters, this process is accompanied by significant two- or threefold compression of the initial pulse, which is of practical interest for the generation of multigigawatt picosecond microwave pulses. Since the soliton velocity lies between the unperturbed group velocity of the radiation and the translational velocity of the particles, another nontrivial effect in the case of interaction with a counterpropagating electron beam is the possibility of a significant deceleration or full stopping of the electromagnetic pulse.

SELF-INDUCED TRANSPARENCY BRAGG SOLITONS IN A NONLINEAR PHOTONIC BANDGAP STRUCTURE

We consider an optical pulse propagation in a one-dimensional nonlinear periodic structure doped uniformly with inhomogeneously broadening two-level atoms wherein the pulse propagation is governed by the nonlinear coupled mode-Maxwell Bloch equations. We investigate the pulse-train like periodic waves as well as bright and dark solitons near the photonic bandgap structure under the influence of self-induced transparency (SIT) effect. Further, we demonstrate that the resulting bright and dark SIT Bragg solitons may be realized both in anomalous and normal dispersion regimes, and this novel concept is ultimately the crux of this paper.

Radiation pressure acceleration of ultrathin foils

The acceleration of sub-wavelength, solid-density plasma foils by the ultraintense radiation pressure of circularly polarized laser pulses is investigated analytically and with simulations. An improved ‘Light Sail’ or accelerating mirror model, accounting for nonlinear self-induced transparency effects, is used for estimating the optimal thickness for acceleration. The model predictions are in good agreement with one-dimensional simulations. These latter are analyzed in detail to unfold the dynamics and self-organization of electrons and ions during the acceleration. Two-dimensional simulations are also performed to address the effects of target bending and of laser intensity inhomogeneity.

Relativistic self-induced transparency effect during ultraintense laser interaction with overdense plasmas: Why it occurs and its use for ultrashort electron bunch generation

A novel explanation of the relativistic self-induced transparency effect during superintense laser interaction with an overdense plasma is proposed. It was studied analytically and verified with direct modeling by particle-in-cell simulations. Based on this treatment, a method of ultrashort high-energy electron bunch generation with durations on a femtosecond time scale is also proposed and studied via numerical simulation.

“Light Sail” Acceleration Reexamined

The dynamics of the acceleration of ultrathin foil targets by the radiation pressure of superintense, circularly polarized laser pulses is investigated by analytical modeling and particle-in-cell simulations. By addressing self-induced transparency and charge separation effects, it is shown that for "optimal" values of the foil thickness only a thin layer at the rear side is accelerated by radiation pressure. The simple "light sail" model gives a good estimate of the energy per nucleon, but overestimates the conversion efficiency of laser energy into monoenergetic ions.