Self-induced transparency in waveguides

A theory of self-induced transparency (SIT) in waveguides, covered by thin films (thickness d ? λ = 2π/cω) of a resonant substance, has been developed. The shape of a waveguiding soliton (waveguiding “2π”-pulse) has been determined, and its velocity as a function of the film thickness and other characteristics of the resonant layer has been investigated.     

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.     

Self-induced transparency of excitons in semiconductors

Self-induced transparency of excitons is analysed in a model where intraband processes are described by density matrices and interband processes by coherent pair amplitudes. We determine the dispersion law of the carrier wave and the exciton wave function. The theory predicts: (a) a forbidden energy gap centered at the exciton line which broadens with increasing intensity, (b) a critical dependence of the effect on intensity, (c) a strong influence of intensity and carrier frequency on the exciton wave function.     

Self-induced transparency for love waves

A theory of self-induced transparency is constructed for the Love wave in a system which consists of a film lying on a semispace in the presence of paramagnetic impurities. The solution is obtained in the form of the 2π-pulse of McCall and Hahn for the Love wave. It is shown that the characteristic parameters of the nonlinear Love wave depend on the transverse-mode profile.     

Self-induced transparency in a dispersive medium

The evolution of the electromagnetic field in a two-level medium occurring in a matrix with finite response time has been studied. An integrable variant of the Maxwell-Bloch equations with allowance for nonlinear dispersion is derived and solved using the inverse scattering problem. It is shown that the nonlinear dispersion caused by the finite response time of the matrix yields a new possibility of controlling soliton parameters. A particular case of the constructed model can be used to describe field pulses in the parameter domain that occurs between the regions of applicability of the quasi-monochromatic approximation and the approximation of unidirectional propagation of pulses with durations on the order of the oscillation period.     

Self-induced transparency of circularly polarized femtosecond pulses

The phenomenon of self-induced transparency in a two-level medium is studied using a new integrable set of evolution equations for the optical pulses with a duration on the order of the energy-transition oscillation period. A mathematical apparatus is developed for the inverse scattering problem and used to obtain solitonic solutions to the model. The characteristics of linearly and circularly polarized pulses are compared with each other.     

Self-induced acoustic transparency in the long-short-wave resonance mode

The effect of self-induced acoustic transparency for transverse-longitudinal pulses propagating along an external magnetic field in a system of resonance paramagnetic impurities with the effective spin S=1/2 is theoretically investigated. In this case, the short-wave transverse component of the pulse causes quantum transitions, and the longitudinal long-wave component dynamically shifts the frequency of those transitions. When the speeds of the longitudinal and transverse acoustic waves in the crystal matrix are close to each other, both components interact in the mode of the long-short-wave resonance, which is described by a system of nonlinear integro-differential equations. It is shown that this interaction results, in particular, in the modulation of the carrier frequency of the circular-polarized component of the pulse. More precisely, the frequency in the neighborhood of the signal’s maximum is less than in the vicinity of its edges. Solutions in the form of traveling 2π-pulses are analyzed analytically and numerically. It is shown that there exist solutions that include a longitudinal component and cannot be reduced to well-known transverse solitons of the sinus-Gordon equation.     

Self-induced transparency with the Stark pulse technique

A theory based on the method of the inverse scattering problem is presented describing propagation of an ultrashort light pulse under the condition that resonant interaction with atoms of the medium is initially switched on by an additional Stark pulse. A Hamiltonian form of the Maxwell-Bloch equation is found without redefining the spatiotemporal variables. The method of the inverse scattering problem is based on a special spectral problem. Equations of the Gel’fand-Levitan-Marchenko type and a soliton solution are obtained.     

Self-induced transparency due to two photon transition

We show theoretically that the effect of self-induced transparency can be supported by the two-photon transition in the system of three-level atoms. The distortionless propagation of the radiation wave is composed of a train of pulses which is described by a trigonometric function, and in one limit, it approaches to a single pulse with lorentzian form for the radiation intensity.     

Self-induced acoustic transparency of three-component longitudinal-transverse pulses

The features of the nonlinear dynamics of three-component elastic pulses in a low-temperature crystal containing paramagnetic impurities of electron and nuclear spins have been analyzed in the slowly varying envelope approximation. The presence of the electron spin subsystem makes it possible to equate the velocities of longitudinal sound and transverse acoustic waves; as a result, all components of the strain field efficiently interact with each other through the nuclear spin subsystem. The system of equations for envelopes of harmonics of the components of the strain field and the spin variables has been derived. The relations between the amplitudes and phases of the components have been obtained, the spectral composition has been analyzed, and the regimes of acoustic transparency of three-component longitudinal-transverse pulses have been discussed.     

Self-induced transparency of very short optical pulses

Solutions to a first order wave equation, appropriate to ultrashort optical pulse theory and to the optical undamped Bloch equations are presented. Detuning is shown to play essential role in the physical interpretation of these solutions. Related cases have been discussed by Courtens and by Lee. It is noted that the rotating wave approximation introduces strong restrictions on the range of validity of possible solutions. Pulses with Lorentzian shapes, while implied by the equations, appear to be without physical significance.     

Self-induced avalanches in relaxing media

A theory of boson avalanches (self-induced waves) has been constructed with allowance for longitudinal relaxation. It is shown that inclusion of longitudinal relaxation requires a completely different approach to the theory of superradiance than that taken previously. For the first time an equation is derived for an avalanche with allowance for longitudinal and transverse relaxation. Numerical solution of this equation makes It possible to establish all the distinctive features of a coherent self-induced wave under the conditions of the action of relaxation mechanisms. An inversion effect is found to occur in the action of longitudinal and transverse relaxation on the delay parameter of a self-induced wave, i.e., the superradiance delay time. Analytic expressions are found of the ensemble-averaged delay time of an avalanche and the relative fluctuations of the delay time as a function of irreversible phase relaxation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 81–86, September, 1986.     

Self-induced transparency and the Anderson localization of light

Self-induced transparency pulses propagating in a random medium embedded in a two-level system can transfer energy to localized Anderson states. This allows the onset of two-level laserlike action.     

Self-induced transparency in a resonance medium with the dipole-dipole interaction

Propagation of a pulse of self-induced transparency in a resonance medium is discussed for the case when it is necessary to take into account the direct electric dipole-dipole interaction between atoms. An equation for the envelope of a wave packet—the sine-Gordon equation—is obtained for the case of durations short compared to ω ₀ ^?1 (ω₀ is the transition frequency). The dependence of the velocity and the amplitude of the soliton on the magnitude of the dipole-dipole interaction of atoms is examined in the adiabatic approximation.     

Self-induced transparency for ultrashort pulses propagating in a multilevel quantum medium

We study theoretically the phenomenon of self-induced transparency for ultrashort pulses (videopulses) propagating in a multilevel quantum medium under conditions in which the method of slowly varying amplitudes and phases breaks down and the pulse spectrum substantially overlaps the quantum transitions. A special class of transitions with one common level is considered. We find that the dynamics of the videopulses in such a medium is described by a double sine-Gordon equation. We establish the conditions under which steady-state traveling 0π-, 2π-, and 4π-videosolitons are formed. It is found that 4π-videosolitons can propagate both in equilibrium media and in some nonequilibrium media, while 0π-videosolitons can propagate only in nonequilibrium media. We study amplification processes in highly nonequilibrium systems and show that, depending on the initial state of the medium, 2π-and qπ-pulses (0<q<1) with increasing amplitudes may be formed. We conclude that the amplification of an ultrashort pulse occurs due to an increase in the photon number density and to an increase in the frequency of each photon. Finally, we study the possibility of an electromagnetic autosoliton being formed in a nonequilibrium dissipative medium. Zh. éksp. Teor. Fiz. 114, 1595–1617 (November 1998)     

Self-induced transparency and self-induced darkening with a nonlinear frequency-doubling polarization interferometer

It is shown that the system polarizer-frequency-doubling crystal(s)-analyzer has a nonlinear transmission for the fundamental wave. The intensity-dependent transmission of this device is due to the nonlinear phase shift that the fundamental beam obtains in the nonlinear crystal as a result of cascaded second-order processes. Depending on the mutual orientation of the polarizer and the analyzer such effects as self-induced transparency and self-induced darkening can be realized.     

Self-induced polarization rotation of a laser beam in resonance media

The single-photon effect of the self-induced optical activity (SIOA) has been investigated experimentally for the first time in the vicinity of potassiumD _1,2 lines. Experimental data on self-induced gyrotrophy and dichroism are presented and compared with the theoretical model proposed earlier. The limiting action of SIOA on the efficiency of resonance parametric generators and polarization spectroscopy is outlined.