Abstract When ultra-short unipolar pulses overlap in a resonant medium, the formation of a dynamic “microcavity”, i.e. a burst of the population difference, is feasible. This paper presents, first, the relations allowing to calculate the parameters of such a microcavity using the analytical solution of the equations for the density matrix of a two-level medium, and second, the dependence of the microcavities’ parameters on the pulse form using the numerical solution of Maxwell-Bloch equations.
Abstract When ultra-short unipolar pulses overlap in a resonant medium, the formation of a dynamic “microcavity”, i.e. a burst of the population difference, is feasible. This paper presents, first, the relations allowing to calculate the parameters of such a microcavity using the analytical solution of the equations for the density matrix of a two-level medium, and second, the dependence of the microcavities’ parameters on the pulse form using the numerical solution of Maxwell-Bloch equations.
Abstract In the case of coherent interaction with a medium of extremely short light pulses (ESPs) having a carrier frequency and harmonic shape (when the pulse durations are shorter than the population relaxation times T1 and polarization relaxation time T2 of the medium), electromagnetically induced gratings (EMIGs) of the population difference, which have a pronounced harmonic dependence on the coordinates, may appear in it. These structures can occur when pulses do not overlap or overlap in the medium. Recently, the possibility of obtaining unipolar electromagnetic pulses in the optical and adjacent ranges of non-harmonic shape, for example, rectangular and triangular, with a duration less or comparable to the duration of the extremely-short pulse in this range, has attracted interest. In this work, using the numerical solution of the system of Maxwell–Bloch equations, we study EMIG formation by rectangular attosecond pulses in a two-level resonant medium. The possibility of inducing an EMIG of a non-harmonic shape in the form of light-induced channels microresonators (microcavities) with a size of the order of the wavelength of the resonant transition of the medium, whose parameters can be controlled, for example, by the amplitude of the incident pulses, is shown. It has been suggested that it is possible to create an EMIG of a predetermined non-harmonic shape only in the general case of using unipolar pulses.
Abstract We report an analytical and numerical study of the dynamics of electromagnetically induced atomic population gratings during collisions of a sequence of unipolar pulses of unusual temporal shape (rectangular and triangular) in a multilevel resonant medium. The possibility of forming dynamic microcavities with Bragg-like mirrors, the shape of which is different at each resonant transition of the medium, is demonstrated. A simple analytical description of such microresonators is proposed based on an approximate solution of the time-dependent Schrödinger equation when the amplitude of the exciting pulses is small. In the case of high-power pulses, when perturbation theory is not applicable, the results of numerical calculations show the disappearance of microcavities and the emergence of nonharmonic gratings with an increase in the number of collisions between pulses. The studied phenomena demonstrate a possibility of using unipolar pulses of an unusual shape for ultrafast control of the medium properties.
In the case of coherent interaction with a medium of extremely short light pulses (ESPs) having a carrier frequency and harmonic shape (when the pulse durations are shorter than the population relaxation times T1 and polarization relaxation time T2 of the medium), electromagnetically induced gratings (EMIGs) of the population difference, which have a pronounced harmonic dependence on the coordinates, may appear in it. These structures can occur when pulses do not overlap or overlap in the medium. Recently, the possibility of obtaining unipolar electromagnetic pulses in the optical and adjacent ranges of non-harmonic shape, for example, rectangular and triangular, with a duration less or comparable to the duration of the extremely-short pulse in this range, has attracted interest. In this work, using the numerical solution of the system of Maxwell-Bloch equations, we study EMIG formation by rectangular attosecond pulses in a two-level resonant medium. The possibility of inducing an EMIG of a non-harmonic shape in the form of light-induced channels microresonators, (microcavities) with a size of the order of the wavelength of the resonant transition of the medium, whose parameters can be controlled, for example, by the amplitude of the incident pulses, is shown. It has been suggested that it is possible to create an EMIG of a predetermined non-harmonic shape only in the general case of using unipolar pulses. Keywords: attosecond pulses, unipolar pulses, rectangular pulses, electromagnetically induced gratings, polarization waves, light-induced microresonators.
Unipolar light pulses with a non-zero electric area due to the unidirectional action on charged particles can be used for the ultrafast control of the properties of quantum systems. To control atomic properties in an efficient way, it is necessary to vary the temporal shape of the pulses used. This has led to the problem of obtaining pulses of an unusual shape, such as a rectangular one. A number of new phenomena, not possible with conventional multi-cycle pulses, were discovered by analyzing the interaction of such unipolar pulses with matter. These include the formation of dynamic microcavities at each resonant transition of a multilevel medium when such pulses collide with the medium. In this work, we compare the behavior of dynamic microcavities in a two-level and a three-level medium when unipolar pulses of unusual shape (rectangular) are collided with the medium. We do this on the basis of the numerical solution of the system for the density matrix of the medium and the wave equation for the electric field. Medium parameters correspond to atomic hydrogen. It is shown that for rectangular pulses in a three-level medium, the dynamics of the cavities can be very different from the two-level model, as opposed to pulses of other shapes (e.g. Gaussian shape). When the third level of the medium is taken into account, the self-induced transparency-like regime disappears. Differences in the dynamics of resonators in a three-level medium are revealed when the pulses behave like 2π pulses of self-induced transparency.
In the case of coherent interaction with a medium of extremely short light pulses from a carrier of a harmonic form (when the pulse durations are shorter than the population relaxation times T_1 and polarization T_2 of the medium), electromagnetically induced gratings (EMIGs) of the population difference, which have a pronounced harmonic dependence on the coordinates, may appear in it. These structures can occur when pulses do not overlap at the same time or overlap in the medium. Recently, the possibility of obtaining unipolar electromagnetic pulses of the optical and adjacent ranges of non-harmonic shape, for example, rectangular and triangular, with a duration less than or comparable to the duration of the PCR in this range, has attracted interest. In this work, using the numerical solution of the system of Maxwell-Bloch equations, we study EMIG induced by rectangular attosecond pulses in a two-level resonant medium. The possibility of inducing an EMIG of a non-harmonic form in the form of light-induced channels, a kind of microresonators, with a size of the order of the wavelength of the resonant transition of the medium, whose parameters can be controlled, for example, by the amplitude of the incident pulses, is shown. It has been suggested that it is possible to create an EMIG of a predetermined non-harmonic form only in the general case of using unipolar pulses.
Abstract The formation of dynamic microcavities (DMs) in the asymmetric collision of a single-cycle π‑pulse and a 2π-pulse of self-induced transparency in a two-level medium is investigated theoretically. The numerical solution of the Maxwell–Bloch equations demonstrates that the interaction of pulses leads to the emergence of two DMs, which are separated in space within the medium. Controlling the shape of the microcavities is possible by altering the number of collisions between pulses. These results pave the way for the development of ultrafast tunable optical devices.