A study is reported of the dynamic characteristics of the superradiance emitted by three-level media. It is shown that the intensity and duration of bichromatic superradiance pulses can be controlled by varying the amplitude reflection coefficients at the boundary of a medium.
The superradiance (SR) phenomenon is considered for the case of a medium consisting of two resonant components. It is shown that the dynamics of emission in this case differs essentially from that for a monocomponent medium. The use of a two-component medium results in a substantial weakness in the requirements for duration of the pumping pulse. The peak pulse intensity of superradiance for the case of a two-component medium can exceed that for each of the components separately. By varying the active medium length and concentration of components we can control the spatiotemporal dynamics of emission. This enables us to transform the broadened pumping pulse of a lower intensity into the ultrashort high intensity pulse of SR.
A method is proposed for substantially reducing the length of superradiance pulses and increasing their intensity. The idea is to introduce an additional coherent resonant component, with a higher Rabi frequency, in a superradiance medium. The superradiance intensity of a two-component medium of this sort can be substantially higher than that of either component individually. The pump pulse can be several orders of magnitude longer than the generation pulse. The parameters of the generation pulse are controlled by varying the length and composition of the active medium.
An orderly account is given of the processes of coherent propagation, amplification, and generation of pulses in polyatomic resonant media. The characteristic features of the propagation of solitons in resonant media of finite length are considered. Comparisons are made of the exponential and lethargic amplification of pulses in resonant media. It is shown that an allowance for the reflection of the field from the boundaries of an active medium gives rise to a qualitatively different dependence of the parameters of the pulses on the reflection coefficients under superradiance and lasing conditions, which makes it possible to introduce a criterion to distinguish lasing from superradiance. An analysis is made of the characteristics of collective superradiance, which is a new case of coherent generation of pulses. Experimental and theoretical investigations of rf superradiance emitted by systems of nuclear spins are reviewed.
An investigation is made of the dynamics of the superradiance of two-component quasiresonant media with similar frequencies of superradiant transitions. It is shown that variation of the detuning of the frequencies of the components can increase the peak intensity of a superradiance pulse and simultaneously reduce its temporal width. The range of the detuning of the frequencies of the components ensuring generation of the strongest and shortest superradiance pulse is determined. It is demonstrated that superradiance pulses emitted by two-component quasiresonant media may be delayed by a considerable time, which is significantly longer than the temporal width of the superradiance pulse itself.
The two—component superradiative medium consists of two species of atoms with the different dipole moments of the quasi-resonant transitions. The atoms with the smaller dipole moment are initially in the excited state, while е atoms of the second type are initially in the ground state. In the initial stage of the superradiance dynamics the first component is amplifying one, the second component is resonantly absorbing. By varying the concentration of the resonantly absorbing atoms it is possible to increase the intensity of superradiance in the few order of magnitude with respect to the monocomponent medium of the amplifying atoms alone. Here we show that the variation in the distribution of the component densities enables us the additional possibilities in the control of the superradiance pulse parameters. The additional increase in the order of magnitude for the peak pulse intensity is obtained at the optimal distribution. The nature of such variation in the pulse profile and its intensity is due to the opportunity for the effective spatial mode selection in the spatial inhomogeneous media. We discuss the algorithms of е numerical solution and show that the enhanced accuracy methods can be developed in this case.