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Quantum Electronics

Transient processes in the parametric interaction of counter-propagating waves

Vitaliy V. Slabko, A. K. Popov, S. A. Myslivets, E V Rasskazova, V A Tkachenko, A. K. Moskalev

Published Dec 28, 2015• 5 citations
Publisher

Abstract

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.

DOI
10.1070/qe2015v045n12abeh015840

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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.
The parametric interaction of three waves, one of which travel in direction opposite to other, is associated with a number of unusual phenomena that find their applications. One of such phenomena is an extremely long transient process of amplitude changing of the output signal. In this paper, the impact of pump-wave absorption and the phase mismatch magnitude on the course of the process is investigated. It is shown that the absorption lead to significant changes in the process time, and the phase causes changes in dynamics but not in duration of the process.
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Energy exchange between counter propagating light waves of equal frequency is possible in media with instantaneous and local nonlinear optical response which, however, provides a special form of nonlinearity tensor. The major requirement is that there has to be no Lagrangian describing the light-medium interaction. There is a limited region of the pump wave intensity where the signal wave amplification takes place. The thermal mechanisms of interaction between light waves and liquid crystals provide examples of "non-Lagrangian" nonlinearity.
Equations describing a transient degenerate four-wave interaction in a resonant medium are derived and solved numerically. The approximation of a "following" nonlinear polarization state is used to determine the range of values of the parameters of the medium and the radiation field in which the efficiency of a transient four-wave interaction is higher than that of the steady-state process. It is found that amplification of weak radiation as a result of transient energy exchange can only be achieved in the four-wave interaction for different pump wave intensities.
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Distributed positive feedback established by a counterpropagating three-wave mixing process in a submicrometer structured second-order nonlinear medium leads to mirrorless parametric oscillation with unusual spectral properties. In this work, we demonstrate experimentally and theoretically that the phase modulation of the pump is coherently transferred to the co-propagating parametric wave, while the counterpropagating wave retains a narrow bandwidth and high coherence. The main mechanisms responsible for these properties are the maximized convective separation between the counterpropagating waves and the associated phase-locking between the pump and the co-propagating parametric wave. This suggests that mirrorless optical parametric oscillators can be pumped with incoherent light and still generate highly coherent backward-propagating radiation.