Multimode Collective Atomic Recoil Lasing in Free Space

Cold atomic clouds in collective atomic recoil lasing are usually confined by an optical cavity, which forces the light-scattering to befall in the mode fixed by the resonator. Here we consider the system to be in free space, which leads into a vacuum multimode collective scattering. We show that the presence of an optical cavity is not always necessary to achieve coherent collective emission by the atomic ensemble and that a preferred scattering path arises along the major axis of the atomic cloud. We derive a full vectorial model for multimode collective atomic recoil lasing in free space. Such a model consists of multi-particle equations capable of describing the motion of each atom in a 2D/3D cloud. These equations are numerically solved by means of molecular dynamic algorithms, usually employed in other scientific fields. The numerical results show that both atomic density and collective scattering patterns are applicable to the cloud’s orientation and shape and to the polarization of the incident light.

Method of Moments Optimization of Distributed Raman Amplification in Fibers with Randomly Variying Birefringence

In this work, we develop a vectorial model, for optical communications, using distributed Raman amplification (DRA) applied to vectorial soliton pulses in monomode fiber optics. The main result, a dependent polarization effective Raman gain coefficient, is calculated considering the random birefringence character of the fiber and the relative mismatch between the continuous wave (CW) pump and the signal. The Method of Moments allows the determination of the optimal initial conditions to achieve a better performance in our system. With these starting values, the simulations carried out with the Split-Step Fourier Method (SSFM) elucidate the influence of the peak power and prechirping initial phase control on the vectorial soliton propagation.