A nonlinear wave coupling algorithm and its programing and application in plasma turbulences

The fully developed turbulence can be regarded as a nonlinear system, with wave coupling inside, which causes the nonlinear energy transfer, and drives the turbulence to develop further or be suppressed. Spectral analysis is one of the most effective methods to study turbulence system. In order to apply it in the study of the nonlinear wave coupling process of edge plasma turbulence, an efficient algorithm based on spectral analysis technology was proposed to solve the nonlinear wave coupling equation. The algorithm is based on a mandatory temporal static condition after separating the nonideal spectra from the ideal spectra. The realization idea and programing flow were given. According to the characteristics of plasma turbulence, the simulation data were constructed and used to verify the algorithm and its implementation program. The simulation results and examples showed the accuracy of the algorithm and the corresponding program, which could play a great role in the study of the energy transfer in edge plasma turbulences. As an application, the energy cascade analysis of typical edge plasma turbulence was carried out using the results of a case calculation. Consequently, a physical image of the energy transfer in a kind of fully developed turbulence was constructed, which confirmed that the energy transfer in this turbulent system was from lower- to higher-frequency regions and from linear growing to damping waves.

Azimuthal modulation of electromagnetically induced grating using structured light

We propose a theoretical scheme for creating a two-dimensional Electromagnetically Induced Grating in a three-level $$\Lambda $$ Λ -type atomic system interacting with a weak probe field and two simultaneous position-dependent coupling fields—a two dimensional standing wave and an optical vortex beam. Upon derivation of the Maxwell wave equation, describing the dynamic response of the probe light in the atomic medium, we perform numerical calculations of the amplitude, phase modulations and Fraunhofer diffraction pattern of the probe field under different system parameters. We show that due to the azimuthal modulation of the Laguerre–Gaussian field, a two-dimensional asymmetric grating is observed, giving an increase of the zeroth and high orders of diffraction, thus transferring the probe energy to the high orders of direction. The asymmetry is especially seen in the case of combining a resonant probe with an off-resonant standing wave coupling and optical vortex fields. Unlike in previously reported asymmetric diffraction gratings for PT symmetric structures, the parity time symmetric structure is not necessary for the asymmetric diffraction grating presented here. The asymmetry is due to the constructive and destructive interference between the amplitude and phase modulations of the grating system, resulting in complete blocking of the diffracted photons at negative or positive angles, due to the coupling of the vortex beam. A detailed analysis of the probe field energy transfer to different orders of diffraction in the case of off-resonant standing wave coupling field proves the possibility of direct control over the performance of the grating.