Researchers study autoresonance to control and excite large amplitude standing ion acoustic waves

A growing field known as plasma-photonics, wherein plasmas are used to manipulate properties of light, has great potential for applications of high-power lasers. Yet, creating the optical elements needed to control lasers from plasma has proven to be a challenge.

Friedland et al. propose using standing ion acoustic waves (SIAWs), oscillations of ions and electrons in a plasma, to control the optical parameters of lasers. Using autoresonance, a phenomenon where an oscillating nonlinear system becomes phase-locked, the team developed theory and computer simulations to show how a small amplitude chirped frequency driver can control large amplitude SIAWs.

To illustrate autoresonant excitation of nonlinear SIAWs, the group presented so-called “water bag” simulations, which trace the motion of groups of particles in phase-space. They observed the formation of large amplitude SIAW in both a warm plasma water bag model and in a Lagranian cold ion fluid limit. “We have successfully formulated the basic model of the autoresonant excitation focusing on weakly nonlinear stage and its stability,” said author Lazar Friedland. “All these theoretical predictions were confirmed by the computer simulations.”

The research is the first theoretical study and demonstration of the new type of large plasma density structure formed using only a small driving force. This allows optical control of laser beams at much higher intensities.

Before the theoretical research can be used to achieve the manipulation of light beyond what is currently allowed by traditional optical elements, the concept of SIAWs needs to be tested in smaller scale laboratory experiments. “As with any paper first proposing a new concept, there are many issues that remain to be investigated, such as the stability, three-dimensional and kinetic effects,” said Friedland.

Source: “Excitation and control of large amplitude standing ion acoustic waves,” by L. Friedland, G. Marcus, J.S. Wurtele, and P. Michel, Physics of Plasma (2019). The article can be accessed at https://doi.org/10.1063/1.5122300 .