Laser Systems Model Extreme Events

Extreme events in nature may be more commonplace and predictable than you might think, says an international group that uses lasers to study such random events.

“Generally it’s a bad idea to experiment with nature,” said professor Nail Akhmediev of the Australian National University (ANU) Research School of Physics and Engineering. “However, modeling extreme events in laser systems is a great way to understand extreme events in nature.”

Scientists from ANU, the University of Burgundy, in France, and the Institute of Optics in Madrid studied the frequency of extreme events, such as hurricanes, tsunamis and bushfires, using an optical laser in a dissipative system.

The Zaca wildfire in Santa Barbara County, California. (Image: US Forest Service Photo by John Newman)

“A crucial factor in the appearance of extreme events, whether in nature or a laser in the laboratory, is the existence of energy, or a background excitation in the system,” Akhmediev said. “This is a basic feature of so-called dissipative systems.”

Extreme events cannot happen without a source of energy. The abundance of energy around us all the time means there is a great potential for extreme events, he said.

“Our cities and our planet are densely filled with energy supplies, and a large source of energy is a potential field for extreme events,” Akhmediev said. “Without this background excitation, the events will stay within expected limits. But a continuous supply of energy can push the event off the expected limits, and into extremes.”

While it is not possible to conduct large-scale dangerous experiments in nature to illustrate the point, the team re-created random events on a much safer and smaller scale through lasers in the laboratory.

“Our experimental results with a laser that operates in a strongly dissipative regime of chaotic multiple-pulse generation resemble the ‘chaotic’ processes in nature,” he said. “What we’ve found is that recorded intensity fluctuations resulting from the ceaseless relative motion inside the laser demonstrate that extreme events happen much more often than people expect.”

Their work appeared in Physical Review Letters.

For more information, visit: www.anu.edu.au