Using Curved Laser Beams to Detect Explosives and Guide Microwaves

  • Published
  • By Maria Callier
  • Air Force Office of Scientific Research
ARLINGTON, Va. --  Research into creating curved laser beams in space may make it possible to someday more readily detect explosives on the battlefield, accelerate charged particles and guide high power microwaves and radiofrequency waves in the air.

With funding from the Air Force Office of Scientific Research, investigation of this technology was undertaken at the University of Arizona's College of Optical Sciences and Arizona Center for Mathematical Sciences under the guidance of Drs. Pavel Polynkin and Jerry Moloney.

"The ability to produce and observe a wide spectrum of radiation kilometers away from the laser source provides a potentially powerful tool for detecting explosives and chemical/biological agents at remote locations," said Moloney.

In the April 10, 2009 issue of Science Magazine, Moloney who conducted the research in collaboration with Professor Demetrios Christodoulides and co-workers from the University of Central Florida, explained the process of the laser beams bending: ' they are made up of a combination of waves, one leading one, which carries most of the beam's intensity, and many smaller trailing waves. These waves interfere with each other so that the leading wave curves one way while the tail bends in the opposite direction.'

"An important practical aspect of Airy beams is their self-healing property. They can quickly re-assemble themselves, after they are blocked or distorted. This allows for distortion-free propagation of these beams through turbulence and foggy environments," said Polynkin.

When powerful laser pulses reach sufficient intensity, they form filaments or peculiar self-guiding beams of light. In order to be useful, these filaments' location and shape must be controlled. Some laser beams (termed Bessel beams) produce longer, plasma channels while self-bending Airy beams generate curved light filaments and plasma channels in the air.

The main challenges for the physicists now are to invent innovative means to extend the light filaments and plasma channels over kilometer-type distances, in order to make these effects useful in real-life remote applications. The scientists plan to further investigate the physics underlying the creation of light filaments and plasma channels in environments where they can duplicate varying atmospheric conditions.

"We will collaborate with scientists at the Human Effects Directorate at Brooks Air Force Base in Ohio to gain a more complete understanding of multiple light filaments and plasma channels in the atmosphere," said Moloney.

"In the future, we plan to conduct experiments in a controlled environment that mimics different atmospheric conditions, including turbulence and high pressure," said Polynkin.

Despite the progress that has already been made, the practical use of laser filaments may be years away.

"Solid understanding of the physics involved must first take place. Since filimentation is a highly nonlinear process, tight control over laser pulses is necessary. Without such control, the experimental results are very limited because they cannot be compared with theory," concluded Polynkin.