Laser bursts pierce fog

Researchers from Claude Bernard Lyon 1 University in France have shown that it is possible to fire laser beams through otherwise impenetrable clouds, haze and fog.

This means it could be possible to transmit data through these opaque media and remotely sense objects or chemicals within clouds, haze or fog. This could lead to more reliable free-space laser communications and new ways to monitor pollution, according to the researchers.

Water droplets usually scatter laser signals. The researchers used intense, very short laser pulses to form light filaments that were only 150 microns wide and hundreds of meters long, and showed that the filaments could cut through water droplets as large as 95 microns without losing much energy. One hundred fifty microns is only about one-third the size of a red blood cell.

When the filament strikes a water droplet, much of the filament's energy is transferred to surrounding photons. However, this energy is transferred back to the filament on the other side of the droplet.

The researchers' next step is to check the phenomenon in the field using a mobile femtosecond laser system. A femtosecond is one million billionth of a second.

The work could find practical applications in two to five years, according to the researchers. The work appeared in the July 14, 2003 issue of Applied Physics Letters.