Air waves may produce optical cables

Imagine being able to instantaneously run an optical cable or fibre to any point on earth or even into space.

In a key discovery, researchers have reported using an "air waveguide" to enhance light signals collected from distant sources.

The "air waveguides" consist of a "wall" of low-density air surrounding a core of higher density air.

The wall has a lower refractive index than the core - just like an optical fibre.

The University of Maryland team broke down the air with a laser to create a spark.

An air waveguide conducted light from the spark to a detector about a meter away.

The researchers collected a strong enough signal to analyse the chemical composition of the air that produced the spark.

The signal was 1.5 times stronger than a signal obtained without the waveguide.

"That may not seem like much but over distances that are 100 times longer, where an unguided signal would be severely weakened, the signal enhancement could be much greater," explained Howard Milchberg, a professor of physics and electrical and computer engineering at University of Maryland in US.

These air waveguides could have many applications, including long-range laser communications, detecting pollution in the atmosphere, making high-resolution topographic maps and laser weapons.

Because the waveguides are so long-lived, Milchberg believes that a single waveguide could be used to send out a laser and collect a signal.

The waveguides could also be used for LIDAR - a variation on radar that uses laser light instead of radio waves to make high-resolution topographic maps.

The paper was published in the journal Optica.