Optical fibres from thin air

It is claimed the air waveguides - developed by Howard Milchberg and his lab at the University of Maryland - could have many applications, including long-range laser communications, detecting pollution in the atmosphere, making high-resolution topographic maps and laser weapons.

Because light loses intensity with distance, the range over which such tasks can be done is limited. Lasers, which produce highly directed beams, lose focus due to their natural spreading, or worse, due to interactions with gases in the air. Fibre-optic cables can trap light beams and guide them like a pipe, preventing loss of intensity or focus.

A single waveguide could be used to send out a laser and collect a signal

Typical fibres consist of a transparent glass core surrounded by a cladding material with a lower index of refraction. When light tries to leave the core, it gets reflected back inward. But solid optical fibres can only handle so much power, and they need physical support that may not be available where the cables need to go, such as the upper atmosphere. Now, Milchberg’s team has found a way to make air behave like an optical fibre, guiding light beams over long distances without loss of power.