Efficient as fiber optic cables are at transmitting data in the form of light pulses, they do need to be physically supported, and they can only handle a finite amount of power. Still, what’s the alternative … just send those focused pulses through the air? Actually, that’s just what scientists at the University of Maryland have already demonstrated in their lab.
In a traditional optical fiber, light travels along a transparent glass core. That core is surrounded by a cladding material with a lower refractive index than the glass. As a result, when the light tries to spread out (as it would if it were traveling through the air), the cladding reflects it back into the core, thus retaining its focus and intensity.
A team led by Prof. Howard Milchberg has created “air waveguides” that work on the same principle.
To make these waveguides, they start by using four lasers arranged in a square formation (one laser at each corner) to send short, powerful laser pulses through the air. As their beams collapse, they form into narrower beams known as filaments. The reason that these form is because in sufficiently powerful laser light, the light at the center of the beam has a higher refractive index than that at the outside.