(ORDO NEWS) — Laser pulses make it possible to heat sections of air in the form of a hollow tube, keeping the temperature inside colder.
The difference in refractive index between them creates the effect of an optical fiber, allowing the signal to be sent with less loss.
Fiber optic cables help to transmit a digital signal with minimal loss. They are based on a glass or plastic core surrounded by a sheath with a lower refractive index.
Such a structure allows photons to move along the core, using the effect of total internal reflection , and practically not scatter along the way.
A few years ago, the team of University of Maryland professor Howard Milchberg demonstrated a technology that helps create an analogue of fiber directly from the air, using specially prepared laser pulses.
Now scientists have managed to significantly improve the performance of such a system by extending the “air fiber” up to 50 meters.
To create an invisible cable, laser beams are passed through a complex optical system, giving them the shape of a donut.
Due to the high frequency of the pulses, individual “donuts” are folded into a long, elongated hollow tube.
The air inside it retains its original temperature, and in the shell through which the laser pulses pass, it heats up.
Due to this, the refractive index of the core of such a “cable” is significantly higher than in the “sheath”, providing signal transmission.
Previously, physicists could only demonstrate the operability of this approach by obtaining an “air fiber” less than a meter long.
The efficiency of its work is not as great as that of a real cable: the output signal was only one and a half times stronger than with a simple transmission over the air.
However, the greater the distance, the more noticeable this gain becomes.
Now, using an improved optical system and more powerful lasers, the authors have brought this figure to 50 meters, which is already quite suitable for some practical applications.
According to scientists, the further increase in the “cable” is a matter of technology, and in the near future they plan to start experiments with even more powerful lasers, which will make it possible to obtain an “optical fiber” about a kilometer long.
Such invisible channels can be used, for example, to quickly organize short-range communications or determine the chemical composition of objects without approaching them.
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