American scientists have created an air light guide, which repeatedly improves the propagation of a laser beam in the air.
The spread of a laser beam in the air, especially if its power is high, is rather limited due to interaction with the atmosphere. The laser heats the gas through which it passes, because of which the density changes, and hence the coefficient of refraction of air in the path of the beam. The atmosphere begins to work like a lens, scattering the beam. Scientists from the University of Maryland at College Park have figured out how to overcome the negative effects of this effect. To do this, they used several additional lasers located around the main one.
Auxiliary lasers give a short femtosecond flash before the main laser turns on. This flash warms the air around the path, along which the main beam will go, forming an air light guide with an elevated pressure zone inside and a lower one - along the perimeter. Due to this, the main beam is scattered much less. A similar principle is used in fiber optics - its outer and inner layers have a different refractive index, which is why light travels with minimal losses, never touching the walls of the light guide. The illustration shows a diagram of the operation of such a fiber and a photo of its profile using four and eight auxiliary lasers.
The effect of the airborne fiber will allow to improve the signal-to-noise ratio by several orders of magnitude wherever the laser beam propagates over long distances in the atmosphere — in lidarch, communications systems, and laser spectroscopes similar to those installed on the Curiosity rover. In addition, military applications are also possible, among the sponsors of the study are the US Air Force and the Defense Threat Reduction Agency (DTRA). As is known, last year successfully passed tests of a laser gun , which is capable of destroying drones and small enemy boats. In the future, such lasers could replace expensive rockets, but they still work only at short distances due to the scattering of the beam.
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Auxiliary lasers give a short femtosecond flash before the main laser turns on. This flash warms the air around the path, along which the main beam will go, forming an air light guide with an elevated pressure zone inside and a lower one - along the perimeter. Due to this, the main beam is scattered much less. A similar principle is used in fiber optics - its outer and inner layers have a different refractive index, which is why light travels with minimal losses, never touching the walls of the light guide. The illustration shows a diagram of the operation of such a fiber and a photo of its profile using four and eight auxiliary lasers.
The effect of the airborne fiber will allow to improve the signal-to-noise ratio by several orders of magnitude wherever the laser beam propagates over long distances in the atmosphere — in lidarch, communications systems, and laser spectroscopes similar to those installed on the Curiosity rover. In addition, military applications are also possible, among the sponsors of the study are the US Air Force and the Defense Threat Reduction Agency (DTRA). As is known, last year successfully passed tests of a laser gun , which is capable of destroying drones and small enemy boats. In the future, such lasers could replace expensive rockets, but they still work only at short distances due to the scattering of the beam.
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Source: https://habr.com/ru/post/231535/
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