Scientists from the United States have figured out how to force a conventional laser beam to pass through dense fog or white walls by changing the spatial structure of its pulses in a special way. The "recipe" for the creation of such laser installations was presented in the journal Nature Photonics.
In recent years, scientists have been actively working on the creation of gadgets that allow you to see through walls and look into inaccessible corners of space. For example, in October 2015, physicists at MIT learned to look through walls and see silhouettes of people using ordinary WiFi transmitters and receivers, and their colleagues in Scotland created a camera that could "peep around corners."
Cao and her colleagues made another device of this kind, "teaching" a laser beam to pass through fog and any other opaque objects that do not absorb but reflect light, observing how a beam of light particles interacted with a thin wall of white material.
Scientists were interested in what part of the photons still seep through such obstacles, avoiding collisions with electrons while moving through an opaque and scattering medium, and what properties of the beam affect their number.
To do this, the Yale physicists positioned two ultrasensitive matrices behind a sheet of compressed zinc oxide nanoparticles that played the role of this wall, and began to monitor how much light passed through its different sections.
Cao and her team carried out these experiments using the so-called spatial light modulator - a special optical device that allows you to flexibly control the spatial structure of beams of electromagnetic waves. Its counterparts can be found in any projector and in many scientific instruments.
It turned out that spatial modulators can set the light beam in such a way that it starts to pass through opaque objects. This will happen if its structure will in a certain way correspond to the width of a kind of "channels" between atoms and electrons, through which light can freely move.
With such a selection of parameters, as the researchers note, the laser beam stopped scattering, and its power increased 4.5 times. In a similar way, according to them, it will behave not only when it collides with a wall, but also with fog or other scattering media.
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Cao and her colleagues hope that their discovery will create automotive lamps that can work in all weather conditions, lasers that can penetrate the tissues of the body of animals and people for medical operations and scientific experiments, and many other useful optical devices.