The shadow of a laser beam appears as a horizontal line against a blue background
Abrahao et al. (2024)
Light usually casts shadows on other objects, but with a little help from a ruby, a beam of laser light can cast its own shadow.
when two laser beams interact, they don’t collide with each other like lightsabers Star Warshe says Raphael Abraham at Brookhaven National Laboratory in New York. In real life, they will pass each other. Abrahao and his colleagues, however, found a way for one laser beam to block another and reveal its shadow.
The crucial ingredient was a ruby cube. The researchers hit this cube with a beam of green laser light while illuminating the side with a blue laser. When green light passed through the ruby atoms, it changed their properties in a unique way and how they then reacted to blue light.
Instead of allowing the blue laser to pass through them, the atoms affected by the green light blocked the blue light, which produced a green-like shadow. laser beam. Remarkably, researchers can project blue light onto a screen and see this “laser shadow” with the naked eye.
Abrahao says he and his colleagues had a long debate about whether what they had created really qualified a shadow. Since the green laser beam moved when they moved, they could see it without special equipment and managed to project it on common objects, like a marker, they finally decided yes.
Historically, understanding shadows has been central to understanding what light can do and how we can use it, and this experiment adds an unexpected technique to scientists’ toolbox for manipulating light.
Tomás Chlouba At Germany’s University of Erlangen–Nuremberg, he says the experiment uses familiar processes to create a striking visual demonstration of how materials can help control light. The interactions of the ruby with the laser, for example, are similar to the materials used laser eye surgerieswhich must be able to respond to laser light by blocking it if it becomes dangerously intense.
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