![\"\"](\"https:\/\/images.newscientist.com\/wp-content\/uploads\/2024\/11\/13170643\/SEI_229443816.jpg\")
<\/div>The shadow of a laser beam appears as a horizontal line against the blue background<\/p>\n
Abrahao et al. (2024)<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Light normally makes other objects cast shadows \u2013 but with a little help from a ruby, a beam of laser light can cast a shadow of its own.<\/p>\n
When two laser beams<\/a> interact, they don\u2019t clash together like lightsabers in Star Wars<\/em>, says Raphael Abrahao<\/a> at Brookhaven National Laboratory in New York. In real life, they will simply pass through each other. Abrahao and his colleagues, however, found a way for one laser beam to block another \u2013 and make its shadow appear.<\/p>\n The crucial ingredient was a ruby cube. The researchers hit this cube with a beam of green laser light while illuminating it with a blue laser from the side. As the green light passed through the ruby atoms, it changed their properties in a peculiar way that then affected how they reacted to the blue light.<\/p>\n Instead of letting the blue laser pass through them, the atoms affected by the green light now blocked the blue light, which created a shadow shaped exactly like the green laser beam<\/a>. Remarkably, the researchers could project the blue light on a screen and see this \u201cshadow of a laser\u201d with the naked eye.<\/p>\n <\/p>\n Abrahao says he and his colleagues had a long discussion of whether what they created really qualified as a shadow<\/a>. Because it moved when they moved the green laser beam, they could see it without any special equipment and they managed to project it onto commonplace objects, like a marker, they ultimately decided in the affirmative.<\/p>\n Historically, understanding shadows has been crucial for understanding what light can do and how we can use it, he says, and this experiment adds an unexpected technique into scientists\u2019 light-manipulation toolbox.<\/p>\n Tom\u00e1s\u00a0Chlouba<\/a> at the University of Erlangen\u2013Nuremberg in Germany says the experiment uses known processes to create a striking visual demonstration of how materials can help control light. The ruby\u2019s interactions with the laser, for instance, are similar to those of materials used in laser eye surgeries<\/a>, which must be able to respond to laser light by blocking it if it gets dangerously intense.<\/p>\n Topics:<\/p>\n<\/section><\/div>\n