{"id":111603,"date":"2020-08-06T09:55:47","date_gmt":"2020-08-06T13:55:47","guid":{"rendered":"https:\/\/www.ucf.edu\/news\/?p=111603"},"modified":"2020-09-01T15:57:14","modified_gmt":"2020-09-01T19:57:14","slug":"ucf-developed-new-class-of-laser-beam-doesnt-follow-normal-laws-of-refraction","status":"publish","type":"post","link":"https:\/\/www.ucf.edu\/news\/ucf-developed-new-class-of-laser-beam-doesnt-follow-normal-laws-of-refraction\/","title":{"rendered":"UCF-Developed New Class of Laser Beam Doesn\u2019t Follow Normal Laws of Refraction"},"content":{"rendered":"
色花堂 researchers have developed a new type of laser beam that doesn\u2019t follow long-held principles about how light refracts and travels.<\/p>\n
The findings, which were published recently in Nature Photonics<\/em><\/a>, could have huge implications for optical communication and laser technologies.<\/p>\n \u201cThis new class of laser beams has unique properties that are not shared by common laser beams,\u201d says Ayman Abouraddy, a professor in UCF\u2019s College of Optics and Photonics<\/a> and the study\u2019s principal investigator.<\/p>\n The beams, known as spacetime wave packets, follow different rules when they refract, that is when they pass through different materials. Normally, light slows down when it travels into a denser material.<\/p>\n \u201cIn contrast, spacetime wave packets can be arranged to behave in the usual manner, to not change speed at all, or even to anomalously speed up in denser materials,\u201d Abouraddy says. \u201cAs such, these pulses of light can arrive at different points in space at the same time.\u201d<\/p>\n \u201cThink about how a spoon inside a water-filled glass looks broken at the point where the water and air meet,\u201d Abouraddy says. \u201cThe speed of light in air is different from the speed of light in water. And so, the light rays wind up bending after they cross the surface between air to water, and so apparently the spoon looks bent. This is a well-known phenomenon described by Snell\u2019s Law.\u201d<\/p>\n Although Snell\u2019s Law still applies, the underlying change in velocity of the pulses is no longer applicable for the new laser beams, Abouraddy says. These abilities are counter to Fermat\u2019s Principle that says light always travels such that it takes the shortest path, he says.<\/p>\n \u201cWhat we find here, though, is no matter how different the materials are that light passes through, there always exists one of our spacetime wave packets that could cross the interface of the two materials without changing its velocity,\u201d Abouraddy says. \u201cSo, no matter what the properties of the medium are, it will go across the interface and continue as if it’s not there.\u201d<\/p>\n For communication, this means the speed of a message traveling in these packets is no longer affected by traveling through different materials of different densities.<\/p>\n \u201cIf you think of a plane trying to communicate with two submarines at the same depth but one is far away and the other one’s close by, the one that’s farther away will incur a longer delay than the one that’s close by,\u201d Abouraddy says. \u201cWe find that we can arrange for our pulses to propagate such that they arrive at the two submarines at the same time. In fact, now the person sending the pulse doesn’t even need to know where the submarine is, as long as they are at the same depth. All those submarines will receive the pulse at the same time so you can blindly synchronize them without knowing where they are.\u201d<\/p>\n Abouraddy\u2019s research team created the spacetime wave packets by using a device known as a spatial light modulator to reorganize the energy of a pulse of light so that its properties in space and time are no longer separate. This allows them to control the \u201cgroup velocity\u201d of the pulse of light, which is roughly the speed at which the peak of the pulse travels.<\/p>\n