Subscribe to our Breaking News email to get real-time breaking news alerts sent straight to your inbox.
Sign up for our free breaking news emails
Scientists were shocked to see “time reversal” in electromagnetic waves – an amazing phenomenon that was not previously assumed.
The effect has been compared to looking in a mirror and seeing the reflection of your back, or to hearing an echo but the sound is reflected when the tape is played backwards.
Scientists have long hypothesized that such an effect exists. But this was hard to notice because the properties of matter needed to change quickly and fundamentally for this to happen.
Now, using a special kind of material, scientists say they’ve seen it happen. By sending signals through a strip of metal and causing rapid changes in physical properties, the researchers monitored the reflection of these signals over time.
“It’s really exciting to see, given when this reflection phenomenon was predicted and how differently over time reflected waves behave compared to waves reflected back from space,” said Andrea Allo, a distinguished professor of physics at the City University of New York in New York. The Graduate Center and one of the authors of the new paper, the author, said in a statement.
“Using advanced materials design, we were able to recognize conditions that change material properties over time, both abruptly and with great variability.”
The reflections we’re used to seeing are spatial reflections: electromagnetic light waves hitting a mirrored surface bounce off and create effects that allow us to use mirrors and more.
This spatial reflection occurs when a wave hits a boundary, such as a mirror. But time inversions are different in many ways — on the one hand, they occur when the entire medium goes through the transition period, simultaneously.
When this happens, the phase of the wave is reversed in time and its frequency changes. This was the effect the scientists expected to see in the new study.
The researchers hope that this discovery will lead to a variety of practical applications, including wireless communications and new low-power microcomputers. Previously, it was thought that these applications would not be possible because it was very difficult to change the medium very quickly.
said Gengyu Xu, co-first author of the paper and a postdoctoral researcher at the Center for Advanced Science Research at CUNY. , in the current situation. “It is very difficult to change the properties of a medium quickly enough, uniformly, and reflect electromagnetic signals with enough contrast over time because they oscillate so quickly.
“Our idea was to avoid changing the properties of the host material and instead create a metamaterial where additional elements could be suddenly added or subtracted via hot swapping.”
“Observing time reversal and broad frequency translation at a photonic time interface” describes the results of a research published in the journal Nature Physics.