Light Can Be Reflected Not Only In Space But Also In Time (scientificamerican.com) 51
Anna Demming reports via Scientific American: [A]lthough so far there's no way to unscramble an egg, in certain carefully controlled scenarios within relatively simple systems, researchers have managed to turn back time. The trick is to create a certain kind of reflection. First, imagine a regular spatial reflection, like one you see in a silver-backed glass mirror. Here reflection occurs because for a ray of light, silver is a very different transmission medium than air; the sudden change in optical properties causes the light to bounce back, like a Ping-Pong ball hitting a wall. Now imagine that instead of changing at particular points in space, the optical properties all along the ray's path change sharply at a specific moment in time. Rather than recoiling in space, the light would recoil in time, precisely retracing its tracks, like the Ping-Pong ball returning to the player who last hit it. This is a "time reflection." Time reflections have fascinated theorists for decades but have proved devilishly tricky to pull off in practice because rapidly and sufficiently changing a material's optical properties is no small task. Now, however, researchers at the City University of New York have demonstrated a breakthrough: the creation of light-based time reflections. To do so, physicist Andrea Alu and his colleagues devised a "metamaterial" with adjustable optical properties that they could tweak within fractions of a nanosecond to halve or double how quickly light passes through. Metamaterials have properties determined by their structures; many are composed of arrays of microscopic rods or rings that can be tuned to interact with and manipulate light in ways that no natural material can. Bringing their power to bear on time reflections, Alu says, revealed some surprises. "Now we are realizing that [time reflections] can be much richer than we thought because of the way that we implement them," he adds. [...]
The device Alu and his collaborators developed is essentially a waveguide that channels microwave-frequency light. A densely spaced array of switches along the waveguide connects it to capacitor circuits, which can dynamically add or remove material for the light to encounter. This can radically shift the waveguide's effective properties, such as how easily it allows light to pass through. "We are not changing the material; we are adding or subtracting material," Alu says. "That is why the process can be so fast." Time reflections come with a range of counterintuitive effects that have been theoretically predicted but never demonstrated with light. For instance, what is at the beginning of the original signal will be at the end of the reflected signal -- a situation akin to looking at yourself in a mirror and seeing the back of your head. In addition, whereas a standard reflection alters how light traverses space, a time reflection alters light's temporal components -- that is, its frequencies. As a result, in a time-reflected view, the back of your head is also a different color. Alu and his colleagues observed both of these effects in the team's device. Together they hold promise for fueling further advances in signal processing and communications -- two domains that are vital for the function of, say, your smartphone, which relies on effects such as shifting frequencies.
Just a few months after developing the device, Alu and his colleagues observed more surprising behavior when they tried creating a time reflection in that waveguide while shooting two beams of light at each other inside it. Normally colliding beams of light behave as waves, producing interference patterns where their overlapping peaks and troughs add up or cancel out like ripples on water (in "constructive" or "destructive" interference, respectively). But light can, in fact, act as a pointlike projectile, a photon, as well as a wavelike oscillating field -- that is, it has "wave-particle duality." Generally a particular scenario will distinctly elicit just one behavior or the other, however. For instance, colliding beams of light don't bounce off each other like billiard balls! But according to Alu and his team's experiments, when a time reflection occurs, it seems that they do. The researchers achieved this curious effect by controlling whether the colliding waves were interfering constructively or destructively -- whether they were adding or subtracting from each other -- when the time reflection occurred. By controlling the specific instant when the time reflection took place, the scientists demonstrated that the two waves bounce off each other with the same wave amplitudes that they started with, like colliding billiard balls. Alternatively they could end up with less energy, like recoiling spongy balls, or even gain energy, as would be the case for balls at either end of a stretched spring. "We can make these interactions energy-conserving, energy-supplying or energy-suppressing," Alu says, highlighting how time reflections could provide a new control knob for applications that involve energy conversion and pulse shaping, in which the shape of a wave is changed to optimize a pulse's signal.
The device Alu and his collaborators developed is essentially a waveguide that channels microwave-frequency light. A densely spaced array of switches along the waveguide connects it to capacitor circuits, which can dynamically add or remove material for the light to encounter. This can radically shift the waveguide's effective properties, such as how easily it allows light to pass through. "We are not changing the material; we are adding or subtracting material," Alu says. "That is why the process can be so fast." Time reflections come with a range of counterintuitive effects that have been theoretically predicted but never demonstrated with light. For instance, what is at the beginning of the original signal will be at the end of the reflected signal -- a situation akin to looking at yourself in a mirror and seeing the back of your head. In addition, whereas a standard reflection alters how light traverses space, a time reflection alters light's temporal components -- that is, its frequencies. As a result, in a time-reflected view, the back of your head is also a different color. Alu and his colleagues observed both of these effects in the team's device. Together they hold promise for fueling further advances in signal processing and communications -- two domains that are vital for the function of, say, your smartphone, which relies on effects such as shifting frequencies.
Just a few months after developing the device, Alu and his colleagues observed more surprising behavior when they tried creating a time reflection in that waveguide while shooting two beams of light at each other inside it. Normally colliding beams of light behave as waves, producing interference patterns where their overlapping peaks and troughs add up or cancel out like ripples on water (in "constructive" or "destructive" interference, respectively). But light can, in fact, act as a pointlike projectile, a photon, as well as a wavelike oscillating field -- that is, it has "wave-particle duality." Generally a particular scenario will distinctly elicit just one behavior or the other, however. For instance, colliding beams of light don't bounce off each other like billiard balls! But according to Alu and his team's experiments, when a time reflection occurs, it seems that they do. The researchers achieved this curious effect by controlling whether the colliding waves were interfering constructively or destructively -- whether they were adding or subtracting from each other -- when the time reflection occurred. By controlling the specific instant when the time reflection took place, the scientists demonstrated that the two waves bounce off each other with the same wave amplitudes that they started with, like colliding billiard balls. Alternatively they could end up with less energy, like recoiling spongy balls, or even gain energy, as would be the case for balls at either end of a stretched spring. "We can make these interactions energy-conserving, energy-supplying or energy-suppressing," Alu says, highlighting how time reflections could provide a new control knob for applications that involve energy conversion and pulse shaping, in which the shape of a wave is changed to optimize a pulse's signal.
Shameful Clickbait Title by Scientific American (Score:5, Informative)
Re:Shameful Clickbait Title by Scientific American (Score:5, Funny)
Scientific American should go back in time and undo their sin.
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Re: Shameful Clickbait Title by Scientific America (Score:5, Interesting)
The Scientific American URL contains "sort of", that's conveniently too many chars for /. so the editor left that out here ;p
That's a thing with article titles that are on the tongue-in-cheek edge, then they go on aggregator sites which yet again give the title a slight touch, commenter misinterprets the detail and eventually it gets so hyperbole that cancer is cured tomorrow but just too late cos the world will explode this afternoon.
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But being honest will hurt profits! So adjust the titles, simplify the summaries, and wait for the clicks to roll in.
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Honestly, are you just addicted to bashing anything out of the ordinary because otherwise your own ordinary humdrum existence wouldn't be justified?
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Re:Shameful Clickbait Title by Scientific American (Score:4, Funny)
It certainly explains that when I look in the mirror I see someone much older than myself.
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phase conjugate reflection (Score:4, Informative)
The 1970s called and they want you to stop rebranding phase conjugate light media with new buzz phrases.
Here's a 1985 article from sci am that did the same thing
https://www.scientificamerican... [scientificamerican.com]
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What if you simply jumped to a conclusion in your eagerness to stamp out the horrible bogeyman of pseudoscience because it just feels so good?
Why isn't seeing on Tuesday what happened on Monday just by reflecting Tuesday's light waves also signified by the title?
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Indeed. Sensationalist crap reporting has become the norm, not the exception.
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Do you often get easily trolled? Are you addicted to spiking emotional responses to text?
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What are you talking about? I just do not like to have to wade through tons of crap to find some actual news.
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Do you think you are cherry-picking? What makes you think I don't experience the same feeling about, like, everything?
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Are you creating a strawman, because the title uses reflect not reverse?
click bait (Score:3)
Re: click bait (Score:2)
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Are you so sure there's a difference?
What if you could reflect a wave back in time and then interfere with it and change its subsequent course?
Can a wave do something, then get reflected back to a point before it did that thing, and be manipulated to do something else, and what fun and useful things might you do with that device?
Well, (Score:4, Funny)
I'll see you yesterday then!
Yes, yes. (Score:2)
Reflection implies light propagation, and propagation implies time. So?
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... the mirror universe in which Spock has a goatee.
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The horror, is that one of the star wars logic elves?
A switching material is all.. (Score:5, Insightful)
So much PR clickbait.. TLDR but it seems they created a metamaterial that can be used for optical switching in the microwave regime. IANAP but it sounds like they describe things you would expect an optical router to have. Which is something for sure, but has nothing to do with time. They are basically altering the waveguide at such a speed that (if you are stupid) it sounds like magic. When it is more like electronic shutter of an LCD mirror.. ick. If anybody actually read the paper wherever it is and can correct me that would be nice but kinda fed up at this point. Sooo much garbage to "polish it up" for the readers. Pretty insulting and distracting AF.
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Is it more stupid to deny magic based on faith in the assumptions (i.e., conclusions without proof) of standard old physics (which makes huge blunders like predicting the zero point energy to be 120 orders of magnitude greater than it is actually measured to be)?
Original paper (Score:4, Informative)
Observation of temporal reflection and broadband frequency translation at photonic time interfaces [nature.com]
Abstract: Time reflection is a uniform inversion of the temporal evolution of a signal, which arises when an abrupt change in the properties of the host material occurs uniformly in space. At such a time interface, a portion of the input signal is time reversed, and its frequency spectrum is homogeneously translated as its momentum is conserved, forming the temporal counterpart of a spatial interface. Combinations of time interfaces, forming time metamaterials and Floquet matter, exploit the interference of multiple time reflections for extreme wave manipulation, leveraging time as an additional degree of freedom. Here we report the observation of photonic time reflection and associated broadband frequency translation in a switched transmission-line metamaterial whose effective capacitance is homogeneously and abruptly changed via a synchronized array of switches. A pair of temporal interfaces are combined to demonstrate time-reflection-induced wave interference, realizing the temporal counterpart of a Fabry–Pérot cavity. Our results establish the foundational building blocks to realize time metamaterials and Floquet photonic crystals, with opportunities for extreme photon manipulation in space and time.
can u steal that much of an article and repost? (Score:2)
disgraceful title (Score:2)
Didn't even take... (Score:3)
Alternate View Column AV-07 https://www.npl.washington.edu... [washington.edu]
Alternate View Column AV-08 https://www.npl.washington.edu... [washington.edu]
Fixed that for you (Score:2)
time-reversed (phase conjugated) light (Score:4, Insightful)
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So do you practice alchemy and drink quicksilver for medicinal reasons?
Dupe! (Score:2)
OMG... TFS?! (Score:2)
That is the most unreadable summary I have ever seen on Slashdot. As a writer and editor, I want to take a machete to that mass of words.
Quite the statement at the beginning. (Score:2)
"Managed to turn back time".
- Scientists are baffled
- Cosmology is collapsing
- Science says you don't exist
And no, I didn't read the article. I only need to go as far as the second half of the first sentence to know it's not worth reading.
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Would you have denied the first mirror because who needs it right?
Can't you get historic time to be out of sync.. (Score:2)
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What if you split a photon into different wave planes through polarization?
"An individual photon can be described as having right or left circular polarization, or a superposition of the two. Equivalently, a photon can be described as having horizontal or vertical linear polarization, or a superposition of the two." - wikipedia
Raises all types of questions. (Score:2)
Can we detect if the microwaves we recieve are interfered with in these ways? If not, how are we sure the images from our different telescopes are not reflections in this way, creating distortions in our understanding of the universe compared to the real thing.
At the same time, this metamaterial sounds like it might be enough to create a computational machine based off of light.
"Microwave-frequency light" (Score:2)
channels microwave-frequency light
Uh, so you mean microwaves then?