Speed of light drops to zero at 'exceptional points'

January 31, 2018 by Lisa Zyga, Phys.org feature
stopped light
Artistic image. Credit: pixabay

Light, which travels at a speed of 300,000 km/sec in a vacuum, can be slowed down and even stopped completely by methods that involve trapping the light inside crystals or ultracold clouds of atoms. Now in a new study, researchers have theoretically demonstrated a new way to bring light to a standstill: they show that light stops at "exceptional points," which are points at which two light modes come together and coalesce, in waveguides that have a certain kind of symmetry.

Unlike most other methods that are used to stop light, the new method can be tuned to work with a wide range of frequencies and bandwidths, which may offer an important advantage for future slow-light applications.

The researchers, Tamar Goldzak and Nimrod Moiseyev at the Technion – Israel Institute of Technology, along with Alexei A. Mailybaev at the Instituto de Matemática Pura e Aplicada (IMPA) in Rio de Janeiro, have published a paper on stopping light at exceptional points in a recent issue of Physical Review Letters.

As the researchers explain, exceptional points can be created in waveguides in a straightforward way, by varying the gain/loss parameters so that two light modes coalesce (combine into one mode). Although light stops at these exceptional points, in most systems much of the light is lost at these points. The researchers showed that this problem can be fixed by using waveguides with parity-time (PT) symmetry, since this symmetry ensures that the gain and loss are always balanced. As a result, the remains constant when the light approaches the exceptional point, eliminating losses.

To release the stopped light and accelerate it back up to normal speed, the scientists showed that the gain/loss parameters can simply be reversed. The most important feature of the new method, however, is that the exceptional points can be adjusted to work with any frequency of light, again simply by tuning the gain/loss parameters. The researchers also expect that this can be used for other types of waves besides , such as acoustic waves. They plan to further investigate these possibilities in the future.

Explore further: 'Exceptional points' give rise to counterintuitive physical effects

More information: Tamar Goldzak et al. "Light stops at exceptional points." Physical Review Letters. DOI: 10.1103/PhysRevLett.120.013901, Also at arXiv:1709.10172 [physics.optics]

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Kalopin
1 / 5 (6) Jan 31, 2018
...the photon is an exhaust emission, following particle explosion to send out cosmic rays [radiation] at anywhere from fifty to five hundred times [the current measured velocity of] the speed of light...

...Voyager1 finds storms of cosmic radiation spinning in retrograde at the edge of the heliopause...
Whydening Gyre
5 / 5 (1) Jan 31, 2018
...the photon is an exhaust emission, following particle explosion to send out cosmic rays [radiation] at anywhere from fifty to five hundred times [the current measured velocity of] the speed of light...

...Voyager1 finds storms of cosmic radiation spinning in retrograde at the edge of the heliopause...

And your point is...?
rrwillsj
1 / 5 (3) Jan 31, 2018
Another frustrating, poorly edited article. Mixing up present tense with future tense throughout the phrasing.

Boil it down, the researchers are claiming that they might be able to devise experiments that might fulfill their speculations about what might occur during the experiments.

Maybe? Perhaps?

The only conclusion I can draw from this article is that their research project has not achieved repeatable results.

But their hoping, maybe, any day now! That maybe they are now on the right tracks prove their hypothesis.

Yeah? Well, maybe...
cardzeus
3 / 5 (2) Jan 31, 2018
'To release the stopped light and accelerate it back up to normal speed, the scientists showed that the gain/loss parameters can simply be reversed.'

I'd appreciate any information on the following:

How is this acceleration described?

What direction does the photon go?
mackita
2 / 5 (8) Jan 31, 2018
researchers have theoretically demonstrated a new way to bring light to a standstill ... in waveguides that have a certain kind of symmetry
The slowing of EM wave is crucial for various antigravity and overunity scenarios: in my theory the overunity is possible, once the energy density of physical system changes faster than the speed of energy propagation within it. Under such a situation the EM wave could effectively propagate faster than it should do in material given. This condition is also necessary for entropic time reversal, formation of magnetic monopoles, time crystals, antigravity thrusters violating inertia law etc (due to correspondence principle the violation of one fundamental law violates also many others related ones.) The propagation of electromagnetic waves along bifilar coils or within saturated ferromagnets comes on mind here.
mackita
2.1 / 5 (7) Jan 31, 2018
Of course the sudden slowing of energy propagation is necessary but not sufficient condition for achieving overunity in this way. On the other hand, this principle shouldn't be limited just to electromagnetic wave spreading. For example overunity observed within many cavitation system may be also related to fact, that the forming bubbles form or disappear faster than the surface waves (sound oscillations) can propagate within them. Under such a situation (sudden quenching of energy state) the inverse population can be reached and the thermal noise of material would assist the energy propagation within material given which could generate mechanical work into account of energy of thermal fluctuations (thus reversing 2nd thermodynamic law). We could say, the abruptly slowed wave gets temporarily cooler than its environment, which can therefore heat it. I explained this concept in more detail bellow article here
Hyperfuzzy
1 / 5 (1) Jan 31, 2018
Superposition!
Whydening Gyre
1 / 5 (1) Jan 31, 2018
Speed slows, spin increases....
KBK
not rated yet Jan 31, 2018
Lets talk about the asymmetrical microwave based EmDrive thruster.

Do you want to get a bus line going back and forth from Mars, or not?

What's it gonna be?

Maybe go mine a choice asteroid or two?

Turn the question around. Find the connection, not the singular isolated dismissal.
Whydening Gyre
3 / 5 (2) Jan 31, 2018
Speed slows, spin increases....

Light doesn't stop - it just moves in another direction.

FTA;
"researchers have {THEORETICALLY} demonstrated a new way to bring light to a standstill:"

These guys have figured out how to make it LOOK like it does, using mathematical manipulation.

show it with experimentation.
rrwillsj
3 / 5 (2) Feb 01, 2018
WG, my point exactly

mack, please be very careful. If my hypothesis of gravity is any where near correct? An anti-gravity device disintegrates itself into a very noticeable KA-BOOM!!
Cause, think about it... Gravity is a condition of Mass. And any machine to create an anti-gravity effect? Is also a mass of matter, that will not appreciate your efforts to reverse the attractor.

KBK, terrific idea. Now do something about it. Are you waiting around for other people to create for you?

Start your own space program. If a kiwi hobbyist can put a disco-ball into orbit? So can you.

I suggest that you start planning a small orbital drone. Crowdsource it for funds and ideas and collaborators.

You can thank me latter when you actually have a working Em Drive at work in space.
Hyperfuzzy
1 / 5 (2) Feb 01, 2018
Simple, charge always complies, fields don't bother fields; however;,and or subtract in space; therefore, your stopping light, is a state.

Stopping Light? I have a magic trick, i can see behind me .
Hyperfuzzy
1 / 5 (2) Feb 01, 2018
O yeah and gravity, just count 'em up, add any motion that obey the law. Stopped light is invisible!

Hyperfuzzy
1 / 5 (1) Feb 01, 2018
Like to see those field equations as a function of charge holistically! Nothing else is there, its a continuous space made of only these items, theoretically, True! Therefore each charge, never created or destroyed is only "a" Field center. Therefore any space may be simulated.
Whydening Gyre
not rated yet Feb 02, 2018
Lets talk about the asymmetrical microwave based EmDrive thruster.

And.... what's asymmetric about it?
Whydening Gyre
not rated yet Feb 02, 2018
WG, my point exactly

mack, please be very careful. If my hypothesis of gravity is any where near correct? An anti-gravity device disintegrates itself into a very noticeable KA-BOOM!!
Cause, think about it... Gravity is a condition of Mass. And any machine to create an anti-gravity effect? Is also a mass of matter, that will not appreciate your efforts to reverse the attractor.
Yes, it is a condition of mass. But way, way, WAY down at atomic level much of Earths mass is more a collection of paramagnetic, collectively un-polarized dipolar magnetic moments... (electro even...) Heat and kinetics cause collective polarization of at least some of it, however...
antialias_physorg
5 / 5 (5) Feb 02, 2018
How is this acceleration described?

I think acceleration is the wrong word (it also doesn't appear in the original paper). Notice also that the "speed zero" they refer to is the group velocity - not the velocity of an individual photon.
Group velocity and phase velocity are different critters. There's a pretty cool animated gif on wikipedia showing that they can even go in opposite directions.
https://en.wikipe...velocity

What direction does the photon go?

Same as before (due to conservation of momentum)
Unless part of its momentum is transferred to a phonon (vibration in the material) in which case the momentum vector changes (again due to conservation of momentum)
mackita
1 / 5 (3) Feb 02, 2018
Inside metamaterials the light can even travel back toward source. You can see it clearly on the simulation of spreading waves through metamaterial slab Their negative refractive index implies, that speed of light gets reversed. Note that this slab is formed by nothing else than mixture of obstacles and holes between them. For certain narrow range of wavelengths such an environment gets negative refractive index (negative slope of curve described by Kramers equations). Therefore it's not so surprising, that the light effectively stops at some places between pair of tuned waveguides with different refraction index.
cardzeus
5 / 5 (1) Feb 03, 2018
Cheers Antialias_physorg. Much appreciated.
TrollBane
5 / 5 (3) Feb 03, 2018
"...the photon is an exhaust emission, following particle explosion to send out cosmic rays [radiation] at anywhere from fifty to five hundred times [the current measured velocity of] the speed of light...
...Voyager1 finds storms of cosmic radiation spinning in retrograde at the edge of the heliopause..."

Word salad to impress the intellectual vegetable?
Da Schneib
5 / 5 (2) Feb 04, 2018
This is a group velocity phenomenon, like the other examples. Group velocity is not the velocity of the propagating wave but of variations in its envelope; that is, in its amplitude. When two waves interfere the group and phase velocities do not describe the velocity of wave propagation but of features of the waves that go beyond the shape of the individual waves.

This is interesting but not really "slowing light down to zero velocity." It's just the group velocity that's slowed down to zero. What would be interesting is if they'd say what the phase velocity is, and that they've done this by changing the phase of the light.
Da Schneib
5 / 5 (1) Feb 04, 2018
@cardzeus, don't get too excited; the basic phenomenon here is interference, and has to do with propagation of the nodal points in the waves, not the waves themselves.

I found that there were a lot of missing articles (in the linguistic sense) in the arXiv preprint which is linked in this article.
KBK
not rated yet Feb 05, 2018
Lets talk about the asymmetrical microwave based EmDrive thruster.

And.... what's asymmetric about it?


The wave system, the resonance pattern is locked, resonant, stable.

The underlying function, or condition being affected, is dynamic and flowing in multiple axis.

The end result is a asymmetrical mass reactionary ratcheting or flow.

Ie, the underlying vacuum is dynamic and requires a stable locked multi-axis resonance acting upon it, in order to gain a foothold, a lock, a 'mass reaction' that can actually work off of it.

As soon as one tries to move the em drive, the resonance changes, it shifts. This tells you all you need to know. Or at least illustrates an important aspect of what is going on. As well, that the effect increases with motion, in most reports.

You're trying to grab hold of and work against a 4 axis flowing dynamic, which requires a minimum 3-axis resonance pattern that is stable and in flow, ie, AC and asymmetric.
Hyperfuzzy
not rated yet Feb 05, 2018
If u can see it then it is not stopped! Else you only see the Espsilon Mu Tensors.
TheGhostofOtto1923
not rated yet Feb 05, 2018
Another frustrating, poorly edited article. Mixing up present tense with future tense throughout the phrasing
Well this is what happens when a fucking pissant tries to understand real science.

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