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Light Can Twist as Well as Spin
NASA -- Astronomy Picture of the Day ^ | 11-19-03 | apod

Posted on 11/19/2003 3:30:55 AM PST by Boot Hill


Explanation:   Light is more complicated than we thought. When astronomers measure light, they are usually concerned with its direction, energy, and spin polarization (sometimes). Recently, however, it has been more broadly realized that photons can also have orbital angular momentum (OAM), an attribute classically analogous to the Earth orbiting the Sun as well as spinning on its axis. Pictured above, the wave-front of a photon with OAM is shown to be twisted, in contrast to the flat plane of zero OAM light. Light with OAM might be used to increase the information content of communication or to discern specific types of astronomical sources. Passing through a common lens, light without OAM focuses to a point, whereas light with OAM focuses to a ring. Most light bouncing around the cosmos, however, is expected to have so little (or zero) OAM that the created ring is too small to measure. Even given other promising methods for measurement, exploiting OAM for astronomical discovery might be as much an issue of observational practicality as theoretical possibility.


TOPICS: Extended News; Miscellaneous; Technical
KEYWORDS: light; optics
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Holy orbiting photon, Batman, we have a new "twist" to optical theory!

Let's see, Maxwell's equations require that the electric and magnetic components of the wave be orthogonal, but nothing requires those two components to be in phase with each other. Is this what's got the photons panties in a twist?

--Boot

1 posted on 11/19/2003 3:30:56 AM PST by Boot Hill
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To: Boot Hill
Given that the shape of photons with OAM is helical, I guess this now qualifies as a light meal.


2 posted on 11/19/2003 3:42:11 AM PST by ovrtaxt ( http://www.fairtax.org **** Forget ANWR. Drill Israel !)
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To: Boot Hill
So, if we consider light a wave of energy rather than a particle, what are the ramifications of other electromagnetic emissions, i.e. any waves across the spectrum such as x or gamma or micro waves, with OAM properties? Maybe a new Muslim Killer for the troops?


3 posted on 11/19/2003 3:48:12 AM PST by ovrtaxt ( http://www.fairtax.org **** Forget ANWR. Drill Israel !)
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To: Boot Hill
Out of phase orthogonals can certainly put ones panties in a twist. :-)
4 posted on 11/19/2003 3:54:41 AM PST by Mind-numbed Robot (Not all things that need to be done need to be done by the government.)
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To: Boot Hill; PatrickHenry; RadioAstronomer; Piltdown_Woman; longshadow; Physicist
Great post, Boot Hill
5 posted on 11/19/2003 3:57:35 AM PST by edwin hubble
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To: ovrtaxt

HOLY RAVIOLI! The way the light is twisting off the plate of pasta makes it seem as if you can see a face in there ;>)

6 posted on 11/19/2003 4:04:31 AM PST by BigLittle
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To: ovrtaxt
ovrtaxt asks:   "...what are the ramifications of other electromagnetic emissions, i.e. any waves across the spectrum..."

It would apply to all wavelengths.

--Boot Hill

7 posted on 11/19/2003 4:13:00 AM PST by Boot Hill
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To: edwin hubble
Thanks and thanks for pinging "the usual suspects".

--Boot

8 posted on 11/19/2003 4:14:18 AM PST by Boot Hill
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To: r9etb
"photons can also have orbital angular momentum"

--Boot

9 posted on 11/19/2003 4:34:31 AM PST by Boot Hill
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Comment #10 Removed by Moderator

To: ovrtaxt
Oooo, exactly! "Light ENERGY"! This she-layman is impressed.

11 posted on 11/19/2003 4:53:55 AM PST by bannie (The government which robs Peter to pay Paul can always depend upon the support of Paul.)
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To: Boot Hill
...we have a new "twist" to optical theory!

Well, plug that into your calculator and smoke it!

12 posted on 11/19/2003 6:01:30 AM PST by randog (Everything works great 'til the current flows.)
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To: Buckhead
Buckhead asks:   "Does this have any implications for the observed red shift..."

It might. While photons have no mass, they do have momentum and a spiraling photon might have to give up some of its momentum to achieve the orbital path described in the thread article. If this occurred, it would seem to imply a shift to a longer wavelength (i.e., red shift).

--Boot Hill

13 posted on 11/19/2003 6:58:07 AM PST by Boot Hill
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To: Boot Hill
Does light have its own DNA?
Looks like a DNA helix.
14 posted on 11/19/2003 7:08:33 AM PST by Chewbacca (I talk to myself because it is the only way I can have an intelligent conversation.)
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To: Boot Hill
Well, this is an odd twist....

If it really is an "angular momentum" in the usual sense of the term, then it should be possible to bend light by (somehow) exerting a torque on the wave front.

I guess that would be part of the explanation for refraction....

15 posted on 11/19/2003 7:46:58 AM PST by r9etb
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To: BigLittle
good one.
16 posted on 11/19/2003 7:49:43 AM PST by null and void (Lord Hildamort! - She Who Must Not Be Named)
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To: Boot Hill
But can light twist and shout?
17 posted on 11/19/2003 7:50:51 AM PST by null and void (Lord Hildamort! - She Who Must Not Be Named)
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To: Boot Hill; petuniasevan
APOD is a regular feature of the day thanks to one of our long-time FReepers. Get on the list, don't miss out.
18 posted on 11/19/2003 9:01:00 AM PST by RightWhale (Close your tag lines)
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To: Ernest_at_the_Beach; sourcery
ping
19 posted on 11/19/2003 9:13:35 AM PST by Libertarianize the GOP (Ideas have consequences)
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To: Boot Hill
TE and TM waves.......... I thought we knew that back in Maxwell's time...
20 posted on 11/19/2003 9:18:03 AM PST by richtig_faust
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