Light Can Twist as Well as Spin

NASA -- Astronomy Picture of the Day ^ | 11-19-03 | apod

[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.

[Boot Hill]

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

[ovrtaxt]

Given that the shape of photons with OAM is helical, I guess this now qualifies as a light meal.

[ovrtaxt]

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?

[Mind-numbed Robot]

Out of phase orthogonals can certainly put ones panties in a twist. :-)

[edwin hubble]

Great post, Boot Hill

[BigLittle]

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 ;>)

[Boot Hill]

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

[Boot Hill]

Thanks and thanks for pinging "the usual suspects".

--Boot

[Boot Hill]

"photons can also have orbital angular momentum"

--Boot

[bannie]

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

[randog]

...we have a new "twist" to optical theory!

Well, plug that into your calculator and smoke it!

[Boot Hill]

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

[Chewbacca]

Does light have its own DNA?
Looks like a DNA helix.

[r9etb]

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....

[null and void]

good one.

[null and void]

But can light twist and shout?

[RightWhale]

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[Libertarianize the GOP]

ping

[richtig_faust]

TE and TM waves.......... I thought we knew that back in Maxwell's time...