Slashdot Mirror
New Way of Observing Light May Boost Info Content
md_seymour observes: "Today's Astronomy Picture of the Day from NASA has a description and image of light that can twist as well as spin, based on research from Miles Padgett and Johannes Courtial of the University of Glasgow. They and their colleagues have apparently been able to sort individual photons by their orbital angular momentum. Since this characteristic of the photon is able to take on an infinite number of values, it may be possible to pack much more information into a light beam."
There's an infinite number because any integer multiple of the base value is possible.
To use your parallel, Planck length places a bound on fractions of 1 meter, but not on multiples of 1 meter.
No, they're different.
Take a beam of circularly-polarized light (without orbital-angular-momentum), freeze time in your imagination, and look at the E-field vectors along the beam. The E-field vectors all point in the same direction. Over time they rotate around the beam axis -- that's what circular polarization means -- but the E-field-vectors are always aligned along the entire length of the beam.
Now instead imagine a beam of light with orbital-angular-momentum, and again freeze the beam in your imagination. Now the E-field vectors make a helix along the beam.
You get circularly polarized light by passing a beam through a polarizer and quarter-wave plate. You get light with orbital angular momentum by spinning the light source around the beam axis.
Yes, actually an infinite number of values. The same way that the integers in discrete, but infinite in number.
Engineers also speak PDE, only in a different dialect.
There's a short article about this property of light in this month's edition of Scientific American. Apparently this propery isn't new but rather largely ignored.
Well, there's spam egg sausage and spam, that's not got much spam in it.
For practical use, we could use it's quirkyness to see earth sized planets orbiting stars without building monsterous interferometers.
Sorry nope. This would do us no good in detecting planets at interstellar distances. First of all, you still need large interferometers (or mirrors) to resolve small angular distances (read planetary orbits at interstellar distances). Secondly, ordinary light (from stars and planets etc. is randomly polarised and the orbital angular momentum would be distributed randumly according to some statistical energy distribution function (there are several and i don't know enough quantum physics to tell which one). Therefore the orbital angular mmentum would not carry any information. You need lasers or similar stuff to encode the angular momentum with information, natural light does not work.
Yours Yazeran
Plan: To go to mars one day with a hammer.