The Light Fantastic

Exploring the Photon Orbital Angular Momentum

Optical Vortices

By David Órdenes D.

ALVA, Lund University

   

See instructions on how to make you own twisted beams below!

 

 

Introductory Bibliography

All Screwed Up, Scientific American. November 3, 2003. Link

"Optical Vortices" Might Extract Abundant Information From Matter, AIP; Physics News Update, Number 721. Link

Twisting the light away, New Scientist, Issue 2451. June 12, 2004.

Light's Orbital Angular Momentum. Miles Padgett, Johannes Courtial & Les Allen. Physics Today, May 2004.

Light With Orbital Angular Momentum. http://www.aip.org/png/2005/229.htm

 

 

Advanced Bibliography

Optical Spin-to-Orbital Angular Momentum Conversion in Inhomogeneous Anisotropic Media. L. Marrucci, C. Manzo, and D. Paparo.

Phys. Rev. Lett. 96, 163905 (28 April 2006)

 

Photon Orbital Angular Momentum in Astrophysics. Martin Harwit

The Astrophysical Journal 597, 10 November 2003

 

Photon orbital angular momentum in astronomy. N. M. Elias II

Astronomy & Astrophysics 492, 883–922 (2008)

 

Measuring the Orbital Angular Momentum of a Single Photon. Jonathan Leach

Physical Review Letters, Vol 88, Number 25, 24 June 2002

 

Optical vortices with starlight. G. Anzolin et al.

Astronomy and Astrophysics, Volume 488, Issue 3, pp.1159-1165 (2008)

(Preprint version: http://arxiv.org/abs/0706.2675)

 

Photon angular momentum: selection rules and multipolar transition moments. Roger Grinter

Journal of Physics B: Atomic, Molecular and Optical Physics

Volume 41, Number 9, 14 May 2008

 

An image of an exoplanet separated by two diffraction beamwidths from a star. E. Serabyn, D. Mawet & R. Burruss

Nature 464, 1018-1020, 15 April 2010

 

The Vector Vortex Coronagraph: Laboratory Results and First Light at Palomar Observatory. D. Mawet et al

http://arxiv.org/abs/0912.2287

 

 

 

Constructing your own fork mask

The image used for the demonstration was taken from the web page "Light Beams in High-Order Modes", of the Colgate University, Physics and Astronomy Department. (Link: http://departments.colgate.edu/physics/research/optics/oamgp/gp.htm). There you can also learn more about the physics behind. :)

Since the image is in jpeg format, in order to obtain a high-quality print copy, it's better to vectorize it. This can be accomplished using tools like Potrace and Autotrace (see links below.)

The result is a cleaner, scalable image in black and white:

Optical Vortices

 

A pdf version can be downloaded here.

This image must be printed in a normal sheet of paper at a smaller scale. A reduced copy of this print is taken in a photocopier, using an overhead slide as final target. This procedure shoud be followed procuring that the final version is about 6 mm on a side. For better results it's better to print the same image several times in the same sheet, with some variation in size, so you can test with different results in the overhead copy. You might want to try first using the smallest versions that retain enough detail.

The reason for using a photocopier is that they usually can yield a much more detailed copy on reduction than a typical laser or inkjet printer.

Use a laser pointer (safety reccomendations in the links below) to illuminate the mask right in the middle, perpendicularly to its plane. (Be careful with reflections, so be sure the mask is being kept stable and is not going to tumble down or turn around, potentially reflecting a fraction of the beam to someone's eyes). You might need to check for a clear pattern with the "dougnuts" several meters away; it will all depend on the characteristics and quality of both your beam and the printed mask. You can apply some clever method to hold and finely change the position of the mask... And that's it!

The result should look more or less like the image on top of the page, or even better. Enjoy!

 

 

Laser Safety Recommendations

http://web.princeton.edu/sites/ehs/labpage/laserpointersafety.htm

http://www.laserpointersafety.com/

 

Image Vectorization Software (free tools)

http://autotrace.sourceforge.net/index.html

http://potrace.sourceforge.net/