Optical Vortices

Interferograms

Interference of a charge one Laguerre-Gaussian and a Gaussian,
experimentally and calculated in Mathematica.


Interference patterns of two Laguerre-Gaussian modes of opposite
topological charge using a Mach-Zender Interferrometer.


Interference of a charge three Laguerre-Gaussian and a Gaussian.
Note the spiraling forks!

Off-Center Incident Beam Patterns

   
   
The centering of the Gaussian beam on the dislocation of the grating is critical.
The diffraction pattern is shown with the corresponding grating location.

Incident Beam Size

Vortices of highest quality are created when the beam covers approximately
seven periods on both sides of the fork.

The Talbot Effect

The Talbot Effect was observed for the fork grating. As a lens is moved farther from the grating, the above images are created. Small changes in distance create dramatic changes in the pattern. This allowed the location and size of the incident beam to be studied.

The above images show the self-image of the diffraction pattern. The last photo is of topological charges -1, 0 and +1. Two forks are seen on either side of a region of parallel lines. One fork is red, the other black; this corresponds to the opposite phases of the opposite charges.

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