BASIC FUNCTIONALITY
WHAT IT SHOWS
Apart from the intensity cross-section in one plane (grey-level), the applet indicates the phase of the interfering beams. It does this in the following way: the figure below shows an example of two different phase fronts (red and blue) of the same light beam (the light beam in the example has 3 hbar orbital angular momentum) but out of phase with each other (by pi or 180°).
The two-beam interference simulation applet indicates the lines of intersection of two such out-of-phase phase fronts with the cross-section plane.
WHAT IT DOES...
It takes 2 light beams with helical phase fronts (top two pictures) and calculates their superposition (bottom picture), taking into account the beams' orbital angular momenta, rotation angles, axis positions, and sizes.
... AND DOESN'T DO
It makes special assumptions about the beams' phase front curvatures (assumption: not curved), inclinations (assumption: beams travel normal to the screen), additional phase differences (assumption: beams in phase), intensities (assumption: same peak intensity), and radial intensity profiles (the intensity profiles are always those of l=1 Laguerre-Gaussian modes).
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state after loading
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grabbing a phase front
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rotating the beam
(by dragging a phase front)
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finding the axis position
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dragging the axis position
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dragging the beam radius
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creating a forked interferogram (through interference with an inclined plane wave;
a small part of a large beam with large l is a good approximation)
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SOME EXAMPLES
forked interferograms for different OAM values (previous measurement of OAM):
OAM = -1 hbar
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OAM = 0 hbar
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OAM = +1 hbar
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OAM = +2 hbar
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OAM = +3 hbar
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interference of two beams that differ only in their rotation angle (mode sorter):
make both beams identical
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rotation angle 30°
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rotation angle 60°
(destructive interference)
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rotation angle 90°
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rotation angle 120°
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aliasing patterns:
complex pattern due to aliasing
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