Laser Diffraction

Computer Simulation

This basic program computes the diffraction pattern of a laser beam incident on various targets such as a slit, double slit, wire, edge or rectangular aperture. Sample output for wire obstacle Sample output from DIFFRACT.BAS.
Diffraction pattern of a thin wire obstacle using a red helium-neon laser with gaussian beam. The central portion of the pattern is a brighter red than the edges because of the radial exponential fall-off of the laser beam cross-section. In practice, this is exactly what you see in the lab. The green lines are the projected boundaries of the geometrical shadow of the wire. There is also a graph overlay in red.

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Details

The beam can be uniform isotropic or with gaussian profile. The laser diffraction pattern can scanned in 1D or 2D and can be plotted to the screen as a graph and/or as a color coded intensity plot. There is a much higher resolution laser printer output option and there are plans for high resolution VRML output in the Java version.

References

For more information and experimental results read 'laser diffraction' (available in WordPerfect format also). This paper describes the above program and several others to test the accuracy and computational efficiency of various schemes to calculate Fresnel integrals (works on any computer) and to produce diffraction pattern animations (works only on an Amiga computer) as one or more parameters are sweeped from a minimum to a maximum.

There is also a related project to determine the 'Effects of polarization on diffraction patterns'.

These programs are currently undergoing conversion into Java applets.

There is two-slit diffraction simulation Java applet by Serge Vtorov.


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