The Fresnel rigorous propagation module is based on Huygens Integral.  It enables propagation of arbitrary wavefront intensity and phase through components with hard edged apertures.  Diffractive effects can be seen when the beam interacts with the aperture.

• Strip geometry  uses Fast Fourier Transform methods
• Circular geometry uses Fast Hankel Transform methods
• Up to 128K sampling point across an aperture means systems with high Fresnel numbers, or the near field case, can be calculated accurately as well as the far field case
• Gain sheets are supported
• Transmission and phase masks are supported enabling studies of the effects on the beam from damaged components  
•  Convenient dialog or powerful scripting modes are supported.

The Fresnel plot shown here is the intensity as a function of distance from the center of the beam for the case of an interaction of an aperture with a top-hat laser beam when the Fresnel Number is 20, a near field case.  As expected from theory the center intensity is zero and ten distinct peaks can be seen moving from the center outwards.  Few programs can predict these diffractive results especially in circular coordinates due to the need for a large number of sampling points.  In this case 4096 sampling points across the aperture were required to accurately calculate this result.  This plot compares very favorably with Dr. Siegman's book "Lasers" P. 730 figure 18-21 for the Nf = 20 case.

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