The Gaussian Position Apodization option scales source rays to have a Gaussian power profile as a function of ray position. This feature is useful for modeling TEM00, higher order TEMm,n Hermite/Laguerre modes or Super-Gaussian profiles. The ray grid dimensions set on the Positions/Directions tab should extend well beyond the 1/e2 semi-width, w, set on this tab in order to accurately model the spatial profile and achieve the correct source power distribution. Note that 99.3% of the power is contained within a radius of (pw/2).
The following image shows a bundle of coherent rays with a 1-inch semi-diameter used in creating the Gaussian beam irradiance profile with semi-width w = 0.5.
This feature can be accessed by selecting Gaussian Apodization (useful for Gaussian beams) as the Position Apodization type on the Power tab of a Detailed Source dialog box.
The Gaussian Position Apodization is applied with n = 2 by default in the Source Primitive type Laser Beam (00 mode).
Note that the semi-width of higher order modes increases with indices n and m. Qualitatively, the mode semi-width is approximately Ö(n) times the lowest order mode semi-width w.
In the coherent case, the Gaussian beam profile is constructed from Gaussian beamlets associated with each ray. As the number of rays on the Position/Direction Tab is increased, sampling of the Gaussian profile with the Gaussian beamlets also increases. However, as the sampling is increased, the diameter of each Gaussian beamlet decreases and results in beamlets with increasing divergence. Consequently, greater divergence of the individual beamlets results in a lower spatial sampling on subsequent surfaces. See Introduction to Coherent Sources for complete description of coherent source properties.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
.png)