There are two options for creating new sources from scratch in FRED, Source Primitives and Detailed Sources.
Source Primitives are intended for rapid modeling of some of the more common source types, including collimated plane waves, point sources, Gaussian TEM00 mode laser beams and astigmatic Gaussian laser diode beams. Selecting one of these source types only allows specification of a source type using a minimum required set of parameters. Internally to FRED, the construction of a Source Primitive utilizes the same underlying set of controls as a Detailed Source and the Source Primitive interface is just a simple UI layer on top of the Detailed Source controls.
Detailed Sources are intended to allow user complete control over all available parameters that define a radiant source. In this way the user can mix and match the available source properties to achieve as accurate a parameterization of the source distribution as possible.
When the user requests that the rays defined in a source be created (usually by calling a raytrace), FRED needs to ensure that the total power in the generated rayset matches the requested total power in the source dialog. Depending on the number of rays, ray type (coherent vs. incoherent), directional and positional power variations, source rays can take a non-trivial amount of time to generate with the requested total power.
FRED attempts to minimize the amount of time spent by the user waiting for ray creation by storing specific information about the ray power scaling and only re-calculating these parameters when a modification to the source properties are changed. The ability of FRED to leverage precomputed information for ray power scaling at the time of ray creation is dependent on the specific settings used in the detailed source model. Sources which have the following characteristics cannot use precomputed information for scaling ray fluxes and, consequently, must recalculate ray flux power scaling every time a rayset is generated. These sources will generally result in longer pre-trace processing than sources which do not have these characteristics. •Ray position specification is random AND the position power apodization specification is non-uniform •Ray direction specification is random AND the direction power apodization specification is non-uniform In addition to the properties above, the Preference setting enabling random reseeding must be toggled active.
Detailed Optical Source (arbitrary user defined source)
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