I have uploaded:

Sim/Tel/msdos/science/
LOTS1_71.ZIP  Optical beam propagation (diffraction) code

     LOTS1 is a computer program (for the IBM computer under 
DOS) to calculate one-dimensional diffraction effects along an 
optical beam path.  It can be used to determine the diffraction 
patterns associated with various initial beam intensity and phase 
profiles after propagation over a distance, transmission through 
lenses, reflection by mirrors, and clipping by apertures and 
obstructions along the path, and other effects.  It is useful to assure 
that the optical elements in a laser system have a sufficiently large 
aperture to avoid unwanted diffraction effects, such as the intensity 
ripple which can easily occur with a high coherence source.  It is 
also of instructional use; for example, repeated application of the 
LOTS1 macro again allows one to see how a Fresnel (near-field) 
diffraction pattern forms and then transitions to the Fraunhoffer (far-
field) case with increasing distance along the beampath.
     LOTS1 can be used either to execute commands one by one, or 
can take as input the name of a macro containing many 
commands.  After the program begins to run, the second screen 
gives first-time users instructions on how to execute a macro that 
performs one simple demonstration.  An included ASCII file called 
TAPE11 contains annotated macros containing command strings to 
perform other analyses; print and read this file to see how LOTS1 
commands can be used in general.  The macros within TAPE11 
can be executed if desired.  It is possible to unintentionally destroy 
the TAPE11 file; a copy of it, called BACKUP.T11, is also included 
in the distribution package.  Another included ASCII file 
(LOTS1.HLP) lists all of the LOTS1 commands and their 
arguments.
     Use this program at your own risk.  Remember that it is NOT a 
two-dimensional code; for serious work, a commercial physical 
optics code is more appropriate.

Special requirements:    The program requires a VGA display, and 
runs best with a co-processor.

Changes:     Version 7.1 is the initial SimTel release.

FreeWare.  Uploaded by the author.

Nelson Wallace
user702495@aol.com
