Holotool.exe is a self extracting program that contains four DOS executables and three pcx drawings totaling just 115 kbytes when expanded by running Holotool. It is probably best to run it in it's own directory, so identifying the individual programs is easy. The programs included are as follows:
EXPAND2.EXE is a menu driven program that asks you for the playback and construction wavelengths, the playback and construction bulk index of refraction of the recording media, the external angles for playing back either a transmission or reflection HOE or hologram and the thickness change multiplier expected from your film. The output is the internal Bragg angle, the spatial frequency and the internal and external construction angles for both before and after expansion or shrinkage of the film. The program toggles through remembering what you did and allowing changes to be made to quickly try out a lot of configurations to find out what will probably work and what will not.
TIR2.EXE is just like Expand2 except that the second angle it asks for is the internal playback angle, which allows you to design total internal reflection (TIR) HOEs or edge lit holograms. The output includes a prompting for a best angle prism to index match to the film substrate and allows you to input any angle prism you may have and then outputs an angle for the non prism side and one for the ray entering the prism if a reflection geometry results or two ray angles measured off the normal to the prism in the case of a transmission outcome. TIR fringes hover around 45 degrees of Brag tilt and are especially hard to make correctly so this is the most valuable of the utilities I use myself and the newest of the three programs.
TIR2.PYW (not part of the holotools package) is a graphical version of TIR2, written in wxPython, for Windows 95/98/NT and UNIX/Linux. To use this program, you will need to download the tir2.pyw program file and the Python Interpreter and the wxPython toolkit. After installing the wxPython software package, the TIR2.PYW program file will be executable. To learn more about wxPython, go to the wxPython home page.
Note: tir2.pyw is a work in progress. Please send all suggestions or bug reports to firstname.lastname@example.org.
CHIRP.EXE is an older Fortran program that models holographic or dielectric mirror stacks using a quarter wave model or Kogelnic's approximation, you get to choose. The inputs are bulk index, center wavelength, film thickness, average expected index modulation, absorption of the holographic film during exposure in percent (gradient), percent change in fringe spacing as a function of depth (chirp) and wavelength range to scan symmetrically around the center wavelength. The outputs are first a plot of index modulation as a function of depth then a plot of density versus wavelength and if you choose to save the file when prompted you can retrieve it with CHIRCALL.EXE and display and print an amplitude reflection plot to use to match up with a spectrophotometer output of a real mirror. This program is useful for measuring the index modulation of a film when things are not linear or uniform as is true for most recording media.
There are three GIF files, EXPAND.GIF, TIR2.GIF and NCHIRP.GIF that give sign conventions and further instructions for using their respective namesakes. These are easily read and printed from Paintbrush and many other programs including word processors. For those that prefer to customize their software, the source code for the two C programs is also available by email.