I just want to take the time to thank you! It will probably be a couple of weeks before I get a chance to build it but I will let you know how it works. If I recall, the heat controlled etalon has less power loss so it will be needed once I get to larger format holograms.
Again I want to thank each and every one of you that has taken the time to support my hunger for holography. It is really exciting being able to actually talk to holographers about holography.
This afternoon I make plates and tonight I do 6 exposures.
I really took the time to clean 12 pieces of glass last night. They are immaculate. My new gelatin from Great Lakes should be arriving today. I studied the etalon last night and feel confident that the laser and etalon is tuned where I need it. Interesting though, I peaked the laser one more time and noticed at max power (precise aligment) there was a black dot in the center of the beam. I had to twist the mirror slightly and retune. There must be a burn spot on the mirror in the laser I did not notice before. I still have not cleaned the optics in the laser yet as the simple Denisyuk Hologram I am making does not require the additional power yet. But cleaning the optics and a heat controlled etalon will, in my appoximation give me about 400 - 600mw as oposed to the 230 - 250mw I am getting now at 22 - 23 amps.
I have not hooked up the shutter to the computer yet but have written the software to controll the shutter. I think I will put one computer down stairs (in the lab) and network it to another upstairs so that I can hook up a camera and shutter. That way I can steal a little bit of the beam before the shutter feed it through my interferometer and monitor it from upstair via the camera. All fun for the future.
Another thing, in doing the testing I found my table must have a flat or two. I was watching the fringes last night while my children were awake upstairs and they the fringes bounced every time the kids bumped. Luckly I am only doing Single beam reflections and this does not need a vibration isolation table but I can see I will have to empty the 8 foot by 4 foot by 1 foot of sand and rebuild my table. I have been meaning to do that anyway because I want to get away from sand. I may keep half the sand and pour 6 inches of concrete on top. But that again if fun for another day!
> I peaked the laser one more time and noticed at max power (precise aligment) there was a black dot in the center of the beam.
Donut form is likely a sign of non-TEM00 operation - potentially
much worse than any problem with longitudinal modes, as the different
portions of a non-TEM00 beam are not necessarily coherent with
respect to each other. I had this problem in the past due to
non-genuine TEM00 mirrors, and this had ruined a few holograms (the
thing could jump to non-TEM00 mode operation just by itself, due
to heating up, eg), and I had to very carefully retune the laser
and monitor the beam profile all the time (sending it through a
lens and then projecting it on the wall). The problem was perfectly
cured by putting in larger-radius mirrors. So if you plan to remotely
monitor the whole apparatus anyway, checking the beam profile may
be prove very valuable as well !