Ok so as a form of content and also so I can remember timelines of events, I am going to try post regular updates on the progress of my research and some academic stuff as well.
So in the search of an inexpensive way to create a computer-gennerated hologram we have been working with 35 mm film and attempting to bleach it to increase efficiency. I have been trying a common holographic bleach and one that was found in the process of emptying out the dark room in the building under construction. The problem though is the common bleach is designed to be used in the developing process, and the other bleach we have no information on its components. The reason this is an issue is that the common bleach is not working, while the unknown one is. So if we are able to get a good slide from the film it would be difficult for someone else to try duplicate the result as the company that made it has been bought several times and has no recollection of ever making the bleach.
Did a few tests today comparing bleached and non-bleached film. With the unknown bleach it does reduce absorbance by about 17% (down to ~40%), and when I tried to check efficiency of converting to either the +1 or -1 order the slide I was using lost too much of its information after bleaching. This may have been do to the slide being under exposed, and thus not enough information was on the film to survive bleaching. The damage threshold of unbleached film (with 532 nm light) turned out to be decent, at f/5 rep rate (4 Hz) it can easily take 23 mJ and at f/2 (10 Hz) it did well with between 20 and 23 mJ only showing a small amount of deformation after a couple minutes.
My advisor took interest in a paper I sent him over a year ago about an inexpensive method to create Laguerre-Gaussian beams. This method involves cracking a piece of optical quality plexi-glass and adjusting the separation of the crack to create a spiral phase plate. The nice thing about this method is there is no diffraction orders to kill the power delivered, giving us a much higher efficiency conversion. The down side is we ideally want a low-order LG beam which means the split needs to be on the order of a wavelength. But for now we will be focusing on getting LG beams before worrying too much about the order of those beams.
Ok need to go check for additional papers on the adjustable spiral phase plate and also to see what I can find out about ferric EDTA bleach which two recipes for are below.
Recipe 1:
|
|
|
|
De-ionized Water: | 1/L
|
|
EDTA di-sodium salt: | 30g
|
|
Ferric Sulphate: | 30g
|
|
Potassium Bromide: | 30g
|
|
30% Sulphuric Acid: | 30ml
|
|
(or 90% Sulphuric Acid): | (10ml)
|
|
Bleach until emulsion clear of black silver.
|
Recipe 2:
|
|
|
|
Ferric sulfate: | 30g
|
|
disodium EDTA: | 30g
|
|
potassium bromide: | 30g
|
|
sulfuric acid: | 10ml
|
|
Bleach until clear.
|
"