Holographic Materials? (Newbie question)

These are all of the old posts from the first two years of the forum. They are locked.
Updated: 2005-03-28 by HoloM (the god)
Bob

Holographic Materials? (Newbie question)

Post by Bob »

With the availability of Saxby's books, I would never recommend "The Holography Handbook". The word "polarization" doesn't even appear in it, the use of a sand table is a recipe for disaster for a newbie, and the film and chemistry information is waay out of date. This book is only marginally better than "Homegrown Holography", and while fresh in 1982, is only misleading 1n 2004.
Tom B.

Holographic Materials? (Newbie question)

Post by Tom B. »

Ah, I see - didn't see the bleach recipe and assumed that this was now proprietary, too. So it's still the Brilland bleach then. I've used this successfully with BB plates and PFG-03M - it seems about as effective as the more traditional ferric EDTA - must compare the two more carefully sometime. It would be nice if he offered his secret developer in dry form for international shipping - it would save on weight and I can imagine some carriers being nervous about transporting liquid chemical brews of unknown composition...
Tom B.

Holographic Materials? (Newbie question)

Post by Tom B. »

Did you mean Iovine's "Homemade Holograms"? I still like this book a lot for its low-budget enthusiasm and think it a good value, but agree that Saxby's book is by far the best.
wler

Holographic Materials? (Newbie question)

Post by wler »

Actually I mixed both EDTA and Brilland bleaches, and couldn't find any difference in the results, on both Ultimate and VRP (which is not surprising as they contain more or less the same active ingredients). At any rate, better (less noise) than dichromate bleach, but that's a different story.
Bob

Holographic Materials? (Newbie question)

Post by Bob »

No, I meant "Homegrown Holography" by George Dowbenko,1978. I really didn't mean to dump so hard on Bob & Fred's book, it's just that Saxby's is waaaaay better and up to date, and without such major omissions.
Michael Harrison

Holographic Materials? (Newbie question)

Post by Michael Harrison »

... the use of a sand table is a recipe for disaster for a newbie

Say what?

In what way? It worked great for me as a beginner and I know one major pro that still swears by the sand table for mastering.







---------------------------
If someone says it can't be done but they haven't tried it, don't believe them.
http://www.dragonseye.com/Holography

Are you going to the next PCG Gathering?
http://www.dragonseye.com/Holography/PCGGI.html
Dinesh

Holographic Materials? (Newbie question)

Post by Dinesh »

"What about the other materials? Where would you get photopolymers, photoresist, thermoplasts or crystals?"

Photopolymers :
Photopolymers is a recurring theme in materials holography. Once upon a (long) time ago, Polaroid used photopolymers, but I believe never actually released it. If you wanted a photopolymer hologram, they would make it. This died around about mid-90's. Du pont had a photopolymer that was available to holographers, but now they've strictly controlled it. There are varying stories: They only want to supply it to 'large' holographic companies because it's not economically feasable to ship to 'small' holographers'. The security industry (ie Applied Holographics, American Banknote Holographics etc who make security holograms) have stopped them from distributing it because of security risks of other being able to reproduce security holograms. I'm sure members of this forum will have heard, or can confirm the Du Pont stories. There is a belief that Dai Nippon Printing in Japan (DNP) are making a photopolymer. Martin and Sergio who post on this forum are in the process of developing a new photopolymer

Photoresists :
These can be obtained from Towne: http://www.townetech.com/holoplat.htm. You can also coat the stuff yourself. Shipley make a resist called Microposit. You need a fairly fast spinner since this has to have a surface thickness of a micron or less. Shipley will also have the developers.

Thermoplasts :
About 20 years ago Newport produced a 'hologram writer' which was basically a thermoplast. At the time I was in a company called NTS and we were using it for real-time holographic non-destructive testing. I believe that was the intention. I don't know if this is still available but I saw a post on this forum a while back where someone had found one on e-bay. I'm not aware of any commercial company making thermoplasts.

Crystals :
This is pretty easy to get, but unfortunately I don't know the names of any particular manufacture. Their booths show up in most of the conventions. I actually had a rep of one of the crystal manufacturing companies tell me that most of the Lithium Niobate crystals are made to order. In this process there's always some waste, some of them being crystals of about 0.5 sq cm lying about. They said they couldn't use them but if I wanted, they'd give me some. The last time I used Lithium Niobate I had the full power of a raw beam from a 5W Argon zapping this thing of only 1 sq cm for 10 minutes and got a grating of about 1% efficency - any porcelain cat would have ended up fried at this energy output!
See http://www.physics.sfsu.edu/~senglish/r ... orage.html
By the way, You can use LCDs as a holographic material, but the response time is slow. Liquid crystals are now being doped to give faster response times: http://www.sciencedaily.com/releases/20 ... 061346.htm

"btw, what are magneto-optics, chalcogenides and PVA? Never heard anything about them.."

Magneto optics

Mostly made of BiMn, these are materials which are ferromagnetic, I believe. Ferromagnetic materials are magnetic up to a temperature known as the Curie Point. Beyond their Curie Point, they lose magnetisation. However, there is a form of magnetism known as paramagnetic where raising the material above the Curie Point and superimposing another magnetic field aligns the mag field of the material itself. If you can locally raise the material temperature (for holography very locally!) that local volume becomes paramagnetic. As such, you can use the Faraday Effect (light alters direction of polarisation as it goes through a magnetic field) or the Kerr Effect (materials become birefringent on superposing an electric field) to alter the light properties through the local volume. Holographically, you zap the BiMn with two pulse lasers to create the light and dark fringes. Where there's light, the local ttemperature raises above the Curie point (assuming the laser has sufficent power)and causes the BiMn to become paramagnetic. Now you use polarised light and take advantage of either changes in birefringence or polarisation twist just where there are light fringes to alter the light pattern according to the paramagnetic areas of the fringes. The paramegnetic state remains only as the material is above Curie.


Chalcogenides

Certain materials, mostly amorphous glasses, have the property that under certain physical conditions (light, for example) the molecular structure converts from amorphous to crystalline. As such, it can be birefringent. Here's an explanation: http://www.cus.cam.ac.uk/~cae20/chalcogenides.html
Clearly any material capable of phase change can be made into a hologram if the phase changes can be localised. Since these materials are glasses (this is determined by the viscosity - glass as is well known is a liquid with an extremely high viscosity)they are transparent and so a hologram can be superimposed onto such transparent state to alter certain optical properties while the bulk material remains transparent.


PVA

Just another photopolymer. The monomer acrylamide is placed in a support of Polyvinyl alcohol (PVA) along with certain initiators. When zapped, the acrylamide polymerises. The interest in this material is the it's capable of DCG-like brightness and DCG-like exposure but apparently is not affected by moisture - a major problem with DCG.


Photochromics

These are materials that change color on excitation with other colors. The work in a very similar way to n or p doped semiconductors. Basically, the materials are semiconductors with an energy level (A) between the valence and conduction bands; the energy levels being too large for thermal interaction. The material is now doped with something to produce another energy level (B) between the valence and conduction:


Conduction---------------------------------------

A............---------..........................
B.........................---------.............

Valence----------------------------------------

Electrons normally sit at B. When excited by light at around 300-500nm, the electrons go up to A and so cause changes in the physical properties - usually the color changes. When hit with light or heat, the electrons go back down to B via the conduction band. So, to write the hologram, you hit it with Argon at 488, to erase the hologram, you heat it (about 150 C) for an hour or so and let it cool slowly.
Bob

Holographic Materials? (Newbie question)

Post by Bob »

You forgot HPDLC (Holographic Polymer Dispersed Liquid Crystal). I've been working with this material for the past 5 years, first at Digilens and now at SBG Labs. It is essentially a photopolymer material with liquid crystals mixed in. Upon exposure, the LC is pushed out of solution by polymerization in the bright fringes and forms micro-droplets in the dark fringes. An electric field may then be used to manipulate the orientation of the LC so that the hologram can effectively be erased, making the hologram electrically switchable.
Bob

Holographic Materials? (Newbie question)

Post by Bob »

Sand is not a suitable material for the base of a holography system. It will work, of course, but so will wood, dirt, rocks, and bricks. The problem with both books I mentioned above is that they recommend one improvised approach to building a hologram recording system without discussion of the basic requirements for stability.

One, maybe three holographers are stuck on sand. You were successful learning on it, but why have you work now on metal for good reasons. My opinion regarding sand tables comes from the fact that many, many students have been introduced to holography on sand tables but very, very few ever continued on. I think there is something very basicly wrong with the way holography has been taught, and see the use of sand as a base material as a big part of the problem.
Dinesh

Holographic Materials? (Newbie question)

Post by Dinesh »

"You forgot HPDLC (Holographic Polymer Dispersed Liquid Crystal)"
Didn't forget it. Just never heard of it! I'm pretty much out of the technical field now (if I was ever in it. Not being a name and having no PhD or string of papers - or even one - which seems to be the standard by which our respect for people now seems to be judged, I guess I don't now know, nor ever did know, anything about the technical/mathematical/physics side of holography). I have no idea what new materials are out there. Perhaps in the interest of free dissemination of information in order to progress holography and expand it's conciousness to the public, you could give us further and complete details. I'm joking! I'm joking!
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