20x20 cm MBDCG Hologram

Cristiano_Perrucci · Post by **Cristiano_Perrucci** » Mon Dec 18, 2006 3:33 pm

Joe wrote:That is a really stunning result, Cristiano, congratulations. It shows what is possible when someone has developed skill with MBDCG, using only a 20mW HeNe. And there should be no worries about mode-hopping with a HeNe of this power level (I have heard of some such problems when using the very large SP-125 with etalon). Considering the long exposures, were you using any special form of temperature control in your lab?

Joe, the laser is a JDS-Uniphase 1145P bought on ebay for 103 USD, without power cable and power supply. The PSU is a simple 230V-1500V AC transformer followed by a voltage multiplier to get the ~4KV 6.5 mA required by the gas tube. This kind of Power Supply Unit is quite unstable and noisy, I really don't know if changes of biasing current might induce mode-hopping.

I don't have any kind of temperature control where I'm shooting my holograms, I just leave the laser on at least 3 hrs before exposing.

MichaelH · Post by **MichaelH** » Mon Dec 18, 2006 5:02 pm

Great job.

Patience and a stable location really pay off!

Sergio · Post by **Sergio** » Mon Dec 18, 2006 10:53 pm

Fantastic DCG hologram. Have you an idea about the emulsion thickness?

Cristiano_Perrucci · Post by **Cristiano_Perrucci** » Tue Dec 19, 2006 2:15 pm

Sergio wrote:Fantastic DCG hologram. Have you an idea about the emulsion thickness?

Sergio,

the percentage of gelatine is ~10%, the scotch thikness is ~80um, I suppose the coating should be around 8-10um.

Cristiano_Perrucci · Post by **Cristiano_Perrucci** » Tue Dec 19, 2006 2:19 pm

I'm posting the link of a short movie of the above holo:

http://digilander.iol.it/crispers/holo20x20.avi

Joe Farina · Post by **Joe Farina** » Tue Dec 19, 2006 5:26 pm

Thanks for the information and photos. The appearance of the hologram is even better in the second frontal photo, I guess your background is darker in that case.

As Michael mentioned, your setup must be very stable indeed if you're able to carry out 15 minute exposures and get that kind of fringe contrast. HeNe's are in no way immune to slow fringe drift, so yours must do very well in that respect also. (Perhaps a lesson can be learned from your 3 hour warmup period.) It's really inspiring to see someone make a DCG hologram like that with a $103 laser and an improvised power supply!

Your success raises a very intruiging question: can stability be refined to such a level that even longer exposures are possible? There are many papers discussing environmental stability for holography, but I wonder, is there still a lot to be learned? We all know that many factors affect table/component rigidity and long-term stability, and that the type of hologram geometry is also important (i.e, transmission or reflection, single-beam or split-beam, etc.). I am trying to implement some of the stabilty-enhancing techniques that I've learned as I build my lab.

Tom B. · Post by **Tom B.** » Wed Dec 20, 2006 3:20 am

Wow. That's a nice hologram!