405nm- any progress

[jsfisher]

By the way, in my setup, the beam spreads to about 200 cm^2. The only optical element is a single front surface mirror. If we assume the laser is dead on at 20mW and the mirror is loss-less, then the dichromated gelatin is getting 3 mJ/cm^2 from a 30 second exposure.

This impresses me.

[jsfisher]

Thinking about it a bit more, I haven't established any coherence length, yet, have I?

Heavy sigh.

I ran through another batch tonight. Less water this time. 3-30-250. So far, I've had very nice things in the final alcohol bath that vanish into ultraviolet upon drying, even with 15 second exposures(!). I need to do some studying on color tuning, 'cause what I'm doing ain't workin'.


/JSFisher, World's Worst Holographer.

[Joe Farina]

Bright images in alcohol, which disappear on drying, can be very frustrating. It's a frequent occurrence.

Standard DCG seems to have a tendency to expand slightly after processing. (Jeff's MBDCG, on the other hand, tends to shrink after processing, possibly due to the presence of TMG.)

Rallison recommended 3-30-200 for "redder" holograms, this should probably appear in his "long" paper on the Wiki. It's in my Lake Forest notes, which appear to be similar to what's on the Wiki.

Since I started using "chemical development" after exposure (a weak solution of aluminum sulfate and sodium metabisulfite), my results improved.

Ageing (hardening) of the plates (either DCG or MBDCG) can often be a big help. (It's probably better to age standard DCG in the refrigerator, since it hardens quickly at room temperature.)

If you're shooting at 405, you need as much expansion as possible. Offhand, there are at least three things you can do. First, do the final drying/heating in a microwave. This will minimize shrinkage, because the layer dries so quickly, the fringes don't get a chance to slowly "densify" and shrink. Second, raise the temperature of the plain water bath slightly (in the range of 20 to 35C depending on the gelatin and its state of hardness). This will tend to "broadband" the hologram. Third, raise the temperature of your final alcohol bath, which should also cause broadbanding.

[Joe Farina]

The comment by Rallison (on the Wiki) is from "Control of DCG and non silver holographic materials," section 7.5 Film Codes; "The mixture code for "red" holograms is 3-30-200."

[dannybee]

The comment by Rallison (on the Wiki) is from "Control of DCG and non silver holographic materials," section 7.5 Film Codes; "The mixture code for "red" holograms is 3-30-200."

I would think this would be a bit too much dichromate for 405... at 457 my mix was 1 to 1.5 dichromate... just a thought here

[msxc]

Hi All!

Nice that there is some stir in 405nm trials:) I don't have time to play with DCG now - but maybe it is good to order some diodes
My nearly single trial was with pre-coated slides 0.5% NaDi as sensitizer. Holo was quite dimm, but reprocessing with warm IPA helped in making it more visible, and green.

As Danny suggests higher concentration may be to high. I have noticed that sensitizing with 2% NaDi resulted in nearly opaque glass (for 405nm), and some paper sheet painted with fluorescent marker will nicely show how much light pass through plate.

greatings!
msxc

[jsfisher]

Offhand, there are at least three things you can do. First, do the final drying/heating in a microwave. This will minimize shrinkage, because the layer dries so quickly, the fringes don't get a chance to slowly "densify" and shrink. Second, raise the temperature of the plain water bath slightly (in the range of 20 to 35C depending on the gelatin and its state of hardness). This will tend to "broadband" the hologram. Third, raise the temperature of your final alcohol bath, which should also cause broadbanding.

Thanks for the suggestions. I would not have thought to raise the water temperature.

[jsfisher]

The comment by Rallison (on the Wiki) is from "Control of DCG and non silver holographic materials," section 7.5 Film Codes; "The mixture code for "red" holograms is 3-30-200."

Yeah, I am familiar with the Rallison article. (By the way, I am the one who added all the Rallison stuff to the wiki ) Rallison also advised that more water (and the resulting thinner emulsion layer) would lead to more broadband results. That's what led me to 3-30-300 as my starting recipe. I have since read some things in this very forum that dispute Rallison's thinner-is-broadband teaching, so I will likely go with less water in the next batch along with less dichromate, perhaps 1-30-200.

[jsfisher]

Hi All!

Nice that there is some stir in 405nm trials:) I don't have time to play with DCG now - but maybe it is good to order some diodes
My nearly single trial was with pre-coated slides 0.5% NaDi as sensitizer. Holo was quite dimm, but reprocessing with warm IPA helped in making it more visible, and green.

As Danny suggests higher concentration may be to high. I have noticed that sensitizing with 2% NaDi resulted in nearly opaque glass (for 405nm), and some paper sheet painted with fluorescent marker will nicely show how much light pass through plate.

greatings!
msxc

Sodium dichromate? I didn't know anyone used that one. I will have to try your fluorescent marker suggestion, though.

[Jeffrey Weil]

If you go to pretty much any general store like Walgreens, Walmart, Target, etc.. they sell a pack of florescent board stock. Usually by crayola but other companies make these packs too. They will contain an 8x10 or larger of lime green, magenta, orange, etc... all florescent.

Much better then a marker.