405nm- any progress

msxc · Post by **msxc** » Wed Jun 05, 2013 11:43 pm

jsfisher wrote:
msxc wrote:Hi All!
Sodium dichromate? I didn't know anyone used that one. I will have to try your fluorescent marker suggestion, though.

Hello

NaDi offers much greater solubility in water than over KDi, and NH4Di, there is nice table about it in:
"Improving the remarkable photosensitivity of dichromated gelatin for hologram recording in green laser light", by Jeff Blyth, Christopher R. Lowe, John F. Pecora- available in Holowiki reading room (BTW- nice improvements in the wiki content and organization- THX for resurecting it!). Authors suggests that this huge solubility also means lower typical purity (other metal ions etc), which may result in faster (unwanted) dark reaction, and plates aging. Fortunately I didn't observe that effect in my trials even with coated plates that waited few days at room temp before exposing (NaDi from Sigma-Aldrich). Or I just don't have good comparison with other salts:D .

NaDi also didn't completely save me from seeing crystallization on DipNshoot plates at 6% concentration, but I don't have comparison with other dichromates in that respect(had to delicately wipe excess NaDi solution after dipping before drying).

msxc

Martin · Post by **Martin** » Thu Jun 06, 2013 8:31 am

jsfisher wrote:Anyone else willing to invest the $20.00 to confirm my findings? (Well, the second one, anyway. The first needs no additional confirmation.)

I'd be interested testing these low power violet diodes - having had to struggle with a couple of health issues and an extremely short coherence length with the 405nm diode I've. I think there's great potential for these lasers. I wouldn't focus on DCG though. The ferric salts showed high sensitivity at that wavelength. Actually, ferric ammonium oxalate sensitized gelatin (FEG) seemed to provide better speed than ammonium dichromate sensitized DCG.

Moreover, some diazo materials may be interesting in that context as well. I've tried DAS, diazidostilbene-2,2'-disulfonic acid salt (see http://www.apug.org/forums/forum42/9273 ... nsfer.html). Mixed with gelatin, it may be another candidate for DCG-like gelatin holograms. There's one downside though: DAS has very limited water solubility. Hence relatively little DAS can be put into a gelatin solution. That's why its speed at 405nm is lower than for DCG or FEG. Maybe there's hope to find some other diazo compounds that have better solubility.

Joe Farina · Post by **Joe Farina** » Thu Jun 06, 2013 8:43 am

Glad you're back Martin.

lobaz · Post by **lobaz** » Thu Jun 06, 2013 11:53 am

jsfisher wrote:Anyone else willing to invest the $20.00 to confirm my findings?

I would like to. Do you use any controller or you just used the power adapter included?

Petr

Jeffrey Weil · Post by **Jeffrey Weil** » Thu Jun 06, 2013 5:59 pm

I just ordered one. I'll do a coherence test on the laser when it shows up.

jsfisher · Post by **jsfisher** » Thu Jun 06, 2013 6:50 pm

lobaz wrote:
jsfisher wrote:Anyone else willing to invest the $20.00 to confirm my findings?
I would like to. Do you use any controller or you just used the power adapter included?

Petr

I use it as-is, with the provided power adapter.

I'm thinking of ordering a few low power diodes and separate controllers with adjustable current levels. I'd like to try running the laser just above threshold; maybe I can get a decent, reliable coherent length that way. All things considered, it is not much of an investment to try out a few different diodes.

Jeffrey Weil · Post by **Jeffrey Weil** » Fri Jun 07, 2013 10:41 am

It's not a good idea to limit the power going into the module to lower its emitted power. There's other things in there that need the full voltage or current to work correctly, tec's, chip, etc....

Usually there's a small pot inside these things to limit the current going to the diode itself. That's a much better way to adjust the output.

Also, if your planing on getting a few different power supplies it's probably a better deal to get a proper voltage and current limited bench supply. You can get them for under a hundred bucks and it'll run everything you throw at it.

holomaker · Post by **holomaker** » Fri Jun 07, 2013 11:58 am

wow this is great thread! It is possible how to make a simple current limiting circuit, just be careful don't interrupt the circut without the proper switch or static. For cooling it is possible to use a heavy thermal mass to keep the temperature from varying if you are running the laser @ a low power it will/could run cool anyways.

Here'
http://www.rog8811.com/laserdriver.htms a neat little driver, easy to build 3 drivers on one PCB and RGB drivers!

holomaker · Post by **holomaker** » Fri Jun 07, 2013 12:59 pm

sorry bad link Ahmet can you correct it , theres the correct one? http://www.rog8811.com/laserdriver.htm

Jeffrey Weil · Post by **Jeffrey Weil** » Fri Jun 07, 2013 1:03 pm

You can make a simple and very cheap current limiting circuit out of a LM317 and a resistor of the correct value. Do a google search for "lm317 current limiting circuit". You should find what you need.

Everyone should really have something like this in their lab. Much better then making circuits and then testing.

http://www.ebay.com/itm/HQ-Power-PS1503 ... 3a8197143e

http://www.ebay.com/itm/Mastech-Single- ... 35c831bec2