DIY simple interferometer question

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gezzer
Posts: 8
Joined: Fri Aug 28, 2015 12:02 pm

DIY simple interferometer question

Post by gezzer »

hello, i want to start on hobby holography, read many materials and i've choosen the DIY way. i first want to make my own normal dichromate plates and pose them with blue/violet laser diodes(i know green laser diodes are not applicable due to their low coherent length caused by their working principle), if i can't find any applicable blue/violet laser diode, i'll then try shooting MB/TMG sensitized DCG plates with red laser diodes. i've choosen the DCG because i want to make holograms on different types of surfaces, like on a wine glass, on whole window, etc.

i've ordered some cheap bleu/violet laser diodes from ebay and want to check them if they are sufficently coherent for a beginner hologram. i've made a simple Michelson Interferometer with not so good optics and i don't know what to look at the interference pattern.

i've built it with first surface mirrors made from regular mirrors by removing the back coating, they have many tiny scratches on them, laser i've used has and under-the-average lens that cannot properly collimate beam at a single point, but seems fine to the naked eye, i've used an half silvered mirror i've obtained from a CD driver, for the imaging sensor i've removed the lens of my DSLR and simply put perpendicular to the beam instead of a screen.

i did the first test with a low power RED laser diode which has a great chance to be sufficiently coherent, but i cannot interpret the interference pattern. what differs between the interference pattern of a coherent and a non-cohorent laser beam?

below i supplied the interference patterns i've recorded, i'm seeking for your help.
Attachments
two beams interfering together
two beams interfering together
1st and 2nd.JPG (569.66 KiB) Viewed 4363 times
second mirror beam
second mirror beam
2nd.JPG (458.55 KiB) Viewed 4363 times
first mirror beam
first mirror beam
1st.JPG (362.07 KiB) Viewed 4363 times
Joe Farina
Posts: 804
Joined: Wed Jan 07, 2015 2:10 pm

Re: DIY simple interferometer question

Post by Joe Farina »

Welcome. It's good to see a new DCG enthusiast.

Interferometers aren't of much help, when trying to determine if a laser is good for holography. Besides making a hologram as a test, the only way to be sure of the laser (reasonably sure, that is) is to use a tried-and-true type such as a HeNe, 315, etc. I think there is a less expensive green DPSS laser out there as surplus (less expensive and less power than a 315) which is also good for holography. Maybe another forum member can identify which one this is.

All of the resources for red or green sensitive (and panchromatic) MBDCG are now easily available, since TMG is on eBay:

http://www.ebay.com/itm/1-1-3-3-Tetrame ... 3f35fd23ee

Also, when Jeff Blyth's MBDCG is sensitized with Rhodamine 6G, I've found that it's very sensitive to green 532nm light. Holograms can easily be made with 10mW of green laser power. This dye is also available on eBay:

http://www.ebay.com/itm/Rhodamine-6G-Ba ... 35cb895ee2

It will take some time to get the parameters straight to make good holograms. Having a stable laser is essential before you get started. If you are always questioning the laser (as to whether or not it's stable) it will be next to impossible.
gezzer
Posts: 8
Joined: Fri Aug 28, 2015 12:02 pm

Re: DIY simple interferometer question

Post by gezzer »

Thank you Joe, your answer is much of help.

i plan to use low power laser diodes since they are cheap and i can be sure of their stability after running in idle for like 10 mins(correct me if i'm wrong), they are also cheap.

Are DPSS lasers diode lasers? i saw many of them but not sure of their cohorency, i also do not want to spend more than $50 on laser. i saw this particular laser on ebay: http://www.ebay.com/itm/Osram-PL520-50m ... 27edc1aa50 it took my interest because it is a direct green laser diode, not like the frequency doubled DPSS ones which i don't have the enough knowledge to determine if they are usable for hologram shooting. in the data sheet it says the spectral width(FWHM) is 2nm, i'm not pretty sure if this means this laser is usable for holography.

I also wonder if those cheap blue/violet lasers are applicable for holography, they are also direct lasers. for instance: http://www.ebay.com/itm/SLD3235VF-5-6mm ... 2c9942db39 this one is 100mW it could be difficult to stabilize but there are lower power versions down to 10-20mW.

And for the dye sensitized DCG part, does sensitizing MBDCG with Rhodamine 6G give it decent red sensitivity or just increase the green sensitivity? is it an alternative to the TMG formula? By the way i live in Istanbul/Turkey, most of local ebay sellers at USA don't send here but i can pretty much find any chemical if i pay, it's like all the chemical supplier companies of Turkey are stacked at a single block(which is also true for the other industries), i just walk into their offices and ask "can you supply me x chemical from merck?"

i would just buy slavich holographic mediums for beginning but in small quantities the prices are a bit high and shipping prices are out of sense. i wish there was a person who buys in bulk and ships with regular international shipping rates.
Steven
Posts: 38
Joined: Sat Jan 31, 2015 8:14 pm
Location: Cornwall, UK

Re: DIY simple interferometer question

Post by Steven »

The critical parameters when trying to use a cheap laser diode for holography is current and temperature stability.
Some cheap laser diodes are totally unsuitable for holography, see links below.

http://hololaser.kwaoo.me/
http://hololaser.kwaoo.me/laser/modeanalysis.html

When starting out, keep it simple. Use a Denisyuk setup without a lens on the laser diode.

Rhodamine 6G makes MBDCG emulsion sensitive to green, but not red.
Rhodamine 6G is also regarded as a carcinogen.

Some have had success using a 445nm laser diode removed from a projector:
http://www.holographyforum.org/forum/vi ... casio+blue

HTH,
Steven.
Success through failure - the amateur DCG holographer's path to enlightenment.
gezzer
Posts: 8
Joined: Fri Aug 28, 2015 12:02 pm

Re: DIY simple interferometer question

Post by gezzer »

Thanks Steven! the resources you gave are very useful and just the thing i was looking for, it seems this osram pl520 green diode is somewhat usable in some ecdl mode i don't understand yet, my question for this topic is answered!

the simple denisyuk setup is indeed i'll go for a long way, maybe later i could try h1/h2 transfers and set the beam ratio by a more complex setup but i just want to see a 3d hologram i made for now.
lobaz
Posts: 280
Joined: Mon Jan 12, 2015 6:08 am
Location: Pilsen, Czech Republic

Re: DIY simple interferometer question

Post by lobaz »

Hi, gezzer,
I think you try to catch too many things at once. Holography can be quite tricky and it is really the best to start with the simplest procedures that should work; and once they work, you replace step-by-step the components until you get it where you want it.
In your case, you want (if I understand correctly) to use
- your own photosensitive material,
- untested laser,
- untested vibration-free environment,
- untested optical components.
Anything here can go wrong and corrupt the whole process. It is then very hard to figure out what exactly went wrong.

If you are really new to holography, I recommend you to purchase a beginner's kit by Integraf. It comes with a few Slavich plates, red laser diode, chemistry and a detailed manual. Once you get your first hologram, you can e.g. try a different laser. If you don't get a hologram, you will know that the laser is the unreliable part. And so on.

You can also contact some experienced holographer and ask for help. There is a strong optical group at the Koc University near Istanbul. I know there Mahdi Kazempour, he is a very friendly guy and a good holographer, maybe he could give you some hints.

Hope it helps
Petr
gezzer
Posts: 8
Joined: Fri Aug 28, 2015 12:02 pm

Re: DIY simple interferometer question

Post by gezzer »

Hey lobaz,
indeed you are totally correct, i'm trying to catch all those at the same time, but this is my nature, it also brings me to failure most of the time. well it's mostly because i don't want to spend a $100 on an integraf kit, i was looking for the cheapest replacement of all those items that needed for holography. there are also many times of success when i approached new things in this way, they gave me a great satisfaction. the kits also supplies you with a very low number of plates/films, that's another reason.

After i try the very DIY method and fail, i might consider buying a kit.

Thank you so much for mentioning Mahdi Kazempour, i didn't even know there was a holographer in Turkey, i'll contact him right away.

I also discovered lately that printing computer generated holograms on transparency paper with a laser printer are possible(corticalcafe.com), it has been a good start to holography for me. they are not actually holograms that you see a 3d image on a film/plate, but they give you the image when a laser beam projected through it. just the image sizes are limited by the low resolution of the printer, you cannot diffract a beam more than a few degrees with a diffraction grating of 600 dpi resolution.
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