HeNe lasershow device

holo_cyware · Post by **holo_cyware** » Mon Oct 05, 2009 9:32 am

What are the chances for an old small HeNe laser-show device (2 tubes, 5 mW each) to work for holography? The frequency is stated to be 632.8 nm on the back label.

Still, will it work for holography?

Jem · Post by **Jem** » Mon Oct 05, 2009 10:58 am

Hi

The chances are that if the beam has polarised output it will make holograms. I started out with a small HeNe and made my first holograms with it. There is something to consider though, and that is, if it states 5mW on the tube the actual output is likely to be less than what it says.

If its an old lasershow device it perhaps has more value as just that. If you take a look over on http://www.photonlexicon.com there are many folks there who collect old lasershow stuff. Try putting it in the Buy/Sell/Trade section, you may be able to get a trade for a bigger HeNe

Cheers

Jem

holo_cyware · Post by **holo_cyware** » Mon Oct 05, 2009 12:23 pm

Well it's not that old, just pre-red laser pointer diode era. On it, it saids 10 mw but the code suggests 2 units of 5 mW each (smth like X2-05).

So it needs to be polatized? What else? How can I know it's multimode?

Joe Farina · Post by **Joe Farina** » Mon Oct 05, 2009 12:41 pm

An unpolarized (randomly polarized) HeNe will work fine for beginning holography. For more advanced setups, a polarized laser will enable you to use Brewster's angle (to reduce reflections in glass or film), rotate the polarization of the object beam to match the reference beam in split beam holography (if your object maintains the polarization), and use a polarizing cube beamsplitter.

holo_cyware · Post by **holo_cyware** » Mon Oct 05, 2009 12:54 pm

Maybe it worth getting it just for the power supply, in the waiting for a better tube.

I can also slam 2 laser diodes in it and resell it. Either way, a win-win.

holo_cyware · Post by **holo_cyware** » Mon Oct 05, 2009 3:21 pm

Is there a way to polarise the laser? With a polarising sheet (from LCD's) I guess I'd be loosing some 50% of the power (if not even more).

Colin Kaminski · Post by **Colin Kaminski** » Tue Oct 06, 2009 12:08 am

If it is a sealed cavity then you are stuck. Most small HeNes are sealed. If the mirrors are separate from the cavity placing a microscope slide in the cavity at Brewster's angle will help the polarization considerably.

Paulos · Post by **Paulos** » Wed Oct 07, 2009 7:25 am

holo_cyware wrote:Is there a way to polarise the laser? With a polarising sheet (from LCD's) I guess I'd be loosing some 50% of the power (if not even more).

It will work.
Alternatively, a polarizing cube beam splitter will split the unpolarized beam in two polarized beams of approx. equal power (50% R / 50% T) with little loss.
They cost over $100 new, but they occasionally sell on ebay for much less.
The second beam could be used for object illumination.

holo_cyware · Post by **holo_cyware** » Wed Oct 07, 2009 11:13 am

This is good news, thanks Paulos.

Apparently there are many of these Wollaston prisms around us, like for instance in the CD drives. And I've got a whole bunch of broken units.

dave battin · Post by **dave battin** » Wed Oct 07, 2009 12:36 pm

be careful as the random polarization laser may rotationally drift causing the two beam's intensities to vary. you could do a test and check how much it drifts by setting up a polarizing filter (like in sunglasses) to totally block the beam off, and then watch it till it warms up and then see if it still wanders or remains semi stable ........