Beam delivery with fibers

Holomark · Post by **Holomark** » Mon Jul 14, 2014 3:15 pm

John,
I am interested in the output when using fibers. I know you said there is a lot of loss, but can you quantify this. Input vs output and divergence of output beam. I currently have 18 different optical components on my table to make a split beam 2 color reflection - there is a lot of loss in my current setup. (FWIW - I generally am sending my reference beam to a 12 in collimating mirror - Object beam gets split into two to illuminate object from left(ish) and right(ish) Because one of my lasers is a HENE I had to add some pathlength to object side to try to match pathlength of reference beam)
Any insight is helpful
Mark

John Klayer · Post by **John Klayer** » Tue Sep 09, 2014 11:14 pm

Here's the crazy octopus I put together with the Toslink splitters:

I really didn't think it would work, but after I got started I had to finish it. No, it didn't work.

I tried a couple of long Toslinks, one for the reference and one for the object:

This is the C315M laser, shutter, 1/2 wave plate, polarizing beam splitter and magnet adjustments to launch the light into the two fibers:

The long fibers didn't work either. Of the several shots I did, I got one very, very faint image.

So, I tried again with shorter fibers. The reference light didn't spread as much as the longer fiber so I added a convex mirror to spread it more:

This time it worked pretty well:

Reconstructed with a 594nm HeNe.

Ed Wesly · Post by **Ed Wesly** » Tue Sep 16, 2014 5:23 pm

Nice job! I like the color of the 594 laser, is it really that orange in real life?

If you have the patience and a 50/50 beamsplitter/combiner, you can take a pair of the fibres and combine their outputs to overlap. If you get it right, you can see fringes, and see how long everything is stable.

John Klayer · Post by **John Klayer** » Tue Sep 16, 2014 6:45 pm

The holograms look the same with a YAG 589nm and the HeNe 594nm. On the computer screen they look kinda orange but to the eye they look yellow.

John Klayer · Post by **John Klayer** » Tue Sep 16, 2014 6:49 pm

BTW, I don't have the YAG 589nm any more. It didn't maintain power, I sent it back and got a refund.

Holomark · Post by **Holomark** » Wed Sep 17, 2014 9:27 am

Still curious - how much light loss compared to using lenses?
It looks like good results! Was your exposure time significantly longer than your old setup?
Mark

John Klayer · Post by **John Klayer** » Thu Sep 18, 2014 12:36 am

holomark, I get about half as much light at the plate with the two fibers than I get with ordinary optics.

The holo in the picture above resulted from an accident. The fiber for the reference fell out of its holder and reflected off the convex mirror differently than I planned. I expected it to be a failure but it turned out the best of the shots I did that day.

John Klayer · Post by **John Klayer** » Sat Sep 20, 2014 2:37 am

Seeing double

I noticed that these 2 multimode fiber holograms have a faint secondary image just slightly behind the main image.
Anybody have an idea what causes it?

John Klayer · Post by **John Klayer** » Tue Sep 23, 2014 10:47 pm

Here's a picture zoomed in on some of the smaller formations of the above hologram. Ghost images are plainly visible behind. If it was caused by mode hopping there would be a sliced bread appearance. If it was from reflection within the hologram plate it should be seen in similar holograms that didn't use the fibers. Anybody have any ideas what causes it?

holomaker · Post by **holomaker** » Wed Sep 24, 2014 7:53 am

I suspect your getting some second image recorded from the reflected image of the backside of the plate, try to flip your plate next time , emulsion away from laser?