PHR-803T - Coherence Length

Hello everyone,

Using lasers for holography mainly, i wanted to know if the LD's in the PHR-803T have sufficiently stable operating regions for holography.

Did anyone ever measure the coherence length of these LD's?

Ahmet

I'm curious about this too

In the meantime i received my LD and made some reflection holograms on DCG plates. The deepest scene was 6cm. This would indicate a coherence length of at least 12cm for the diode tested.

Between 70mA and 90mA there is a broad stable operating region.

I was quite surprised that it was possible to get any hologram at all, because the broad spectrum published for eg. the Sharp Bluray- LD (GH04P21A2GE) had made me to expect nothing good from this LD.

Years ago I made a couple of holograms on the 8E75HD plates and I've always dreamt of using DCG one day. The arrival of the cheap 405nm's has also renewed my interest. Am I correct that you can use it without a sensitizer at 405nm? Or do you still use some kind of sensitzer dye, goahead?

About the coherence length, I once read an article where they used the backreflection from a simple microscope coverglass in the collimated beam to force the laser into single longitudinal mode operation. Might be worthwile to experiment with that.

Sorry i did not reply earlier.  It's a DCG mixture without sensitizer because it's not needed at all with 405nm.

The components for the mixture were: 2g gelatine, 1.7ml 5% Ammoniumdichromate (85mg), 16.5ml H20.

The sensitivity was around 2mJ, so the exposure times were a few seconds.

You can read here about how it went:
http://holographyforum.org/phpBB2/viewtopic.php?f=20&t=6493&sid=d88c1f012b85504f5aeefbf1a93357cf

I'm using the reflections off a  glass plate to see the fringes and to find the most stable current range, but never tried using a microscope coverglass  as etalon. It might be worth a try.

Thanks for the tip.

Thanks for sharing your recipe! I will certainly give it a try. Since this thread is not that active anymore I'll join the one on the other forum. Will also send you a PM about the article.