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.
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 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.