Archive for June, 2009

Opnext HL6385DG….

June 24, 2009

I just got a few of those 150mW/642nm diodes, which are characterized by “single longitudinal mode” in their data sheet. There was a special price for them during this months; and also a group buy at photonexicon.com.
Obviously of potential interest to holographers…the warm color would be well suited for color holography, and it would work well with optics intended for HeNe lasers such as waveplates.

I immediately ran tests on one of them, with disappointing results at first, but subsequent more careful tests revealed single mode regions at high power and low temperatures, see here. This now seems very promising and I will test more of those diodes, also in ECDL setups – stay tuned.

PS 09.09.09: I found, not unexpectedly, that the HL6385 does fine in an ECDL setup, for details see here.

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ECDL reloaded

June 3, 2009

My first attempt at an external cavity diode laser (ECDL) didn’t work nicely at all, it didn’t run single longitudinal mode and thus was completely useless for holography purposes. Recently I just put in other types of diodes, notably a high power “open can” DVD burner diode, and immediately things worked out perfectly! See for details here. I wonder about the great difference – perhaps it is just the missing output window of the diode?

I also used another sample of those diodes in an commercial ECDL laser that was originally designed for 780nm. And voila, it worked again very well. Some info on this (quite simple) conversion of this laser is here.

Finally, I wanted to see how a “blu-ray” 406nm diode works in an ECDL setup; before I had found that the bare diode by itself is totally unsuitable. I found that in my ECDL configuration the diode can run single longitudinal mode but only to powers of approx 15mW. See for details here.

PS. Aug 28: I was playing with a Mitsubishi ML101J27 in an ECDL and it worked fine .. until I changed polarization and the stronger feedback killed the diode despite I thought was careful. Good that I learned this lesson with that diode and not with an Opnext HL6285… one lesson is to determine the diffraction efficiency of the grating, for both polarizations, and then estimate the maximal drive beforehand. But there is no really safe way to find out what the maximal power of an ECDL is. At any rate, I plan to try an Opnext soon.