ECDL reloaded

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.

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5 Responses to “ECDL reloaded”

  1. D Says:

    Interesting read. Is the ECDL setup as sensitive to back reflection as a bare diode?

  2. rxlaser Says:

    Hi, I have read somewhere in the literature that an ECDL is supposedly less sensitive to back reflection, and that would even be another reason for considering ECDL’s in the first place – but I can’t find the refenence any more ;-(.

  3. D Says:

    Do you have any experience with Faraday isolators? I wonder if it is difficult and expensive to build one.

  4. rxlaser Says:

    No I don’t yet have and I think it would be expensive (two polarizers and rotator crystal incl coatings). I just received one for the Verdi SPSS laser (those are on ebay right now), but that’s for a DPSS laser and so is matched to green/IR wavelengths. I doubt that it would cover red wavelenghts, but I dont really know. I am tempted to try this one for red wavelengths, now that you ask.

    See for example
    http://www.thorlabs.de/NewGroupPage9.cfm?ObjectGroup_ID=2996
    from which it appears that isolators are wavelength sensitive. Some are broadband adjustable, like 780-1000nm, so in principle it may work.

  5. ray n Says:

    I found an sdl 800 (powers up ok)and several heads at a flea mkt..near WPAFB I tinker but this is over my head…amateur radio hobby.

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