Opnext HL6385DG….

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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12 Responses to “Opnext HL6385DG….”

  1. D Says:

    Exciting!

  2. Holofan Says:

    Hello, would you be able to sell a laser unit with this diode and if, for how much? How about ECDL?

  3. rxlaser Says:

    Well indeed I intend this but first I need to see how stable I can get this to work, one problem being the low temperature necessary for single mode operation and this gives trouble with moisture condensation, at least right now for this hot weather. Not sure about the price, though… certainly the diode is pricey. An ECDL version will be considered for the future.

  4. D Says:

    How is it going with the ECDL tests with the Opnext diode?

  5. rxlaser Says:

    Not yet done – I am busy with the laser heads. Also I am a bit afraid killing a diode.. but it has to be done! Better not to test the limits….

  6. rxlaser Says:

    Update: so far I didn’t do ECDL tests for the Opnext diode, rather I was trying to get it stable enough in a free running system. However this turned out to be really hard, the reason being the very narrow single mode operating zone. In effect it can happen, despite stringend temperature control, that the diode runs into some chaotic regime after a while. This is quite different to the well-tempered Mitsubishi diodes that run stable single mode over many hours. So I ponder to equip my laser heads with the Mitsubshi diodes for the time being, and make ECDL versions for the Opnexts.

  7. D Says:

    Do you mean it will be easier to maintain the single mode behavior of the Opnext diode with an ECDL setup, compared to just using precise temperature and current regulation? Will a dialed in ECDL setup force the diode to stay in a stable region?

  8. rxlaser Says:

    D, ups I had written an answer that had vanished…
    .. well an ECDL setup helps but does not guarantee single mode behaviour, actually I found some diodes that work better in ECDL than free running, and diodes for which it is the other way around. I guess many factors go into that, for example the reflectivity of the output coupler facet of the diode. I think one can just go on and try, as even for diodes of the same brand the results can be different.

    Even if an ECDL configuration works, one needs a very tight temperature control as there can be mode jumps. In a transition zone between modes the output is as noisy and chaotic as it can be, so one needs to stay clear from such zones, and it is not obvious that one can maintain this for a long time without re-adjustment; there could be factors like diode ageing coming into play. And if a laser would need to be re-adjusted often, it would be it impractical for daily holographic use.

    Whether some sensible setup can be achieved remains to be seen, at any rate this probably requires quite some more development time, so that’s why I focus at the more robust and stable Mitsubishi diodes for the moment!

  9. Phil Bergeron Says:

    These are NOT SLM lasers! I have been in contact with Opnext and they have admitted it is all a horendous blunder. They are single transverse mode (TEM00) but NOT single longitudinal mode. I bought two diodes. Mike Lawson built one into a nive laser. Is is MLM at all currents and temperatures. It should provide SLM output with a grating in an ECDL setup. But THE DATA SHEETS ARE WRONG; THE BROCHURE IS WRONG; DO NOT WASTE YOUR $150. What a mess…there are no 150 mW SLM red diodes for $150.
    Phil Bergeron, 142laser , USF Physics Department, Tampa

  10. rxlaser Says:

    Well I have performed extensive tests and found that these diodes can do like 60-90mW single mode at very special current/temp regions. I sold a few of complete lasers and the users were quite happy. In ECDL mode the maximal power is not much more, but SLM operation is widespread.

    See http://redlum.xohp.pagesperso-orange.fr/laser/modeanalysis.html#HL6385
    for free runnning diodes and http://redlum.xohp.pagesperso-orange.fr/laser/ECDL-test.html#HL6385 for ECDLs.

    -RX

  11. Phil Bergeron Says:

    I am not saying that you can not find SLM operating points just that the Opnext Company has admitted to me that their data sheets are wrong and that the produdt is NOT designed to run SLM at all at any current. It is designed for good transverse mode quality with a low astigmatism Guassian shape beam. Nice red laser diode…NOT SLM. I bought two diodes…$310 with shipping! CRAP! 🙂 Phil

  12. Phil Bergeron Says:

    Ondax sells real 35 mW SLM 638 nm red diodes…for $1,100 each. These have 2 meter coherence length out of the box…for $1,100 (bare diode). That is why 150 mW for $150 was so exciting…but it is not real.

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