Revitalizing the Coherent Sapphire 488-20

There was a moderately good ebay deal to be had and so I decided to bring a Coherent Sapphire 488-20 laser head plus driver board back from my trip to the US – along with 20kg of other laser goodies ;-). This is an interesting, though not too powerful optically pumped semiconductor laser (OPSL). The board looked new but the head was used and sold as “probably not up to specs”. Indeed so, I measured 9.6mW instead of 20mW, but I figured out, by some reverse engineering, how to bring it up back to specs, ie, 20mW with clean stable single longitudinal-mode operation. Adding a housing for the driver board and a few analog and digital controls, et voila… system ready for holography! For details see here.


3 Responses to “Revitalizing the Coherent Sapphire 488-20”

  1. Phil Bergeron Says:

    This is absolutley excellent work. I have been saying that many ordinary (not SF) Sapphires run SLM for some time and it seems like very few people believed me. Many heads have calibration drift issues; now with your mods some may be tuned up. Great work. BTW the 200 mW heads are the same way; many run SLM at least most of the time. Here is a cool trick…if you crank up the laser and it goes MLM you will loose all fringes-gone. Just tap once on the laser heat sink with one fingernail and the laser will almost always settles to SLM. No…I am NOT kidding…:) Best, Phil Bergeron, 142laser

  2. analogtionline Says:

    Great post with nice info.It is interesting….ATI offers a broad range of laser diode controllers: AC input laser drivers and DC input laser controllers. The latter includes high efficiency laser controllers, ultra low noise laser controllers, and dual mode laser controllers.

  3. Phil Berheron Says:

    Spam reply post? Bummer. (

    Many Sapphires are SLM. Use l=0, 15 second delay and l=1 to reset from MLM to SLM output. :). good luck!

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