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315M Laser fringe issues, help needed...

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Andrew Way

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May 19, 2020, 2:36:20 PM5/19/20
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Hi there,
I have a working 315M DPSS laser, with the controller, power supply, and a weird autostart dongle without the ready light...
I am trying holography again (thanks Fred unterseher) in my livingroom with this new laser, but I think it may be having trouble stabilizing...?
It starts up just fine, but when I run it though the interferometer it performs this “breathing” routine, where the fringe pattern moves a little in a regular manner every 3-4 seconds, contracting in. I have eliminated the possibility of table, pump, or fan movement- as my other cheapo chinesium diode laser settles just fine in no time. (I converted the 315M-100 to water cooling, but the weird fringe behavior persists even with the pump off for 15 mins).
I have tried the recommendations in the laser faq for this model, DC voltage is good/stable, checked all ribbon cable conn’s (visually, as i'd hate to brick it by poking around with a multimeter). I have also tried adjusting the pot down for a lower current/power setting to no avail- it resets and takes its 6mins to find a new stable setting, but the fringes never settle.
I do not have a oscilloscope or power meter handy as of yet, but it seems to be stuck in a loop. Any suggestions would be appreciated!
-Roo

gghe...@gmail.com

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May 25, 2020, 10:42:59 PM5/25/20
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hmm, no 'scope. I don't know these lasers, but is there both a current
control loop and thermal control? Can you look at those signals?
A few minutes sound like it might be the temperature.

George h.
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