315M Laser fringe issues, help needed...
 

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 €œbreathing€� 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 conns (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

315M Laser fringe issues, help needed...
 

On Tuesday, May 19, 2020 at 2:36:20 PM UTC-4, Andrew Way wrote:
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 €œbreathing€� 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 conns (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

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.