Interpreting diode laser datasheets
Posted by papergeek
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Re: Interpreting diode laser datasheets December 09, 2013 02:36PM |
So basically managing the temperature is the key. I'm not familiar with the physics of diode lasers but it sounds like it is the high temperature and runaway current effect that leads to higher temperatures that destroys them, not just higher current.
I'll need to re-run my tests with a higher ambient temperature. The ambient in my garage is usually around 15C during my normal hacking hours, and after running at 1.8A for 45 minutes I measured temperature just outside the copper diode housing (in my copper heatsink) of 26C. I have not yet used thermal grease between the plates but I am measuring from the plate with the tightest fit. So I should probably be safe allowing another 4-5C between the diode can and where I am measuring.
Picture attached - I have copper plates drilled out to 12mm and secured to an aluminum block which I've tapped. The aluminum block has a heatsink on top with a fan blowing over it, and I still need to see how successful that will be in creating a downhill gradient for heat from the diode. The copper seems to be performing as well as I'd expected (having nearly twice the thermal conductance of aluminum). Total weight is about the same as a stepper motor (around 450gm). The metal supply place turned out to have a supply of 4mm copper plate precut in small and medium squares, sold for USD $6 per pound.
One surprise I had was that my tests have been run with the beam inside a cardboard box with the end well outside the focus of the beam (about 40-50cm). At that point the beam has diverged to around 8cm. After 20 minutes or so I smelled hot cardboard and found there is a tiny hotspot in the center of the diverged beam. Fortunately I would not have run something like this unattended. After that I switched to a cardboard tube around a concrete target.
I'll need to re-run my tests with a higher ambient temperature. The ambient in my garage is usually around 15C during my normal hacking hours, and after running at 1.8A for 45 minutes I measured temperature just outside the copper diode housing (in my copper heatsink) of 26C. I have not yet used thermal grease between the plates but I am measuring from the plate with the tightest fit. So I should probably be safe allowing another 4-5C between the diode can and where I am measuring.
Picture attached - I have copper plates drilled out to 12mm and secured to an aluminum block which I've tapped. The aluminum block has a heatsink on top with a fan blowing over it, and I still need to see how successful that will be in creating a downhill gradient for heat from the diode. The copper seems to be performing as well as I'd expected (having nearly twice the thermal conductance of aluminum). Total weight is about the same as a stepper motor (around 450gm). The metal supply place turned out to have a supply of 4mm copper plate precut in small and medium squares, sold for USD $6 per pound.
One surprise I had was that my tests have been run with the beam inside a cardboard box with the end well outside the focus of the beam (about 40-50cm). At that point the beam has diverged to around 8cm. After 20 minutes or so I smelled hot cardboard and found there is a tiny hotspot in the center of the diverged beam. Fortunately I would not have run something like this unattended. After that I switched to a cardboard tube around a concrete target.
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