Power output in 405 nm laser

[MillieMonster]

Hello everyone!

I'm a research chemist who bought the wicked lasers E3 series in lunar purple (405 nm) for use in a photochemistry experiment. Sadly, I broke it and I was looking for some advice on how not to do the same thing once my replacement comes in the mail . I needed more than the 30 minutes of continuous output that batteries got me so I hooked the laser up to a lab power supply and monitored the output power as I slowly increased the current. As I ramped up the current, I got a linear relationship between current and voltage up to the maximum of 600 mA my power supply would provide. The laser spec says the current max is 700 mA and at 600 mA, I still wasn't seeing as high of a power output as I got using batteries.

Somewhere along the line, I found that if instead of ramping the current up, I attached the leads with the current already fairly high, I would get a significantly higher power output even though the power supply read a current output of only 320 mA. In this case if I turned the knob to increase current, nothing would happen (i.e. the reading stays at 320 mA) but if I turned the knob to decrease current, it would drop into the linear I-V region I described in the paragraph above. I decided to run the laser in the 320 mA mode because I wanted the high power output but the laser suddenly died.

What I'd like help figuring out is: 1. What was causing the two distinct types of current-voltage behavior? and 2. If I'm determined to try again with the external power supply, is there any way I can do a better job of choosing a current.

I appreciate any thoughts anyone has! Thanks!!

 

[anselm]

Hello and welcome to the forum!:wave:

I'm a research chemist who bought the wicked lasers E3 series in lunar purple (405 nm) for use in a photochemistry experiment.

If that part in bold is true, then why did buy a freaking pointer instead of a proper
lab module, something like this?
405nm 500mW laser module /TTL [OL-405-500] - $105.99 : Welcome to O-Like.com, Your source for laser products
I guarantee you, you'll be much happier in the long run. Besides the fact that this
is heatsinked properly for a 100% duty cycle, you also get the ability to modulate
the lasers output.

Handheld pointers aren't meant to be run continuously, they overheat and get damaged,
as you were able to witness...


BTW, how did you measure the output power?

 

[Bluefan]

If you're a research chemist you have the budget to buy stuff from spectra physics or coherent. And you increased the current on your power supply? Did you connect the diode directly to the power supply? Then you just blew your diode. If you connect it to the driver then you fail because the driver takes a fixed voltage.
Putting a current source to the driver which expects a voltage source gives this weird behaviour, at some point you probably hit the voltage limit set on your power supply, at that point the current won't increase anymore.
Just set the power supply to the fixed voltage the batteries would give, the current regulation is done by the driver, so you can set your power supply to a high current, as long as it's high enough not to limit.