Greens and reds and stuff....

[Aiki1]

So, I got a couple of 650nm 10-40mw modules recently, they seem really good, can run them for as long as I want so far, haven't tried for hours but they show no duty cycle so far, as was told to me by the company I got them from. Good.

Also have a 10mw 532nm green module from extremelasers, and it's really good - Very bright, good heat sync (sp?) and seemingly no duty cycle either.... Good.

Got a 5mw 532nm green from the first supplier above, nice tight beam,but the case is smaller in diameter than the 10mw green, and as soon as it gets hot, it fades a lot.... this sucks.... it will get brighter again when it cools down - duty cycle I guess? Is it just that it doesn't have as good a heat sync? This is the second one they sent me, as the first was mode hopping or something....

What to do.... are there other 5mw modules out there that I can leave on? I need one, not this.... I know extremelasers sells one for $105 + $5 shipping, if it's as good as the 10 from them I guess it's worth it....

Here's a pic:

5mw and 10mw green modules....

 

[allthatwhichis]

Are you wanting to go that low on power? I saw a few 20mW modules that looked like they were taken out of a pointer, had a spring for the power... I forget how much they are but I think they are less than $100. There is a 30mW module similar to mine for $125 somewhere on eBay also. I'd leave links but my job's firewall restricts me from going to eBay and I don't have my laptop on...

 

[Aiki1]

I have a lumia idea that my 10mw is too bright for, it kind of overpowers the red in this case, so I thought I'd use a 5 - but I wonder if my 10 is actually more powerful or something, it's really bright.... don't feel like being without it to get it tested though

 

[allthatwhichis]

You can do what I do to "dilute" my 100mW green and use microscope slides. It's a little ghetto but it works. Then you also have more green beams to play/deal with...

 

[Aiki1]

So is it normal for a 5mw green to have a short duty cycle? Is the reason my 10mw module seemingly doesn't have one simply because it has a good heat sync, and the 5 doesn't?

 

[Lasernerd]

Heat sink not (sync)

 

[allthatwhichis]

I'm not sure. I had a 15mW pointer style that I killed by keeping it on for about an hour non stop. I would think it may have a duty cycle, but may be wrong.

 

[Athoul]

Yeah they have duty cycles, unless they have a good heatsink (or distribute heat away from the pump diode efficiently). Even a 5mW green will have at least a 200mW pump diode and this is what heats up so fast. Once the diode heats up, the temperature will cause the diode to red shift slightly further into the IR, 808nm will become 809 or 810nm for example. This results in the crystals no longer lasing properly and a huge reduction in output. Heat will also effect the crystals aswell, adding to the thermal issue. Thus you need to supply a better heat sink in order ot have the output remain stable.

On the flip side, to much cooling will result in the output blue shifting towards UV, so the 808nm pump will shift to 807 or 8086nm etc.. having a similar effect on your output.

 

[45/70]

On the flip side, to much cooling will result in the output blue shifting towards UV, so the 808nm pump will shift to 807 or 8086nm etc.. having a similar effect on your output.

Ummmm, you're just kidding here, right? I mean, unless you're cooling the diode with liquid nitrogen or something exotic like that, the diode isn't going to get any cooler than when it first fires up.

Dave

 

[allthatwhichis]

Ummmm, you're just kidding here, right? I mean, unless you're cooling the diode with liquid nitrogen or something exotic like that, the diode isn't going to get any cooler than when it first fires up.

Dave

Couldn't using a TEC get it down enough? They get computer CPUs to well below freezing, I would think a laser would stay cooler that a CPU...

 

[45/70]

Couldn't using a TEC get it down enough? They get computer CPUs to well below freezing, I would think a laser would stay cooler that a CPU...

After thinking it over and doing a little research (I'm still learning here!), I conclude you are correct. With a laser module, if the cooling parameters are not set properly, you could, in fact, overcool the diode (or the reverse). That, of course, brings us to Athoul's statement. So........

Athoul, you weren't "just kidding". :thumbsup:

As for TEC CPU cooling, a setup that can freeze a modern CPU under load, I would call "exotic". I think I'll stick with water cooling.

Dave

 

[Aiki1]

So, this leaves me with my 10mw doing fine when I leave it on, but my 5mw.... not good at all.... what to do, just bite the bullet and buy another one with a really good heat sink like my 10er?

 

[Athoul]

Is the module housing metal or plastic? You could just incorporate a heat sink to the module, unless it's plastic and you didn't want to hack it apart. Either way you would need to sand off the painted finish and use thermal past when attaching the heatsink. Perhaps it's more feasible to just purchase one with a heatsink already.

45/70 > Yep, wasn't really a joke though it is not an easy undertaking to do. For some applications and experiments cooling a diode to extreme temperatures is desired.