Normally unstable of defective ?

Hi All,

I've received my first "real" portable green laser yesterday (the first two were cheap pointers from dealextreme).

It's very heavy, big, powerfull (400mW but I'm not yet equipped to measure it) and expensive but I quickly noticed that it wasn't stable.

I've extensively searched this site and others about the instability of green DPSS lasers but I have the feeling that this laser has a problem. It's like there's a living thing inside it that wants to go out.

When focused to a small point it seems to flicker a lot, and it keeps doing so even after several minutes. Then it shuts down itself after a few minutes (the site indicates "thermoelectric diode driver output power automatic power reduction based on temperature"). But it seems that the reduction is from 100% to 0 % after less than 8 minutes with room temperature of 22 °C.

So I decided to unfocus it to make the larger possible dot (as large as a door from 4 to 5 meters distance). But as you'll see it's not a dot anymore and there are a lots of artifacts. I'll do some pictures later.

Here's a video of the problem (constant flicker, random frequency):

http://ardennes.free.fr/LASER/UnstableGreen.mov

This video is about 120 seconds in real time but as been recorded at about 1/10 of real time so it lasts about 11 second.

My 2 cheap green pointers (5 mw and 30 mw officially) don't exhibit such instability.

That's why I'm not pleased with the symptoms of this one and wanted to ask experts:

If you had paid more than 400 bucks for that laser, would you keep it ?
Do you think that it's defective or am I asking too much ?

TIA.

PS : Sorry, I can't fix the subject line that should be:
"Normally unstable or defective ?"

I am kind of a NOOB, but I have a 400mw 532nm, it has a duty cycle of about 1 minute on, 1 minute off, I would never consider running it till the thermal protection kicks in, that is just asking for something to fail. My laser tends to fluctuate exactly like yours, and has since I bought it second hand, and it tests just slightly higher than specification, and I always just thought it was changing modes from one to the other as the efficency in the diode changes, I look forward to the answer from more knowlegeable members, as although I never really cared about the little flickering before, now you have piqued my interest.

I think it's a jetlaser?

I don't know, perhaps there are users here, but even with TEC i don't think it's a good idea to gun a 400mW for 8 mins.

The slight dip in power is normal for my 532s, but i'm not sure about your particular higher quality one and need other users' verification. But as long as it does not dim for > 0.05 sec it should be ok. Mine is just a very very fast flicker every once in a while, nothing to worry about. Yours actually look ok.

The artifacts around it is ok.

This phenomina is called "mode hopping"

It occurs when crystals inside the module "heat" I had a laser that mode hopped in a review! it also provides you some more information about mode hopping.

http://laserpointerforums.com/f52/517mw-peak-h532l-s300b-skylaser-review-73410.html

Anyhow mode hopping mosly occurs on lower quality builds. However that does not mean this laser is low quality. It would help if you specify where you bought this laser and what kind it is.

Some reputable companies would offer you a replacement for this kind of mode hopping.

As for the laser to decrease and increase in power, you cant see that with your eyes.. You will need a laser powermeter to confirm that.

And about the shutting off, you might want to check if there was a dutycycle specified with this laser. You should never get your laser get to hot. It can do damage!

If i were you i would contact the seller with this issues and ask for a replacement.

greetings,,

I think the experienced "duty cycle" of 8 mins is just fine, in fact its really good. Remember that it uses Peltier TEC. Such systems in a small host are at best 5% efficient compared to ~ 50% for refrigerant systems. That means to say its is not going to wick a hot of heat away, and even if it does the host would get extremely hot. For a 400mW 532nm I guess it'd be the order of approx. 1.5-2A draw for the diode itself.

I am don't have much experience in lasers but I have quite a bit of experience in LEDs, but for a LiCo 3.7V source at 1.5A-2A (not sure how's DPSS efficiency), that's quite a bit of heat for a 8 min run on such a small host for the TEC to work on (relative to flashlights).

Hello,

Thank you for your answers.

RCpilot: If it has a protection then I really want (need) to know if it works and I'm not sure if it does. From what they say, the power should be reduced. At the end of that test, maybe the battery was near empty. I'll have to retest with a fully charged one. What I don't know is how much time it should be able to work on a new "TrustFire Protected 18650 3.7V True 2400mAh".

From their site: " Auto Thermoelectric Regulation: Automatic power reduction based on temperature increase. It means the laser can run continuously at no risk of burning the laser diode."

2100: Yes, it's a PL-D Pro, 400 mW. How did you know ? This model does not have a TEC despite what the description seems to imply ("Continuous; thermoelectric diode driver output power automatic power reduction based on temperature"). Note that it doesn't say "cooling".

offroadfreak8582: Yes, mode hopping, I found that in the FAQ before asking but I thought that it should not be permanent and as visible and with several changes per seconds (never more than a few seconds stable), especially on this brand/model. Your answer convinces me that I should report this problem to Gray. It wasn't very hot at the end, less than my o-like 1 W blue after 30 seconds. But I'll try again with a fully charged battery.

2100: I was expecting more than 8 minutes because it should be able to do it. The description on the site is not accurate (under "more info"):
"6 Modes activated" this model has only 2 modes full power and pulsed mode at about 3 or 4 Hz. But I like the simplified code switch and the metal on/off button at the bottom.