Trying to troubleshoot power/brightness issue

[ElectricPlasma]

I bought a very cheap 532nm laser off of eBay, from China.

My guess is that it's about 70 mW, or was 70 mW at least. When I first got it and put in a newly charged battery, it seemed like a solid 70mW. I don't have a LPM though, so I can't say for sure; just a guess.

However, a few days ago I noticed something. Every time I powered it on, it would be full brightness and then 0.5-1 seconds later it would get noticeably dimmer. No fading or anything, just straight from bright to not-as-bright. This occurs every time I power it on. My first guess had been low batteries...

The laser takes 1x18650 battery, so I fully charged the one I had been using with this laser pointer. Put it back in, same result. Bright for 0.5-1 seconds, and then dim. So my second guess, battery had reached the end of it's lifetime.

I tried another 18650, fully charged. Same result. I'm pretty damn confused at this point, because I doubt the issue would be batteries based on the fact that I had just tried two charged 18650s.

:wtf:

Temperature maybe? I mean I doubt it... My house is room temperature and the host is a giant heat sink. Maybe the driver is screwed up somehow? I haven't dropped the laser or anything, maybe it's just defective.


Any ideas LPF?

 

[GSS]

I hate to say this but (cheapie) may be the magic word. I got a couple of these that drive me crazy, at times they light a match instant and other times I cant light one for the life of me. Since they are a DPSS laser ive also tried the warm up thing wether I kept it cuffed in my hand or in my pocket or again just powering it to warm it up. Try pressing the switch harder or moving it around as little as it will let you. Ive had to press hard on some of my pens and these use the same type momentary switch I believe.

 

[diachi]

Could be a whole range of things with DPSS, a decent quality unit won't generally have those issues though.

Diode wavelength could be shifting, crystals could be shifting as they heat up, KTP might be going outside it's optimal temperature, could be an electrical issue with the driver or some such. Even something like too much pump power into a crystal set that's too small could show similar symptoms. DPSS can be very picky, it really doesn't take much to drop all of your output power - especially on cheaper units.

Even on higher quality units you can have these issues at start up. My 473nm labby starts as TEM00 at maybe 30mW or so then drops off to some non-TEM00 mode and about 10mW after a few seconds. Once it heats up and everything stabilizes for 15 minutes or so the beam goes back to TEM00.

 

[Benm]

I'd bet on some thermal issue here.

DPSS lasers are prone to thermal sensitivity, and it can be quite sensitive. One thing that can easilly become a problem is a mismatch between output wavelength of the pump diode and solid state laser. Sometimes this can happed quite rapidly due to the thermal resistance between the laser chip and it's case, regardless of how well the thermal design of the overall enclosure is.

 

[ElectricPlasma]

Interesting, seems like picky DPSS laser from China for 10$ has it's down sides :crackup:

I'd bet on some thermal issue here.

Also, benm, I'm not quite sure if it's a thermal issue. Been fiddling around with the laser, and it seems to be the exact same delay before it goes dim every time. Maybe a design flaw though, not sure.

 

[Marco Polo]

Weighing in late because I just found this thread. I'm convinced that the lasers installed into the 30x hosts are factory rejects or 'seconds' that are used in some other manufacturing process.

I still enjoy my 301's and 303's, have had very few failures so far (fingers crossed). The greens tend to mode-hop a lot, the violets are prone to early failure but if they make it past that they seem to do fine. Not much experience with the reds. I have one in 450nm as well.

An issue that does come up is that the 'tactile' feel of the button will not last forever, and once it goes out it will take almost no pressure to close the switch and turn on the laser. I have had to fix multiple holes that were burned into my coat pockets this way.

only thing I'd change about them is replacing the key switch with a click on/off (much easier to use), replacing the crappy switch (which is only rated at 50mA btw) and replacing with a bigger one. Also, using more-common thread sizes. The threads used in these lasers are fairly obscure, and I have had zero success finding anything to fit them, or dies/taps to cut them.

The 301 family is actually fairly easy to work on... the problems, really, come down to not being able to find parts, and the need to build up a tool set specifically for them. Do that and you can probably build anything you want into a 301. If I can ever stop being flat broke, that's what I want to do but I've been saying that for years now so really have no hope in that regard.

But back to the original question the green ones mode hop all the time, it is hit or miss and you basically get what you get. If you want something more stable you will have to go with a LaserBTB or similar, or a custom build. The C6's are good for building, despite the metal being paper-thin, particularly the threads under the front ring. If you want to build your own, I'd go with a C6 or one of its variants. If you just want green, I'd go with a PL520 direct diode and skip the DPSS issues, although that 532nm sure is pretty

 

[Link]

I bought a very cheap 532nm laser off of eBay, from China.

My guess is that it's about 70 mW, or was 70 mW at least. When I first got it and put in a newly charged battery, it seemed like a solid 70mW. I don't have a LPM though, so I can't say for sure; just a guess.

However, a few days ago I noticed something. Every time I powered it on, it would be full brightness and then 0.5-1 seconds later it would get noticeably dimmer. No fading or anything, just straight from bright to not-as-bright. This occurs every time I power it on. My first guess had been low batteries...

The laser takes 1x18650 battery, so I fully charged the one I had been using with this laser pointer. Put it back in, same result. Bright for 0.5-1 seconds, and then dim. So my second guess, battery had reached the end of it's lifetime.

I tried another 18650, fully charged. Same result. I'm pretty damn confused at this point, because I doubt the issue would be batteries based on the fact that I had just tried two charged 18650s.

:wtf:

Temperature maybe? I mean I doubt it... My house is room temperature and the host is a giant heat sink. Maybe the driver is screwed up somehow? I haven't dropped the laser or anything, maybe it's just defective.


Any ideas LPF?

I recently had a very similar issue with a 532, they're quite temperamental.

Either way it sounds like its either a bad connection somewhere (unlikely) or the diode/crystal has issues or is on its last legs (pun intended).

Someone might be able to cast some more light (another pun) on this but from experience that's likely what is happening, you might find it dies completely soon.