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How to roughly estimate the beam power of a 532 nm laser?

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VioletGiraffe

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I just bought a [relatively] cheap 532 nm today. It's Chinese with no stated power rating to speak of. It draws 300 mA at 3 Volts, but that stat is of no use because it clearly has a linear current regulator inside (the current stays the same as voltage goes up beyond 3 V).

I assume it's a 5 mW toy, but I hope it could be more than that in practice. Is there any way, an experiment, to roughly guess its power? On the scale of 1-5-20-50 mW?

I seem to get a burning sensation if I cover the aperture with a finger or hand, but I'm not even 100% sure I'm not imagining it, it's so subtle. And I assume that if the sensation is real, it may well be from IR and not from the 532 nm light?..
 
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paul1598419

paul1598419

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That is why they make laser power meters. You'll need one eventually if you even plan on knowing the actual power of your lasers.
 
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hakzaw1

hakzaw1

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Try contacting a lab at nearest University--they have LPMs.
OR.. you may find a member close enough to visit and use their meter.

more.
 
paul1598419

paul1598419

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I've had poor luck with contacting universities I am currently not attending to give me help. I tried when I was setting up my spectrometer. At least they called me back to say "NO". Finding a member who has an LPM is a great idea, though.
 
Cyparagon

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300mA at 3V is 900mW. The driver is likely linear, and the pump diode is 2Vf, which gives roughly 600mW to the pump diode. IR pump diodes at this power are at most 50% efficient, so you have at most 300mW of output power. We have absolutely no idea how much of this is converted from here, as conversion efficiencies vary wildly based on too many factors to list. The most you could hope for is ~30% for CW, but you also know nothing about the IR leakage. We can say the output is less than 300mW in some unknown ratio of green and IR, but anything beyond that is a practically useless guess. My practically useless guess is 20mW of green.
 
hakzaw1

hakzaw1

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yep... hopefully he will make an 'intro' post and find a local member (lpm owner)---unlikely but who knows??
 
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steve001

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VioletGiraffe said:
I just bought a [relatively] cheap 532 nm today. It's Chinese with no stated power rating to speak of. It draws 300 mA at 3 Volts, but that stat is of no use because it clearly has a linear current regulator inside (the current stays the same as voltage goes up beyond 3 V).

I assume it's a 5 mW toy, but I hope it could be more than that in practice. Is there any way, an experiment, to roughly guess its power? On the scale of 1-5-20-50 mW?

I seem to get a burning sensation if I cover the aperture with a finger or hand, but I'm not even 100% sure I'm not imagining it, it's so subtle. And I assume that if the sensation is real, it may well be from IR and not from the 532 nm light?..
Click to expand...
This site may help.
https://www.repairfaq.org/sam/laserioi.htm#ioihlpm
 
paul1598419

paul1598419

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Yes. Sam Goldwasser is the man to look for in all things laser related. The best thing you can do is put a link to it permanently in your browser. To read it all would take a huge chunk out of your life, but it is the best compendium of laser related material in one place that you will ever find.
 
lasersbee

lasersbee

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VioletGiraffe said:
I just bought a [relatively] cheap 532 nm today. It's Chinese with no stated power rating to speak of. It draws 300 mA at 3 Volts, but that stat is of no use because it clearly has a linear current regulator inside (the current stays the same as voltage goes up beyond 3 V).

I assume it's a 5 mW toy, but I hope it could be more than that in practice. Is there any way, an experiment, to roughly guess its power? On the scale of 1-5-20-50 mW?

I seem to get a burning sensation if I cover the aperture with a finger or hand, but I'm not even 100% sure I'm not imagining it, it's so subtle. And I assume that if the sensation is real, it may well be from IR and not from the 532 nm light?..
Click to expand...
A link to the actual Laser would be helpful...
Maybe someone on the Forum has a similar
one that has been power tested...


"Cheap 532nm Chinese Laser" is just not
enough info.


Jerry
 
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diachi

diachi

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At 300mA current consumption your highest possible green output is somewhere around 100mW. Slope efficiency of the 808nm pump diode is usually 1mW/mA or there abouts. That gives you 300mW pump power. Highest conversion efficiency (best case) is 30%, leaving you with at most 100mW of 532nm out.

Realistically it won't be that efficient, so the actual output is likely somewhere closer to 50mW of green plus some IR.

Linking us to the laser you purchased, or providing us with a picture, could help us guess based on testing done by other people. There's really know way to know true output power for sure without an LPM.
 
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VioletGiraffe

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The reason I provided no link is that I bought it offline, it's noname, and the markings are useless: <1000 mW (I don't doubt it's less than 1000 mW!), class III (not IIIa or IIIb, just III).
I doubt it's 50 mW, but I'll be happy if it's 20 and not 5 or even 1.

DzPXmjD.jpg


Also, I understand you need a proper measurement device to measure power precisely. That's why I used the term "estimate". After all, measurement means comparing something to a reference, and I could think of a number of possible observable effects that can be used. For example, the thickness of a certain sheet material that the beam is able to penetrate / shine through. Heck, a number of sheets of 80mg/m2 white office paper in a stack that the beam remains visible on the other side of is not the worst metric, should be reasonably reliable and reproducible. Or am I wrong?
 
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paul1598419

paul1598419

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That particular pointer is of very low power. I have one that does about 30 mW to maybe 40 mW. They can be had in quantities of three. A red 660nm or 635nm, a 532nm and a 405nm for less than $10.00. They run on two AAA batteries and for the price, aren't a terrible deal if they all work when they arrive. Be careful of them as they tend to have problems with the switch after some time. As far as using office paper to measure the output power of lasers, it doesn't account for the energy density in the beam profile. Also the eye cannot make these judgments as the farther away from 555nm, the less the eye can see of the light. a 405nm is a perfect example of this as it is not a particularly visible wavelength.
 
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V

VioletGiraffe

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paul1598419 said:
They can be had in quantities of three. A red 660nm or 635nm, a 532nm and a 405nm for less than $10.00.
Click to expand...
Where?! o_O

Also, 30 mW is just about what I need. I suspect this one is less. But since I have no reference to compare to, I can't say.

Also, I obviously wasn't talking of comparing different wavelength lasers. Only of the exact same wavelength.
 
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