">5 mW" Burner

[Dvorhagen]

Just wanted to get peoples' opinions on this, since I have little experience with greens (and lasers I didn't build myself). I bought a supposedly 5 mW green laser off eBay for about $12. Recently, just for the hell of it, I broke off its metal cap and realized I could adjust the lens nut with a screwdriver. So I focused it to about 8" from the aperture, and discovered, to my delight and slight alarm, that it would ignite flash paper in seconds and smoke black stuff.

This has got to be way over-spec, right? From what I understand, the IR pumping diode has to be fairly powerful..could this thing just lack an adequate IR filter?

 

[wee40811]

Sometimes it's just because the leaking IR from the laser cause the burning. But in this case if the laser is not too weak focus the beam is the good way to concentrate the energy. My 50mwlaser can smoke black paper and cut the tape without focusing the beam so it's not unusual that 5mw laser can do this with focus the beam.

 

[denton808]

well i think it's just a matter of the focusing ability. i mean if you look at it this way.

a 50mw with a 2mm dot and then a 5mw with a .5mm dot. i'm pretty sure a focused dot is smaller than .5mm, but let's just use that as a easily obtainable example.

a 2mm dot as compared to a .5mm dot, the 2mm dot has 4 times the diameter. in geometry it has 16times the area. that means the amount of energy per area for the .5mm dot is greater. if u made 16 .5 mm dots fit into that one 2mm dot you'd have 80mw of power. so you can see that when focused, the burning power is greatly improved.

of course my analogy is devoid of calculations of factors such as the amount of energy lost when traveling the distance and w/e else. mine is just a simplified conceptual thing. i dunno if this is how light works 100%, but this my understanding of light. correct me if i'm wrong XD

 

[Greenmechanic]

5mW of any wavelength will not burn anything. Your laser is overspec.

Most of the <5mW greens I have bought off of eBay measure between 25-40mW
The sellers only list them as 5mW because that's as high of power as eBay will let you sell.
Here's a tip when buying an eBay laser; look at the mA rating of the pump diode.(if listed)
This will give you an idea of how powerful it will really turn out to be.

I wanted a "safe" green to play with my cats.
I had to buy 7 of them before I received one under 10mW,
(and then only because it went from TEM00 to TEM12, or who knows what)
It was 27mW when I received it, but lasted about 10 minutes at that power.
First time in my life I was glad to see a laser go south.

My cats don't react to 650nm anymore (bored?)
But the 532nm is just like when they first saw a 650nm, all over again.
They hate 405nm for some reason.
If I turn one on, they all run and hide. (hurts their eyes?-maybe?)

 

[Dvorhagen]

Thanks for your replies! I figured it had to be outputting way more than 5 mW.

 

[kingdave2357]

yea, my cats dont like red anymore either, I think they get used to or adjusted to the color and it doesnt excite them anymore thought im not really sure, they love greenies and blu-rays the most...