Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

Are these real?

V

Videogamer555

0
Joined
Jun 5, 2012
Messages
58
Points
0
On ebay I so often see green laser pointers for just $5 that are rated at high power levels like 100mW. Are they REALLY 100mW? I can't believe that a $5 laser would be able to put out that much power. I mean if I put in front of a properly callibrated laser power meter intended for measuring 532nm lasers, would it really read out as 100mW, or maybe something lower like 20mW? I know there are hacks that you can do to boost 5mW lasers to 20mW, but I've never heard of a hack that claims you can get full 100mW out of it. I'm guessing these people just buy 5mW laser pointers, hack them according to some online instructions, and then resell them on ebay. But are they really 100mW? I would like to know, because if it is possible for a cheap laser pointer to be "upgraded" to 100mW, why are official 100mW green science-lab lasers often around $1000 or more?
 





ZRaffleticket

ZRaffleticket

0
Joined
Feb 4, 2010
Messages
3,280
Points
113
bulky lab lasers are also designed to have better beam specs and less power fluctuations
 
Danny K

Danny K

0
Joined
May 29, 2012
Messages
82
Points
0
Of course not! Probably a chinese piece crap that will break in a week.
 
V

Videogamer555

0
Joined
Jun 5, 2012
Messages
58
Points
0
Danny K said:
Of course not! Probably a chinese piece crap that will break in a week.
Click to expand...


I bought a 5mW green laser once on Ebay for $5. I got it , and it was dead on arrival (well ALMOST dead). I noticed the beam appeared VERY DIM green, I further noticed that when looked at with a B&W CCD security camera, I could see a BRILLIANT light at the laser dot, meaning it had the IR blocking filter removed. It was better as a near-IR laser pointer than a green laser pointer, LOL. I opened it up and noticed that one of the things wrong with it was the photodiode-sense pin had been cut (probably to boost the light output, by not alowing the photodiode to moderate the driver output). I found that the brass KTP crystal mount when screwed on ALL the way to the laser-diode mount, didn't emit green light. However when I slightly unscrewed it, so it was loose, it worked. Only thing I can think of is VERY POOR MACHINING on the mounts, so you actually had to UNSCREW it a bit to reach the critical distance.

I also noticed that the green output dimmed over several seconds as the beam was allowed to run, likely a result of the laser diode not being power limited (rememmber the photo-diode lead was cut), and thus it probably overheated, and I know that increase in LED or laser diode temperature can reduce light output. This idea was confirmed, by allowing it to cool for several seconds, and turning it back on caused the beam to be back at full intensity again. Deciding that this was useless as a green laser (way to many things wrong with it to make it usable for pointing), I ended up just throwing away the optics and KTP crystal, and keeping it as an uncolimated near-IR laser. And a high power one at that.

Remember that a KTP laser crystal isn't very efficient, so the result is that to get 5mW green you need about 100mW near-IR. Since this was modded for probably 20 to 30mW green, that means the near-IR laser diode was likely outputting 400 to 600mW as a result. That's upper end of Class IIIb into the lower end of Class IV range!!!!! As with all laser diodes, uncollimated the beam is a highly divergent eliptical beam. At the output aperature of the laser diode it is an infintesimally small point, but after it travels just a couple feet and it diverges to about 4 or 5 inches in one axis and 1 to 2 feet in the other axis. At just a quarter inch from the laser diode though, it is just a like 4 millimeters in the long axis and 2 or 3 in the short axis. Now this is some high intensity IR here, and I found that if I put black colored plastic in front of the beam at this close range, it melts holes into the plastic!!!!! At farther distance though, at about half an inch to an inch away, the beam has diverged to the point that it no longer has any burning capability. Of course at long range, it makes an EXCELLENT near-IR illumination for my security camera! Of course it still has an overheating problem (in about 10 seconds of continuous-on time, it gets almost too hot to touch). I still will have to find some kind of heat sink to mount it in.


Well point of the story, these are cheap china crap, but even if they are broken for pointers, they easily still work as high powered near-IR lasers, and it's even better if they've been modded for high power green laser operation, cause that means they'll be even an MORE HIGH POWERED near-IR laser.
 
Danny K

Danny K

0
Joined
May 29, 2012
Messages
82
Points
0
Videogamer555 said:
I bought a 5mW green laser once on Ebay for $5. I got it , and it was dead on arrival (well ALMOST dead). I noticed the beam appeared VERY DIM green, I further noticed that when looked at with a B&W CCD security camera, I could see a BRILLIANT light at the laser dot, meaning it had the IR blocking filter removed. It was better as a near-IR laser pointer than a green laser pointer, LOL. I opened it up and noticed that one of the things wrong with it was the photodiode-sense pin had been cut (probably to boost the light output, by not alowing the photodiode to moderate the driver output). I found that the brass KTP crystal mount when screwed on ALL the way to the laser-diode mount, didn't emit green light. However when I slightly unscrewed it, so it was loose, it worked. Only thing I can think of is VERY POOR MACHINING on the mounts, so you actually had to UNSCREW it a bit to reach the critical distance.

I also noticed that the green output dimmed over several seconds as the beam was allowed to run, likely a result of the laser diode not being power limited (rememmber the photo-diode lead was cut), and thus it probably overheated, and I know that increase in LED or laser diode temperature can reduce light output. This idea was confirmed, by allowing it to cool for several seconds, and turning it back on caused the beam to be back at full intensity again. Deciding that this was useless as a green laser (way to many things wrong with it to make it usable for pointing), I ended up just throwing away the optics and KTP crystal, and keeping it as an uncolimated near-IR laser. And a high power one at that.

Remember that a KTP laser crystal isn't very efficient, so the result is that to get 5mW green you need about 100mW near-IR. Since this was modded for probably 20 to 30mW green, that means the near-IR laser diode was likely outputting 400 to 600mW as a result. That's upper end of Class IIIb into the lower end of Class IV range!!!!! As with all laser diodes, uncollimated the beam is a highly divergent eliptical beam. At the output aperature of the laser diode it is an infintesimally small point, but after it travels just a couple feet and it diverges to about 4 or 5 inches in one axis and 1 to 2 feet in the other axis. At just a quarter inch from the laser diode though, it is just a like 4 millimeters in the long axis and 2 or 3 in the short axis. Now this is some high intensity IR here, and I found that if I put black colored plastic in front of the beam at this close range, it melts holes into the plastic!!!!! At farther distance though, at about half an inch to an inch away, the beam has diverged to the point that it no longer has any burning capability. Of course at long range, it makes an EXCELLENT near-IR illumination for my security camera! Of course it still has an overheating problem (in about 10 seconds of continuous-on time, it gets almost too hot to touch). I still will have to find some kind of heat sink to mount it in.


Well point of the story, these are cheap china crap, but even if they are broken for pointers, they easily still work as high powered near-IR lasers, and it's even better if they've been modded for high power green laser operation, cause that means they'll be even an MORE HIGH POWERED near-IR laser.
Click to expand...
Hahah. I don't have time for all that lol.
 
jeffreythe00

jeffreythe00

0
Joined
Jan 13, 2010
Messages
2,516
Points
63
To answer some of your questions and add a few of my opinions

When your dealing with eBay and Chinese or anything in life. 9 times out of 10 if it sounds too good to be true. It usually is.

Those scientific lasers you see for 1000$. They are VERY stable lasers designed for specific applications where you need very specific characteristics. For instance. If you are doing something like examining biological organisms. You may want a specific wavelength and you may need the beam specs to be VERY good and you might not want the laser to go under OR over 1mw else you won't be able to view your biological organisms because power has fluctuated or you toasted them. It cost a lot of money to developed and fine tune lab Lasers.

Also if you are playing with high powered IR diodes. PLEASE for the sake of your eyes. Get proper glasses! IR is extremely dangerous and can blind you permanently without you realizing you were doing damage until its too late! PLEASE be careful should you choose NOT to get a pair of glasses (which I suggest you do!)

IR is the most dangerous wavelength you could be playing with. So please do some reading about it.
 
V

Videogamer555

0
Joined
Jun 5, 2012
Messages
58
Points
0
jeffreythe00 said:
IR is the most dangerous wavelength you could be playing with. So please do some reading about it.
Click to expand...

IR is dangerous because of the fact that it is so "visually dim" that your eye doesn't have the automatic iris closure response, not do your head muscles have the "turn away from the light" reflex. However the wavelength's effects on the eye are identical (if the power level is the same) if those biological safety features aren't taken into account.

For example, if I some how could "disable" my head's "turning away from the light" reflex for ALL wavelengths, and "disable" my iris's closing down for ALL wavelengths. The damage that a 500mW green laser would do, would be identical to that of a 500mW red laser, and would be identical to that of a 500mW near-IR laser.

Only once you get down in wavelength to blue, violet, and near-UV wavelengths, do you find that the wavelength itself becomes a hazard (same reason that a welding arc is so dangerous).

In other words, if I follow the same safety precautions (don't shine the beam into the eye) that I would follow for any other laser, the near-IR laser is not going to be any more dangerous than a visible light laser. Only when in the course of scientific research the researcher for some reason has to point the beam in the direction of his face or put his head near the beam, do you find that the safety precautions have to differ from one wavelength to another (different color goggles to block different wavelengths). If I'm using it to shine AWAY FROM MY FACE (like at a piece of paper that I wanna burn with the laser), then there is no difference in safety that is needed between a green laser and an IR laser of the same power.

In fact I've used more power full "lasers" than this before. I used a large fresnel lens before in the sunlight to burn wood (or even instantly set paper on fire). It was the size of an ordinary sheet of paper (8.5 x 11 inches, or 0.2 x 0.3 meters) which has an area of 0.06 m^2. And sunlight at sealevel has an intensity of about 1000 W/m^2 which means the total power in that focused dot of sunlight is 0.06*1000 = 60 Watts of power!!!!!!!!! That is 100 times as powerful as the highest power level that I suspect my modded green laser pointer's IR laser diode may be emitting (0.6 Watts), and is in fact in the range of power levels that a CO2 laser would emit!!!!!!!

I have NEVER received eye damage by using this oversized magnifying glass in the sunlight before. I didn't receive eye damage from the magnifying lens, becauase I wasn't dumb enough to focus the light at my eye. Same goes with this high power near-IR laser diode. As long as I don't like put it right up to my eye and shine the beam right into my eye, but instead shine it AWAY from my eye (at a target I wanna burn or melt like paper or plastic), I will be perfectly safe.
 
Danny K

Danny K

0
Joined
May 29, 2012
Messages
82
Points
0
Danny K said:
Hahah. I don't have time for all that lol.
Click to expand...
For anyone that misunderstood. What I meant by "I don't have time for all that" was referring to the actual process he described. I didn't mean I didn't have time to read it. I read it and it was pretty interesting. Sorry for the misunderstanding.
 
You must log in or register to reply here.




Top