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monika

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Hi guys,

I am trying to understand a bit more about lasers and have come up with some questions which I hope some of you can help with.

1) I there any relationship between wavelength and power? For example is a 1W 808nM any more or less powerful than a 1W 980nM laser?

2) What defines power? I have seen many lasers from different manufacturers which clainm to be the most powerful in existance yet range from mW to W in power. Is this hyperbole on the manufacturers part does the types or wavelengths of the laser have any effect?

3) I understood (maybe incorrectly) that the ability of a laser to burn has some relationship to the area of the beam ie the smaller the beam, the power is more cncentrated transferred conversly the bigger the area, the power is dispersed over that area? If this is correct, I am confused with the video at Spyder 3 Arctic Blue Laser Pointer | Wicked Lasers. It looks as if it has quite a large diameter beam with the burning attachment so if that was reduced to a mm for example wouldn't that increase the power with respect to the area hence burn quicker?

4) On DragonLasers website it details how a 125mW laser is capable of melting rubber and some plastics. Although it does say that the power, beam width, object colour and mobility are facors, doesn't the distance also as this would effect the focal length?

If anyone can help with these questions or perhaps point me in the direction of the answers, I'd appreciate it.

Thanks

Monika
 

IsaacT

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1. The lower the wavelength, the better it will be at burning. However, it will have the same power. 500mW 650nm and 500mW 405nm will have the same output power, however the 405nm will burn better because the lower wavelength/higher frequency causes the energy to hit much closer together such that the substance cannot dissipate the energy as much as with the 650nm laser.

2. Yes, these are hyperboles. There is nothing mystical about power. The more mW you have the more power you have. Burning power however will also depend on minimum beam diameter at focus, since the energy will be spread out over that area. Example: A 2W 445nm laser with a terrible focus spot may not burn nearly as well as a 750mW 405nm with an amazing focus spot. The 445 has more power but the 405 burns better. Probably.

3. Don't pay attention to Wicked Lasers. Not sure what burning attachment you refer to however. If you mean the beam expander, what that does is increase initial beam diameter such that long distance beam characteristics are much improved. Since Beam Diameter and divergence are inversely related, a wider initial beam translates to a better divergence typically.

4. The distance will affect the beam width. So mentioning it would be somewhat redundant. But yes, a 125mW laser will not burn anything past a meter or two I would think without extra optics to focus the beam.

Hope that helps, any other questions feel free to PM me.

Thanks,
Isaac
 

Leodahsan

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1) I there any relationship between wavelength and power? For example is a 1W 808nM any more or less powerful than a 1W 980nM laser?
Not a relationship like this. Lets say, 1W of any wavelength, is 1W, so the power is the same.
The relationship is that shorter wavelengths photons (405nm, violet lasers, 445nm, blue lasers) have a bigger energy per photon, BUT thats compensated by the diode outputting less photons.

405nm diode > few photons of high power
808nm diode > many photons of lower power
but both could have the same total power, like 100mW.

AND if you're thinking about burning, different diodes have different divergences (how much the laser beam "defocus" with distance) and different surfaces reflect different colors.
IE A blue laser will have a harder time burning a blue sheet of paper, but will light on fire a red sheet.

2) What defines power? I have seen many lasers from different manufacturers which clainm to be the most powerful in existance yet range from mW to W in power. Is this hyperbole on the manufacturers part does the types or wavelengths of the laser have any effect?
Power is measured using an LPM (laser power meter) that uses a special kind of "calorimeter" to measure power, so its defined as heat power... :thinking: I may be wrong tho.

3) I understood (maybe incorrectly) that the ability of a laser to burn has some relationship to the area of the beam ie the smaller the beam, the power is more cncentrated transferred conversly the bigger the area, the power is dispersed over that area? If this is correct, I am confused with the video at Spyder 3 Arctic Blue Laser Pointer | Wicked Lasers. It looks as if it has quite a large diameter beam with the burning attachment so if that was reduced to a mm for example wouldn't that increase the power with respect to the area hence burn quicker?
Thats power density. Obviously, if you focus the laser, it will concentrate and burn more @ focal point.

I'll not talk about wicked lasers claims.

4) On DragonLasers website it details how a 125mW laser is capable of melting rubber and some plastics. Although it does say that the power, beam width, object colour and mobility are facors, doesn't the distance also as this would effect the focal length?
Another factor is spec'ing the laser. Dragonlasers probably would sent a >200mW laser, rated 125. Reputable companies does that.
Distance affects beam width because of divergence. Search about that.

Searching of BOLD terms is recommended.

Hope that this helps. (and everything is right)

Edit: Isaac beat me to it :p
 
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monika

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Thanks guys very much for your replies, it is appreciated :thanks:

This got me thinking a bit more about the shape and focussing of a laser beam. I'm not sure whether I am correct in this assumption, that a laser beam is essentially collimated light so taking into account divergence the beam stays relatively constant and therefore has an infinite focus unless a focussing lens is used?

With a focussing lens the focal point (and the highest power density) is achieved at x distance from the laser. If this is correct where does a beam expander come in? From what I understand, they reduce the beam divergence by a factor or x over a distance.

Bearing this in mind, how do you focus a laser over say 10m?

Out of interest, what is it with WickedLasers? Are they a bit of a dubious company?
 

nueces

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Thanks guys very much for your replies, it is appreciated :thanks:

This got me thinking a bit more about the shape and focussing of a laser beam. I'm not sure whether I am correct in this assumption, that a laser beam is essentially collimated light so taking into account divergence the beam stays relatively constant and therefore has an infinite focus unless a focussing lens is used?

With a focussing lens the focal point (and the highest power density) is achieved at x distance from the laser. If this is correct where does a beam expander come in? From what I understand, they reduce the beam divergence by a factor or x over a distance.

Bearing this in mind, how do you focus a laser over say 10m?

Out of interest, what is it with WickedLasers? Are they a bit of a dubious company?
Your curiosity and thoughtful questions are impressive. I'm the last one to answer any of your questions but I've learned a lot by reading the stickies in the front of the individual forums. I've also picked up some technical grasp of the subject on wikipedia. :)
 

Blaster

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Thanks guys very much for your replies, it is appreciated :thanks:

This got me thinking a bit more about the shape and focussing of a laser beam. I'm not sure whether I am correct in this assumption, that a laser beam is essentially collimated light so taking into account divergence the beam stays relatively constant and therefore has an infinite focus unless a focussing lens is used?

With a focussing lens the focal point (and the highest power density) is achieved at x distance from the laser. If this is correct where does a beam expander come in? From what I understand, they reduce the beam divergence by a factor or x over a distance.

Bearing this in mind, how do you focus a laser over say 10m?

Out of interest, what is it with WickedLasers? Are they a bit of a dubious company?
The above answers are correct and well explained as to wicked lasers the main issue is they are overpriced for what you get but they are wicked looking if you get my drift,
 




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