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09-22-2012, 06:59 AM #1
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cosmarchy
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Laser Power Question

Hi,

I've found this formula on this webite to calculate the power of a laser and was posted by Arayan back in 2011

BP=power/(π(beam diameter-beam divergence*distance)^2)/2

Can anyone please tell me the units?
Power is in watts I assume and divergence in mRad but what about distance and diameter?

Also, is this dependent on the wavelength of the laser?

Thanks

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09-22-2012, 07:32 AM #2
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Bionic-Badger
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Re: Laser Power Question

That's not laser power; that's power density. After all, power is already one of the inputs in the calculation. All that equation is doing is dividing the power by area, but calculating the area as a function of the beam's properties.

Yes, power is in Watts. Use whatever units you want or have available for distance and diameter (meters, etc.). They're all inter-convertible, and often you can just punch the values, with units, into Google's calculator (or a TI-89's) and it'll convert things for you.

Wavelength isn't in the equation because it is probably incorporated into one of the other input parameters such as divergence and power. Beyond that, it'll only apply if you're considering wavelength-dependent interactions, such as how light at a wavelength will be absorbed by the surface.
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09-22-2012, 06:09 PM #3
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cosmarchy
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Re: Laser Power Question

Thanks for your reply, Bionic

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