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Old 11-18-2007, 09:45 PM #1
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Default laser-induced plasma channel

I'm curious how powerful a laser you would need to create a laser-induced plasma channel.
Would a laser that is capable of burning suffice?
I'm guessing that a plasma channel is created when using a burning laser.


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Old 11-18-2007, 10:10 PM #2
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Default Re: laser-induced plasma channel

I've seen a laser ionise air by exceeding its breakdown energy, but that takes a hell of a lot of power. I don't know exactly how much, but it is way beyond the capability of any continous wave laser you could buy or construct yourself.

Pulsed lasers however, can quite easily do this. A Nd:YAG with a collimating lens will create nice spraks in mid air with a pulse energy of a few 100 mJ.
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Old 11-18-2007, 10:33 PM #3
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Default Re: laser-induced plasma channel

To create an ionized channel you would need a huge amount of energy. Doing very simple calculations by assuming the channel is truly cylindrical you could come up with a value. You would need to look up the first ionization energy for the gases in the atmosphere and calculate the energy required to ionize a cross section of the beam path based on the various gas partial pressures. You could then apply that energy to the length of the cylinder created by the beam path and add a factor to account for divergence (or you could use the definite integral of the divergence function using the disc technique, or you could do a sample test until you begin to see ionization and measure the energy and apply Riemann sums). Once you have ionized atmospheric gases you need to determine if those gases will now absorb the wavelength of the laser you intend to use. By stripping electrons you expose electrons in other sub-shells altering their propensity to absorb and release energy.
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Old 11-18-2007, 11:48 PM #4
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Default Re: laser-induced plasma channel

I have a co2 laser and an Nd-YAG that can spark the air when focused down with a short focal length lens.
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