Can lasers create visible plasma channels in air?

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Discussion Overview

The discussion centers around the possibility of high-power lasers creating visible plasma channels in air. Participants explore the conditions under which this might occur, including the ionization of air and the visibility of laser beams in different environments.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a high-power laser could create a visible plasma channel, drawing a parallel to electric arcs.
  • Another participant asserts that lasers are non-ionizing radiation, suggesting that they cannot ionize air to create plasma.
  • Some participants propose that if the power absorbed by the air is sufficiently high, it could heat the air enough to ionize it, potentially creating a plasma channel.
  • A historical reference is made to research on laser-steered charged particle beams for anti-missile systems, which involved ionizing a channel for the beam.
  • One participant notes that while laser beams are generally invisible, they can be made visible through scattering, especially in the presence of dust particles.
  • Another participant discusses the phenomenon of laser breakdown of air, mentioning that powerful lasers can produce long plasma channels, particularly with the use of focusing lenses.

Areas of Agreement / Disagreement

Participants express differing views on whether lasers can ionize air to create visible plasma channels. There is no consensus on the feasibility of this phenomenon, with some arguing for its possibility under certain conditions and others disputing the ability of lasers to ionize air.

Contextual Notes

Discussions include references to specific power levels, types of lasers, and historical research, but the exact conditions and parameters for creating visible plasma channels remain unresolved.

kuartus4
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I have a question. In an electric arc, the electric current going through the air makes a visible plasma arc as so:

http://upload.wikimedia.org/wikipedia/commons/7/7a/Electric_arc.jpg

My question is this: Could a high power laser create a visible plasma channel through its path. I ask because laser beams are invisible in clear air, but what if it was powerful enough to ionize the air into plasma? Would there be some type of visible laser channel?
 
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hi there

As far as I am aware ... Lasers are NON-ionising radiation, so no ionising could occurlets se ewhat others have to say :)

Dave
 
I believe they could IF the power absorbed by the channel of air is sufficiently high, as that would heat the air high enough to ionize it. I believe small particles present in the air may make this easier. But it's got to be a LOT of power in a small amount of time.
 
Back in the 1980's there was some research on laser-steered charged particle beams for anti-missile systems. The notion was to use high-intensity beams to ionize a channel for the beam by the means Drakkith described. I think the concept was dropped when it was realized that a high-intensity laser could be more easily constructed that was by itself sufficient to disrupt a ballistic missile. A prototype airborne anti-missile laser was built and successfully tested (see "Airborne Laser Laboratory", "Airborne Laser Testbed", "Boeing YAL-1"). This program was canceled by the Obama administration.
 
kuartus4 said:
Could a high power laser create a visible plasma channel through its path. I ask because laser beams are invisible in clear air, but what if it was powerful enough to ionize the air into plasma? Would there be some type of visible laser channel?

Powerfull laser beam of visible wavelength is visible in the air under day light. For example 532-nm laser beam with few millimeters in diameter can be visible at power of several watts. The main reason of its visibility is scattering on dust particles. But even in dust-free air there is some scattering as well.

Concerning plasma channels there is such phenomenon as laser breakdown of air. It takes place near focus of a focusing lens. There is an examle - . Here the laser spark is very short, but its length can be made much longer using powerful laser and long-focus lens. E.g. I'd observed about 2-m long lasers sparks with aid of 50-J, 10 ns lasers pulses.

Very long plasma channels can be produced using very-high-power fs lasers pulses. At this level of power self-focusing of the beam in air is obtained making the beam to be self-collimated. http://www.dmphotonics.com/fs_filamentation.htm
 
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