Understanding Laser Blooming & Intensity

  • Context: Undergrad 
  • Thread starter Thread starter Kalrag
  • Start date Start date
  • Tags Tags
    Intensity Laser
Click For Summary

Discussion Overview

The discussion revolves around the phenomenon of laser blooming and the conditions under which a laser can create plasma. Participants explore the mechanics of laser intensity, energy concentration, and the implications of these factors in various applications, including potential methods for sustaining plasma beams.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that a high-energy-density laser can create plasma by superheating air at a critical intensity (~1 megajoule per cm3), which affects the laser's effectiveness.
  • Another participant suggests that the plasma formed is more of a cloud that diffuses the laser beam rather than a sustained beam, and its presence diminishes with distance from the source.
  • There is a mention of the possibility of using multiple small lasers to create a "plasma column" by focusing on a point and moving the focal point along a linear axis.
  • A participant emphasizes the importance of specifying the threshold in terms of megajoules/cm3, indicating that a weaker laser can still cause air breakdown if focused properly.
  • One participant questions the electrical conductivity of plasma, seeking clarification on its properties.

Areas of Agreement / Disagreement

Participants express varying views on the nature of the plasma created by lasers and the feasibility of maintaining a plasma beam. There is no consensus on the specifics of how to achieve or utilize plasma in this context.

Contextual Notes

Participants discuss the conditions under which laser blooming occurs and the implications for laser applications, but there are unresolved aspects regarding the exact mechanics and definitions involved.

Kalrag
Messages
104
Reaction score
0
Alright, I have sources (Wikipedia) that say that when a Laser hits a certain intensity it "blooms" and creates a plasma (around a megajoule). How does a Laser achieve this and how big is the laser? Can anyone help me?
 
Science news on Phys.org
Hi, Kalrag,

I'm not exactly sure what info you're looking for, but I'll try to answer your questions. A high-energy-density laser, fired through the atmosphere, will superheat the air at some critical point (~1 megajoule per cm3) and create a plasma (atoms of gas stripped of electrons) which essentially absorbs/scatters the beam and prevents it from reaching its target at full intensity. It isn't so much the absolute power output of the laser, (although it would have to be fairly high), but the energy concentration of the beam. Solutions include spreading out the energy density of the beam using a mirror, or--as is most often used--pulsing the beam on and off very quickly so that the heated air can dissipate between each pulse. As Wikipedia states, the effect is most pronounced when the air is not clear (fog/smog/etc.) as the particles absorb more energy and more quickly heat up the surrounding environment.

Does that help?
 
Yes that does help. Thanks for posting, But I would still like more. LikeIf it could create a sustained beam of plasma or something like that.
 
The plasma is not so much a beam as a cloud that forms and diffuses the coherent laser beam. It would be greatest near the source of the beam, and peter out as the beam lost energy further away. As long as the laser was operating with a power that passed the point of 'blooming', the plasma would remain. A beam of plasma would be difficult to produce and maintain in the atmosphere at any distance, but it is routinely used to cut metal and other materials at short range--it's known as a plasma torch.
 
It's important to note that the threshold should be stated in megajoules/cm3 (not just "megajoules"). This means a much weaker laser can be used, as long as the focusing point is correspondingly less. Some common-sized lab lasers can cause air breakdown, and PLD (http://en.wikipedia.org/wiki/Pulsed_laser_deposition) is becoming a widespread method of producing thin films out of laser-induced plasmas.

www.gentec-eo.com
 
Also, I read that I is a good electrical connductor. Is this true?
 
"I" is a good electrical conductor? I'm not sure I understand.
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 17 ·
Replies
17
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 22 ·
Replies
22
Views
4K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 26 ·
Replies
26
Views
6K
Replies
5
Views
512