Understanding Laser Blooming & Intensity

In summary, a high-energy-density laser fired through the atmosphere will create a plasma around a megajoule. It is not the power output of the laser that matters, but the energy concentration of the beam.
  • #1
Kalrag
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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?
 
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  • #2
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?
 
  • #3
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.
 
  • #4
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.
 
  • #5
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
 
  • #6
Also, I read that I is a good electrical connductor. Is this true?
 
  • #7
"I" is a good electrical conductor? I'm not sure I understand.
 
  • #8

1. What is laser blooming?

Laser blooming is the phenomenon that occurs when a high-powered laser beam is fired into the atmosphere. The laser beam heats up the air molecules, causing them to expand and create a temporary "bubble" in the atmosphere. This bubble can distort and weaken the laser beam, known as blooming, making it less effective at its intended target.

2. How does laser intensity affect blooming?

The intensity of the laser beam plays a significant role in blooming. A higher intensity laser beam will cause more heating of the air molecules, leading to a larger and more pronounced blooming effect. Lower intensity beams are less likely to cause blooming, but can still be affected by atmospheric conditions such as humidity and air density.

3. What factors can contribute to blooming?

Aside from laser intensity, other factors that can contribute to blooming include atmospheric conditions, such as temperature, humidity, and air density. The angle and distance of the laser beam from its target can also affect blooming, as well as the type of laser used and the power source.

4. How can blooming be reduced or mitigated?

One way to reduce blooming is by using adaptive optics, which involves using sensors and deformable mirrors to adjust the laser beam's shape and compensate for atmospheric distortions. Another approach is to use shorter laser pulses, as shorter pulses will have less time to heat up the air molecules and create blooming. Additionally, choosing optimal atmospheric conditions and carefully calibrating the laser beam can also help mitigate blooming.

5. What are the practical applications of understanding laser blooming?

Understanding laser blooming is crucial for scientists and engineers working with high-powered lasers, as it can affect the accuracy and effectiveness of laser-based technologies such as laser weapons, laser communication systems, and laser-based measurement devices. By understanding and mitigating blooming, these technologies can be improved and used more effectively in various fields, including defense, telecommunications, and scientific research.

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