Intersecting 2 continuous laser in thin air to create a dot

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Discussion Overview

The discussion revolves around an experiment involving the intersection of continuous wave lasers in thin air to create a visible dot. Participants explore the visibility of the intersection point, the behavior of laser beams in air, and the necessary conditions for visibility.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes using continuous wave laser diodes and questions whether the intersection point would be brighter than the individual sources, suggesting a potential increase in brightness proportional to the number of sources.
  • Another participant questions the visibility of laser beams in thin air and the expectation of seeing something when two beams intersect.
  • A participant mentions that with sufficient power, a laser diode can produce a visible track, similar to those seen in laser shows, and invites corrections to this claim.
  • It is noted that laser shows often use smoke to make the laser paths visible, and that using high power to make air glow could be dangerous, potentially leading to thermal blooming and plasma formation.
  • One participant suggests that using two UV beams in a nonlinear medium could create a visible effect at their intersection if the frequencies are appropriately matched for optical difference frequency generation.

Areas of Agreement / Disagreement

Participants express differing views on the visibility of laser intersections and the conditions required for visibility, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

There are assumptions regarding the power levels required for visibility and the effects of air as a medium, which remain unquantified. The discussion also touches on the safety implications of using high-powered lasers.

GregoriusGery
I am planning on making an experiment about intersecting continuous wave laser from 2 or more source on 1 point in thin air. The laser i am planning to use is the simple laser diode, pumped with continuous wave, instead of using pulsed wave as in the usual laser pointer as i don't need it to reach a great distance.
What I'm asking is would the intersection point be brighter then the initial source of laser? like twice as bright if I use 2 source, or 3x as bright if i use 3 source?
I'm hoping for suggestions here before I started to put money and energy into building this experiment.
 
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What happens along the path of a normal laser beam in thin air? Do you see anything? Why do you expect to see something when you cross two laser beams?
 
Gigaz said:
What happens along the path of a normal laser beam in thin air? Do you see anything? Why do you expect to see something when you cross two laser beams?
as i know, if you put enough power to it, the diode can emit laser which tracks is visible, like in laser show
please do correct me if I'm wrong
 
GregoriusGery said:
as i know, if you put enough power to it, the diode can emit laser which tracks is visible, like in laser show
please do correct me if I'm wrong

In a laser show, the room is filled with smoke to make the laser track visible. It would be incredibly dangerous if they'd use enough Laser power to make the air glow. If you are somewhat good at physics you can probably calculate the laser power that you need to see the Thomson scattering of air molecules. I would expect that it is really large and probably in the thermal blooming regime where you instead see a glowing plasma.
 
Perhaps two UV beams could beat where they cross in a non linear medium. Get the frequencies right for an optical difference frequency.
 

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