Trapping Light with Elliptical Mirrors: Possibility or Impossibility?

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Discussion Overview

The discussion revolves around the feasibility of trapping light using elliptical mirrors and other mirror configurations. Participants explore theoretical and practical considerations regarding the alignment, efficiency, and environmental conditions necessary for sustaining a laser beam within a reflective system.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes using a set of mirrors to keep a laser beam bouncing after the laser is turned off, suggesting a beam splitter as a potential solution.
  • Another participant acknowledges the idea but highlights the difficulty of aligning mirrors to sustain light for long periods, suggesting that two parallel mirrors might be simpler to align.
  • There is a question raised about the nature of elliptical mirrors, with one participant explaining that they are conic sections with two focus points, which could theoretically aid in trapping light.
  • Concerns are raised about the efficiency of mirrors, noting that they do not reflect 100% of light and will absorb some, leading to rapid degradation of the light beam.
  • One participant argues that visibility of the light would lead to additional loss, as photons would escape into the observer's eyes, and suggests that the setup would need to be in a vacuum to minimize interactions with air particles.
  • A participant concludes that while indefinite containment of light is deemed impossible, it may be possible to sustain it for increasing periods with significant effort.

Areas of Agreement / Disagreement

Participants express a range of views on the feasibility of trapping light with mirrors, with no consensus reached on the practicality of using elliptical mirrors or the overall possibility of sustaining light indefinitely.

Contextual Notes

Participants note limitations regarding mirror efficiency and environmental factors, such as the necessity of a vacuum to prevent light absorption by air particles, but do not resolve these issues.

ffleming7
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I was wondering if you could put a laser beam into a set of mirrors and then once you turn the laser off, have the laser still bouncing off the mirrors. The only way I could think of was if you used a beam splitter like in the diagram.
 

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What you are suggesting could work, but it would be very difficult to align the mirrors welll enough to sustain the light for any long period of time.
Also it would be much simpler to use two parallel mirrors (easier to align).
Depending on your application, perhaps an elliptical mirror would work better (although, i don't think that's especially feasible either...)
 
lzkelley said:
Also it would be much simpler to use two parallel mirrors (easier to align).
That makes sense.
lzkelley said:
Depending on your application, perhaps an elliptical mirror would work better (although, i don't think that's especially feasible either...)
either...)
What is an elliptical mirror?
 
Not really any reason why it can't be done, other than the fact that mirrors don't reflect 100% of the light incident on them, they will alway absorb a little bit of it. The quality of the mirror will dictate how much it reflects/absorbs. Because light is so fast, it will get a lot of bounces very quickly and degrade into nothing in a few microseconds...
 
.. and I'm assuming you want to suspend a beam of light because it will "look cool." Problem is, it won't work if you can see it. Seeing it would mean photons are bouncing off something and flying into your eyes, a.k.a. more light lost.

In fact you couldn't really do it in air at all, it would have to be in a vacuum.
 
An elliptical mirror is one that is designed in an elliptical shape --> which is a conic section, or closed curve - like a squished circle. Ellipses have the special property of 2 very elegant focus points, which would make it a lot easier to trap light in a region at the same time as having a place to insert it from.
It would certainly need to be in a vacuum to remain for long periods of time (so as to prevent the light from interacting / getting absorbed by particles in the air).
Mirrors can't reflect all light anywhere close to 100% efficiently, but to my knowledge, when created for a particular frequency (or small frequency range), mirrors can be made to essentially (though still not quite) 100% efficiency.
The general conclusion is that keeping light bouncing back and forth in any small, defined region, indefinitely, would be impossible; but with a lot of trouble you can keep it contained for increasing periods of time.
 

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