Capturing Light

I was thinking about this one as we discussed optics in my physics class.

Is there a method of capturing physical light, as in the waves or photons themselves? The only way I could imagine doing this is utilizing high-quality mirrors.

So I imagined a capsule-like structure. It is lined with mirrors, with zero area absorbing light. If such a perfect structure were possible, how would you get the light in without it escaping? Well it seems simple, just put a light source inside. The light casing body would absorb light though, wouldn't it?

Say, though, the light source's body didn't absorb any of the light and light was now contained within this structure. The next part would be to put a wireless camera inside so we can even know that light is being contained within.

Presently, there is no appreciable reason to want to even contain light in such a manner, but still, it would be interesting in my opinion.

My question is, would this work? Can physical light be contained?

I always thought about this as a kid for some reason. I imagined a perfect sphere that is hollow with a perfect mirrored surface inside. Then you pulse in a laser through a tiny opening that seals itself after the pulse.

What would happen?

The other though i had was could you "fill up" the sphere totally? and if you could do that, can you make it "overflow" with light and what would happen?

Forgot all about that! Cool, thanks...

Lasers use a similar technique, fiber-optic cables also use a similar technique.

Yes. Just take a box with a flashlight in it. If you don't see anything, it's being contained. With every reflection off a surface, a little energy is lost, but as far as you're concerned, yes you can.

Yes, and you can do it outside a laboratory. Take a flashlight, of moderate size, no pocket or hand held varieties, and turn it on. Now slowly take the flashlight aim it away from your body, then begin to rotate it towards you. Stare directly into the flashlights blinding path for 4 seconds and remove. That big black and purple spot you see are all the photons trapped in your eye, eating way at your retinae. Nah, just kidding.

Seriously, can't photons be stopped in the earth's atmosphere? I would suggest using similar methods if this is true.

Does light lose energy from traveling through an atmosphere? I would assume so, but I never knew.

This concept is employed in a technique called "cavity ringdown spectroscopy." A laser is injected into the region between two very reflective mirrors and allowed to bounce around until the light dies away. Typical cavity ringdown mirrors have reflectivities on the order of, say R = 0.99998 or better.

Because there is no such thing as a perfect reflector, the light in the cavity slowly decays, even if the absorption / transmission is only 1 part in a million per bounce. The technique was originally called "Cavity Attenuated Phase Shift" or CAPS, because the phase of the coherent laser light changes as a function of the material between the mirrors. The CAPS method was not nearly as powerful as just looking at the bulk absorption produced by millions of passes in a laser cavity and the ringdown time of the light wave in the cavity.

If the mirror spacing is just right, additional phenomena are observed such as mode beating, and other wave-based effects.

This technique is often used to measure really, really tiny absorptions because of the enormous path lengths generated by millions of light traversals of the cavity.

A company that has developed commercial instruments based on this concept is Los Gatos Research, Inc.

[edit to add info and fix grammar]

[edit on 5/4/2005 by ChemicalLaser]

scientific american article

I thought I remembered reading an article about slowing down light emitted from lasers and after a little bit of searching I found it. Physicists are doing seemingly impossible things all the time, but it gets no coverage in the mainstream media. Anyway its very interesting stuff.

What if a mirror like this were used and somehow bent into a sphere? For this to work best, it would have to be a vacuum inside the mirror.


external image

My guess is that it would absorb light energy until the pressure got too much and then would explode. Very interesting topic, I've wondered about this before.

Yea, I bet it would start to get really hot. (Maybe use something the equivalent of a one way mirror.)

I think the observer would have to be traveling at the same speed as the light photon in order to actually capture it in a meaningful way were you could observe and manipulate it. I dont think you could catch it without disolving it. You could run next to it and perhaps observe it and some minor minipulations to it. To stop light you would have to catch it.... if you did that you might find yourself traveling through time

Well, are we really talking about 'stopping' light as much as some container with a mirrored inside, in which it would continually move ?

It doesn't matter what shape the mirror is. Like I said above, there are no perfect reflectors. The reflection percentage may be as high as 99.999%, but still a small fraction will be absorbed or transmitted by the mirror. Furthermore, the 'sphere' does not necessarily have to contain a vacuum. If the gas inside has no absorption at the wavelength of the light inside, it wouldn't matter if it was a vacuum or pressurized to many atmospheres. Some light scattering effects such as the Raman effect might occur. In principle, light generated by Raman processes could eventually generate heat, but that's a really tiny effect. You would have to add a tremendous amount of laser light to generate enough heat to make the pressure increase enough to make a solid sphere explode.

I remember reading about this kid who did a science project involving this technique. He used mirrors to make a solar powered oven. Supposedly it worked really well. Interesting.