# The Naked Scientists Forum

### Author Topic: Can we trap light for long periods of time?  (Read 7365 times)

#### mdubois82

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##### Can we trap light for long periods of time?
« on: 16/02/2009 16:30:02 »

If light can travel for thousands of years could we use the high percentage reflective materials to trap light in a looped pattern in a vacuum box to create a design or pattern for long periods like years or decades?

What do you think?

#### swansont

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##### Can we trap light for long periods of time?
« Reply #1 on: 16/02/2009 16:49:03 »
The problem with storing light using reflections is that light moves really fast, so you get lots of reflections:  for mirrors separated by L, c/L gives you the number of reflections per unit time.  If they are 3 meters apart, that's still a hundred million reflections per second.  Even for highly reflective materials the cumulative loss on each reflection will eventually dampen the wave to essentially nothing very quickly.  With a reflectivity of 0.99999999 you will have about a third of your light left after a second.

#### yor_on

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##### Can we trap light for long periods of time?
« Reply #2 on: 16/02/2009 18:15:16 »

#### Bored chemist

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##### Can we trap light for long periods of time?
« Reply #3 on: 16/02/2009 19:33:11 »
It depends on the definition of "a long time"
This trick
http://en.wikipedia.org/wiki/Cavity_ring_down_spectroscopy
relies on effectively "keeping light in  a box made of mirrors" but the time is on the order of a millisecond which is a bit different from years.

#### yor_on

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##### Can we trap light for long periods of time?
« Reply #4 on: 16/02/2009 21:31:55 »
On the other hand we seem to be able to trap 'light' in a BEC.
For quite some time.

http://www.physorg.com/news6123.html

And this is even cooler if it is correct.
As it states that stopped light turn into 'matter' or at least that lights 'information' becomes 'imprinted' on 'matter'.

http://www.abc.net.au/science/news/stories/2007/1843012.htm

#### swansont

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##### Can we trap light for long periods of time?
« Reply #5 on: 17/02/2009 20:48:41 »
On the other hand we seem to be able to trap 'light' in a BEC.
For quite some time.

http://www.physorg.com/news6123.html

And this is even cooler if it is correct.
As it states that stopped light turn into 'matter' or at least that lights 'information' becomes 'imprinted' on 'matter'.

http://www.abc.net.au/science/news/stories/2007/1843012.htm

Light did not turn into matter.  Ugh.  A scientist uses their poetic license, and then it gets blown further out of proportion by a credulous reporter.  Hau does some incredible physics, but the press releases are nightmares.  It's this sort of thing that's the reason that almost all quantum teleportation articles in the popular press talk about Star Trek.

http://blogs.scienceforums.net/swansont/archives/412

#### yor_on

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##### Can we trap light for long periods of time?
« Reply #6 on: 17/02/2009 23:13:26 »
"This interaction gives them a momentum kick, because the photons with which they are interacting have momentum, so these atoms are now moving at some small speed (around 6 cm/s). They travel into a second BEC a short distance away and interact with it, “imprinting” their phase information. The coupling laser is turned on, which recreates the original light pulse in all its glory."

How the light 'imprinted' itself, and what 'energy' the 'coupling laser' might have transfered to those 'imprinted' atoms? As those two was, sort of, 'unknowns' in the article.
And that pdf the site had looks good too.

Nice one Swansont:)

#### Vern

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##### Can we trap light for long periods of time?
« Reply #7 on: 18/02/2009 14:01:15 »
Quote from: yor_on
How the light 'imprinted' itself, and what 'energy' the 'coupling laser' might have transfered to those 'imprinted' atoms? As those two was, sort of, 'unknowns' in the article.
And that pdf the site had looks good too.
I can visualize how the information might be stored in the atoms as an excitation in the electron clouds of the atoms. I remember Richard Feynman described the interaction between atoms and light as "the light does a little dance with each atom" as it penetrates a substance. The dynamics of atomic electrons is still open for more discovery I suspect.

#### Bored chemist

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##### Can we trap light for long periods of time?
« Reply #8 on: 18/02/2009 19:53:32 »
"that lights 'information' becomes 'imprinted' on 'matter'."
So what?
It's not that exciting an idea.
Hundreds of years ago smugglers used signal lamps to convey information. The people on the shore remembered seing the lights and remembered what information those lights carried.
The details of human memory are complex and, at least from my point of view, not well understood but they clearly involve making a recodr of that information on the matter in the brain- perhaps by strengthening conections between synapses.
In any event, the light converyed information that was imprinted on matter.

#### JP

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##### Can we trap light for long periods of time?
« Reply #9 on: 18/02/2009 20:41:35 »
"that lights 'information' becomes 'imprinted' on 'matter'."
So what?
It's not that exciting an idea.

What's exciting is that measuring and recording data actually makes it so you can't perfectly reconstruct the original photon's state.  The whole point of these experiments to slow or stop light by 'imprinting it' onto matter is to do so without measuring/recording it, so that the original photon is still there in all its quantum glory.

#### swansont

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##### Can we trap light for long periods of time?
« Reply #10 on: 18/02/2009 21:38:23 »
"that lights 'information' becomes 'imprinted' on 'matter'."
So what?
It's not that exciting an idea.
Hundreds of years ago smugglers used signal lamps to convey information. The people on the shore remembered seing the lights and remembered what information those lights carried.
The details of human memory are complex and, at least from my point of view, not well understood but they clearly involve making a recodr of that information on the matter in the brain- perhaps by strengthening conections between synapses.
In any event, the light converyed information that was imprinted on matter.

As I said in another thread it's more like a hologram; you can break a holographic exposure into small pieces and the information about the hologram is contained in each one, meaning the information density is really larger.  If you don't think that's exciting, so be it.

#### yor_on

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##### Can we trap light for long periods of time?
« Reply #11 on: 19/02/2009 00:08:09 »

#### syhprum

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##### Can we trap light for long periods of time?
« Reply #12 on: 19/02/2009 07:20:26 »
I understand that resonant cavities made of 'high temperature super conducting materiel's' are used in some communication systems, they are in effect boxes that hold light (albeit of a low frequency) for a short period.
Gas discharge lasers do the same thing and as you say they require very high grade mirrors.

#### The Naked Scientists Forum

##### Can we trap light for long periods of time?
« Reply #12 on: 19/02/2009 07:20:26 »