Talk:Laser cooling

Definition of thermodynamic temperature

There is this statement in the text: "For an ensemble of particles, their thermodynamic temperature is proportional to the variance in their velocity."

In the wikipedia page for thermodynamic temperature (where there is the definition and properties of it) there is no mention of variance of velocity.

Is it a wrong statement or the "thermodynamic temperature" wiki page is incomplete? — Preceding unsigned comment added by 5.14.129.47 (talk) 07:41, 7 August 2023 (UTC)

Mechanism needs clarification

We currently have this:

Because the light is detuned to the "red" (i.e. at lower frequency) of the transition, the atoms will absorb more photons if they move towards the light source, due to the Doppler effect. Thus if one applies light from two opposite directions, the atoms will always scatter more photons from the laser beam pointing opposite to their direction of motion.

I don't think this is clear enough. The word "thus" joins a sentence about absorbtion with a conclusion about scattering, with no explanation of how the two are related. I don't know enough about the topic to fix this. --Doradus 13:25, Jun 24, 2005 (UTC)

I agree. I think a much easier-to-understand explanation is possible. ... Hmmm, that ended up being *much* longer than I expected. Feel free to condense it down and post to the article. --DavidCary 12:46, 26 July 2005 (UTC)

OK, I put my rough draft into the article. --DavidCary 00:14, 1 December 2005 (UTC)

the Laser Teaching Center at Stony Brook University http://laser.physics.sunysb.edu/projects/ seems to show a lot of people working with "Laser cooling", and with related ideas such as "MOT's" (magneto-optical traps), "Optical tweezers", etc. Should we ask nicely for some photos?

Overall, I think this article is very successful in explaining the basic concepts of laser cooling. I'd like to make a few more minor edits when I have time, especially on the history of the subject, which is subject to a surprising amount of misinformation. Dave Kielpinski 06:08, 18 December 2005 (UTC)

Old request for information

I apologize for the delay responding; I'd missed the original request, then gotten extremely busy. If any of the information in the laser cooling thread in my talk page archives is useful, by all means use it. --Christopher Thomas 03:54, 8 January 2006 (UTC)

question

How effective is laser cooling? does it cool fast? can it only cool to ex. 0 celcius, or can it cool to minus degrees too? Are there any real implementations? how much would such a cooling cost? how big would such a cooling device be? Imagine cooling your computer with that. ;) —The preceding unsigned comment was added by Frap (talk • contribs) on 21:13, 20 May 2006.

First please use four ~ (~~~~) marks to automatically insert a signature with datestamp after your talk-page comments.

Secondly several of your questions are already answered in the article. It cools far below 0 degrees centigrade. Target temperatures are millikelvin or lower (lowest I'd heard cited was nanokelvin). These cooling systems are in widespread use in physics laboratories for studying things like Bose-Einstein condensates.

The cooling systems are fairly cheap as far as laboratory systems go, costing several thousand dollars to a few tens of thousands. I don't have information on rate of cooling, but I imagine it would be quite slow (you're using light pressure to bleed off kinetic energy of molecules, _and_ it's only a statistical average effect, _and_ absorption rate difference will drop as the molecules slow down, slowing cooling). The devices range from the size of a computer monitor on up (they're vacuum chambers with lasers shining into them and usually magnetic field coils around them, generally small enough to bolt to a lab bench).

This would be useless for cooling a computer. What you need to do when cooling a computer is to keep the outer surface of the chip module (or die, for chips mounted with the bare die exposed) as cool as possible. The active parts of the silicon will still be at 50-100 degrees centigrade; you're just using a larger heat difference to the outer surface of the chip to increase the rate at which heat flows out of the system. This takes a system with high throughput, but doesn't require absolute temperatures anywhere near this low. See overclocking for more information.

--Christopher Thomas 23:37, 20 May 2006 (UTC)

Just to add this article is very simliar to doppler cooling, as indeed it is the same process being used. There is no mention of the optical molasses technique which utilises 3 pairs of lasers doing this process (and subsequently the magneto-optical trap which uses the this and oppositely directed magnetic fields).

Lastly there is also the application of atomic lasers... —Preceding unsigned comment added by 131.227.231.210 (talk) 19:06, 9 December 2007 (UTC)

No mention of laser cooling of solids

The first experimental demonstration of laser cooling in solids (Yb-doped glass) took place in 1995 at Los Alamos National Labs by Epstein et al. Published in Nature, 1995.64.106.62.179 18:25, 4 September 2007 (UTC)

There is no mention of laser cooling of solids in this article. The first instance I'm aware of this happening was published in: Phys. Rev. Lett. 78,1030 - 1033 (1997)

Since this kind of laser cooling uses an entirely different mechanism (that of anti-stokes fluorescence, should it be made into a separate article?

I agree that anti-stokes cooling deserves an article (I was looking for a Wiki link for that) - whether it should be part of the atomic version of "laser cooling" or put on a separate page with a disambiguation is unclear. Probably depends on how much gets written. Tarchon 01:12, 26 April 2007 (UTC)

Since laser cooling of solids is also called "laser cooling", what should we call the page that talks about cooling of solids? Ebudiu 02:28, 29 May 2007 (UTC)

I think "optical cooling" would be the higher level topic which would subsume the various laser cooling techniques and other non-laser optical cooling approaches. I would also leave out "of solids" as being unnecessarily restrictive. The basic process of using thermal-photonic interactions to cool doesn't have any inherent restriction to solids to my knowledge.Tarchon 00:30, 26 October 2007 (UTC)

The name "Laser cooling" includes all methods where you use a laser cools to cool a system; the process which we're talking about here (where you use a red detuned single frequency cooling laser) is called "Doppler Cooling". Rickky678 (talk) 15:22, 14 September 2009 (UTC)

Historical factual errors

The article says that laser cooling was first demonstrated by Letokhov, Minogin and Pavlik. What is ment by "demonstrated" here? The first experiments that utilized these ideas are experiments performed by Wineland, Drullinger and Walls in 1978 who cooled Mg ions and the same year Neuhauser, Hohenstatt, Toschek and Dehmelt cooled Ba ions. I would think the original poster is talking about this article by Letokov et al but that is a theoretical thesis and doesn't contain any experimental data. The other two papers are here and here. --ojs (talk) 13:44, 20 November 2007 (UTC)

First, the Letokhov paper "Cooling and trapping of atoms and molecules by a resonant laser field" of 1976 is here [1]. It was earlier than Wineland and Dehmelt papers. (As far as I remember, Wineland visited the seminar which Letokhov gave in USA and then stated his work). Second, Wineland/Dehmelt 1975 theoretical communication on laser cooling is not accessible and has a title which has nothing to do with laser cooling. Third, even Phillips (who got Nobel price for laser cooling - which was probably a mistake by Nobel price committee which they almost accepted later) stated that trapping of atoms were suggested by Letokhov in 1968 - see his Nobel lecture. Hence, I suggest to restore some justice and indicate that Letokhov did make a large contribution to development of laser trapping and cooling of atoms and ions. — Preceding unsigned comment added by Iskander32 (talk • contribs) 13:18, 20 February 2019 (UTC)

I added references to the proposal by Hansch and Schawlow, this seems to supersede the work by Letokhov, and the bulletin post by Wineland and Dehmelt. Though the title of the Wineland and Dehmelt work does not reference laser cooling, the note describes laser cooling. Bill Phillips references Letokhov work from 1968 in his Nobel lecture, but the work was concerned with dipole trapping and apparently did not include laser cooling. I'll try and include this reference on the "Optical Tweezer" page, which redirects from dipole trap. Darth luigi (talk) 02:10, 9 November 2023 (UTC)

Is this really cooling?

Any incident energy on an atom, does not cool an atom, it increments that atoms internal kinetic energy. What happens is that after succesive interactions, the atom reaches a higher internal kinetic state (or lower), where all energy interactions are resolved internally, without any external motion. This is possible, if for example the atom emits two photons in equal and opposite directions at the same time.

Just because an object is motionless within a reference framework does not imply that it is cooler in the sense of colder. Defacto, it is cooler in the sense of, more stable, more controlled, less random in it´s emision and absorbtion, but the atom is defacto, hotter, not colder.

In terms of core-shell beta emission/absortion ratio´s, that also implies that the internal beta emission/absortion would be more stable, and that could imply addicional core stability (or the exact opposite, close to the edge of blowing it´s top). Would that matter? Not if the alpha or neutron emitted cannot leave the core-shell enclosure, and therefore the atom itself, can be said to be in a state of continuous fusion/fission reactions, completely resolved within it´s own space confinement.

(See: single atom plasma fusion/fission processes)

Kabloom: What happened? Sorry sir, apparently that what we thought was pure matter X, had matter Y impurities associated and it blew. — Preceding unsigned comment added by 201.248.124.113 (talk) 12:05, 2 March 2013 (UTC)

Removal of content

In recent edits Mfpars removed some information, including some equations that purported to explain how laser cooling worked. Mfpars, can you say something more about why you think the article is better without this content?

Thanks for being bold and making changes. Blue Rasberry (talk) 16:22, 9 June 2015 (UTC)

Laser cooling of liquids by an unknown process

http://www.washington.edu/news/2015/11/16/uw-team-refrigerates-liquids-with-a-laser-for-the-first-time/

My best guess is that they're doppler cooling the Brownian motion of the chrystal, and waiting for the heat to conduct in from the surrounding liquid, but the publicity blurb is detail-free and doesn't say so. ArthurDent006.5 (talk) 08:22, 23 November 2015 (UTC)

Figures/movies

I'm considering adding an animation to show the reduction of phase space as a function of time. Any thoughts or feedback is welcome before I undertake this. Darth luigi (talk) 00:35, 13 September 2023 (UTC)