Lasers can be used to cool objects down.

[The Angry Intellect]

Greetings,

 

I was reading about this in a news article and was completely flabbergasted as to how a laser could be used to cool somethinf down instead of heating it up.

 

Correct me if I'm wrong, but doesn’t light give off energy/is energy, producing heat to some degree?

 

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

 

From what I gather, they aim the laser at a certain kind of crystal, which then reacts in a way which cools down which ever liquid it is in...

 

I would just like to know, is it actually possible to user lasers without aiming at a particular crystal to directly cool down an object?

 

If so, the possible applications are awesome!

 

I can think of a few examples this can be applied to: For instance to cool down microchips or during surgery, high-tech fire-fighting - aim a few lasers at some gas bottles or other areas that are in risk of over-heating or exploding and cooling them down just enough to stop this from occurring.

 

I'm still unsure how exactly they do this, but it is rather interesting considering what I was taught about light could be wrong!

[Strange]

Laser cooling has been used for a long time.

http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lascool.html

[The Angry Intellect]

Cool!

 

They talk about limits in the reduction of temperature using those methods, and how things can be further cooled using magnetic trapping... Sounds great, but it's all straight over my head haha

 

Thanks for that Strange, now I'm wondering just how much they really can cool things down given the current technology and the power requirements for such lasers, to make it a more practical alternative to other technology currently used to cool things down, e.g. a fan.

[swansont]

Cool!

 

They talk about limits in the reduction of temperature using those methods, and how things can be further cooled using magnetic trapping... Sounds great, but it's all straight over my head haha

 

Thanks for that Strange, now I'm wondering just how much they really can cool things down given the current technology and the power requirements for such lasers, to make it a more practical alternative to other technology currently used to cool things down, e.g. a fan.

 

 

The power is not what you're worried about, it's the temperatures you can access. We laser cool rubidium atoms in our atomic fountain clocks; they get to about a microkelvin or two (i.e. a millionth of a degree above absolute zero). At that temperature the rms residual motion is about a cm/sec, so the cloud of atoms doesn't expand too much as we measure them. You can't use a fan to cool them. Or any other mechanical technology. Even state-of-the-art systems that can cool bulk systems (e.g. dilution refrigerators) are screaming hot when compared to laser-cooled atoms.

 

Bose-Einstein condensates can get to even lower temperatures. There's interesting physics you can do with cold atoms.

[Sensei]

Correct me if I'm wrong, but doesnt light give off energy/is energy, producing heat to some degree?

Say we have atoms that are not in ground state.

If we send photon beam with right properties, which is enough to bump atom's electron to even higher energy level, than now,

once electron go back to ground state, it can emit photon with even larger energy, than it absorbed from initial photon.

 

Like in Hydrogen case, to visualize it.

Suppose so it has n=2,

transition from n=2 to n=3 require absorbing 13.6 eV / 4 - 13.6 eV / 9 = 1.8889 eV

but then Hydrogen can go straight from n=3 to n=1 by emitting photon with 13.6 eV - 13.6 eV/9 = 12.08889 eV

Edited March 1, 2016 by Sensei

[The Angry Intellect]

hrmm.

 

I guess my biggest question is: Can a single laser be used without the need for an additive to be introduced to the object you are trying to cool, to be able to cool it down?

 

From what I gather, you need a few lasers or else something has to be added to an object which the laser aims at in order to get a cooling action going.

[swansont]

hrmm.

 

I guess my biggest question is: Can a single laser be used without the need for an additive to be introduced to the object you are trying to cool, to be able to cool it down?

 

From what I gather, you need a few lasers or else something has to be added to an object which the laser aims at in order to get a cooling action going.

 

 

For a very few isotopes, you can do it with one laser. The beams are divided up, but just one laser. We trapped K-38m this way (that's an isomer of K-38, with a lifetime of around a second)

[The Angry Intellect]

What is the half-life of 38K? (I'm joking).

 

Thanks for the useful feedback swansont & Sensei, I appreciate it.