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Quote from: alancalverd on 09/08/2022 10:42:20Quote from: hamdani yusuf on 09/08/2022 03:03:44Do laser cutters decrease entropy?no.So, they don't have negative temperature.
Quote from: hamdani yusuf on 09/08/2022 03:03:44Do laser cutters decrease entropy?no.
Do laser cutters decrease entropy?
There's also nothing special about lasers for cooling.
Quote from: Bored chemist on 08/08/2022 12:51:13Using a laser is by far the most sensible way but, in principle you could use a different light source.What other kinds of light can be used for cooling? Do you have any source?
Using a laser is by far the most sensible way but, in principle you could use a different light source.
I'd have to do lots of complicated maths but, for the sake of discussion, let's pretend that I have done it and the answer is minus 5000K.What use are you going to make of that information?Because, if you don't have a good answer, I'm going to take it as further proof that you are a troll.It will prove that you were just trying to trick me into doing lots of pointless work.
with the same heat capacity
It seems like you are trying so hard to look like you know more things than you actually do.
If that's not the case, then saying that the laser has negative 5000K is erroneous in the first place.
How to cool things using light other than laser?
Quote from: hamdani yusuf on 09/08/2022 23:20:14How to cool things using light other than laser?The same way that you would do it using a laser, but using a different light source.The fact that you ask this proves that you don't understand how laser cooling works.
Or is it just your hypothesis?
No, it's a deduction.
There is no way for the atoms being cooled to know if the photons hitting them came from a laser or from some other source, is there?So the idea that they might behave differently is a bit silly, isn't it?
A laser differs from other sources of light in that it emits light which is coherent. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum. Alternatively, temporal coherence can be used to produce ultrashort pulses of light with a broad spectrum but durations as short as a femtosecond.https://en.m.wikipedia.org/wiki/Laser
What are the differences between laser and other light sources?
Until it's confirmed experimentally, your deduction will remain as a hypothesis.
A laser differs from other sources of light in that it emits light which is coherent.
Electroluminescent cooling using light-emitting diodesThere is a multitude of areas where sub-zero temperatures are required in space, from the storage of lunar material [1] to the cooling of infrared (IR) cameras and other sensors [2]. Because the transportation of equipment and materials from Earth results in huge costs, with an estimated price of around 500 000 €/kg to the Moon in 2008 [3], lightweight cooling systems are highly sought [1].For almost 60 years [4], we have known that when an electron-hole pair recombines in certain light-emitting diodes (LEDs), the energy of the emitted photon (light, energy Eout = hν) can exceed the energy of the injected charge carriers (applied current, energy Ein = qV). For this phenomenon, hν > qV, to make physical sense, a portion of the energy of the photon must be taken from somewhere - in this case phonons (heat) in the crystal lattice. The result is that the LED can function as a cooling element, drawing heat from the crystal. In this situation, the wall-plug efficiency (WPE), defined as the ratio of the total optical output power to the input electrical power and therefore also called the electrical-to-optical power-conversion efficiency, has a value above unity.Electroluminescent cooling (ELC) is only feasible, however, if the combined cooling effect from all radiative recombination events exceeds the heating caused by all parasitic, non-radiative recombination events. For every time an injected electron fails to recombine with a hole or a photon is absorbed in the structure, heat is produced.Only if the external quantum efficiency (EQE, the ratio of successfully extracted photons to injected charge carriers) of the LED is close to unity or the photon energy hν is considerably higher than the applied voltage qV to the LED, the WPE = EQE × ( hν / qV ) can exceed unity [5].Although the theoretical potential of ELC has been known for a long time [6], it was only recently that ELC was demonstrated in the laboratory - although for extremely low cooling powers [5]. With the increase in the efficiencies of LEDs in general, several groups have started looking into the use of ELC for practical purposes [7-10].
Have you ever thought why can't we just simply replace the lasers in laser cooling with LED or other incoherent light sources?
Not really, no.We know from other experiments that a photon is a photon is a photon.If it has the same wavelength and polarisation it will act the same as any other photon with that wavelength and polarisation.
Yes, I have.I didn't need to think about it for very long before I realised the answer.
Can you think of some property of laser light that might explain why lasers are typically used for cooling and other light sources are not?Here's a hintNd YAG 1064 nmNeNe 632.8nmHeCd 422 nm
Quote from: Bored chemist on 12/08/2022 18:53:31Can you think of some property of laser light that might explain why lasers are typically used for cooling and other light sources are not?Here's a hintNd YAG 1064 nmNeNe 632.8nmHeCd 422 nmLaser frequency and wavelength can be tuned at will, by changing the length of light-emitting cavity or its temperature. Temperature can also change frequency of LED. Incandescent light produces continuous spectrum. Prism or diffraction grating can be used to select desired frequency.
but has difficulties to explain some others.
Quote from: Bored chemist on 12/08/2022 18:53:31Yes, I have.I didn't need to think about it for very long before I realised the answer.What's the answer?
Quote from: hamdani yusuf on 12/08/2022 23:41:53 but has difficulties to explain some others. Which?