Is it possible to create light?

[TeethWhitener]

The phonon dispersion is continuous.

Yes. I should not have said discrete. I don't know if you typed this before, during, or after my edit (re: the low temperature part). But the point that I was trying to make is that blackbody radiation is largely material-independent, whereas optical phonon modes are not. Of course, acoustic modes technically aren't either, but for a bulk material, their spectrum extends all the way to zero energy, so that those modes are always populated (i.e., the density of states at low energy is essentially material independent).

 

[DaveC49]

Again this is incorrect.

If you have solved the simplest 1D chain that is a standard exercise in any undergraduate solid state class, you would have seen two types of phonon modes: acoustic and optical. The optical mode has a vibration similar to the electric dipole oscillation. In other words, this mode is optically active. It can absorb and it can emit photons.

This is not an atomic transition.

Zz.

Thanks for that. The optical phonon modes look like the go. Undergrad solid state was 40 years ago and I haven't touched SS much since then. I'll dig up a copy of Kittel and refresh my failing memory.

 

[sophiecentaur]

Thanks for that. The optical phonon modes look like the go. Undergrad solid state was 40 years ago and I haven't touched SS much since then. I'll dig up a copy of Kittel and refresh my failing memory.

HAHA. I have a copy on my shelf. I found the SS hard enough in those days so, today, it's really going to make my brain ache,

 

[nasu]

@Dr Claude Agree. The original explanation by Einstein was in terms of Bose Einstein statistics, but when Dirac developed the quantum mechanical treatment of electrons as fermions where the electrons cannot occupy exactly the same energy state. This of course is what creates the band of states known as the conduction band in metals.
@ZapperZ .

I am afraid you confuse the statistics of the phonons in a cavity with that of the electrons.
The photons, beeing bosons, can be described by a Bose-Einstein type of distribution. Sometimes called Plank distribution as it was first introduced by Plank.

But electrons has to be described by Fermi-Dirac distribution, even for Einstein. I don't think he used a BE distribution for electrons. Do you have any reference to this?

 

[Mark Harder]

https://www.uni-wuerzburg.de/en/sonstiges/meldungen/detail/artikel/die-erste-elektrisch-betriebene-lichtantenne-der-welt/

Is this device an electrical diode? In other words, does the asymmetry in its structure produce an asymmetry in conductivity? Tunnel diodes are semiconductor devices in which electrons penetrate a classically insulating junction by means of the QM tunnelling effect. I've never heard of it, but do/can tunnel diodes emit light?

 

[rootone]

There are many ways in which light can be created by using electrical energy.
Light generated from magnetic fields is much less well known, but you might want to check this out.
http://www.nature.com/articles/srep00492

 

[Mark Harder]

Electron beam synchrotrons also emit light. Magnets are used to steer the electrons in curved paths. The electrons are therefore accelerating toward the center of curvature. Maxwell's laws guarantee that accelerating charges emit electro-magnetic waves. Special relativity demands that at their near-luminal velocities the electrons emit photons in a focused forward directed beam. Synchrotron light sources radiate in the extreme UV to X-ray region of the EM spectrum. The tightly focused, intense radiation finds many uses in chemical and physical studies, x-ray crystallography for instance. If the electrons are circulating in bunches, then the radiation is emitted in very short but high-frequency pulses; hence, such devices can be used to time extremely fast molecular processes. I don't know if synchrotrons are used to generate IR to visible wavelengths. I would think the existence of lasers would make this application less important. Related electron beam devices called 'wigglers' or 'undulators' work according to the same principles; but in these cases, the beam passes through a gauntlet of permanent magnets that alternate in polarity along the beam path. This causes the particles to follow a zig-zag path. At each turn, they emit EMR in the forward direction. Unlike the synchrotron, this arrangement causes the forward-directed photons to interact with the particles further on down the device. I seem to recall that this has some sort of laser-like stimulated emission effect. I'm afraid the explanation gets a little fuzzy at that point, so I'll stop there. Except to say that the EMR produced has applications similar to synchrotron radiation. However, in the case of wigglers/undulators, the only application is EMR generation. These devices can also be made on a much smaller scale than synchrotrons, the size of small labs in some cases.