photons and reflection

stand it (big qualifier

I would like to hear you discuss photoluminescence and Raman scattering!

Thanks for the words of sanity!

other

t all?

Well, that explains lasers. No, wait, it doesn't.

Too bad you refuse to enter the real world.

Mark L. Fergerson

So, when do you plan to eat the golden bullet? 'Cause otherwise, you're going to be one one day.

Good Luck! Rich

hat

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at all?

But it doesn't explain a rainbow. Emission can be quantized but not all of the time.

Mitch Raemsch

I am one already getting even oldfer.

Bill

Here's how the theory can be described (simplified, obviously):

(a) solve Maxwell's equations for a suitable system, and get a set of normalizable basis functions allowing you to describe any field configuration.

(b) these basis functions usually have both electric and magnetic field contributions; they are usually called "mode functions", and tend to oscillate in space and time (although not all will).

(c) quantize the field inside each mode; this gives you a countable series of possible mode excitations.

(d) to describe some chosen field configuration, you combine a suitable set of modes containing appropriate quantum excitations. You may need to account for non-trivial correlations between the modes, and between the quantum states in the same and different modes.

There is no "particle of light". Instead there are countable excitations of the wave-like field modes. These modes usually combine both electric and magnetic contributions.

It's not a particle, it's a wave. But you _can_ count the excitations.

"> Neither wave or QM theory does a thorough job of explaining the observed

Louis, do you have any specific examples in mind? I thought the theorists had a good handle on light. (I'm an experimentalist and am certainly not going to come up with any theories of my own..... I've got enough trouble understanding E&M, let alone QM.) When I measure light it always comes as photons. With a Si Photodiode I get one electron generated for each photon absorbed.

George H.

kinsle/

Paul, I feel I'm in way over my head, but is there something wrong with calling the excited quantized mode a photon?

George H.

Agreed. That's absolutely the classic (not classical!) approach to quantum analysis of e-m problems.

But any thoughts on how to extend this approach (or connect it) to the whole class of "open systems" (all the systems like unstable resonators/gain-guided waveguides, etc) where the actual operating or oscillating or amplifying modes of the system (the "real modes", not just some set of basis functions) are non-orthogonal, non-Hermitian, non-self-adjoint, biorthogonal, so that you run into the Petermann excess noise factor and "adjoint coupling" concepts and so on.

Obviously you can choose any more or less arbitrary set of Hermitian basis functions to use in analyzing these systems; but since these basis functions will _not_ be the actual "modes" that the system actually operates in, your superposition will in general, and more or less unavoidably, be a very inefficient way of describing the system.

I believe (and I think Han Woerdman does) that the nonhermitian biorothogonal modes + Petermann excess noise factor approach predicts the correct quantum results for these systems (or at least some of the important quantum results?), and futhermore does so in an efficient and simple fashion. But, I've never really understood how this approach ties into, or can be connected to, the classic approach you describe.

kinsle/

There are only a very few quantizations in light energy quantities of the atom. Certainly not enough for white light we see. This does not correspond to the reality of the full spectrum produced by the white light. A light bulb passed through a prism produces a full spectrum of energy levels but does not have enough quantized states in its atom to do so.

Mitch Raemsch

Calling a single (extra) excitation of a mode a "photon" is pretty much exactly what you should do. Just don't call it a particle as well.

/~kinsle/

Mitch, The light bulb can be thought of as a black body radiator. It doesn't matter what kind of atoms the black body is made of. All that is important is the temperature.

George H.

Oh, maybe (I never had cause to use this for anything though)

Brown S.A.; Dalton B.J.

rg

uk/~kinsle/

diation

George my point is that energy transitions cannot be quantized in the case of a white light. You might have a light filliment composed of a few different atoms but these could not produce the full spectrum of all the light energies noticed when its light is passed through a prism.

Evidently only sometimes is light energy quantized.

Mitch Raemsch

.org

c.uk/~kinsle/

radiation

Ahh, there are two types of quantization here. For an atom you have quantized electron states. The photon emmited when the atom goes from one state to the other has a particular 'quantized' frequency. But this is just because of the uderlying quantized electron states. There is then the quantization of the EM field that is called a photon....(And I'll never call it a particle again.) When you measure light you either see one photon or none....never some fraction of a photon. (OK, most times you see lots of photons, but always an interger number.)

George H.

(I was afraid you were going to ask, "From where comes the photon emmited by a black body?" I don't have a good picture of that process.)

le

--

cs.org

.ac.uk/~kinsle/

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to

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hat

y_radiation

The electron state is simply which of the 4 shells it is in. There are only 4 fundamental sizes to the atom because of these round shells that science calles energy levels of the electron.

White light from a surface composed of a few different atoms is evidence that emmision is not always quantized.

Mitch Raemsch

However, in quantum mechanics the amplitude of this wave is quantized. A wave with a quantized amplitude is fare different than a wave that has an amplitude that can be contiuously varied.

I don't think there is always a large difference between a wave with quantized amplitude and a particle. If one has a "wave" at a high quantization state, then I suppose it acts a bit like the classical "wave". However, at small energy densities the energy has to become somewhat localized. I remember far back reading a mathematical analysis that showed that a boson field with a quantized amplitude behave in all ways like a "boson particle," except with regard to the ground state of the excitation. The ground state of the boson excitation tends to have "nonparticle" properties no matter how weak the field. However, at quantum amplitudes that are not too low and not too high, a particle description is valid. Hence, describing photons as a "particle" is somewhat accurate. I agree with your larger point. Photons are not classical particles, and shouldn't be presented as such. Newton's corpuscular theory is dead. However, his corpuscular theory is a -well- reanimated corpse|;-)

The nature of light is "?" .

The upper part represents the wave aspect; the lower part represents the particle aspect.

-- Befuddled Bill